Archived Lift pump question

[BEnglish]

Please help I’m down.

I was doing routine maintenance and changing my fuel filter yesterday when I ran into a problem;lift pump thought my lift pump went out, so I drove my wife’s truck to work today and got a new pump from Cummins and just finished putting it in and it doesn’t come on. #@$%! I tested for voltage at the pump plug and it reads 4 volts. Is this correct? If this is low, what could make it 4 volts. And the relay is a little warm.

Thank you for replies.

 

[JLandry]

When you bump the starter (but do not start the engine) and leave the ignition key in the run position, the lift pump should receive 12 volts for approximately 25 seconds. If you're only getting 4 volts under this test condition, that's not normal.



The lift pump does not use a relay or a fuse. That relay in the PDC (Power Distribution Center) labeled "FUEL PUMP" is for the VP44 fuel injection pump. The lift pump receives power direction from the ECM (Engine Control Module). The ECM is located on the driver's side of the engine block. The lift pump is grounded to the vehicle chassis.



You should first check for 12 volts on the yellow/white wire in the lift pump wiring harness to a bare engine ground immediately after the starter is bumped (as decribed above). If you don't have 12 volts there, you should try and probe either pin 15 or pin 35 at the ECM and try the test again (bump the starter). Assuming you have 12 volts at the ECM connector, then you have a problem in the lift pump wiring harness you'll need to track down.



Now if you're not getting 12 volts at pin 15 or 35 of the ECM, then unfortunately I would have to assume the ECM is bad and needs to be replaced. It's not inconcievable some sort of internal electronic relay in the ECM could go bad.



Good luck,



John L.

 

[BEnglish]

There is 4 volts at the yellow and white wire at the pump plug and 4 volts at both pin 15 and pin 35.

Do you think it is the ECM??

Could it be anything else??

How much is a new one??

Where is a good place other than Cummins??

Is there anything else I can do other than replace the ECM??



Can I just run keyed 12v to the pump for now, so I can get to work tomorrow?

And if so do I run it to just the white and yellow wire only?

Is the other wire a ground or is the pump ground through the bracket?



THANK YOU



I fell off my stool and cut my arm on the wing nut on the battery. Just thought I'd share. :-laf

 

[JLandry]

There is 4 volts at the yellow and white wire at the pump plug and 4 volts at both pin 15 and pin 35.

Do you think it is the ECM??

Have you checked for Diagnostic Trouble Codes? Do you have a code scanner? If not, you may be able to see DTC's in the odometer window by cycling the ignition key as follows: run-off-run-off-run (leaving it there on run). Any DTC which have been set will be displayed.



Before I gave up on the ECM, I think I would also try to remove the multipin connector at the ECM and make sure all of the pins are clean and getting good contact. I've also heard sometimes the ECM itself might not have good contact (grounding) with the engine block, so it might be worth taking it out cleaning the ECM case, and putting it back on. I'm not saying this is the cure, but it can't hurt to try.



Off hand I can't think of any other reason other than a bad ECM as to why you wouldn't get 12 volts at the lift pump when you bump the starter.



As to where to buy one, I've read here on TDR where people have ordered replacement ECM's from NAPA with good results. NAPA includes the software flashing service in their price. Street prices are around $350 to $400 as I recall.



If you do a Google search on "Chrysler ECM" you'll find lots of online retailers. One is www.cryslerecu.net and their price is $395.

Can I just run keyed 12v to the pump for now, so I can get to work tomorrow?

And if so do I run it to just the white and yellow wire only?

Is the other wire a ground or is the pump ground through the bracket?

I'm not sure if that would work or not... I suppose in an emergency you could try it. I don't think you'd damage the lift pump.



According to the service manual the ECM limits the duty cycle of the pump when starting to the engine. This is because the VP44 injection pump has difficulty with higher fuel pressures when trying to start the engine. But I'll bet the engine would start with regular fuel pressure from a stock lift pump... maybe with a bit of extra cranking needed.



Yes... the yellow and white wire is the power supply and the other wire is simply a ground.



Let us know how you make out.



Regards,



John L.

 

[BEnglish]

Have you checked for Diagnostic Trouble Codes? Do you have a code scanner? If not, you may be able to see DTC's in the odometer window by cycling the ignition key as follows: run-off-run-off-run (leaving it there on run). Any DTC which have been set will be displayed.



Before I gave up on the ECM, I think I would also try to remove the multipin connector at the ECM and make sure all of the pins are clean and getting good contact. I've also heard sometimes the ECM itself might not have good contact (grounding) with the engine block, so it might be worth taking it out cleaning the ECM case, and putting it back on. I'm not saying this is the cure, but it can't hurt to try.



Off hand I can't think of any other reason other than a bad ECM as to why you wouldn't get 12 volts at the lift pump when you bump the starter.



As to where to buy one, I've read here on TDR where people have ordered replacement ECM's from NAPA with good results. NAPA includes the software flashing service in their price. Street prices are around $350 to $400 as I recall.



If you do a Google search on "Chrysler ECM" you'll find lots of online retailers. One is www.cryslerecu.net and their price is $395.



I'm not sure if that would work or not... I suppose in an emergency you could try it. I don't think you'd damage the lift pump.



According to the service manual the ECM limits the duty cycle of the pump when starting to the engine. This is because the VP44 injection pump has difficulty with higher fuel pressures when trying to start the engine. But I'll bet the engine would start with regular fuel pressure from a stock lift pump... maybe with a bit of extra cranking needed.



Yes... the yellow and white wire is the power supply and the other wire is simply a ground.



Let us know how you make out.



Regards,



John L.

thanks... I'm on it.

 

[BEnglish]

Yea! Its running!Oo.

I took the plug out of the ECM and cleaned everything as much as I could. I also checked all the grounds I could and undid and cleaned and added some of those electrical contact washers that kind of dig in. I hooked a test light to the hot lead to the pump and started running cycles to prime the pump. At first it would only kick on for a second then it started coming on sporadically then it started working. Then I killed the batteries. Then I recharged them and got the injection pump to prime and then it cranked.

Thank you so so much for helping me, well my wife says dinner is ready, look at that I didn’t even miss dinner.

 

[JLandry]

Yea! Its running!

Congratulations!



Glad it worked out for you.



John L.