Engine/Transmission (1998.5 - 2002) Loss of power to lift pump

[RCamp]

have a problem I can be driving along and the power to my lift pump dies, I recently put a pressure guage where the illumination on it will light when there is power to the lift pump also relocated the lift pump to the frame. I can be riding along (at different speeds and the light will go out (of course no pressure ) If this happens at hiway speeds the truck will start misssing or hestiation. I pull over turn off the switch let it set for a few seconds and the power comes back. Is there a relay on the power to the lift pump ? It gets power from the ECM doesn't it?

anybody out there had this problem ? What about wiring the pump up to run all the time from the ignition switch?

 

[JLandry]

RCamp,



There are no relays for the lift pump external to the ECM. The ECM supplies power directly to the lift pump without anything in between. So assuming there are no wiring harness problems, then the ECM is likely to blame.



And yes... you can definitely wire up a separate relay to power the lift pump when the ignition key is turned to the run position. Others here on the forum have done this in similar situations. Just make sure you add fuses to the circuits to protect the wiring in case of an accidental short.



Let me know if you need any help figuring out which wire to tap into to power the relay and I can look it up in the service manual.



Best regards,



John L.

 

[RCamp]

Thanks John, Do you think an ecm failure is in the near future because of this problem ? It would be very helpful if you coul give Ideas on where to tie in to an ignition the easiest. Randy

 

[Ram4Sam]

Rc, John will probably spank me for this, but I will tell you anyway.

I had the same deal a few years ago, pump had no power to it. In the power box under the hood, there is a relay marked "fuel ciruit or pump relay", something like that. I swapped it out with the relay from the fog light circuit.

It restored power to the pump, been fine since then. John said in a previous thread that should not have fixed it but it did. Try it, see if it works for you.



Sam

 

[JLandry]

Rc, John will probably spank me...

Now Sam, please don't let your fantasies get out of control. :-laf



I'm glad swapping that relay fixed your lift pump problem, but it only could have been a coincidence because that particular relay is only for the VP44 fuel injection pump. That aside, it is pretty amazing there's no relay, or even a fuse, for the lift pump external from the ECM. It probably wouldn't hurt to add both regardless of whether or not any problems exist. I'll have to add that to my list of mods to do.



John L.

 

[JLandry]

Thanks John, Do you think an ecm failure is in the near future because of this problem ?

Randy,

No... Others have lost proper functioning of the lift pump circuit without the rest of the ECM being affected.

It would be very helpful if you coul give Ideas on where to tie in to an ignition the easiest.

A good place to drive a relay for the lift pump would be the same circuit the ECM uses to turn the VP44 fuel injection pump relay on and off. To do this, you'll need to find the 18 gauge Brown/White wire running between pin 36 of the ECM and the PDC (Power Distribution Center). The PDC is that black box full of relays and fuses located on the driver's fender under the hood. Tap that wire, and for safety sake, insert a low amperage fuse before the relay. Ground the other side of the relay. When the ignition key is turned on, the ECM will provide current to the relay, which will switch it on. See the attached wiring schematic below.

Here are the ECM connector pin outs which might help you locate the correct wire:

#ad


For the lift pump (switched) side of the relay, take power directly from the battery if possible. I'd install a 15 amp fuse prior to the relay, because according to the Dodge service manual, the lift pump normally draws 12 amps.

Let me know if you need any more help.

Good luck,

John L.

 

[SKuyper]

Hmmm, I was always led to believe the ecm had no internal circuitry other than 5 v circuits and to control external components that ran on 12 volt and high amperage circuits the ecm only controlled ground circuits via relays... . that's the way it all works on Cummins powered agricultural equipment ( combines, tractors etc) The ecm is not capable of controlling high amperage loads internally... at least in everything else Cummins powered. In tractors and combines, the lift pump is controlled by the ECM via signal power from the injection pump and oil pressure sensor and done through a relay that the ground from the actuating coil is controlled by the ECM... ie no direct current through the ECM.

 

[JLandry]

Hmmm, I was always led to believe the ecm had no internal circuitry other than 5 v circuits and to control external components that ran on 12 volt and high amperage circuits the ecm only controlled ground circuits via relays... .

I guess the ECM's on our Dodge trucks are unique then. See the attached wiring diagram from the diesel fuel delivery section of the Dodge service manual. If you trace the wiring from the ECM to the lift pump, you can verify this is indeed the way the wiring is.



12 amps. No fuse. No relay. Scary isn't it?



John L.

 

[SKuyper]

Yeah... Thats scary... looks like two 12volt supply sources... I'm assuming the first is key on, engine off, timed at 1-3 seconds and the second power supply is possibly keyed off oil pressure or crank sensor before it gets power???... . I'm thinking if mine ever gives me crap, I'll do the separate relay thing. On ag equipment the ground side of the fuel pump relay coil goes back to the ECM and the relay itself is hot all the time. The ECM in those applications controls the ground.

 

[BDahm]

on construction equipment with cummins its the same way, ecm gives the ground. Wow i learn something everytime i come on here! Nice work with the diagrams and explainations John, we appriciate it.

 

[RCamp]

I got the relay put on today I sure hope this solves my problem . I don't want the injector pump, I replaced early this year to loose lubrication . Thank you guys for the replies . Randy

 

[JLandry]

... looks like two 12volt supply sources... I'm assuming the first is key on, engine off, timed at 1-3 seconds and the second power supply is possibly keyed off oil pressure or crank sensor before it gets power???.

I'm 99% sure those 2 wires suppling power to the lift from the ECM energize at exactly the same time. I suspect the designers of the ECM had to use two separate solid-state relays inside the ECM in order to safely carry that much total current



John L.

 

[JLandry]

I sure hope this solves my problem .

Randy,



Please be sure and let us know if this works.



Best of luck to you,



John L.

 

[RCamp]

So far, so good put over 200 miles on the truck over the weekend . I do have a noise that came along when I stared having lift pump problems . I only hear it during acelleration thinking it might be the pressure gauge I put on to keep acheck on the fuel pressure, or the fuel return line ? I can only hear it in the cab under acelleration with the the truck moving. Randy

 

[JLandry]

Randy,



Glad to hear it's working well for you.



For what it's worth, the plastic line leading to the mechanical fuel pressure guage I have installed in my truck used to buzz under just the right combination of engine speed and load. I suspect this was caused by pressure waves traveling up the line from the fuel injection pump. I was able to eliminate it by making sure the plastic line couldn't move by zip-tying it to other wires and components along its way to the gauge.



Regards,



John L.

 

[RCamp]

Thanks , John I will give that a try. Thanks again for all the help in solving my problem with the lift pump. Randy

 

[JLandry]

Thanks again for all the help in solving my problem with the lift pump. Randy

My pleasure. The TDR is here to help!



John L.

 

[Gordon Maney]

I have installed my new VP44 and Raptor pump. The truck is not able to power up the Raptor. There is no voltage at the lead that is supposed to power the lift pump [now Raptor].

I have a test lead made up with the correct connector part and can connect to the Vulcan harness and power up the pump. As an aside, I am believing the relay in the Raptor harness is participating in this functioning circuit, as my jumper lead is powering the circuit from the same point the engine's lead would.

I say that because that would seem to eliminate the need for a separate relay such as is mentioned in this thread.

Regarding the connection to the lead powering the VP44, how do you actually suggest making the connection? I detest Scotchloks. Do you strip the wire and solder to it, or cut it and use crimped, solderless connections?

I would think there would be another hot when key on lead that would be more conveniently accessible and less critical than the VP44 relay signal lead going to pin 36.

I may continue working and jump the pump circuit so I can see if I can start the truck. I don't want to buy an ECM just for this.

Some of this causes me to believe the old lift pump did not work for a long time.

 

[JLandry]

Regarding the connection to the lead powering the VP44, how do you actually suggest making the connection? I detest Scotchloks. Do you strip the wire and solder to it, or cut it and use crimped, solderless connections?

There are a lot of acceptable ways to make a serviceable splice. It comes down to preference and what you think is best I guess.



A few years ago when I installed an aftermarket alarm / remote start system in my truck, for every splice I had to make (and there were a lot of them), I took the time to strip back about 1/2" of insulation from the vehicle's wire. Then I stripped about 5/8" of insulation from the alarm system's wire. Then I wrapped the alarm system's wire tightly around the bare section of the vehicle's wire and soldered the connection using a good quality solder and flux. Once it cooled I wrapped the connection with high quality electrical tape. The alarm system hasn't skipped a beat yet and the remote start still works great.

I would think there would be another hot when key on lead that would be more conveniently accessible and less critical than the VP44 relay signal lead going to pin 36.

There are many ignition-on circuits you could use.



Good luck,



John L.

 

[Gordon Maney]

I was just reading another thread in which you posted; you mention the ASD relay and its role. I need to go check that.

https://www.turbodieselregister.com/forums/2038406-post6.html