I have been chasing an air leak on my 2001 LB7 for a couple weeks now and I still don't have solved. Its better but not good. If it sits for a couple days I can hear the air working through the injectors and it takes 20-30 seconds of cranking to get it to start. I have replaced all the fuel hoses on the engine, replaced the filter housing, found a small leak at the FICM and took care of that, blocked off the vacuum test port. I am thinking about shimming the pressure relief valve, maybe I am loosing some pressure there? Before I replaced the injectors 65000 miles ago, it started to crank longer than normal before starting and has been that way ever since. I considered that maybe the injectors are bypassing but, the balance rates look good. The worst one was 2.2. That wouldn't explain the air getting into the system either. Any ideas?
At my wits end........
- Thread starter madmathew
- Start date
If you have even a small leak, a lift pump should be able to show where it's located fairly easily.
a gas cap with an air chuck end drilled into it and some regulated down shop air will pressurize the lines real quick and tell you if you have a leak
Injectors can bypass a lot and still have perfect balancing rates. What exactly do you mean you can hear the air working through the injectors?
When it starts its rough and loud for the first few seconds until all the air goes out.
Its brand new. I am going to try the air and going over the system piece by piece with a Mityvac. That filter head is new but maybe there's something wrong with it. It wouldn't be the first bad new part I've seen.
I have now checked it with pressure and vacuum and can't find any leaks. With the return side hose pinched off it held 15 inHg for 3 hours. It drives great once started and hasn't thrown a code in years. I drive it today and shut it off, popped the hood and tried seeing how many pumps on the primer it would take and I could pump it 38 times. It still sounds like there is air in the system when I start it. WTF?
I have not tied shimming the pressure relief valve yet, do you think it bleeding off could cause this? I saw the could posts where people had said that 2001 trucks had problem with the relief valves. It really sounds like it has air in the system when it first starts. It sounds like a gas engine detonating and runs for about 5 seconds.