Engine/Transmission (1998.5 - 2002) no FP power

[MT McGroin]

guys need suggestions, have the Carter lift pump style set up. pump is mounted to the engine block, not in the tank. power failed recently. checked to see if it was ground (positive lead @ FP harness plug - neg @ battery) issue. still no 12+. checked the relays, all good. pulled out slightly to get test leads to blades and see 12+ flowing through. seems to get lost between relay & plug. am I missing a fuse? have factory manual & no fuse shown, only a relay. thanks guys

 

[petersonj]

Need more information about your fuel system.

If the lift pump wiring is still OEM, there is no relay for the lift pump. The lift pump is powered directly from the ECM.

The fuel pump relay in the PDC is for the VP44 injection pump, not the lift pump.

If the lift pump wiring has been modified, then you are on your own to find the source of power and ground and to find whether or not a relay has been added.

- John

 

[MT McGroin]

Need more information about your fuel system.

If the lift pump wiring is still OEM, there is no relay for the lift pump. The lift pump is powered directly from the ECM.

The fuel pump relay in the PDC is for the VP44 injection pump, not the lift pump.

If the lift pump wiring has been modified, then you are on your own to find the source of power and ground and to find whether or not a relay has been added.

- John

stock wiring

 

[BigPapa]

Need more information about your fuel system.

Also, need to know what truck you have.

 

[MT McGroin]

02' 3500 cab & chassis. 2 wd. 5.9L 5 spd manual. all stock.

 

[BigPapa]

John is correct, no lift pump relay. Lift pump is powered directly by the ECM.

Not that I didn’t trust what you posted, John. I’ve learned that I must verify what I say before posting it.

 

[MT McGroin]

questions
1. is it ok to run a separate relay off the power supply to the pump to help w the load going through the ECM?
2. since mine is toast can I run a separate power & relay set up w out doing more damage to the ECM?
3. is there a kit that includes all the recommended mods for the wiring of the alt & cable upgrade?
thank you for helping me. already put me way forward towards fixing this issue. love that ugly beast.

 

[petersonj]

First, I would check again for power coming from the ECM. The ECM supplies power to the lift pump under three different conditions

1. With ignition switch "On", engine off - lift pump runs for 1/4 second.

2. With ignition switch "bumping the starter" (no engine start), then returned to "On" position - lift pump runs for about 25 seconds.

3. With ignition switch "On" and engine running - lift pump runs continuously.

So, depending on how you performed your test, it may have been normal to not have had power to the lift pump.

It is a good idea to relay the lift pump, even if the ECM output is still working. The relay coil draws less than 200 milliamps, so the ECM would be wired to the coil. Typically, a 20 amp fuse in series with battery and the load part of the relay would be used.

If the relay cannot be triggered by the ECM, a good alternative would be to add an auxiliary oil pressure switch to allow the lift pump to run continuously while the engine is running, and to add a momentary switch to override the oil pressure switch when the lift pump needs to be primed. The purpose of the extra steps here is to reduce the risk of fire should the vehicle be involved in a serious accident under certain conditions that could involve a fuel leak and a continuously running lift pump.

Relays and a 2-pin Deutsch connector can be purchased from Amazon. The connector will make it easy to continue wiring from the ECM if the circuit is still operational.

- John

 

[MT McGroin]

John,
thank you for taking the time to help me here. I have performed all 3 test situations, all failed. FP will run when on battery directly. I found your earlier thread w the relay info in it and that's what led me to this spot. good point regarding the oil press switch.
would it OK to leave the ECM alone for now and run the separate relay circuit? (unplug the factory end @ FP) would it result in further damaging the ECM?

 

[MT McGroin]

oh yeah forgot, I have an electronic fuel pressure gauge installed on the pillar. was showing pressure up till this episode. second is a pyrometer but I haven't had the bung welded in yet

 

[petersonj]

would it OK to leave the ECM alone for now and run the separate relay circuit?

To my knowledge, yes, it would be okay to just bypass the ECM. Be sure to seal off the connector so corrosion won't occur.

Let us know how everything turns out.

- John

 

[MT McGroin]

will do. thank you

 

[Ozymandias]

oh yeah forgot, I have an electronic fuel pressure gauge installed on the pillar. was showing pressure up till this episode. second is a pyrometer but I haven't had the bung welded in yet

What bung you want to weld?
It is drill & tap action at the manifold for the probe.

 

[BigPapa]

What bung you want to weld?
It is drill & tap action at the manifold for the probe.

Sounds like he's going post-turbo in the down pipe.

 

[MT McGroin]

yup. down pipe

 

[BigPapa]

Different strokes for different folks, but my preference is always in the manifold, pre-turbo.

 

[BigPapa]

Post-turbo is popular with the gassers for two reasons, convenience of installation and they want to know the temp of the turbo. We’re more concerned about the temp of the cylinder/pistons.

 

[MT McGroin]

hi guys, FYI i got my computer back from AUTO COMPUTER SPECIALIST. they did a great job, all fixed up. sent a report of possible causes and even included the wiring diagram for my VIN. the factory manual is hard to follow so this is a major bonus in my eyes. total was less than $300. would recommend them highly. still have some codes so now i think its time for a new HP pump & injectors. yeah

 

[MT McGroin]

PS good call on the placement of the EGT sensor. will be mounting it on the manifold. thanks guys

 

[gtwitch]

MT, did you get the no voltage issue cleared up as I ask because I am having same problem, I have no volts to the lift pump at any time see my other post on this problem and I am trying to find the voltage from the ECU that drives the FP / lift pump. I have replaced ( 10 years ago ) the VP44 and wondering if there is something in a feed back loop that tells the ECM that the VP 44 is ready for fuel and supply that voltage to the lift pump???? gtwitch in wyoming