have recently changed fuel filters on my md7a. it has the lucas c.a.v. injector pump. a fairly simple procedure that has turned into nightmare. new engine is looking more and more inviting.
after shearing two bleed bolt(screws) gently turning them to bleed filters, they still broke off in pump and at fuel return on forward injector. luckily had replacements on hand in kit. so system is finally bleed many many times yet I'am still picking up air somewhere. no air in suction side, translucent fuel lines allows viewing fuel for quite a ways. no apparent leaks on pressure side everythings snugged down. following point by point bleeding, finally getting to injectors themselves.
now heres the problem. engine will start and run to max rpms 2600 at this point while engine is running its easy to bleed injectors, paper towels and such in place, loosen fitting and fuel spits out, both injectors go through this step by step. the aft injector still puts out a little foam with the fuel. this passes, engine runs fine, I shut the engine down, now it used to fire up within seconds, being well warmed, but now it just cranks along sometimes not starting at all until i bleed system again. or it slowly picks up rpms with starter until it finally runs on its own.
any words of wisdom out there, is bleeding volvos such a major hassle every time?
filters were filled with fuel before re-installing.
bleeding fuel system on my bobcats and tractors is nothing like this has become. at the end of my rode. any help will be welcomed. ben
btlandscapers@imagina.com
fuel bleeding volvo md7a
Moderator: Jim Walsh
-
Larry DeMers
Re: fuel bleeding volvo md7a
Ben,
Wow.. You said that there was no air in the low pressure side. and that the problem is on the high pressure side..and I agree that is likely. The high pressure side is taking on air after the engine shuts down.
Now, your bleeding procedure I am not so sure about. What I do that seems to work quite quickly, is to have my wife turn the engine over with the decompressor's up, while loosening the bolt holding the banjo fitting in place on the first injector top. It will spit air and fuel and then slowly more and more fuel flows..slowly retighten the bolt on the banjo fitting as this happens. Shut down the starter. This should not take more than 30 sec. Don't forget that the engine is pumping water at the shaft rpm, and filling that waterlift muffler up. If the engine does not fire and force the waterlift mufflers contents out through the exhaust hose, it will back up into the engine, giving you grief with hydrolock, and other ugly consequences. So 30-45 sec. max. then repeat for the other injector. This should work.
Other tings that could be happening; A good bleeding is ruined by the checkvalve at the base of the Injector Pump. Mine locked open, which allowed air to replace fuel as gravity pulled the fuel down the pipe while sitting overnight.This took a inj. pump rebuild to find.
I would look at the output pipes of the injector pump and connectioins at the injectors. The mating surfaces of the connection must be exquisitly clean before assembly. All bolts must have new brass crushable washers under them, to absorb the irregularities of the two mating surfaces.
That's all I have for you using your symptoms. If you want, try the things I mentioned and then come on back with the new symptoms. The more detail the better on this one.
Good Luck,
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~~Sailing Lake Superior~~~
demers@sgi.com
Wow.. You said that there was no air in the low pressure side. and that the problem is on the high pressure side..and I agree that is likely. The high pressure side is taking on air after the engine shuts down.
Now, your bleeding procedure I am not so sure about. What I do that seems to work quite quickly, is to have my wife turn the engine over with the decompressor's up, while loosening the bolt holding the banjo fitting in place on the first injector top. It will spit air and fuel and then slowly more and more fuel flows..slowly retighten the bolt on the banjo fitting as this happens. Shut down the starter. This should not take more than 30 sec. Don't forget that the engine is pumping water at the shaft rpm, and filling that waterlift muffler up. If the engine does not fire and force the waterlift mufflers contents out through the exhaust hose, it will back up into the engine, giving you grief with hydrolock, and other ugly consequences. So 30-45 sec. max. then repeat for the other injector. This should work.
Other tings that could be happening; A good bleeding is ruined by the checkvalve at the base of the Injector Pump. Mine locked open, which allowed air to replace fuel as gravity pulled the fuel down the pipe while sitting overnight.This took a inj. pump rebuild to find.
I would look at the output pipes of the injector pump and connectioins at the injectors. The mating surfaces of the connection must be exquisitly clean before assembly. All bolts must have new brass crushable washers under them, to absorb the irregularities of the two mating surfaces.
That's all I have for you using your symptoms. If you want, try the things I mentioned and then come on back with the new symptoms. The more detail the better on this one.
Good Luck,
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~~Sailing Lake Superior~~~
ben thomas wrote: have recently changed fuel filters on my md7a. it has the lucas c.a.v. injector pump. a fairly simple procedure that has turned into nightmare. new engine is looking more and more inviting.
after shearing two bleed bolt(screws) gently turning them to bleed filters, they still broke off in pump and at fuel return on forward injector. luckily had replacements on hand in kit. so system is finally bleed many many times yet I'am still picking up air somewhere. no air in suction side, translucent fuel lines allows viewing fuel for quite a ways. no apparent leaks on pressure side everythings snugged down. following point by point bleeding, finally getting to injectors themselves.
now heres the problem. engine will start and run to max rpms 2600 at this point while engine is running its easy to bleed injectors, paper towels and such in place, loosen fitting and fuel spits out, both injectors go through this step by step. the aft injector still puts out a little foam with the fuel. this passes, engine runs fine, I shut the engine down, now it used to fire up within seconds, being well warmed, but now it just cranks along sometimes not starting at all until i bleed system again. or it slowly picks up rpms with starter until it finally runs on its own.
any words of wisdom out there, is bleeding volvos such a major hassle every time?
filters were filled with fuel before re-installing.
bleeding fuel system on my bobcats and tractors is nothing like this has become. at the end of my rode. any help will be welcomed. ben
demers@sgi.com