Help: lmm maxed out rail pressure at idle

[02bigstrokin]

2010 lmm with mpi twins and dual cp3s. after we changed the y-bridge over to a solid rdl unit, put it all back together and now the truck is idling at 26k. both fpr's are plugged in we have check all wires going to the plugs. the fuse for the dual fueler controller is fine. everything is plugged in on the motor. any ideas?

 

[cuminstrkmydmax]

ECM- been there and done that. Dont know exactly how it happens, but seems that 12V somehow gets backfed into the ECM and short circuits the FPR controls. I replaced the ECM and all was fixed.

GOOD LUCK -Steven

 

[02bigstrokin]

ECM- been there and done that. Dont know exactly how it happens, but seems that 12V somehow gets backfed into the ECM and short circuits the FPR controls. I replaced the ECM and all was fixed.

GOOD LUCK -Steven

wonderful. yeah i was talking with george and thats what he was thinking too. he said to check the middle wire on the pigtail going to the valley fpr and it should have 1.8-1.9 volts. its gots 3.5? he wasnt exactly sure about the numbers 100% but does 3.5 sound wrong

 

[cuminstrkmydmax]

Im pretty sure that 3.5 is wide open- non regulated. The 1.7 is idle voltage.

It took us a while to track it down- but it finally led back to the ECM.

I have a good ECM here from Socal if you need one-

-Steven

 

[770JOHNNYW]

How much?

 

[770JOHNNYW]

When your truck was doing this did it sound like an lb7 with the rp maxed out or just a little rough on idle then real loud when you bring it off idle?

 

[770JOHNNYW]

bump ecm did not fix it

 

[JoshH]

I've seen this once, and it was the plug at the little jumper harness. I'm guessing a wire was damaged or a pin was pushed out when you swapped the y-bridge. It makes sense since you were working in that area when the problem started.

 

[Dan@PPE]

Who's kit?

 

[770JOHNNYW]

I've seen this once, and it was the plug at the little jumper harness. I'm guessing a wire was damaged or a pin was pushed out when you swapped the y-bridge. It makes sense since you were working in that area when the problem started.

Ive checked everything man that's not it either. It's an ats kit

 

[juddski88]

try a different dual cp3 controller, and does it do it with the dual cp3 disconnected completely?

 

[770JOHNNYW]

try a different dual cp3 controller, and does it do it with the dual cp3 disconnected completely?

Yes it does

 

[cuminstrkmydmax]

Did you check the new ECM with the dual fuelers disconnected? If not you may have fried the new ecm-

-Steven

 

[Dan@PPE]

Have you checked your fuel temp sensor? If so what is it reading?

 

[MMLMM]

Highly doubt this is an ecm issue. Ground, pinched wire, unpluged or not fully plugged in, twin cp3 controller, FPR or like dan said check fuel temp sensor.

 

[770JOHNNYW]

Have you checked your fuel temp sensor? If so what is it reading?

no i havent what should it be reading and why would that max press out

Highly doubt this is an ecm issue. Ground, pinched wire, unpluged or not fully plugged in, twin cp3 controller, FPR or like dan said check fuel temp sensor.

its ****ed up because it ran perfect until we changed the y bridge and didint really even unplug anything...im in a bind with this one customer lives in another state and i have his primary vehicle here as of today broke as hell

 

[jeramoosh]

This happened to us one time on a lly. It was a ground wire we forgot to bolt back down. It was on the drivers side of the motor

 

[770JOHNNYW]

This happened to us one time on a lly. It was a ground wire we forgot to bolt back down. It was on the drivers side of the motor

didnt mess with any of that but ill sure check in the a.m thanks.:thumb:

 

[Dan@PPE]

no i havent what should it be reading and why would that max press out

It should be reading a real number (not -40 or +300 or somthing like that). Why? Ask GM. Its just one of those things...

Also check the IAT #1 and #2 and see if they have a strange reading.


its ****ed up because it ran perfect until we changed the y bridge and didint really even unplug anything...im in a bind with this one customer lives in another state and i have his primary vehicle here as of today broke as hell

...

 

[770JOHNNYW]

...

Ill check it out thanks