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Stalling while driving, Hot start/stall

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Hi everybody, my first question on Mopar1973Man.

I have a  stock 2001 Dodge 24v . In Jan.2012 had a lift pump failure & cooked VP44. Replaced with rebuilt VP44,and a Air Dog 150. About a month ago started to have a problem with hot starts, would start and stall.

I only had the idiot light for the fuel pressure warning, never came on. Problem continued to get worse. Bought a real fuel pressure gauge and discovered I had 13lbs. at idle and would drop below 10 lbs. any thing above idle, replaced filters, both were only a month old, no change. So I put the 17lb spring into the Air Dog  that came with the pump. Now I get 15lb at idle , and the pressure drops to 13lb anything over idle. WOT will cause a drop below10lb.

Called Air Dog and they are sending a new pump, still waiting for the UPS to deliver. I have codes P0122 and 1689. I am doing the tests listed by Mopar73man for these codes tomorrow.

Truck runs strong when cold, even at these fuel pressures, but as soon as it reaches 160 degrees the stalling and hard starts return. Removed thermostat helped some, but I live in central Florida, and everything is hot here

I think the VP-44 is on its way to death.

Any suggestions ?

Thanks Sam Y

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Next time it does it, pour cool water over the computer on the injection pump. Most likely the computer is getting hot. I cant look up the other codes right now. But if you can, clear the codes and see if they come back

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    • Author

    Hi Mopartechnican,  I forgot to mention that I have done that several times. I have used a garden hose and ran  cool water over the VP44 , and it does make things better until the temp comes back up. But the temp range seems to be getting lower all the time. It was stalling at 160 degrees and yesterday it as stalling at 140. And as you know driving and having the engine shut off is un-nerving .

    I cleared the codes today but have not test drove it to see if they come back, yet.

    • Author

    I just tried your test for the code 1689. As per the video ,removed the relay and cranked the starter. Yes it set the 1689 code again, but unlike your video my pressure gauge read 0 pressure during the cranking. Is this because I am using an Air Dog pump ?? Or am I missing something about the test.

    Still waiting for UPS to deliver the new replacement for my Air Dog, hopefully Monday.

    Had the same problem about the mo. ago,The power to the lift pump from the ecm would quit when the temp got over 170.I could jumper the power to the lift pump and it would start right up and run good. Sounds like a bad ecm.The are several articles that I've read  an  alternate power  supply off a   keyed  ignition source.I had to have my ecm rebuilt ,but it took the one I used in Fl. three times to do it right.Cost me 800 bucks but runs good now.I think you can get a rebuilt one from cummins ,but they aren't cheap maybe someone out their knows of a reputable rebuilder, because you can't get new ones any more.

    • Owner

    Since the P1689 code is present I would lean on that for the reason for the stalling right now. If communication with the VP44 fails then it most likely stalls out. On of the reasons for P1689 code is a fuel pump relay issue in the PDC. Don't confuse this with the AirDog relay or think this relay in the PDC is for the lift pump. It controls the VP44 power supply. So start easy. also the ground for PCM, ECM, and VP44 are all on the battery cable none of them go to body grounds. Most of the body grounds are lighting and aux stuff...

    • Author

    Thanks for all of the advice everybody!

    Here is an update, received the new pump from Air Dog, installed it brought the pressure up to 16lb at idle. Replaced the fuel pump relay.

    All codes were cleared and have not returned.

    But the truck still stalls, and still is hard to start when hot, @ average operating temp 190 degrees.

    But when I run cool or cold water over the VP-44 it will start and run fine , until it gets hot again.

    Still no codes.

    I am pretty sure the low fuel pressure issue with the lift pump has done its damage to the VP-44 .

    Any other ideas would be great, hate to buy another VP-44 this one is only 2 1/2 years old, less than 50K miles on it.

    Thanks Sam Y

    • Author

    Shame no one rebuilds the VP-44 computer. I was a computer tech for 15 years," old school" I'm  sure it is only a  half cooked transistor, that can't take the heat in the kitchen.

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