2000 lift pump only turns on for 2 seconds

revolutiondsl

revolutiondsl

Cat buys my Cummins parts
Joined
Jun 3, 2007
Messages
1,391
I put a new injection pump and air dog on a 2000. Now it will Just turn the air dog on for like 2 seconds and it won't run when Your cranking on it or if you bump the starter. It worked before. No codes and can't find any blown fuses. I understand the ecm is what turns the pump on but What does it go off of. I've racked my brain on this and can't figure it out. Has anyone dealt with this before.
 
Have you put a test light on the pump lead wire to see if it's getting power or jumped the relay to make it run? If that checks out, then test the trigger wire and see what that tells ya.
 
If you are utilizing the factory lift pump plug in to trigger the air dog, then it should only run for approximately 2 seconds and turn off until the truck is running. Some VP44 pumps don't like a lot of pressure at start up when warm, so they only run the lift pump for a second to make sure its primed and then it should run constantly when the truck is running.
 
At thus point its dry because the air dog is new and the injection pump is new so it shouldn't have any pressure. I can't get it to run long enough to prime the pump
 
Diesel Powered said:
Have you put a test light on the pump lead wire to see if it's getting power or jumped the relay to make it run? If that checks out, then test the trigger wire and see what that tells ya.
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I've put a test light on the plug that goes to the factory lift pump. The one that the air dogplugs into. It comes on Just for a second then goes off
 
If the airdog has a relay in the wireing harness jump around it and put 12v to the pump.
 
Ya I get that l. The pump works I just can't figure out why it wont run for more then 2 seconds. I've put quite a few on and normally it will kick on when you bump the starter. You do That until it gets fuel to the injection pump. I can wire around it and get it to come on I Just want to know why the ecm won't turn it on
 
Maybe jump around it until you get the system primed and then see if it will work correctly after everything is primed and the truck is running.
 
twin64 said:
Maybe jump around it until you get the system primed and then see if it will work correctly after everything is primed and the truck is running.
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That is what I was getting at. LOL I just didnt type it.
 
well I'll mess with it again but it didnt even seem like it was working while cranking.
 
It shouldn't be running while the truck is cranking, that's how you get hard starts from too much pressure. When you bump the key are you getting power at the grey 2 pin connector up by the engine (the plug our harness plugs in to)?

If your ECM is causing the problem you can always cut the plug off our harness up by the engine and wire one end to ground and the other to a power wire that's hot when the truck is running. Or wire one constant hot and the other ground through a switch.
 
No im not getting power at the grey connector. Thats my issue. How can I tell if the ECM is even going to run VP and why woul the ECM have went bad. The truck had been ran with the stock lift pump and a TST for a while so I knew the VP was on its way out but I cant figure why the ECM is giving me trouble. At one point after the injection pump was on but before the Air Dog I turned the key on to check mileage and the factory lift pump worked and pumped diesel all over the floor and now nothing.
 
I have seen the LP circuit only go out on many ECM's before, but usually with another pump being run from it besides the factory unit. Have you checked to see if you are getting power to what is now the relay activation wire with a starter bump? The "Run for 20 seconds" code that is enabled with just bumping the starter is fairly hard coded, it should always do it, but only with a fresh key cycle.
 
I messed with it today. It has a P1693 code and I dont have a way to read the codes except in the dash. I have checked the power at the LP wire and it will have 12V for maybe 2 seconds then like 8V. I jumped the wire off the battery and got fuel up to the injection pump. I started cranking on it and got fuel out of a couple of the injectors but the batteries gave up so I had to put the charger on them for the night. Im thinking I'm just going to wire it up to run key on since its something in the ECM. Ive never seen anything like this.
I checked the voltage right out of the ECM and thats where I got the 8V. I did that to make sure there wasnt a short or bad wire.
 
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Faulty/weak circuit in the ECM, once the batteries are back up to full charge check it again, you might have the voltage needed to run the relay.
 
i ran into this issue when i installed my fuel lab pump and monster pump. THE TRUCK WOULD RUN BUT NO FUEL PRESSURE. it was pulling through the fuel lab pump. i bought a relay and wired it with a constant 12v source and bypassed the entire fuel circuit. no problems since
 
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