relief valve

[Diesel Power]

I thought this was gonna be a good thread when it started, but I'm almost as confused now as I was before :-laf



I thought my rough idle, intermittant high pingy idle, loss of fuel mileage, seemingly loss of power etc etc was gonna be because of a bad relief valve. And I would have understood due to running an EZ for almost 150,000 miles. But, based on this thread, my relief valve is good and my CP3 isn't.



I pulled the banjo bolt and pulled the line back out of the way. At idle I stuck my finger over the relief valve like you would a garden hose and got a small fine misty spray out from around my finger. At the same time, fuel was dribbling out of the return line. Not hard enough to spray to the opposite of the inside of the banjo fitting, but a good solid dribble.



Is it my relief valve? CP3? Or as RBattelle suggested, my FCA?



I finally found what sounds like a reputable shop about 30 miles away, but as usual I'm leaving in the morning and won't be back until Sunday, they can't scan it until Monday.

i would say your relief valve is bad due to it leaking, cp3 sounds normal

 

[GWoody]

Don't be puttin your finger over that releif valve!!!!!!!!!!!!!!!

 

[Mark1si]

Ok and in my case where the R/V is not the problem?

 

[F-15I Ra'am]

no it does not work that way fuel goes from the cp3 to the filter block and the relieved pressure of the valve during a high pressure event then allows fuel to also flow through the same line, they are both hooked into the same line----so fuel should only go from the cp3 to the tank and from the valve to the tank

That may be the case when everything is hooked up but once you unhook the return line from the overflow valve, return fuel from the cp3 is gonna come out of the line. If the relief valve is bad you will get a leak or spray coming from the valve itself as well. When you do the test pull the return line gently to one side so you can tell if fuel is coming from the return line,relief valve, or both.

 

[Diesel Power]

That may be the case when everything is hooked up but once you unhook the return line from the overflow valve, return fuel from the cp3 is gonna come out of the line. If the relief valve is bad you will get a leak or spray coming from the valve itself as well. When you do the test pull the return line gently to one side so you can tell if fuel is coming from the return line,relief valve, or both.

thats correct, you can also hit the peddle and see if the valve squirts fuel out---it is another way to tell

 

[betterthanstock]

#1 Don't put your finger next to a high pressure line-- it goes right through your skin an injects diesel into your flesh. Nasty and dangerous.



#2 I've seen a picture of that valve taken apart, and you can add a thin 0. 030" washer under that spring and see if that fixes it. Don't go too big on the washer at first, you don't want to raise the pressure too much. I think that while you have the valve apart you may be able to check the condition of the valve seat, and maybe put some valve lapping compound on it and turn it by hand to make it seat better. Clean the abrasive stuff real good before re-assembling it. (I have not done this myself, so I don't know how doable it is, but it's worth a try compared to a $600 replacement valve)