Dodge Cummins Diesel Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
433 Posts
Discussion Starter #1
I am having an issue with my lift pump going into 50% duty cycle (cranking mode) when the engine is running.
I need to know where the ECM gets it's signals for run/crank and the theory behind the system. It doesn't make sense that it is just from the ignition key for lots of reasons. One being the lift pump completes it's run cycle even when the key is turned off after bumping the starter.
 

·
Registered
Joined
·
2,495 Posts
Redo your Q.
you can not have crank and eng run at the same time.
State how you know this too (fuel pressure gage ?)
The ECM tells the L.P.to run.
You can run a wire to the L.P. from somewhere else and have F.P. when you want it
 

·
Registered
Joined
·
433 Posts
Discussion Starter #3 (Edited)
Fuel pressure gauge is plumbed in temporarily with tapped banjo bolt @ IP.

I do not have running signal and cranking signal at same time. While the engine is running the LP is switching to cranking mode and not running 100% of the time. :confused013: I tested the voltage at LP when under normal cranking and also while running with the LP acting up. I got the same reading/results
 

·
Registered
Joined
·
1,379 Posts
So the signal coming to the lift pump starts cutting out while running?
 

·
Registered
Joined
·
433 Posts
Discussion Starter #5
So the signal coming to the lift pump starts cutting out while running?
Yup, That is what was happening. It would go into starting (enging cranking) mode while running :confused013: I got the ECM flashed with the latest and greatest and it seems to be working correctly now.

One difference between old program and new program is the lift pump curcuit now runs only 25% duty cycle when cranking instead of 50% like before.
 

·
Mopar1973Man.Com
Joined
·
26,302 Posts
That's just weird... :confused013:

I know its a ECM control issue but why? I don't know? :confused013:
 

·
Registered
Joined
·
433 Posts
Discussion Starter #7
I'm not out of the woods yet. As far as I am concerned it's still in the probation period. I'm watching the test gauge pretty close.
It wasn't a big deal when it would run 50%. I could still hold good pressure but now with it only running 25% in cranking mode I don't think it will keep up.
 

·
Mopar1973Man.Com
Joined
·
26,302 Posts

·
Registered
Joined
·
433 Posts
Discussion Starter #9
It worked flawlessly when cranking. (i did the test as described in your video) It would just go into cranking mode when it wasn't supposed to.
 

·
Mopar1973Man.Com
Joined
·
26,302 Posts
Well hopefully the flash fixed your problem... :confused013:
 
1 - 10 of 10 Posts
Top