Rail pressure fluctuate

[Filipino_Redneck]

Fuel pressure Fluctuate

When I go to start the truck, it would crank for a long time I would then crank it again and it would start. Would happen again when I shut it down and tried to restart. Seems like rail pressure is draining FRP will fluctuate from 5 to 7 then drop down to 1/2 for a split second go back to 5/7 at idle when on the highway it would do the same thing drop low and I can feel it.
I changed my injectors, CP3, FCA, injector lines, FPRV, RP sensor. Camshaft sensor. Installed air dog when my FASS DRP went out.
Would a bad ECM cause all this? Reason I’m asking this, before my FASS went out it started to run all time when you turn the key on. Also my instrument cluster would flicker on/off every now and then but when I plug in my Edge w/At it would flicker anywhere from 2-10 second.
Thanks for any info
Joe

 

[AH64ID]

Does it do it with the Edge completely removed from the truck?

 

[Filipino_Redneck]

Yes. I disconnected everything and it still did it.

 

[Wayne M.]

The 5-7, is that PSI? You’re talking about a FASS. Sounds like lift pump pressure.

 

[Filipino_Redneck]

The 5-7, is that PSI? You’re talking about a FASS. Sounds like lift pump pressure.

No it’s the rail pressure after starting,

 

[Wayne M.]

Do you have any DTC’s?

 

[Filipino_Redneck]

Do you have any DTC’s?

No codes

 

[Wayne M.]

Are you willing to do a fuel return volume test? You’ll need some special items, some time, patience, and good batteries.

 

[Filipino_Redneck]

Are you willing to do a fuel return volume test? You’ll need some special items, some time, patience, and good batteries.

I can give it a try. Will have Saturday and Sunday to mess with it. How and what do I need.

 

[sag2]

Try disconnecting the FCA and see if it still does it. Had you done that to begin with you could have avoided replacing the pump, injectors, and FPRV. We know what it isn't. The only thing left is the wiring and ECM. With the dealer scan tool you can see the desired and actual rail pressure. If desired also moves down to 500 it would more likely be the ECM. If it doesn't it would more likely be wiring.

 

[Filipino_Redneck]

Try disconnecting the FCA and see if it still does it. Had you done that to begin with you could have avoided replacing the pump, injectors, and FPRV. We know what it isn't. The only thing left is the wiring and ECM. With the dealer scan tool you can see the desired and actual rail pressure. If desired also moves down to 500 it would more likely be the ECM. If it doesn't it would more likely be wiring.

I disconnected the FCA it peg out to max. My injectors and pump was bad. I’m going to check my FCA wire to see if there is a short and clean my ECM wire harness

 

[Ozymandias]

FCA wiring is prone for failure.

To me it sounds like an electrical problem, maybe a ground wire. Can you monitor the current voltage that goes to the ECM and the 5V Sensor feed line(s).
All that can have a major impact on the system.

 

[Filipino_Redneck]

FCA wiring is prone for failure.

To me it sounds like an electrical problem, maybe a ground wire. Can you monitor the current voltage that goes to the ECM and the 5V Sensor feed line(s).
All that can have a major impact on the system.

I have no way of monitoring the ECM. May be able to hook a jumper to the FCA then to my meter

 

[Wayne M.]

Exactly what kind of truck are we dealing with here? Can you please establish a signature with that info?
You should probably invest in some kind of diagnostic equipment. Once we know what truck you have, we can help recommend. We’re asking for info that obviously you can’t see. This info is very important to repair the truck.

 

[Filipino_Redneck]

Exactly what kind of truck are we dealing with here? Can you please establish a signature with that info?
You should probably invest in some kind of diagnostic equipment. Once we know what truck you have, we can help recommend. We’re asking for info that obviously you can’t see. This info is very important to repair the truck.

Ok think I updated the sig info. Sorry.

 

[Filipino_Redneck]

Well I think I figure it out. My in tank suction line was crack and I think was causing my system to get air bound. I install a fuel sump tank that came with my air dog. At idle it was around 5/6 and didn’t fluctuate. Took it for a spin and was a total new truck. Will find out in the morning when I try to start it and if it take a long time.