I'm having a problem with my truck surging while driving. It doesn't do it at idle and it typically only does it over 45 mph. It's like I lose power but I can immediately give it more fuel and the truck takes off and acts like it should until it does it the next time. It might be immediately that it does it again or it might be a day later. It feels as if it's not getting the correct amount of fuel to the motor. I posted about it here but I'm stilll having the same problem

https://www.dieseltruckresource.com/...hlight=Surging

I first thought it was a lift pump so I've replaced my lift pump. I've double checked all of the wiring and grounds going to it as well. I changed my FCA thinking that could be the culprit but nothing has changed. My APPS went out in November and was replaced with a Cummins/Dodge part as well.

I removed my Outlook monitor and it had no effect. Programming the Bully Dog to stock makes the problem less severe but still present.

Could this be a failing pressure relief valve or rail sensor? I don't know what a truck feels like when these parts fail so I'm lost. The problem is getting progressively worse. At first it was barely noticeable and now I'm worried about being stuck on the side of the road.

What do I need to check? Could the CP3 itself be failing? If it is the pressure relief valve or rail sensor do I have to go through a dealer to get them? I just want to get it fixed and I'd prefer to do it myself if I can. Thanks

 

Reinstall your Outlook monitor and let us know what the rail pressure is doing when it is acting up.That will help narrow it down some.Could be all the stuff you listed.I doubt its the relief valve cause I would think if it was leaking it would be a consistant problem,not random.

 

if your relief valve was popped you would be having trouble building enough rail pressure to get it to start. It could leak a little by and re-seat itself but usually if they are leaky its not enough to make a noticeable surge. Not sure thats your problem but if you wanted to make sure john at floor it diesel makes a solid replacement for the relief valve that screws into the rail for ~$65. I think the 1/8 npt plug in the banjo bolt fix is sketchy myself, but thats like $3 worth of parts. Otherwise its cheaper to get a new rail with new pressure sensor and relief valve from cummins (not dealer) than to just replace the valve. I'm not sure but i would think you would be getting a CEL and codes if cp3 was bad because there would be a discrepancy in rail pressure called for from cp3 and that measured by the pressure sensor.

 

I'll hook up the monitor again and see. I watched it before I removed it and the stumble happened so fast that I couldn't look at the monitor quick enough to see if there was a difference. Now it seems to last a few seconds so I might be able to tell a difference. I changed the lift pump because I couldn't see a change in rail pressure before. Thanks for the input.

 

The digital read out does make it difficult to see.Intermittent problems can be a real pain.I've had a few myself and it can get expensive throwing parts at it blindly.If you can figure out how to make it do it on command(figure out exactly what gear,rpm,throttle position)then a DRB tool(dealer) will find the problem on a test drive.Don't buy any parts you don't have to from the dealer.The RP sensor can be bought from Cummins or Hoelslidiesel for under $200 and there is always a low mileage cp-3 popping up on here in the classifieds.Also being you have aftermarket inj.,have you verified the wires are tight on the solenoids?Have you checked for any codes?Keep us posted.

 

I would check for any wires that look chaff'd around the front of the engine. I've read here (don't remember even what it was for) that a few people were having irratic problems with as similar issue to yours & if I remember correctly it was some wires that were grounding themselve out.

 

I haven't checked the injector wiring but it is something I should look at.

I can't seem to make it do it on command. I try and it throws me off every time. There doesn't really seem to be a pattern to it, just sometimes worse at certain speeds. I say that and then it will act completely different today

I'm currently not getting any codes. I keep hoping that I'll get one and it might lead me in the correct direction. Right now it's driving me crazy not being able to figure it out! I'm at the point where I want something to fail so I can find it and get it fixed!

Thanks for the input. I'll look into the things you've suggested

 

I've had a chance to play with it a little more this weekend. It now does it the same regardless of stock programming or with the Bully Dog programs. I think before it was just spurratic and it just happened to occur with the programmer on worse than without it.

I hooked the Outlook Monitor back up but I don't really see anything out of the ordinary. It's hard to tell if something is wrong because of how quickly it happens.

I pulled the valve cover and checked the wiring to the injectors and nothing was loose or chaffed. I followed them down the motor and couldn't find anything. I was really hoping this would be my problem.

I still don't have any codes. I've got gauges on the way from DieselManor so I will be able to tell the fuel pressure. Where else should I check? What other wires could be chaffed that would cause this problem? I might have to swallow my pride and take it to the dealership.

 

Have you checked this?
https://www.dieseltruckresource.com/...ad.php?t=81936

 

I had similar symtoms, turned out my turbo had a crack in it due to excessive heat. They rebuilt my turbo, I now run a 13ss. No more surging at the higher RPM's.

 

I looked into the wire from the link - mine has wire loom on it and there doesn't appear to be any chaffed wiring there.

I keep watching my monitor and I think that I'm losing boost. The rail pressure does seem to stay fairly constant. It might fluctuate about 300 psi or so but nothing major. My boost seems to drop 3-4psi and I think that's what I'm feeling. I had been concentrating on the fuel pressure so much I didn't really notice the boost. It's more obvious now because it seems to last longer when it stumbles/surges.

I'm taking it to a dealer tomorrow to let them check it out. If it is my turbo my wife can no longer use the "there's nothing wrong with the one you have" reasoning. Hopefully it's my turbo...

 

I know this sounds really obvious... but could your fuel supply be restricted? Plugged/partially plugged filter?

 

I don't think that's the problem. It was the first place I looked when this started. I've changed the fuel filter and put a new lift pump on the truck since this started happening and it had no effect on the problem. I've got a fuel pressure gauge on the way that should help me diagnose it if the dealer can't figure it out today. I'm pretty confident that it's not a low pressure fuel issue though.

 

So I took the truck to my local dealership - the only Chrysler dealer around with a diesel mechanic.

I told the mechanic what was happening and what I had done to try to solve the problem. He then, looking at my truck's motor, said "A lot of these VP44 trucks have fuel delivery problems." I told him it was a CP3 pump and that I doubted it was on the low pressure side because I installed a new lift pump and the characteristics of the truck hadn't changed. His response was "I've never seen an aftermarket fuel pump that holds up. You probably need to change to the tank mounted pump" I explained that this was a kit designed specifically for these diesel trucks, it was brand new, and that the factory one couldn't keep up with my fueling needs. He's going to check it just in case...

I left the truck with him and I hope that he can find something with the Starscan tool. After all of that he seemed to think it was a loose pin on the ECM. I want to give him a fair shot to fix it and I sure hope he can. It was just a little frustrating that I knew more about the truck than someone Chrysler pays (and I'm having to) to work on them all day. Vent Off

 

Well based on my personal experiences with the dealership, they know nothing, I mean c'mon VP44?? Sorry, I hope you get lucky. I will never use a dealership again, they wasted 1 month of my time and came up with nothing....