I've been having an issue with the lift pump not doing the prime cycle when the key is turned on.

Every other time the key is turned to the "on" position, it will take 5-6 seconds for the lift pump to do it's 2 second prime. Once the truck is actually started, the pump runs fine and acts normal. 

 

If I try to start the truck once the key is on, and before the pump has ran, the truck will not start, it just turns over. If I immediately turn the key off after cranking, then the pump will run for 25 seconds, even after a the key is off.

 

I'm running a FASS HPFP, and this issue started about a year after I installed the new system. I've checked connections, and all seems to be good. 

When the key is turned, and the delay happens, the FASS relay does not click, so that tells me (most likely) the ECM is not triggering the relay. I did some reading, and it seems like a fairly common issue, and most people say the ECM is at fault, and the best thing to do is make a new circuit and put the pump on a switch.

 

Although, the truck should start without the 2 second priming sequence, if the fuel system is staying primed. (like with a mechanical pump) So I'm in the process of tracking down any fuel leaks.

 

I also thought about excessive AC noise causing this?? Possible... But my meter doesn't read low enough to test it.

 

Any opinions, or anything else to test?

 

1 hour ago, dripley said:

i dont know of any new ones being available any more. Even the one that I got near 5 years ago was a reman from Cummins. It cost me $1400 with programing and install. At the dealer then they were well over $2000. 

 

Yikes!

 

1 hour ago, Texas CTD said:

 

From what I've read, that seems to bee accurate.

 

I need to get a meter that reads low enough AC voltage so I can check for AC noise. That could be the root of this problem.

 

Very well could be!

As far as I know there is no more new ECM everything from this point forward is remanufactured. As for the lift pump delay, Wait to start delay, and VP44 power up delay are caused from memory errors in the ECM and difficulty to boot the software at key on. This failure is typically caused from excessive AC noise created by bad diodes in the alternator. 

5 hours ago, Mopar1973Man said:

As far as I know there is no more new ECM everything from this point forward is remanufactured. As for the lift pump delay, Wait to start delay, and VP44 power up delay are caused from memory errors in the ECM and difficulty to boot the software at key on. This failure is typically caused from excessive AC noise created by bad diodes in the alternator. 

May I add, not only diodes but also brushes and what they ride on. I rebuild my alternator and it got better but only after I changed brushes and I belive armature, only then my vac went down to an exepteable level. 

6 hours ago, Mopar1973Man said:

As far as I know there is no more new ECM everything from this point forward is remanufactured. As for the lift pump delay, Wait to start delay, and VP44 power up delay are caused from memory errors in the ECM and difficulty to boot the software at key on. This failure is typically caused from excessive AC noise created by bad diodes in the alternator. 

Any chance a reflash could cure it?

 

The flash isn't the problem... Is the actual RAM tied to the CPU during booting stage of the ECM the checksum keeps failing. So it calls to reboot again and again till the RAM checksum matches. So the flash is fine just got damaged memory on the circuit board. 

 

If the flash was bad then it would never start period because the checksum would fail 100% of the time. The ECM would never come online because it would never boot. 

 

This why even normal PC's have issues with dirty power it causes damage to memory and CPU's. Same here in the ECM. Big square is the CPU, the two smaller chip on the bottom if I'm not mistaken is the RAM.

 

Edited July 17, 20168 yr by Mopar1973Man