Fuel Problem On A 427

[cxn613]

I have been having an issue with my 2004 cxn613 w/427. The truck sometimes will loose its fuel prime. It can loose it over night, over a period of a few hours, and its even went almost a month before it lost prime. It has a Davco fuel filter. We have installed a new check valve in it, and checked lines for leaks. The problem is still there. Any suggestions will be greatly appriciated. thanks ryan

[reapermp]

I am sure if this will help but, it might possible be an injector leaking down, or there is the posibility of a computer problem, now I know that sound crazy but, we have one in the shop now that is doing the same thing the tech swapped the computer on the side of the motor and it started right up.

[Mackpro]

I had a humidity sensor going bad one time , making a hard starting problem, we thought it was loosing prime and we replaced everything and still had problem. The only way we found it was watching active code screen on laptop while cranking engine and code would pop up for 2 seconds then off then back on. By-pass the Davco then try it, also if fuel supply pump has plastic small screen/filter hanging off the bottom, change it also.

[jerrymac]

Check for bubbles in the Davco filter with engine running. There should be NO bubbles. If there are you might have an o-ring in the Davco unit leaking. Also check for any film of fuel, even minor at the connections on the EECU cooling

plate, especially if the inlet side is the plastic push-on type fuel line. Since these are suction lines you generally won't

find a noticable leak, but will let air into the system. Also, have you checked the fuel pressure with engine running?

It should be about 50 to 85 p.s.i. Could be a leaking fuel pressure regulating valve.

Oh yeah, by the way, does it ever seem to 'make it's own oil' ? If it does it could be a shaft seal on the supply pump

leaking, or an o-ring on an EUP leaking.

Edited June 18, 2008 by jerrymac

[fjh]

Check for bubbles in the Davco filter with engine running. There should be NO bubbles. If there are you might have an o-ring in the Davco unit leaking. Also check for any film of fuel, even minor at the connections on the EECU cooling

plate, especially if the inlet side is the plastic push-on type fuel line. Since these are suction lines you generally won't

find a noticable leak, but will let air into the system. Also, have you checked the fuel pressure with engine running?

It should be about 50 to 85 p.s.i. Could be a leaking fuel pressure regulating valve.

Oh yeah, by the way, does it ever seem to 'make it's own oil' ? If it does it could be a shaft seal on the supply pump

leaking, or an o-ring on an EUP leaking.

I don't trust anything with a see thru bowl on it when chasing problems like this bypass the filter and try it.

also replace the fuel drain back valve on the block if the problem persists!

[bobo]

check the return fuel pressure check valve it may be losing the prime, do you notice a change in the idle? is it surging? you will find it on right side of engine between 4th and 5ft eup. if it needs changing MAKE SURE you put the same vavle as stock, they come in 3 diff. pressures! and check the eup Orings in the block for leaking.

Edited October 17, 2008 by bobo