half of "diesel" is "die"

[hmeyrick]

The years appear to weigh heavily upon the tired shoulders of my MD7A. With every passing season, the poor dear takes more and more cranking before, reluctantly, she fires up. Suspecting poor compression, I emptied the port lazarette of PFDs and crawled down to try to turn the flywheel by hand. Although I could feel the resistance with (what must have been) the compression stroke, it wasn't particularly hard to turn. Now, I'm no geologist, but I suspect that this is NOT a good sign.

As far as I can see, poor compression must be due to either the valves and/or the rings being compromised.

So, to the august members of this board I ask the following:

1.) Is there a simple test I can do to tell me the cause of my compressional difficulties?
2.) Is it reasonable to hope for a mechanic to be able to effect a cure in situ, or should I resign myself to having my engine removed for X weeks? What has been the experience of others?
3.) Are Volvo-Penta parts really as difficult to obtain as I have heard? (Note: By "difficult", I mean "expensive")
4.) While I love my Volvie, should I recognize that nothing lasts forever, and thus plan to buy a whole nother engine? I bet that'd cost some serious dough!
5.) Should I practice sailing to the dock?

I suspect that I'm not the only Cape Dory owner with a 27 year old engine. I'd love to hear any and all insight that you could share.

[Oswego John]

There is one thing you could try. Buy a quart of Lucas Heavy Duty Oil Stabilizer and see if it helps. Costs $7.00 or $8.00 a quart. Use a minimum of 4:1 oil to Lucas, whatever your oil system capacity is.

Some guys swear by it, some swear at it. I've used it for years. It works for me.

Good luck.
O J

[Sailing Soldier]

My experience has been that parts have indeed become increasingly hard to get & expensive for the old MD-7A.

Combine that with the unreliability with any engine of the age and I've decided to repower.

I did end up buying a new Volvo. I figured if the old one lasted almost 30 years, what the heck!

[S/V Necessity]

I dunno the reliability of this test. But I was told long ago that it can be used. Your mileage my vary... But check the compression, add some relatively heavy oil directly to the cylinder, and check it again. If it doesnt change at all, then it points towards the valves being the leak. The idea being that the oil is pooled on top and around the piston, not on the valves... If it improves significantly then it points towards the leak being at the rings.

On the flip side.... Either way the fix involves removing the head, so I just yank the head and go from there... If the valves look like crap, and the cylinder doesn't show any excessive wear. I would try just doing the head. Take the head to a decent machine shop and they do the rest. You just bolt her back on. The shop should also be able to tell you if there is anything wrong with the head.

A professional mechanic is more likely to recommend re-doing the whole thing though. He doesn't want to gamble, and with his labor rates you might not either. The cynic might also say that he wants to get as much $$ out of you as possible also...

From what I've been able to gather it might be worth it to buy a new modern engine instead of rebuilding. With the exception being that if *you* are going to be spinning the wrenches, then you might be able to just re-grind a couple of valves buy a new head gasket and be up and running for many years to come for very little money. Or it might backfire and you would have to buy a new engine! The same thing you would do if you didn't try anyways.

[sgbernd]

The logic I would use is as follows;

1) Can you get it started and does it run well enough to use reliably? If so, try to get another season out of it. If you pull the head or engine at this point, you could lose most or all the season before you are back in the water. Also, if you pull the head, you may find it is not going back together as sometimes you discover more is wrong than you thought.

If it won't run, you don't have much choice. Sometimes, a low compression diesel can be started up by injecting some heavy oil into the cylinders to seal the rings enough to get it started. Once started, it may loosen up enough to get another season.

2) When the season is over, you can pull the head/engine and make the call for the best plan.

I have the MD7B which suffered from, among other things, a broken head stud and hard starting, over-heating, smoke, oil in exhaust, etc. Over one winter, I pulled the head, burnt out the rust with acid and drills, had the injectors rebuilt, fixed the stud and it has run reliably for 3 more years and it is still going strong. But the whole effort took almost 6 weeks chasing machine shops, getting parts ordered from Volvo, getting the wrong sized injectors installed and returning them and waiting for correct ones....

If you can schedule that for Janurary, it isn't so bad if it takes twice as long as it should have.

[hmeyrick]

Thank you all for your replies. Once she gets going, she normally runs well enough, so I'll probably finish this season before doing anything drastic.....

One other clue, or maybe its a clue, but possibly not important, is that after running the engine I tend to get a little oil dripping out of the end of the air filter. Seems to me it must be coming from the cylinder via a valve? Does anybody else get a few oily drops from the air filter?

[S/V Necessity]

Does the crank case vent to the air filter? If so you might be getting enough "blow by" (past the rings) that it's forcing some oil up to the filter....

[hmeyrick]

I don't honestly know if the crank case vents to the air filter. Obviously, the air filter attaches to the cylinder head over the air intake, but there may well be some mysterious subterranean venting going on beneath the inscrutable cast iron facade. There is also a hose running from the filter to somewhere, possibly the valve cover, but I'm not at the boat now and can't say for sure.

I have always had this drip, and just kind of got used to it and sort of assumed that it must be normal. But as the engine appears to ail, I feel I really ought to contemplate all signs, no matter how innocent I once may have thought them.

[Boyd]

Do you get a slick of black soot on the water from the exhaust at start up? Black soot on the water at start up combined with long cranking times is an indicator of low compression.

Partially clogged filters will also cause a long cranking time at start up. Change all filters and and rework your fuel system and see if the problem goes away. Make sure you have fresh fuel.

Blue smoke or whitish smoke at start up is oil getting into the cylinder. Do you have any smoke during running? Normal diesel exhaust is clear to very light grey smoke.

The "oil" in the air cleaner may be from the intake valve stem seal failing. This would then be leaking into the cylinder as well. A small quantity of oil in the cylinder could make starting sluggish also. If the intake valve is leaking compression the "oil" may be diesel fuel blown back into the manifold.

The use of Lucas oil stabilizer can increase the viscosity of the oil sufficiently to slow down the cranking speed to the point where it actually makes starting harder. I dont recommend using it untill you have confirmed that you do have a compression problem. More is not better with this stuff. Just use the least amount necessary to get the job done. At 1:4 it will increase the viscosity of 30W to over 60W making cold cranking quite slow.

If indeed you find that the culprit is low compression and want to nurse another season out of it, WD-40 works as an emergency starting aid. Spray some in the intake manifold while you are cranking the engine. If she is going to start at all that should do it. This is not a good practice for a healthy engine but you are just trying to get by till you rebuild.

Pull off the air cleaner and listen at the intake manifold while someone slowly hand cranks the engine. If the intake valve is leaking you will hear the air hiss by it. The same can be done with the exhaust valve.

Using oil in attempt to get an engine start is risky if not done properly. Squirt some oil in the intake manifold or into the preheater holes for each cylinder. Hand crank the engine through two compression cycles slowly before trying to start. That clears the oil from the combustion chamber and spreads it on the rings sufficently so you wont over stress the connecting rod or crank. Basically you are preventing a hydrolic lock situation.

ALWAYS PULL THE ENGINE STOP (FUEL CUTOFF) TO THE STOP POSITION BEFORE HAND CRANKING. You dont want the cylinder to kick while you have a wrench on the crankshaft pully nut.

Nothing I have said removes the need for a compression test. It will tell you more about whats happening than anything else.

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.

[GrFa]

[quote="Mark Dierker"]I dunno the reliability of this test. But I was told long ago that it can be used. Your mileage my vary... But check the compression, add some relatively heavy oil directly to the cylinder, and check it again. If it doesnt change at all, then it points towards the valves being the leak. The idea being that the oil is pooled on top and around the piston, not on the valves... If it improves significantly then it points towards the leak being at the rings.quote]

I would start out with this test if you really doubt the amount of compression in the engine. It is quite a small engine so I wouldn't be surprised if it is normal to be able to crank it by hand.

Disregarding whether you know the compression is low or high lets take a step back. How long do you consider a long time to start up her up? When our Volvo is cold it needs a good 5 or 10 cranks until it catches at idle speed.

How is it to start when it is already warmed up (say when you try to restart after not being off for more than an hour)? Ours will usually start back up on one or two cranks when warm.

And then some simplier questions, has the performance suffered (won't reach hull speed or push you through a seaway, has it always been maintained, etc.)

I would start simple and then work your way to the more complex stuff. I have been continually impressed with our Volvo and wouldn't be in a rush to rip it out unless I knew there was something majorly wrong.

[hmeyrick]

Thanks, Boyd.

As to the smoke, I can't say that I've paid much attention... I always check the exhaust at start-up to verify that cooling water is flowing, but I haven't noticed anything sufficiently alarming about the smoke to cause my "Alert Synapses" to fire. I shall pay more attention next time.

Thanks, Gfra.

When the ambient temp is cold- say 60 degrees or less- and the engine hasn't been run recently, she requires 45 seconds, maybe a minute to fire. (my starting battery is new this season) It is less when it is hot out. When recently run, she requires maybe 10-15 seconds of cranking, less if its pretty warm out. Performance- fine in calm water at low speeds, but last year in an anchor-dragging squall, it was touch and go to get the boat to turn up into the wind and waves to regain a safe distance offshore to reanchor. Fortunately the CQR set nicely the second time around, and my anchor watch was uneventful. But I don't consider that adequate engine power. In terms of maintanance, I have always changed the fuel filters once a year, the oil once a year (sometimes a second time if I took a long cruise.) I've never had the valves adjusted nor the injectors rebuilt. I cannot tell you how she was maintained for the 20 years before I purchased her.

It is true that it may not be unusual for this engine to be turned by hand. I don't know. Nigel Calder writes that you shouldn't be able to turn a healthy diesel by hand, and he is often considered knowledgable. I know I can turn over the engine, by hand- without a wrench- without much difficulty. As Boyd mentioned, a compression test provides the definitive answer.