The truck's back from Cummins....They can't fix it.

[Jeff Clark]

After 4 days Cummins Southern Plains called and said they can not leagally work on my truck because of the "hot rod" parts on it. The service writer did say they diagnosed the problem as a short in the wiring to the lift pump. Problem is the lift pump is running when the truck won't start. If the lift pump was shorting out, it wouldn't be running.

I can't figure it out. I know where the wiring problem is. I don't know if I can fix it short of replacing the whole harness (the problem is in the truck's harness, not in the pigtail off the pump). We'll see.

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98. 5 3500 QC 4x4, Driftwood/Mist Grey, 5 spd, 3. 54, 19. 5 Alcoa's, Ranchhand bumpers, DeeZee toolbox, "Physcotty Air", TST PowerMax2, VA, 275's, Autometer Gauges, Centerforce clutch, Upgraded fuel lines (JRE and Aeroquip), MagHytec Diff Cover, PacBrake, Cowl Induction Hood

"If it ain't broke, it ain't a Dodge"

 

[csutton7]

Jeff--maybe you've done this or thought of it but here goes---you said you know where the problem is so why not wire around it, if you can isolate the starting point cut the wire wire and splice it with a new wire and run it to where you need to and see what shakes--chris

 

[Jeff Clark]

Thats what I plan to do tonight.

It still doesn't explain why the pump runs while I'm trying to crank it. If the pump was shorting out, it wouldn't be running.

[This message has been edited by Jeff Clark (edited 04-23-2001). ]

 

[csutton7]

your lift pump runs--so maybe the VP44 is shorting itself out--try to isolate that wire and wire around it & see what happens--it sures seems to me that that could be the problem---put a fuse in the wire to be safe-better to blow the fuse than something else----chris

 

[Max340]

here is a dumb thought, may or may not be true.

Is the pump running on two different leads, one for "start" and one for "run"?


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Y2K 2500 QC Sport 4x4 LWB
72 Dart 340
89 LeBaron GTC 2. 2 TI

 

[Mopar-muscle]

the pump is running when the truck won't start ???? what does that mean ??? they can't work on it because it has hot rod parts ??? are you sure you didn't take it to DODGE ????

i'm really confused . the problem starts withthe line and is escalated with thought that more pressure is good .

jeff do you still have the STOCK PARTS ???? time to reverse engineer your fuel system , the fact that it will run good for a period tells you something is correct , the wiring harness is wrapped and not shorting to the frame , if that was the case you'd be blowing fuses .

 

[Jeff Clark]

I don't even want to begin to try to wire around the VP44.

MM, yes I did go to Cummins. The lift pump runs every time I bump the key. I know it's not shorting out. They told me they didn't want the liability of working on my truck, so basically it's up to me to figure out and fix. I have most of the stock parts but I can't replace all of the sending unit parts to go back to stock without buying all of it.

The thing I can't figure out is this. First, this setup has worked flawlessly for 50,000 miles. Now all of a sudden, it doesn't. Second, when the truck starts, it runs like nothings wrong. I just have a hard time getting it to start.

 

[mikel]

Jeff,
I'm coming in kinda late here, and I have not read all of your threads about this, so if I repeat something, I'm sorry.

We used to have an old tractor at the shop that would randomly decide to not start, but eventually with enough swearing and messing it would get going. Once it started (wether it required alot of work to get it going or not) it ran fine. We finally figured out that the problem was air getting in the fuel line at a fitting on the side of the injection pump. We eventually fixed it so that it started all the time like it should, but before we got it actually fixed we installed a small electric pump in the fuel line with a toggle switch. We could then crack open the fitting on the side of the injection pump and turn on the electric pump to purge all the air out of the system up to the pump. It made a mess, but it always got the tractor started.

You may want to try the same thing. Crack open the line at the side of your injection pump and feed 12 volts to the lift pump (or wahtever you are using instead of the lift pump) and see if any air will purge from the fuel system. If so then air is being drawn back in to the injection from somewhere, and finding that somewhere will be your next challenge...

Hope this helps,
Mike

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'99 QC 2500 SLT Driftwood 2wd SB 24v Auto 3. 55 LSD
ISSPRO boost and pyrometer, Autometer 3 gauge replacement pillar, Walker 24168, DTT VB
'00 Durango SLT 360, 3. 55, Patriot Blue
-- email address removed --
Howdy Agg's!

 

[Mopar-muscle]

jeff , maybe your air leak is inside the tank ????? has taken 50k of vibration to loosen something up , what parts do you need to get the stock pickup back in place ? i have access to a stock pickup , can either send you the parts missing to try out or you'll have to go out and buy a pickup , start checking the local wrecking yards , a gasser pickup may yeild you the missing parts , only difference would be a pump inside the tank ??? you should drop the tank and peek inside .

 

[Jeff Clark]

I have been thinking of all the places that air could get in and I've checked them all. In all of this I have overlooked something that seems very obvious to me now. The truck starts fine when it's cold, won't start when it's hot. How about the coolent temp sensor?
I bought a new one today. I'm about to put it in and take a a drive to get it warm and see if it works. I'll let you guys know.

 

[Jetson]

Remember there is a T fitting at the back of the head where the return that is in the head from the injectors meets the main return line. I'm still wondering in the ECM may be getting hot and not running the lift or injection pump.

 

[Tom C]

Jeff, if your getting air in the system. you can just bump the starter 3 or 4 times to cycle the lift pump each time to help purge any air. then press excelerator down 1/2 way and try cranking.

PS hope you temp senser fixes your problem.

 

[Jeff Clark]

Tom, I have tried that. The pump can run all day long, but it won't start when it's hot. Starts fine when it's cold.

 

[csutton7]

Jeff - I was just looking in my manual and it said if the overflow valve at the VP44 is stuck is will result in hard starts--it doesn't say whether this would happen in hot or cold engine conditions--but maybe that thing is getting stuck when the engine is hot---just more info----usually these things are so simple its hard----chris

 

[frijole]

Somebodys check valve stuck open?? Bypassing fuel back to the tank?

 

[Bill Kondolay]

How does the truck run with a full tank of fuel?

 

[Jeff Clark]

Craig, the check valve is brand new. Shouldn't be stuck open. The truck operates the same as it did with the old one.

Bill, The truck runs great regardless of the amount of fuel in the tank. I've thought of the split intake tube also.

 

[Jetson]

Wasn't HVAC having a similar problem with power supply to the lift pump? It supposedly comes from the computer, maybe they computer is not always sending the power to the pump. I had a hot wire to the battery terminal with a wing nut I connected before I started the truck. I ran my 2nd pump that way for a week. That would be easy enough to try. The pump could also develop cracks from the fittings screwing into it.

 

[Brandon]

have you yourself tried a scanner and see what codes are in the puter?????????
just wondering
still think you are chasing a leak in the fuel system allowing loss of prime

 

[Tom C]

Jeff, Are you getting different fuel pressures when cold versus hot? It sounds like something is getting stuck open. might check the check valve. just because its new does not mean its right.

I have a brand new hand tool. it works perfect when hot but the trigger gets stuck in the on position when cold.

food-4-thought

let us know what you find.