rail pressure issue

H

Hotroderick

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May 18, 2013
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I have an 03 with 90 HP injectors, cp3 has bag of parts, air dog 150 and an additional adjustable dad's 150 run inline with it, homemade compound setup with silver 62 over a TV7512. I have good rail pressure always first starting and after that it's intermittent. I thought maybe lift pump hence the the dual pumps. But I have a mechanical gauge hooked up and it occasionally will drop to 8psi on a hard run. I then capped the prv. I thought also maybe the fca so have swapped it back and forth with the stocker with no avail. I thought maybe a leakdown due to injectors tubes but have done the whole install procedure twice by the book twice using torque wrenches. It's not a case of being up to temp and fuel leaking at the tubes because going down the road I can throw it neutral, kill it, start it back up and the rail pressure sometimes will go back up. Cascade valve perhaps?
 
Autometer analog gauge. The gauge is definitly right. It runs like a turd when the pressure drops
 
210k assuming it was not replaced by previous owner. I know that is a lot of miles, but even if the pump were lazy why would the rail preasure be random? I now know it's not the cascade valve because I took one of a Dmax pump I got for my pieces together twin pump setup I plan on doing. I hate acting like the hairless ape that I am and throw $hit (unneeded parts) at it. If I uplug it it hits Max pressure.
 
Grounding/electrical issue perhaps? I am not good with eletrical stuff so how would I go about testing it?
 
Have you put the stock fca back in and tried it? I have seen modded fca's do some crazy stuff. I had 1 in a stage 3 pump that would randomly go to max rp a cruising speeds. Chased my tail thinking intermittent electrical problem. There are also several threads on here about bad fca plugs. Good luck with it. Gremlins can be hard to find and can make you waste $$ in the process!

Sent from my XT1080
 
Yes I have switched it out a couple times. I also put dielectric grease on the connector
 
How low does the RP go? To be clear, the RP problem happens at all loads and idle?
 
Last edited:
What did you torque the connector tubes to?

How is your Autometer gauge tied in to the FP harness?
 
DarkDiesel said:
How low does the RP go? To be clear, the RP problem happens at all loads and idle?
Click to expand...

So it will hit 4-5k. Usually have good rail pressure right after startup then it fluctuates all over. I can throw it neutral going down the highway, kill it, restart it and pressure will go up again for a short while, then it goes back to bouncing around.
 
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