Archived Electrical Problem on 1999 2500 that mechanic can't diagnose

[REdmon]

Our 1999 Dodge Ram 2500 wouldn't start at the store for my wife (stuck). After calling me on my way home from work, she said it started and I told her to drive directly home. 1 minute later, she calls and the truck died in the street. I made it down (30 miles away) and had it towed to the closest reputable diesel shop. After checking it out the next day, the mechanic called and said the injector pump was bad. I told him to replace it. The next day he calls and says there is an additional problem with the lift pump acting sporadic. I tell him I have a new spare (problematic lift pumps I was aware of being a member) and I drop it off. He installs the lift pump and calls back stating the pressure is a little better (10 PSI down to 8 PSI on acceleration), but that there is an electrical intermittent occurring in which the lift pump doesn't always feed. If the truck is running and you turn it off, 1 out of 5 times it won't start back up and you have to turn the ignition back off. A second try will get the truck started. He doesn't know what the issue could be and couldn't get back onto the job for 2 weeks due to schedule being booked. I will pick the truck up tomorrow and take it to my local mechanic, but is there specifics that may be causing this issue?? Your help or suggestions are greatly appreciated.

Thanks

Ron

 

[hcole]

Redmon, the best thing to do is install your own relay for the lift pump. Come off the battery, install fuse, then relay and use normally open contact to feed pump. Then find a fuse at the fuse box under the hood that is only hot when you turn on the ignition switch to run. You will use this to power the relay coil. This relay can be mounted next to the fuse box. Now you have power on the lift pump when you turn on the switch. The factory never fused the lift pump and came off the ECM directly and fed the pump. VERY POOR design. I changed mine 3-4 years ago. Works GREAT!

 

[cerberusiam]

It may not be a problem with LP not running, it may be a problem with the LP running too much. The VP-44 does not like a big shot of constant pressure on start up, it will refuse to start at times and possibly hurt the IP after so long. There is a flash to limit the run time of the LP when the engine is not running to address this issue, you might want to check and see if that has been done.

As the electronics age connections start to fail and it will periodically act like there is a high amp draw and the LP won't run. The best solution is isolate the LP supply thru a relay that is controlled by the factory LP circuit so you retain the short run time on start up. The amp draw for the relay should be very low and may resolve any high draw issues. I would not hurt to pull the ECU connectors to clean the pins, check for loose pins in the connector and reseat them.

Wiring a direct LP control for a switch on condition is probably the worst thing you can do. Good for a get-home solution but a bad idea for a permanent fix.

 

[Gary - K7GLD]

Redmon, the best thing to do is install your own relay for the lift pump. Come off the battery, install fuse, then relay and use normally open contact to feed pump. Then find a fuse at the fuse box under the hood that is only hot when you turn on the ignition switch to run. You will use this to power the relay coil. This relay can be mounted next to the fuse box. Now you have power on the lift pump when you turn on the switch. The factory never fused the lift pump and came off the ECM directly and fed the pump. VERY POOR design. I changed mine 3-4 years ago. Works GREAT!

YUP - separate relay, keyed by the LP circuit, but powered off the battery thru a fuse - sorta like THIS:

.

 

[dknoch]

I spent a couple of months chasing a weird problem on mine. Turned out to be the ECM. It was sending a random shutdown signal to the VP44. Info from Bluechips diesel.

 

[REdmon]

Thank you for your help. The truck is 45 miles away from the house and was towed to a diesel shop. I spoke to the mechanic and he said he has installed the fused relay powering the LP on other vehicles and recommends it as well. I will go that route. I know I have had a few issues with my truck over the years, and TDR members always come through. Thanks all. I appreciate it.

Ron

 

[Bob4x4]

The factory lift pump replacement kit is operated off a relay.The kit is ideal for any stock powered truck

 

[HHhuntitall]

I spent a couple of months chasing a weird problem on mine. Turned out to be the ECM. It was sending a random shutdown signal to the VP44. Info from Bluechips diesel.

Unfortunately, I've ran into this several times the last year. The ECM is fairly expensive, especially putting it on a $2500 truck with 400k on it. So wiring the relay to run with ignition on is the most viable alternative in this situation, IMO. I've done several dozen the last year, and they've all run when leaving here.... The worst problem is the intermittent signal burns up the injection pump. Ghost codes, no starts, and even random CELs with no codes given are the signs of a bad ECM....

 

[dknoch]

Never had any codes on mine. Made it very difficult to diagnose. VP44 should still pull fuel without the lift pump, results in early failure. According to BlueChips, I could have just cut the wire and it it would have worked. I am not to the point of bandaid fixing my truck yet, deffinately agree it is the way to go as things get older. If the new injection pump did not fix the problem, I would start to suspect and try to rule out the ECM.