Engine/Transmission (1994 - 1998) Mystrery Problem

[DU516]

I was just reading the threads on the "mystery problem" My truck is doing almost that exact thing mine runs fine cold or on a full tank of fuel ,but mine as soon as it gets up to operating temperature it starts running like it's missing, stalls when i come to a stop but it will refire fine every time but then usually it will keep doing it until the truck sits for and extended period of time. It seems like if I only let it sit for awhile and it hasn't cooled down the problem reoccurs much faster for the past two weeks I have been only putting in a few dollars of fuel at a time and my truck has been doing it every day I drive about 15 miles one way to work if I go out of my way at all it acts up. I have replaced the overflow valve and the lift pump with no success I also replaced the rubber fuel lines feed and return behind the pump. I 've only had this truck since November the truck sat alot it's a 94 2500 with only 53000 on it. It had 48000 on it when I bought it, ran fine the first 2 months. Has anyone found a way to solve this mystery problem yet for sure. I posted on the 911 page that I talked to a local Injector service man and he thinks one of my injectors isn't closing all the way and on the compression stroke it is sending air back to the pump, Has anyone tried replacing or having your injectors rebuilt? I gave up on my local dealer so I'm on my own any help is greatly appreciated.

 

[A Johnson]

Why don't you try cracking the injector lines one at a time and see if one has more foam or definate air coming out of it and then if it does pull only that injector and either have it checked or swap it out. Be careful and don't let the high pressure fuel contact your skin.



Also you should check the suction side of the fuel system for air, I do it by using a simple ball valve on a hose to a tapped banjo in the inlet of the P-7100, and with the engine running dump the fuel into a bucket when you get an inch or two in the bucket put the ball valve in the fuel and look for foam or bubbles.



A Johnson

 

[Joe G.]

One simple thing you might try is to loosen the cap on the tank. The vent might be plugged.

 

[kaffine krazed]

When it happens check to see if your fuel shut off solenoid is in the up position.

 

[DU516]

Checked the fuel cap no vacuum and also checked the fuel solenoid it doesn't move it 's still up .

 

[Berrigan]

The only thing I know for sure isthat on my 90 350 and my 98 3500 both trucks would drop idle speed and sometimes stall after long hard pulls. Engine temp and ambient temp seemed to make no difference. ILLFLEM seems to think hot fuel mey have something to do with this. I agree. Inever experienced low power or rough running though like some others have.



My trucks have done this with near full tanks also, but I live in Arizona so hotter temps may account for that.



Does hot diesel ariate or foam up more than cold diesel?



Has anyone asked Cummins what they think?

 

[DU516]

I drove the truck this morning until it started acting up. I then stopped and got fuel,filled it up this time. The pump stopped pumping at about 17 gallons I pulled the pump to see what was going on, it was all foam. I then had to fill the tank the rest of the way very slowly. I then started it up and ran the truck about 35 miles with no problems. Here's what I'm guessing from what I read in the other post. I am getting air into my return somehow and it is causing the fuel to foam up. how is this happening?

 

[illflem]

The problem with your air in the fuel theory is that it almost always causes hard starting even if air is coming in the return line. You didn't mention that.

The bad injector pumping compression air idea sounds good but I've never heard of it. Seems if you have a bad injector you would notice poor running all the time. Most diesel shops will test your injectors for cheap or even free if you remove and bring them in.



Not sure if I posted this in the older thread but another problem I had with my 3500 that was separate from the 2500's mystery problem was stalling with less than a half tank. After much searching it was traced down to a self tapping screw in the tank module that had poked a pin hole in the pickup tube. Whenever the hole was above the fuel level it sucked air. What lead to discovering this was the engine would cut out only going uphill when the fuel sloshed back to the opposite tank end from the pickup. Cummins tech said this problem is rare but does happen.

 

[PUMPERDUDE]

This might be a long shot. But I think it would be worth pulling the fuel tank module to check if your pickup tube is chaffed halfway down. That would explain alot of your symtoms. Just a guess. Let us know what you find. Good luck

 

[PUMPERDUDE]

Ya beat me to it Bill.

 

[DU516]

Just a update

Pulled my injectors the other day took them in and they checked out fine. I going to pull my P7100 now and have it checked.