strange vibration or miss/stumble under light acceleration

[okredneck]

I've got a 2002 2500 5speed that's developed a vibration or a miss under light acceleration. This all started after the wiring fried on my relocated ddrp. I've said since repaired the wiring but sometimes the truck acts like it has either a leaking injector line or its getting air in the lines. However its only noticeable at 30 mph in 4th gear putting through town. I dont have any codes except for a p0177 and I know there's no water in the tank or lines. One last thing as soon as I accelerate or downshift to raise the rpms it goes and away. Any help or suggestions would be greatly appreciated. Thanks

Edited June 9, 2015 by okredneck

[rburks]

what is ddrp???    did you have this issue before you had wiring problems???

Edited June 10, 2015 by rburks

[rburks]

Have you changed filters?? Need more info on your set up, like Are you still funning factory carter lift pump or in tank factory pump or have you installed AIRDOG OR FASS,   Factory injectors???,  are you running a programmer or timing box???     do you have Gauges???

    be nice if you new if fuel pressure was dropping when this occurs.....

Edited June 10, 2015 by rburks

[okredneck]

Fass ddrp fuel pump. Its a slightly better than stock fuel pump I bought when I replaced the vp44 about 3 years ago.

[okredneck]

Changed the fuel filter last month and I do have gauges(fuel pressure and pyro) but as far as I know the injectors are stock and I've never ran a programmer or box on it. The only upgrades I've done have been the fass ddrp pump and 7/16 fuel lines. Also the fuel pressure doesn't drop when it does this it stays at about 19 psi at idle and 15 going down the road

[rburks]

Did it do this before the wiring fried

[okredneck]

No it didnt

[Buzzinhalfdozen]

Could you elaborate a little bit on what fried the wiring and where it was damaged. On the extension harness or was it on the factory side of the LP plug in?

[rburks]

Changed the fuel filter last month and I do have gauges(fuel pressure and pyro) but as far as I know the injectors are stock and I've never ran a programmer or box on it. The only upgrades I've done have been the fass ddrp pump and 7/16 fuel lines. Also the fuel pressure doesn't drop when it does this it stays at about 19 psi at idle and 15 going down the road

when you say 7/16 fuel lines i assume you are talking about the line going from lift pump to VP Pump??? are you sure you don't mean 1/2 inch line cause 7/16 is stock

[okredneck]

It shorted out on the extension harness in the plug that connect it to the engine harness. The extension harness I used has a relay on it is o provide power to the pump directly from the battery so all the factory wiring does is control the relay.

[okredneck]

Its been 3 years since I put the lines on but I remember the lines were one size larger than stock and I was assuming the stock lines were 3/8ths. I'll look in the morning though.

[rburks]

No it didnt

Well good news is your problem is isolated to the area where the wiring fried, bad news is now you got to find it. i would undo what ever you done to piece it back and go from there. it has to be a bad connecting plug maybe the heat melted the plastic and pins are loose or a frayed wire somewhere, a good place to start is the signal wire that comes from ECM to activate the pump

[rburks]

It shorted out on the extension harness in the plug that connect it to the engine harness. The extension harness I used has a relay on it is o provide power to the pump directly from the battery so all the factory wiring does is control the relay.

WHY DID IT NOT Blow a fuse, or trip the relay,  it sounds like you didn't install a fuse ln the power wire, your connecting wires from engine harness are already fuse.d  the relay must be huge to withstand that did you replace the relay????

Edited June 10, 2015 by rburks

[okredneck]

The only reason I'm not sure its related to the fuel pump is I dont get any fluctuations in fuel pressure when it does this. I've got a mechanical gauge for fuel pressure and the only movement I see in it is when I press the skinny peddle. The last time it did it today FP was at 16-17 psi and being in 4th gear I was running about 1100-1150 rpms @30 mph. I'm definitely gong to look into the plug since I used the old plug off the factory pump to repair it.

[okredneck]

It did blow the fuse. I bought the harness of eBay and for the last few years its worked great so I dont think its the harness. I didn't mean fried as in melted or caught fire but it started blowing fuses every time I would hit the key and kick the pump on. I narrowed that problem down to the plug on the extension harness so I cut off the problem plug and replaced it with the plug from the factory pump I had saved as a spare.

[okredneck]

No I didn't replace the relay it still works fine it closes as soon as I hit the key.

[rburks]

Well if it didn't do it before you have to start with the issue at hand, it makes no sense to start looking elsewhere before you rule this out or it fixes it one

[rburks]

No I didn't replace the relay it still works fine it closes as soon as I hit the key.

RELAY COULD HAVE BEEN WEEK'ND AND TRIP'N OUT UNDER AMP LOAD FROM LP

[rburks]

If you had a fuse in power wire id say bridge #85 &86# over on relay and see if it solves it but better not do that...try replacing the relay first, it may be the culprit

 

sorry i just seen where you replied if did have fuse

Edited June 10, 2015 by rburks

[Buzzinhalfdozen]

Well if it was just popping fuses and its working fine now I have a hard time believing the misfire is related to LP wiring. Does it ever crank over longer than normal this would be an indication that you're getting air in the fuel system.