[gdp]

2002 stock 7.3liter with 31 gallon standard tank, 145,000 miles. Last few months the engine has sputtered and surged when going down the road at even throttle or a slight increase. Runs fine when accelerating or idling. No check engine light. Usually runs ok when the tank is full and starts sputtering around half full on the tank. Running with diesel treatment/antigel seems to clear the problem up. temps are warm in the 60s. I dropped the tank last weekend and everything inside looks perfect. Fuel filter is clean and no water in the bowl. I'm thinking it must be the inline electric filter along the frame but looking for advice or input from someone that has seen this or knows what it likely is. One dumb question, the unit inside the tank looks like it's just a mixing chamber and not a pump. Wires only went to the sending gauge. Is the pump along the frame the only pump? Thanks for any help.

 

[redtopman]

I don't know much but your rig is the same as mine. The fuel transfer pump is located on the inside of the frame close to the drivers door. when you turn the key on you should hear clicking from the pump. Another check is to open the drain valve on the fuel filter and drain into pan. Turn on the key and if your pump is working you should see a strong fuel flow into the pan. Also check voltage to the pump.


Just so happens I believe my pump has failed and I will be checking the voltage in a little while since it is not pumping.

 

[petwolf]

As above, frame pump is only one. In tank is just the pick up and by pass. I would check fuel pressure. May have trash in pump inlet.

 

[ArcticDriver]

When you had the tank dropped and you removed the white plastic unit that you described as a "mixing chamber" did you happen to disassemble it?

If so, you found the two small cylindrical filter screens. Did you clean those off? What condition were they in?

The best way to diagnose your fuel system is with a fuel pressure gauge tapped into the fuel filter bowl and the gauge installed full-time in the cab.

Thanks

 

[gdp]

Thanks for the replies. Hired a mechanic that's works "offline" and right away he thought it was the ICP, IPR or EBP sensors. He checked fuel pressure and is steady and good at 60psi. Found the ICP was leaking oil and changed it. Truck runs better but still some surging at near even throttle. His computer reads everything on the truck except the ECM. He's looking for another computer to read the ECM before we throw more parts at it.

 

[Graupp]

Just a WAG, but that particular statement sounds like it could be your
Throttle Postion Sensor [TPS]...:surprise:

 

[ArcticDriver]

Just a WAG, but that particular statement sounds like it could be your
Throttle Postion Sensor [TPS]...:surprise:

If the tech looking at the truck has a scanner then he should be able to diagnose it a bit better than ICP or IPR or EBPS.

I wonder if the OP has adjustable height pedals? :grin2:

 

[klhansen]

If it's got cruise control, just set that and see if it still surges. If so, it's not the accelerator pedal. Cruise overrides the pedal.

Could an IPR issue, but like ArcticDriver said, it's best to get the scan tool on it and monitor the parameters to see what's going on. Set it up to monitor ICP, IPR, Accelerator pedal position, and maybe Engine load (that's not exactly what it's called, but you get the picture). If you can do a snapshot when it acts up, that will help pinpoint the problem.

Early in my truck's life, it would surge on a feathered pedal position. I'd also hear the jet engine sound from the exhaust when it did it. Turned out to be the EBP system. The tube to the sensor will clog with soot and make the EBP valve hunt. Only did it when it was cooler out and before the engine warmed up, which takes the EBP system out of the equation.

 

[gdp]

SOLVED and luckily a simple fix. I accidentally figured out the problem. I decided to use engine degreaser to get everything clean before doing more work and the sputtering stopped! About a week later it came back slowly over a few days. So I started looking for an oil leak on top of the engine and found 2 issues. The plug to the ICP was oily at the inside connection, had changed the ICP a few weeks earlier but did not change the elec plug. I know that many recommend changing it but I don't like cutting OEM wiring harnesses. I wound up soaking the plug in laquer thinner which worked great. Don't ask me how and do so at your own risk due to flammability issues but it worked for me. Second issue was a leaking seal where the HPOP hose connects to the drivers side head. I changed the fitting with a new one.
Truck runs great now and mileage went from 14 to 16, but part of that improvement was probably the seasonal change from winter to summer fuel at the station. Throttle response is noticeably better too. I think the oily ICP plug was the real problem for surging but I'm glad I found the other leak before it got worse. I really appreciate the help on this issue and hope this solution helps someone else.

 

[redtopman]

Thanks for the closure.