I have the stock lift pump mounted to the block. The lift pump will only run for about 1/2 sec. when the key is turn on, when I bump the starter the lp won't run, I tested the voltage at the plug to the lift pump, reads 8 volts.Anybody have any ideas? thanks for the help....

  asens said:

I have the stock lift pump mounted to the block. The lift pump will only run for about 1/2 sec. when the key is turn on, when I bump the starter the lp won't run, I tested the voltage at the plug to the lift pump, reads 8 volts. Anybody have any ideas? thanks for the help....

Are you getting the 8 volts when you bump the starter or when you turn your key to the "on" postion?

the 8 volts stay constant when turning the key on or bumping the starter

ECM controls the lift pump directly... There is no relay in between the two...

So that would point to a problem with my ecm? Do you think its something that could be flashed.......

Thanks for the diagram, I had been looking for that information.....just in the wrong places......thanks

I would check the electrical connection to the pump first. Then disconnect the pump and check your power without the pump hooked up.

I would check for error codes. Because if the pump is internal shorted or internal open then there would error code set. But check the pump resistance and it should be no higher than 200 ohm and no less than 20 ohms. Check the ground behind the starter. This is the location of the ECM ground...

  Mopar1973Man said:

I would check for error codes. Because if the pump is internal shorted or internal open then there would error code set. But check the pump resistance and it should be no higher than 200 ohm and no less than 20 ohms. Check the ground behind the starter. This is the location of the ECM ground...

I checked the codes I get P0645 which I believe is unrelated...I checked the ohms at the pump, it read 2 ohms, so I might have a problem there.....Checking the ground will be a good idea, I replaced the crankshaft position sensor 1 month ago, maybe I tweaked the ground...... thanks for the help I'll check on that now......gotta love these nice alaskan days with no garage....

  asens said:

I checked the codes I get P0645 which I believe is unrelated...I checked the ohms at the pump, it read 2 ohms, so I might have a problem there.....Checking the ground will be a good idea, I replaced the crankshaft position sensor 1 month ago, maybe I tweaked the ground...... thanks for the help I'll check on that now......gotta love these nice alaskan days with no garage....

Ground looks fine, I traced the ground wire into the bundle of wires and it looked fine as far as I can see.... hmm still searching...gotta love elect. problems

I've come to a conclusion...I wish I knew a tenth of what Mopar man knows!

  dobienut said:

I've come to a conclusion...I wish I knew a tenth of what Mopar man knows!

Who do you trust to help you with your vehicle? In this order: 1 Enthusiasts 2 Private truck repair shop 3 My kid 4 Mr. Magoo 5 The dealer

  dobienut said:

I've come to a conclusion...I wish I knew a tenth of what Mopar man knows!

I'm going to be totally honest and straight forward... Back in 2002 if you asked me about a Cummins diesel I would give you a weird look and go huh? Well all my knowledge is from read post on forum, asking questions, and talking to people. Now the web site started out really small back in 2003 with basically write ups of my BOMBs and common issues like gauges, and fuel pressure. By 2007 I bought my domain then added a forum and extend the web site even more. Now in the late 2009 I had to upgrade the server because of the amount of traffic. This web site is basically collection of information found on the internet that started out being just my personal notes then other had get idea or suggestion so they came forward and helped as well. As these new tidbits come, or I repair my truck, or other trucks, I've learned from past experiences. So as I do something new i learn from these experiences so I either update a current write up or I'll create a new write up. I'm not ASE certified... I did not go to college for this... But I'm be turning wrenches and doing repairs on my own vehicles since I was 15 years old. I still own my first vehicle which is a 1973 Dodge Charger SE. This is where is started from. Then led me down the rock bumpy road of visiting wrecking yards, part houses, talking to people, and learning. I never given up or quit I just kept going forward knowing one thing... "It worked before... It's broke now... So I can't hurt it any more that what it is!" always kept the logical mind about myself and kept going... Sorry to steal the thread...

You know, I think that it is the 15 year old back yard mechanic kid that ends up making the best mechanics. Like the old saying goes, it's in your blood from a young age and you learned as yo went, not sitting in a classroom with your nose drove in a book seeing how it's done on paper and thinking you can do anything. My problem is I can read it, but just to do it is another thing

Finally got it worked out...I tried getting the truck started by running batt power straight to the lp, this is when I found out I didn't have any activity at my injection pump either....ended up being the crank shaft position sensor. The truck didn't know it was cranking.....About a month ago I got a p code that the sensor was out so I replaced it. This time it didn't throw any codes when it went out.......Thanks everyone for the help

  dobienut said:

You know, I think that it is the 15 year old back yard mechanic kid that ends up making the best mechanics. Like the old saying goes, it's in your blood from a young age and you learned as yo went, not sitting in a classroom with your nose drove in a book seeing how it's done on paper and thinking you can do anything. My problem is I can read it, but just to do it is another thing

You said it well. I was one of those kids tearing down mini bikes and other power equipment before I was a teenager. Mechanics are born, not trained. Even my grandfather was a jack of all trades. I have a couple of step sons that never did any thing beyond their key board, but they think they know every thing, because they have Google, Wikapedia, etc. I would like to see them make it with out their computers.