fuel pressure question

[pwhite]

what should i check if I do not get the 1psi increase per one # of boost. I have a hot wired 307 and when I get in the boost th fp climbs to about 50 and then drops to about 38.
my alt is putting out about 12.5 v at wot (on the sm), I dont think thats enough is it . if not how makes a good replacement should I get a high out put one . what else should I check as far as the pump goes sorry for all the dumb questions


thanks

 

[y-hate]

Do you have an adjustable fuel regulator? What boost are you running?

 

[pwhite]

adj. fpr yes set to 45 line off

the boost was about 13-14 #s

 

[2QUIK6]

I would suspect a bad regulator or fp check valve, or bad fp...the later 2 require a new pump anyway. I would suspect the pump before the regulator since the pressure falls from 50 to 38. Most reg can be rebuilt, just a rubber diaphram in it and a spring.
If in doubt to the reg or pumps age, I'd replace them both.

 

[pwhite]

I am pretty sure the check valve is bad because it wont hold any pressure after the key is off. goes from 45 to 0 in like 3 sec. would the check really hurt wot fuel pressure ?

 

[2QUIK6]

Originally posted by pwhite
I am pretty sure the check valve is bad because it wont hold any pressure after the key is off. goes from 45 to 0 in like 3 sec. would the check really hurt wot fuel pressure ?

If the check valve is bad, then the pump has to do double work to keep the pressure from going back thru itself from what I understand, that is if its severe enough..maybe not.
A good way to check for a bad check valve it to build up pressure and have someone put vice grips on both the supply and return lines, return first then the supply right when you cut the key off....if it holds pressure for a few minutes, then remove the vice grips on the supply and see if the pressure drops fast...if so, then the check valve is definitely not holding.

Make sure the key is off before clamping the return line...otherwise you could build up way too much pressure too fast...have them clamp it right when they hear the pump stop running. And if for some reason it doesn't hold pressure when both lines are clmaped, that means you have a leaky injector, but wouldn't be the cause of the fp drop.

 

[pwhite]

I clamped off the hoses and this test leads me to believe it the check at the pump. It has been droping all fuel pressure as soon as the keys off for some time now. the loss of pressure under wot is a new deal. could the check be the problem.

 

[y-hate]

I would replace the fuel pump? how old is your pump