More on glowplugs and hard starting Universals

[Tom]

I just finished putting in new glowplugs on my model 25, 3 cylinder, Universal diesel.

Some interesting things I discovered. First, none of the old glowplugs
was bad. They all tested fine so the whole thing wasn't necessary to do in
the first place. Checked the voltage on both sides of the glowplug
switch. On the "in" side it was 12 volts but on the "out" side the voltage was 10. Thought that was a little much and would expect to see around 11 volts on the out side, but it probably wasn't enough to affect things.

Next I measured the volts at the first (rear) glowplug and saw 7 volts. Thus in the circuit between the battery and the glowplugs there is a 5 volt drop or almost half the voltage. This certainly is too much. Probably a result of poor connections on the ends of the wire between the glowplug switch and the glowplugs. The project for next weekend is to run a new wire from the glow plug switch to the glowplugs. This time I will use marine grade pre-tinned wire and solder the connectors to the ends. Incidentally this is the white/blue fat wire that runs into the wiring harness that brings all the wires to the engine.

Now if you're starting with 7 volts in that circuit and then adding the starter motor to it you could have a voltage drop big enough that the starter solenoid wouldn't engage and thus the starter wouldn't crank. This might explain why some boats don't have the problem and some do. On some, the wires and connectors have corroded badly enough to cause a big voltage drop and on others the wires and connectors haven't (yet). The connectors were crimped on by the factory rather than soldered so they will corrode in time.

If you're having trouble with intermittent cranking and haven't done the wiring change we figured out last year, or if you've done the change and are still having problems, you might check the voltage at the glowplugs before you do anything else. It could be you've got voltage drop in the feed wire to the glowplugs and starter solenoid. I'm going to leave those wires in place and run auxilliary wires in addition to them.



TomCambria@mindspring.com

[Ken Coit]

I don't know the specifications for the glow plugs in your Universal, but there may well be current limiting resistance wire in the circuit that would cause the voltage readings you are getting at the glow plugs. I'd make sure of that before ripping it out. Certainly, the bad connections need to be corrected. Having a 2 volt drop across the switch seems like bad news. Does it get hot too? There should be little resistance across that switch, much less than 1 ohm. Maybe it is time to replace that rather than the wire?

All that said, does the fuse still blow? Where is the current going? There must be a short somewhere.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

I just finished putting in new glowplugs on my model 25, 3 cylinder, Universal diesel.

Some interesting things I discovered. First, none of the old glowplugs
was bad. They all tested fine so the whole thing wasn't necessary to do in
the first place. Checked the voltage on both sides of the glowplug
switch. On the "in" side it was 12 volts but on the "out" side the voltage was 10. Thought that was a little much and would expect to see around 11 volts on the out side, but it probably wasn't enough to affect things.

Next I measured the volts at the first (rear) glowplug and saw 7 volts. Thus in the circuit between the battery and the glowplugs there is a 5 volt drop or almost half the voltage. This certainly is too much. Probably a result of poor connections on the ends of the wire between the glowplug switch and the glowplugs. The project for next weekend is to run a new wire from the glow plug switch to the glowplugs. This time I will use marine grade pre-tinned wire and solder the connectors to the ends. Incidentally this is the white/blue fat wire that runs into the wiring harness that brings all the wires to the engine.

Now if you're starting with 7 volts in that circuit and then adding the starter motor to it you could have a voltage drop big enough that the starter solenoid wouldn't engage and thus the starter wouldn't crank. This might explain why some boats don't have the problem and some do. On some, the wires and connectors have corroded badly enough to cause a big voltage drop and on others the wires and connectors haven't (yet). The connectors were crimped on by the factory rather than soldered so they will corrode in time.

If you're having trouble with intermittent cranking and haven't done the wiring change we figured out last year, or if you've done the change and are still having problems, you might check the voltage at the glowplugs before you do anything else. It could be you've got voltage drop in the feed wire to the glowplugs and starter solenoid. I'm going to leave those wires in place and run auxilliary wires in addition to the

parfaitNOSPAM@nc.rr.com

[Tom]

I wish I had some specs on the glowplug. Universal as you know was bought out. When I took the plug to the glowplug shop the guy looked it up and said there is only one place to get them now and they have to be special ordered out of Minnesota at 58 bucks per copy. He tested mine by putting them across a 12 volt battery directly with no resistance circuit in line. Since he had looked them up in the book I concluded they were meant to run at 12 volts. There isn't any real "circuit". The wire runs from the glowplug button into the wiring "harness" which is really just electrician's tape wrapped around all the wires running from the control panel to the engine. The wire comes out the end of the taped section and attaches directly to the first glowplug without going through any even buss bar connection. There is no fuse in that circuit and no fuse has ever blown on the boat. There is a fuse in the starter circuit but it has never blown either. That fuse is downstream from the glowplugs. Incidentally if that fuse were ever to blow it would be living hell to get to on a dark night in a pitching sea as you have to crawl in the port locker to get to the case it is in and cut the wire ties off of the case. I'll bet that most people don't even know there is a fuse in there to look for. Either that or remove the whole control panel and pull it out, but I digress.

I supppose it is possible that there is a resistor in line that is wrapped up inside the tape, but it hardly seems likely. Surely you would put the resistor outside at the glowplug switch on the panel or down at the engine after the wire exits the harness and not wrap it up in tape in the middle of the wires. The electrician who was working with me advised me to run the new wire, so he didn't think there was a resistor circuit anywhere.

Ken, have you actually ever seen a resistance wire wrapped up inside a wiring harness on a glowplug circuit? There wouldn't seem to be any reason to do such a thing. A glowplug is just a heater coil that you want to get red hot. Putting resistance in a circuit like that would just make it harder to heat the coil and unnecessarily slow down what you're trying to achieve. Surely anyone designing an engine that runs on 12 volts wouldn't design in things that defeat the 12 volt system. That would be like designing your electric water heater at home to run on 60 volts when the house current is 120 volts so you'd have to put in resistance to run it. Why would anybody designing something do anything like that? It seems much more likely to me that the voltage drop is due to corrosion in the stranded wire or bad connections on the ends as we know that these things happen regularly.

As far as replacing the switch, I'm already on my second switch. The first thing I did was replace all the switches with no improvement. Well, maybe it was a little better for the first month or so. I believe what happens to cause the voltage drop across the switch is this: The switch is a push button type which you push in and hold for 30 to 60 seconds to heat the glowplugs. Each time you press it you, of course, get an arc across there and you probably don't have good contact the entire time while you're holding it in, and thus the surfaces inside the switch get pitted and blackened. After a few years of using the switch it develops some internal resistance.

I've captained boats that have the Perkins 4-108 engine like the one you have, but I can't remember now whether it uses glowplugs or not. It seems to me it doesn't, but if it does, what kind of glowplug switch do you have? A pushbutton type like we do or one of those where you turn the key the opposite way to energize them like most diesel cars do it? What kind of voltage drop do you see across your switch when there is no load on it? Are your glowplugs running on 6 or 7 volt feed? I can't imagine that, but I learn stuff every day often on this board.

Beam winds and following seas,

Tom

I don't know the specifications for the glow plugs in your Universal, but there may well be current limiting resistance wire in the circuit that would cause the voltage readings you are getting at the glow plugs. I'd make sure of that before ripping it out. Certainly, the bad connections need to be corrected. Having a 2 volt drop across the switch seems like bad news. Does it get hot too? There should be little resistance across that switch, much less than 1 ohm. Maybe it is time to replace that rather than the wire?

All that said, does the fuse still blow? Where is the current going? There must be a short somewhere.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

I just finished putting in new glowplugs on my model 25, 3 cylinder, Universal diesel.

Some interesting things I discovered. First, none of the old glowplugs
was bad. They all tested fine so the whole thing wasn't necessary to do in
the first place. Checked the voltage on both sides of the glowplug
switch. On the "in" side it was 12 volts but on the "out" side the voltage was 10. Thought that was a little much and would expect to see around 11 volts on the out side, but it probably wasn't enough to affect things.

Next I measured the volts at the first (rear) glowplug and saw 7 volts. Thus in the circuit between the battery and the glowplugs there is a 5 volt drop or almost half the voltage. This certainly is too much. Probably a result of poor connections on the ends of the wire between the glowplug switch and the glowplugs. The project for next weekend is to run a new wire from the glow plug switch to the glowplugs. This time I will use marine grade pre-tinned wire and solder the connectors to the ends. Incidentally this is the white/blue fat wire that runs into the wiring harness that brings all the wires to the engine.

Now if you're starting with 7 volts in that circuit and then adding the starter motor to it you could have a voltage drop big enough that the starter solenoid wouldn't engage and thus the starter wouldn't crank. This might explain why some boats don't have the problem and some do. On some, the wires and connectors have corroded badly enough to cause a big voltage drop and on others the wires and connectors haven't (yet). The connectors were crimped on by the factory rather than soldered so they will corrode in time.

If you're having trouble with intermittent cranking and haven't done the wiring change we figured out last year, or if you've done the change and are still having problems, you might check the voltage at the glowplugs before you do anything else. It could be you've got voltage drop in the feed wire to the glowplugs and starter solenoid. I'm going to leave those wires in place and run auxilliary wires in addition to the

TomCambria@mindspring.com

[Ken Coit]

Tom,

No, there are no glow plugs on the 4-108, but I believe that some diesels that do use glow plugs also use resistance wire to limit the current and distribute the heat. The 4-108 does have resistance wire in the alternator circuit. As for the fuses, I must have you confused with whomever started the thread on glow plugs that blow fuses. I think I would fuse the line given how much trouble a short could cause.

I agree that switches can get pitted and not make perfect contact, but if the resistance gets very high, then the 5 to 10 amps each plug requires will soon result in all the power being disappated in the switch rather than the glow plugs. At a hypothetical 15 Amps and 2 Volts, your switch is consuming 30 watts. Have you ever grabbed the end of a 30 watt soldering iron? All that heat is not good.

You are probably on the right track by checking out the wiring. If you send me the info on your glow plugs, I will try to get some info for you.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

I wish I had some specs on the glowplug. Universal as you know was bought out. When I took the plug to the glowplug shop the guy looked it up and said there is only one place to get them now and they have to be special ordered out of Minnesota at 58 bucks per copy. He tested mine by putting them across a 12 volt battery directly with no resistance circuit in line. Since he had looked them up in the book I concluded they were meant to run at 12 volts. There isn't any real "circuit". The wire runs from the glowplug button into the wiring "harness" which is really just electrician's tape wrapped around all the wires running from the control panel to the engine. The wire comes out the end of the taped section and attaches directly to the first glowplug without going through any even buss bar connection. There is no fuse in that circuit and no fuse has ever blown on the boat. There is a fuse in the starter circuit but it has never blown either. That fuse is downstream from the glowplugs. Incidentally if that fuse were ever to blow it would be living hell to get to on a dark night in a pitching sea as you have to crawl in the port locker to get to the case it is in and cut the wire ties off of the case. I'll bet that most people don't even know there is a fuse in there to look for. Either that or remove the whole control panel and pull it out, but I digress.

I supppose it is possible that there is a resistor in line that is wrapped up inside the tape, but it hardly seems likely. Surely you would put the resistor outside at the glowplug switch on the panel or down at the engine after the wire exits the harness and not wrap it up in tape in the middle of the wires. The electrician who was working with me advised me to run the new wire, so he didn't think there was a resistor circuit anywhere.

Ken, have you actually ever seen a resistance wire wrapped up inside a wiring harness on a glowplug circuit? There wouldn't seem to be any reason to do such a thing. A glowplug is just a heater coil that you want to get red hot. Putting resistance in a circuit like that would just make it harder to heat the coil and unnecessarily slow down what you're trying to achieve. Surely anyone designing an engine that runs on 12 volts wouldn't design in things that defeat the 12 volt system. That would be like designing your electric water heater at home to run on 60 volts when the house current is 120 volts so you'd have to put in resistance to run it. Why would anybody designing something do anything like that? It seems much more likely to me that the voltage drop is due to corrosion in the stranded wire or bad connections on the ends as we know that these things happen regularly.

As far as replacing the switch, I'm already on my second switch. The first thing I did was replace all the switches with no improvement. Well, maybe it was a little better for the first month or so. I believe what happens to cause the voltage drop across the switch is this: The switch is a push button type which you push in and hold for 30 to 60 seconds to heat the glowplugs. Each time you press it you, of course, get an arc across there and you probably don't have good contact the entire time while you're holding it in, and thus the surfaces inside the switch get pitted and blackened. After a few years of using the switch it develops some internal resistance.

I've captained boats that have the Perkins 4-108 engine like the one you have, but I can't remember now whether it uses glowplugs or not. It seems to me it doesn't, but if it does, what kind of glowplug switch do you have? A pushbutton type like we do or one of those where you turn the key the opposite way to energize them like most diesel cars do it? What kind of voltage drop do you see across your switch when there is no load on it? Are your glowplugs running on 6 or 7 volt feed? I can't imagine that, but I learn stuff every day often on this board.

Beam winds and following seas,

Tom

I don't know the specifications for the glow plugs in your Universal, but there may well be current limiting resistance wire in the circuit that would cause the voltage readings you are getting at the glow plugs. I'd make sure of that before ripping it out. Certainly, the bad connections need to be corrected. Having a 2 volt drop across the switch seems like bad news. Does it get hot too? There should be little resistance across that switch, much less than 1 ohm. Maybe it is time to replace that rather than the wire?

All that said, does the fuse still blow? Where is the current going? There must be a short somewhere.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

I just finished putting in new glowplugs on my model 25, 3 cylinder, Universal diesel.

Some interesting things I discovered. First, none of the old glowplugs
was bad. They all tested fine so the whole thing wasn't necessary to do in
the first place. Checked the voltage on both sides of the glowplug
switch. On the "in" side it was 12 volts but on the "out" side the voltage was 10. Thought that was a little much and would expect to see around 11 volts on the out side, but it probably wasn't enough to affect things.

Next I measured the volts at the first (rear) glowplug and saw 7 volts. Thus in the circuit between the battery and the glowplugs there is a 5 volt drop or almost half the voltage. This certainly is too much. Probably a result of poor connections on the ends of the wire between the glowplug switch and the glowplugs. The project for next weekend is to run a new wire from the glow plug switch to the glowplugs. This time I will use marine grade pre-tinned wire and solder the connectors to the ends. Incidentally this is the white/blue fat wire that runs into the wiring harness that brings all the wires to the engine.

Now if you're starting with 7 volts in that circuit and then adding the starter motor to it you could have a voltage drop big enough that the starter solenoid wouldn't engage and thus the starter wouldn't crank. This might explain why some boats don't have the problem and some do. On some, the wires and connectors have corroded badly enough to cause a big voltage drop and on others the wires and connectors haven't (yet). The connectors were crimped on by the factory rather than soldered so they will corrode in time.


If you're having trouble with intermittent cranking and haven't done the wiring change we figured out last year, or if you've done the change and are still having problems, you might check the voltage at the glowplugs before you do anything else. It could be you've got voltage drop in the feed wire to the glowplugs and starter solenoid. I'm going to leave those wires in place and run auxilliary wires in addition to the

parfaitNOSPAM@nc.rr.com

[Ed Haley]

Just finished solving the problem I had with hard starting. The battery ground was connected to a bracket that held a fuel filter on the side of the engine wall. The bracket was cracked and caused a bad ground. I found another suitable bolt to attach the ground to and tried starting the engine. I swear is starts like it's new.

Check your ground. Could be your solution!

Good hunting

Ed Haley
Captain s/v Mokita
CD330 #1
Kingston, ONT

Finally made it thru the Erie/Oswego Canals

Mokita stands proud in Confederation Basin



eghaleyNOSPAM@twcny.rr.com

[Tom]

Thanks Ed, Actually I solved my problem last yeat with the wiring solution I posted. I decided to replace my glowplugs this year as preventative maintenance and in the process discovered the information I posted here in case there was someone else out there still having problems. I thought I might be able to save them some hunting. My engine cranks every time now and starts within a second or two. But what I had deduced was the original problem, i.e., resistance in the glowplug switch, I now don't believe that was the problem -- although it will solve it for a little while. Thus these additional thoughts might help someone when the original fix starts going bad and not working. I'm still just speculating that this is the real problem and putting it out there for what it's worth for everyone.

Just finished solving the problem I had with hard starting. The battery ground was connected to a bracket that held a fuel filter on the side of the engine wall. The bracket was cracked and caused a bad ground. I found another suitable bolt to attach the ground to and tried starting the engine. I swear is starts like it's new.

Check your ground. Could be your solution!

Good hunting

Ed Haley
Captain s/v Mokita
CD330 #1
Kingston, ONT

Finally made it thru the Erie/Oswego Canals

Mokita stands proud in Confederation Basin

TomCambria@mindspring.com

[Tom]

Ken, After reading your post this morning I went down and talked to the local diesel mechanic about glowplugs. He said that actually there are glow plugs that run on two volts. The early Mercedes car diesels put the glowplugs in series with an indicator light also in series. If the indicator light burned out it would fry all the glowplugs by letting too much juice get to them. Also if one plug went out, none of them would work. What you'd expect from a series wired set up.

However the Universal engines and as far as he knows all other boat diesels are wired in parallel these days. Rather than being rated at 12 volts, however, they are usually rated at 10 or 11 volts to allow for resistance in the switches and wires. He thought you had to be careful testing them across 12 volts because you might fry them if you went directly to 12 full volts on a battery with no switches or wires in the circuit.

He thinks 7 volts is too low for a feed current and the plugs might only be getting warm rather than hot at that voltage. He didn't see any problem with running an additional wire. This is just one mechanic's opinion, of course.

As far as adding a fuse to the glowplug circuit goes, I don't follow your logic on that one. As you know the circuit is only energized for the 30 seconds that you're holding the button down. Once the engine starts that circuit isn't on line at all. If you developed a short while you were holding the button down you could simply let up on the button and kill the circuit -- essentially do the same thing a fuse would do. If you developed a short it would remove current from the glowplugs and thus they wouldn't be damaged, so what are the dire consequences that might happen from a short in the glowplug circuit?

Unfortunately I didn't bring a glowplug home with me. They are on the boat 130 miles away so I can't read off any information for you, but I will get it the next time I'm down there. As I recall the new plugs said 10 volts on the side but I don't remember the rest. I looked through the CD engine manuals but couldn't find any specs on the glowplugs. The engine wiring schematic doesn't show any resistance in the glowplug wire, but maybe if you had a resistance wire as opposed to a resistor it wouldn't show on a schematic?

If Dave Stump is the nautical traditions guru, I recommend we appoint you as the technical information guru. You've got a tremendous amount of technical information, diagrams, and specs stored in your computer and/or brain. There's virtually nothing mentioned on the Board that you don't post a picture of the next day, together with the specs and ordering information. You're a great asset to the BB. Thanks for the information and input and as you always say:

Keep on Sailing!

Tom,

No, there are no glow plugs on the 4-108, but I believe that some diesels that do use glow plugs also use resistance wire to limit the current and distribute the heat. The 4-108 does have resistance wire in the alternator circuit. As for the fuses, I must have you confused with whomever started the thread on glow plugs that blow fuses. I think I would fuse the line given how much trouble a short could cause.

I agree that switches can get pitted and not make perfect contact, but if the resistance gets very high, then the 5 to 10 amps each plug requires will soon result in all the power being disappated in the switch rather than the glow plugs. At a hypothetical 15 Amps and 2 Volts, your switch is consuming 30 watts. Have you ever grabbed the end of a 30 watt soldering iron? All that heat is not good.

You are probably on the right track by checking out the wiring. If you send me the info on your glow plugs, I will try to get some info for you.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

I wish I had some specs on the glowplug. Universal as you know was bought out. When I took the plug to the glowplug shop the guy looked it up and said there is only one place to get them now and they have to be special ordered out of Minnesota at 58 bucks per copy. He tested mine by putting them across a 12 volt battery directly with no resistance circuit in line. Since he had looked them up in the book I concluded they were meant to run at 12 volts. There isn't any real "circuit". The wire runs from the glowplug button into the wiring "harness" which is really just electrician's tape wrapped around all the wires running from the control panel to the engine. The wire comes out the end of the taped section and attaches directly to the first glowplug without going through any even buss bar connection. There is no fuse in that circuit and no fuse has ever blown on the boat. There is a fuse in the starter circuit but it has never blown either. That fuse is downstream from the glowplugs. Incidentally if that fuse were ever to blow it would be living hell to get to on a dark night in a pitching sea as you have to crawl in the port locker to get to the case it is in and cut the wire ties off of the case. I'll bet that most people don't even know there is a fuse in there to look for. Either that or remove the whole control panel and pull it out, but I digress.

I supppose it is possible that there is a resistor in line that is wrapped up inside the tape, but it hardly seems likely. Surely you would put the resistor outside at the glowplug switch on the panel or down at the engine after the wire exits the harness and not wrap it up in tape in the middle of the wires. The electrician who was working with me advised me to run the new wire, so he didn't think there was a resistor circuit anywhere.

Ken, have you actually ever seen a resistance wire wrapped up inside a wiring harness on a glowplug circuit? There wouldn't seem to be any reason to do such a thing. A glowplug is just a heater coil that you want to get red hot. Putting resistance in a circuit like that would just make it harder to heat the coil and unnecessarily slow down what you're trying to achieve. Surely anyone designing an engine that runs on 12 volts wouldn't design in things that defeat the 12 volt system. That would be like designing your electric water heater at home to run on 60 volts when the house current is 120 volts so you'd have to put in resistance to run it. Why would anybody designing something do anything like that? It seems much more likely to me that the voltage drop is due to corrosion in the stranded wire or bad connections on the ends as we know that these things happen regularly.

As far as replacing the switch, I'm already on my second switch. The first thing I did was replace all the switches with no improvement. Well, maybe it was a little better for the first month or so. I believe what happens to cause the voltage drop across the switch is this: The switch is a push button type which you push in and hold for 30 to 60 seconds to heat the glowplugs. Each time you press it you, of course, get an arc across there and you probably don't have good contact the entire time while you're holding it in, and thus the surfaces inside the switch get pitted and blackened. After a few years of using the switch it develops some internal resistance.

I've captained boats that have the Perkins 4-108 engine like the one you have, but I can't remember now whether it uses glowplugs or not. It seems to me it doesn't, but if it does, what kind of glowplug switch do you have? A pushbutton type like we do or one of those where you turn the key the opposite way to energize them like most diesel cars do it? What kind of voltage drop do you see across your switch when there is no load on it? Are your glowplugs running on 6 or 7 volt feed? I can't imagine that, but I learn stuff every day often on this board.

Beam winds and following seas,

Tom

I don't know the specifications for the glow plugs in your Universal, but there may well be current limiting resistance wire in the circuit that would cause the voltage readings you are getting at the glow plugs. I'd make sure of that before ripping it out. Certainly, the bad connections need to be corrected. Having a 2 volt drop across the switch seems like bad news. Does it get hot too? There should be little resistance across that switch, much less than 1 ohm. Maybe it is time to replace that rather than the wire?

All that said, does the fuse still blow? Where is the current going? There must be a short somewhere.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

TomCambria@mindspring.com

[Ken Coit]

Thanks for the good words, but I am a piker compared to some. I am an engineer who loves to solve problems, so this is just a great place to entertain myself when I can't be aboard Parfait solving my own problems.

If there were resistance wire it should be shown on a wiring diagram or at least labled as such. The glow plugs I found awhile back, I think they were for a U18 HP engine, required about 5 amps, so it doesn't take a lot of resistance to drop the voltage: one ohm would give you a 5 volt drop. Three plugs at 5 amps would give you 15 amps total and one ohm would drop the 12 volts to ZIP. I think you are on the right track, getting that wiring up to snuff. With much resistance in the wiring, you won't be able to pull much current through the glow plugs.

Good luck!

Ken

Ken, After reading your post this morning I went down and talked to the local diesel mechanic about glowplugs. He said that actually there are glow plugs that run on two volts. The early Mercedes car diesels put the glowplugs in series with an indicator light also in series. If the indicator light burned out it would fry all the glowplugs by letting too much juice get to them. Also if one plug went out, none of them would work. What you'd expect from a series wired set up.

However the Universal engines and as far as he knows all other boat diesels are wired in parallel these days. Rather than being rated at 12 volts, however, they are usually rated at 10 or 11 volts to allow for resistance in the switches and wires. He thought you had to be careful testing them across 12 volts because you might fry them if you went directly to 12 full volts on a battery with no switches or wires in the circuit.

He thinks 7 volts is too low for a feed current and the plugs might only be getting warm rather than hot at that voltage. He didn't see any problem with running an additional wire. This is just one mechanic's opinion, of course.

As far as adding a fuse to the glowplug circuit goes, I don't follow your logic on that one. As you know the circuit is only energized for the 30 seconds that you're holding the button down. Once the engine starts that circuit isn't on line at all. If you developed a short while you were holding the button down you could simply let up on the button and kill the circuit -- essentially do the same thing a fuse would do. If you developed a short it would remove current from the glowplugs and thus they wouldn't be damaged, so what are the dire consequences that might happen from a short in the glowplug circuit?

Unfortunately I didn't bring a glowplug home with me. They are on the boat 130 miles away so I can't read off any information for you, but I will get it the next time I'm down there. As I recall the new plugs said 10 volts on the side but I don't remember the rest. I looked through the CD engine manuals but couldn't find any specs on the glowplugs. The engine wiring schematic doesn't show any resistance in the glowplug wire, but maybe if you had a resistance wire as opposed to a resistor it wouldn't show on a schematic?

If Dave Stump is the nautical traditions guru, I recommend we appoint you as the technical information guru. You've got a tremendous amount of technical information, diagrams, and specs stored in your computer and/or brain. There's virtually nothing mentioned on the Board that you don't post a picture of the next day, together with the specs and ordering information. You're a great asset to the BB. Thanks for the information and input and as you always say:

Keep on Sailing!

Tom,

No, there are no glow plugs on the 4-108, but I believe that some diesels that do use glow plugs also use resistance wire to limit the current and distribute the heat. The 4-108 does have resistance wire in the alternator circuit. As for the fuses, I must have you confused with whomever started the thread on glow plugs that blow fuses. I think I would fuse the line given how much trouble a short could cause.

I agree that switches can get pitted and not make perfect contact, but if the resistance gets very high, then the 5 to 10 amps each plug requires will soon result in all the power being disappated in the switch rather than the glow plugs. At a hypothetical 15 Amps and 2 Volts, your switch is consuming 30 watts. Have you ever grabbed the end of a 30 watt soldering iron? All that heat is not good.

You are probably on the right track by checking out the wiring. If you send me the info on your glow plugs, I will try to get some info for you.

Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

I wish I had some specs on the glowplug. Universal as you know was bought out. When I took the plug to the glowplug shop the guy looked it up and said there is only one place to get them now and they have to be special ordered out of Minnesota at 58 bucks per copy. He tested mine by putting them across a 12 volt battery directly with no resistance circuit in line. Since he had looked them up in the book I concluded they were meant to run at 12 volts. There isn't any real "circuit". The wire runs from the glowplug button into the wiring "harness" which is really just electrician's tape wrapped around all the wires running from the control panel to the engine. The wire comes out the end of the taped section and attaches directly to the first glowplug without going through any even buss bar connection. There is no fuse in that circuit and no fuse has ever blown on the boat. There is a fuse in the starter circuit but it has never blown either. That fuse is downstream from the glowplugs. Incidentally if that fuse were ever to blow it would be living hell to get to on a dark night in a pitching sea as you have to crawl in the port locker to get to the case it is in and cut the wire ties off of the case. I'll bet that most people don't even know there is a fuse in there to look for. Either that or remove the whole control panel and pull it out, but I digress.

I supppose it is possible that there is a resistor in line that is wrapped up inside the tape, but it hardly seems likely. Surely you would put the resistor outside at the glowplug switch on the panel or down at the engine after the wire exits the harness and not wrap it up in tape in the middle of the wires. The electrician who was working with me advised me to run the new wire, so he didn't think there was a resistor circuit anywhere.

Ken, have you actually ever seen a resistance wire wrapped up inside a wiring harness on a glowplug circuit? There wouldn't seem to be any reason to do such a thing. A glowplug is just a heater coil that you want to get red hot. Putting resistance in a circuit like that would just make it harder to heat the coil and unnecessarily slow down what you're trying to achieve. Surely anyone designing an engine that runs on 12 volts wouldn't design in things that defeat the 12 volt system. That would be like designing your electric water heater at home to run on 60 volts when the house current is 120 volts so you'd have to put in resistance to run it. Why would anybody designing something do anything like that? It seems much more likely to me that the voltage drop is due to corrosion in the stranded wire or bad connections on the ends as we know that these things happen regularly.

As far as replacing the switch, I'm already on my second switch. The first thing I did was replace all the switches with no improvement. Well, maybe it was a little better for the first month or so. I believe what happens to cause the voltage drop across the switch is this: The switch is a push button type which you push in and hold for 30 to 60 seconds to heat the glowplugs. Each time you press it you, of course, get an arc across there and you probably don't have good contact the entire time while you're holding it in, and thus the surfaces inside the switch get pitted and blackened. After a few years of using the switch it develops some internal resistance.

I've captained boats that have the Perkins 4-108 engine like the one you have, but I can't remember now whether it uses glowplugs or not. It seems to me it doesn't, but if it does, what kind of glowplug switch do you have? A pushbutton type like we do or one of those where you turn the key the opposite way to energize them like most diesel cars do it? What kind of voltage drop do you see across your switch when there is no load on it? Are your glowplugs running on 6 or 7 volt feed? I can't imagine that, but I learn stuff every day often on this board.

Beam winds and following seas,

Tom

parfaitNOSPAM@nc.rr.com