Well I just took my beasty in to the dealership , has been acting funny at 70 Mph. engine surge. I first took it to Cummins and had a mechanic come for a test ride. He definitely noticed the surging. But because it was still on warranty he told me to take the dealership. The mechanic at the dealership put the computer on it and checked the codes. Funny thing is I sort of had a snoop of what he was writting down, one of the comments he wrote was fuel pump failure?. But they end up telling me that they couldn't find anything that stood out as a problem. So the mechanic figures its the LP as they have lots of problems with them. I told him that my pressure readings are 14PSI Idle, 11 PSI 60MPH not sure at wo. But everything runs great until you push it past 70 MPH then it starts its surging pattern. They just replaced the LP 6 Months ago. I think there guessing at this .The guy from cummins said it could be something in the turbo system or fuel system, he didn't really get into details. I'm frustrated

 

SURGING ..when it surges does it seem like it looses a lot of power then picks right back up? your LP readings seem fine, could be your VP-44 on it's way south...how low were the readings 6 mos. ago when they had to replace the LP? It may have damaged the VP before if the readings were really low...just a thought

 

Hey Barracuda, No it doesn't lose any power it just surges a little bit ( If your truck was idling and you just touch the pedal you can rev the engine without effecting the rpm and FP if you can gather what I'm saying?) . You can hear it more than feel it. The FP flucuates so little, the needle barely moves, maybe 1/2 a needle width. Fuel pressure before they changed it last time was about 11 idle , 8 cruising. It's very hard to describe it but I hope you get my drift.

 

yeah i got ya'...doesnt sound like a VP and your readings are not really that bad..possibly electronic related, some one will chime in i am sure, some of these guys are really knowledgeable, you will probably have it diagnosed by the end of the day! good luck

 

Thanks Guy, I really don't have too much faith in the dealership but if they want to keep putting new parts on until they find it thats OK maybe will end up with complete new fuel system until they find it.HA HA!!! I'll keep bringing it back until they fix it. Warranty

 

Are you reading fp pre or post filter?

 

Reading FP at the Injector Pump Schrader Valve

 

this problem sounds familar to me also. although i would describe my surge to feel like when you are following a semi and feel the push and pull of the turbulence. tach just barley fluctuates maybe a half a needle or so when i feel this I also want to hook up a fuel pressure gauge but am still not sure where to hook it up to. anyone have a picture of a pump that points it out? my truck is a 98 24 v 90,000 miles two months old to me brought from origanal owner says fuel filter changed with every oil change @ 5000 miles who is working with me to solve this problem sounds like the dealers like to install new parts that him and I would rather not pay for if not needed

 

Like barracuda says Lp and Vp sound fine.

Try resetting the APPS.

Disconnect batteries and turn ignition switch to on for about 30 mins.

reconnect batteries and apply safety/park brake.

turn ignition to on and slowly move gas pedal to the floor and slowly back up.

Release park/safety brake

 

I thought my LP was going out again (87,500). It was surging slightly at idle, crappy start-ups and stalled recently after changing the filter. The tach would also flucuate at idle. Took it to the dealer. LP is fine they said. All the did was "re-program" or "update" the computer. All is fine for now. This was a head scratcher for me. I guess I will wait and see.

 

Thanks Guy's I'll try the Apps reset. Call me slow but what is APPS????? Should I do this before taking to dealer??? Will it harm anything????

 

I will make a suggestion that you may look at me crosseyed, but try it. Try tightening your rear axle u bolts. I get a lot of rear axle chug from the spring wind up. I used to think it was the engine but it is not.

 

Thanks, I tried the reset procedure that was posted the other day, Still doing it. I'll have to see if Dealership can fix with LP replacement, I doubt that it will fix the problem. May have to see if they will authorise Cummins to have a look if that doesn't work. I really don't want to start getting nasty, but it may come to that if they can't fix it.

 

stonewall,

a little off topic, but what did the dealer say about your gauges?