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View Full Version : LB7 sucking air into fuel system, help me!



viperbluelx
06-17-2011, 11:53
Alright I've told the story before. In March the truck got new injectors installed, $3700 later the truck still wouldn't start so the guy sold it not running.

Next owner buys it and puts a new CP3 pump on it, but it still won't fire up on it's own and fuel system won't hold a prime.

So, I bought it last week. On the advice of a friend that works on diesels he said replace both lines off the fuel filter housing with clear tubing(temporary) to see if I'm getting air before or after the filter housing. There were no bubbles from the FICM to the filter housing, but there was a constant flow of bubbles from the housing to the CP3. Sooo, I thought the housing was cracked so I ordered a brand new one with new everything attached to it. I installed it and pumped the primer and it got nice and hard and held a prime. We every time you spin it over it looses prime. I got it to fire of a small squirt of WD40 and now there was bubble from the FICM to the housing!!! So I went to the dealer and got new washers for the banjo bolts and installed those and it seemed to fix that issue but now I've got bubbles from the housing to the CP3 again.

With the truck running should diesel completely fill the hoses at idle? Reason I ask is neither hose completely fills with diesel but they both flow fuel constantly while running. I'm out of ideas without taking it to a shop and leaving it with them.

JohnC
06-17-2011, 14:11
Once you get the air out with the primer pump it should not come back. One thing you can try is to pressurize the fuel tank (be very careful; not more than 3-4 psi!) then see if you can locate a leak. Anywhere that fuel can leak out, air can get sucked in. The problem could be in the tank pickup.

markelectric
06-17-2011, 20:10
Sounds like a good canidate for a lift pump....

DmaxMaverick
06-17-2011, 20:30
Sounds like a good canidate for a lift pump....

Good call.....But AFTER the leak is found and fixed.

viperbluelx
06-18-2011, 06:06
I think I'm going to put one of these inline to see if it will pinpoint the leak.

http://www.dragcars.com/parts/img/mr-gasket-12d-micro-electric-diesel-fuel-pump_320688306153.jpg

markelectric
06-18-2011, 07:34
I was thinking that the lift pump idea may help the process of finding the leak.
instead of a sucker leak....maybe a spewer...

DmaxMaverick
06-18-2011, 09:35
I think I'm going to put one of these inline to see if it will pinpoint the leak.




This pump would probably work OK for fuel supply system diagnostics, but DO NOT try to run the engine with it. It is a transfer pump, NOT a fuel supply pump. It will restrict fuel flow with the engine running, even at idle.

Save the $50-$60 and just apply 2-4 PSI shop air to the tank. A new fuel filler cap is about $10. Use your old cap to make an air adapter (drill a hole through it and install a tire valve stem).