Engine/Transmission (1998.5 - 2002) Lift pump will not run when key is turned on

[roundabout]

A couple weeks ago while starting the truck the left pump did not start. To get the truck to start I had to turn the key to on and back to off and repeat several times (as filling the fuel filter), then the lift pump would run on turning on the key and the truck would start normally. The truck runs normally after it starts. (Fuel pressure running at 13/14 lbs. on 2 different guages. )



This situation is slowly getting worse, to the point now that sometimes the lift pump won't start at all. (Just wait a few minutes and it will start. ) I have checked the electrical connections to the pump, looked from air leaks due to any leaks in fuel system, none that I can find.



Could the overflow valve on the return line be a problem? Open for ideas.

 

[JLandry]

When the lift pump doesn't run, the first thing to do would be to find out if the lift pump circuit is getting power. You can disconnect the lift pump electrical connector, put a volt meter across the terminals, bump the starter, and then see if 12v or greater is present.



The bad news:



If the lift pump isn't getting power when you bump the starter, then 99% of the time it's the ECM going bad. The ECM supplies power directly to the lift pump with no relays or fuses protecting the circuit... seems like a tad weak design.



The good news:



You can rewire the lift pump circuit to come on through a relay whenever the ECM energizes the VP44 fuel injection pump. See THIS POST for more information.



Good luck,



John L.

 

[roundabout]

Thanks for the information. I will not have a chance to check the voltage until this afternoon. If it turns out that this is the problem, would it just be better to replace the ECM to avoid further problems down the line with some other issue. . With my luck it would undoubltly happen at a very poor time.

 

[gmanv23]

this is how i solved the problem i change the fuel filter every 10K. I have relocated the fuel lift pump(a problem on these trucks) down to the frame by the tank with a Vulcan “Big Line” kit and have not had any issues since then. I have a fuel pressure check gauge to check it each time I replace it. And no problems since then

 

[JLandry]

If it turns out that this is the problem, would it just be better to replace the ECM to avoid further pronlems down the line with some other issue.

My personal feeling is no... if this is the only problem the ECM is having, then it's a lot more cost effective and simpler to power the lift pump via a different circuit with a relay and a fuse.



I say this because new ECM's are no longer available, so at a minimum you're looking at getting a used ECM from someplace like eBay with an unverifiable history and then no assurance the same problem won't happen again. You'll also need to make sure a used ECM has EXACTLY the same firmware to match the version you currently have. There are two reasons for this: 1. Using the wrong software for your particular engine / transmission configuration can create all sorts of strange behaviours (no wait to start light, no lift pump activation, no intake heater activation, etc. ). 2. It's not possible to change the ECM firmware to another configuration in the field. This can only be done using specialized equipment that even a Dodge dealer doesn't have. This is a failsafe feature in the normal programming equipment (Chrysler DRBII scan tool) to prevent mechanics from inadvertently flashing the completely wrong firmware into an ECM when attampting to load an upgrade.



If you buy a so-called refurbished ECM from one of the several rebuilders on the Internet for around $875, that can be a real crap-shoot because some of these questionable sellers seem to barely even clean the devices before shipping them out to customers without even bothering to test them first. I've read where customers had to send back one or two "rebuilt" ECM's before getting one that worked properly. On the positive side, these sellers will (should) be able to load the correct firmware for your configuration, so that wouldn't be an issue.



Cummins and Dodge sell rebuilt ECM's which should be trustworthy, but in excess of $1500. They're often subject to lengthy backorders. Then you still have to have the correct firmware loaded by Dodge or Cummins after the ECM has been installed on the engine... at an added cost of course.



I don't mean to sound so negative about getting an ECM, but honestly a lift pump power problem is easily worked around at a very low cost. IMHO, it just doesn't rise to the level justifying a complete ECM replacement.



Best regards,



John L.

 

[roundabout]

John thanks for the information on the ECM. I did not realize this could be such a problem.



I checked the voltage to the lift pump, it flucuates between 7. 5 volts to 8. 5 volts, with spike to 12 volts now and then. (When you turn the key off and it runs for 20 sec or so, the voltage is 12 volts plus a little. )



I will get a relay and use your example to rewire the lift pump curcuit. I will let you know how this works out for me.



For the note left by gmanv23, I usually change the fuel filter every 8,000 mile and like you I have moved the lift pump to the frame rail with the Vulcan kit. This pump has over 80,000 miles on it with no problems with fuel pressure.

 

[Ram4Sam]

Eighty thousand miles on a stock, crappy lift pump is alot of miles..... that may be all or part of your problem right there.



Sam

 

[fox]

I didn't read those whole thread, but you need to understand the key on thing doesn't run the lift pump continuously!

turn the key on, the LP will just pulse. It you turn the key on, then bump the starter it will run for 25 seconds or so.

This is the way to refill the filter after replacement. I do it 2-3 times to get normal fuel pressure before starting it.

 

[JLandry]

I will get a relay and use your example to rewire the lift pump curcuit. I will let you know how this works out for me.

Please do let everyone know how this turns out.



Some additional thoughts:



Be sure and use a fuse to protect the new lift pump circuit.



Any existing circuit which energizes when the ignition key is in the run position should be fine to trigger the relay for powering the lift pump. The one I chose coming from the ECM seemed to make sense because it's already used to trigger a relay for the VP44 fuel injection pump. Obviosuly you want the lift pump running when the VP44 is powered on.



For safety reasons, the ECM is supposed to cut power to the lift pump if the engine stops running for any reason (like an accident for example). If you power the lift pump through a relay triggered by some other circuit, then you'll loose this safety feature. Keep this in mind and turn off the ignition in case of an accident or engine stall so you don't keep pumping fuel.



Best regards,



John L.

 

[JMetzger]

John, Are we starting to see ECM problems now? I think it is a crying shame that you can not buy a new ECM any more. About normal. When I was having a code on my 02 for No Communication between Injection Pump & ECM they thought it might be & ECM but all it was dirty connections.

 

[JLandry]

John, Are we starting to see ECM problems now?

From the posts I'm seeing here on the forum, no more than usual.

The transistors used to power the lift pump are a weak point and prone to failure. If Dodge (or Cummins) had used an external relay and fuse for the lift pump circuit, ECM failures might have been greatly reduced.

John L.

 

[JMetzger]

John,Thanks for the answer.

 

[MGrantham]

Is 80k a normal life expectancy for a lift pump??

 

[JLandry]

Is 80k a normal life expectancy for a lift pump??

I'd say that's a reasonable lifespan.

Obviously some don't last that long, and some last much longer.

Best regards,

John L.

 

[jeepit]

John,

Great info... I am packing relays, fuses and wire just in case I need this along the road somewhere.

Cheers

 

[AABEN]

a couple weeks ago while starting the truck the left pump did not start. To get the truck to start i had to turn the key to on and back to off and repeat several times (as filling the fuel filter), then the lift pump would run on turning on the key and the truck would start normally. The truck runs normally after it starts. (fuel pressure running at 13/14 lbs. On 2 different guages. )



this situation is slowly getting worse, to the point now that sometimes the lift pump won't start at all. (just wait a few minutes and it will start. ) i have checked the electrical connections to the pump, looked from air leaks due to any leaks in fuel system, none that i can find.



Could the overflow valve on the return line be a problem? Open for ideas.

what year?? Need to fill in what you have!!

 

[GW208]

John,

Great info... I am packing relays, fuses and wire just in case I need this along the road somewhere.

Cheers

X2



Does anyone happen to know if the ECM sets a trouble code when the output to the transfer pump fails?

 

[roundabout]

I have finally had the time to work on my truck, due to time restaints I used a couple of the circuits off of a 7-circuit auxilary fuse block that has been on the truck of some time. I put a switch in the keyed feed line to the relay as a way to shut the pump off while the key is on.



Everything works fine, the lift pump starts when the key is turned on, the pump pressures are the same as before (13/14psi).



My only question at this point is on the truck starting. Before this problem the truck would start immediately when the key was turned to start. Now it turns over several times before starting. (I let the pump work of several seconds with the key in the on position before attempting to start the truck. )



Any idea on what the diffence is?

 

[roundabout]

The year on the truck is a 1998 1/2 24 valve.

 

[JLandry]

My only question at this point is on the truck starting. Before this problem the truck would start immediately when the key was turned to start. Now it turns over several times before starting. (I let the pump work of several seconds with the key in the on position before attempting to start the truck. )



Any idea on what the diffence is?

Try starting the engine immediately without letting the lift pump run for several seconds and see if that makes any difference.



I'm not sure why, but for some reason the VP44 doesn't seem to like having full fuel pressure shoved into it while starting the engine. To prevent this, the ECM is programmed to operate the lift pump at a reduced duty cycle during starting, which results in lower fuel pressure to the VP44. By powering the lift pump when the ignition key is on, this reduced duty cycle at starting mode is eliminated.



As long as the engine eventully starts, and assuming you have good fuel pressure, you can safely ignore a bit of extra cranking.



Best regards,



John L.