jbawden

Does the IP generate any suction? In other words, could a clogged fuel filter cause restriction that could damage something either inside the IP or anywhere between the lift pump and IP? Seems to me that after the lift pump, I would see a leak if there was a problem there, but I'm sure thats incorrect.

1992gen1_fan

I believe the IP does generate some suction, it pulls fuel. Too much restriction can ruin an IP.

93flatbed

Yes it does have some BUT not enough to run without a lift pump. So for diag purposes you could get a fresh can of fuel and run a line to the ve and see if it still smokes. But you CANNOT drive like that. That test would eliminate the whole supply system from the truck and narrow it down.
I've never had a leak between the ip and the lift pump so I couldn't tell you, I would also assume it would leak but I'm not certain.

Santaclaus

Running the engine like that would allow you to put a clear hose on the output side of the lift pump and check for aerial aches and check for air leaks. Free flowing like that would create the maximum vacuum on the fuel system. My two cents, mike.

jbawden

I appreciate all the responses, I'm frustrated by this issue and the smell of the exhaust is making me sick. In addition to the stinky haze and won't start unless I give it some throttle, I took the fuel filter off to double check that area and it was only about half full? So, I guess I'll run a hose to the lift pump directly from a can and see what that does.

jbawden

Purchased 2.5 gallons of new diesel and ran it straight to the lift pump, no change in condition. So, that effectively eliminates anything from the lift pump back (including the lift pump). Also installed another new filter. Sooo, white haze and hard to start unless I give it throttle...what does this mean!?!?

93flatbed

That would not eliminate the lift pump, just lift pump to tank would be out of the system. What's the pressure out of the lift pump to the IP? If you shut it down and try to start it right back up, do you still have to do the .25 throttle thing?

jbawden

Lift pump is good. I carry a spare in my truck and swapped out the existing one with the new one with no change in symptoms. That was one of the first things I did, based on Mark's post. I don't have a fuel pressure gauge.

jbawden

Any chance the WIF sensor could cause an air leak? Does not appear to be leaking fuel, but air?

To answer your question 93FB, it does start normally (no throttle) if I try to start immediately after shutting down.

fjkfta

Mine was doing the same thing and it was the pump timing had retarded somehow. Timed it back plus about 1/8 and runs like a champ now. Check your timing.

jbawden

The timing marks are lined up (on pump and back of case), but I suppose I could mess with timing a bit and see what happens. The nuts appear to show evidence of a wrench being on them, so who knows.

93flatbed

If it starts up just fine if after shut down then I would say you have an air leak in the supply side, I understand you don't feel that's the problem but all of the symptoms point to that.

jbawden

Actually, I've never disputed that air is getting in the system and have only ruled that from the lift pump back is fine. Changing lift pumps did not change the condition either, so I've ruled that out too. I've speculated that somewhere from the exit of the lift pump to the injectors lies the problem. The thing I can't understand is that once at the lift pump and the fuel is exiting under pressure, how is air getting in and no fuel leaking out, at all? I guess if there is a weak supply from the LP and the IP is creating a vacuum, then air could get in. The WIF sensor seems a little funky, but I don't see fuel leaking. I guess what I'm looking for is the best way to diagnose an air leak in this segment of the fuel system.

Santaclaus

If you suspect the WIF sensor, you could either get one of the other fuel filters that doesn't have a drain in the bottom or get a container that will fit around the fuel filter fill it with fuel and hold it over the filter housing or you shut down the engine. Doing one of these preferably the first will emanate the WIF sensor. Have you carefully checked all the fittings on the lift pump and at the filter housing? And for something truly off-the-wall maybe find something like Silly Putty, or maybe heavy axle grease, and work around the fittings. My thought is that it wouldn't suck past the Silly Putty. I bet by now you have gray hairs over this, good luck. Mike

1992gen1_fan

I had a really leaky WIF sensor valve on my truck couple years ago that would sometimes soak the underside of my truck and it didnt really affect how the engine started or ran, just killed the mpg's.