I have a fuel pressure gauge that mounts to my rail. After I turn off my car it has about 35 psi. How long should the pressure hold in the rail. I am wndering if I have a small leak in a fuel injector.

Thanks for the help.

 

never really look to see how long it is supposed to hold. to test, shut the car off, clamp off the feed and return. if it drops it has to be an injector.

to check the reg, if pressure holds, clamp the feed, remove the return clamp. to check the check valve in the pump only clamp the return line.

 

simple. I like it. thanks. I will give it a shot. and see what I find out.

 

so i did a little science experiment over the weekend.

2 scenarios.

#1 - drove home from work and shut car off

41psi - 4:50pm
90psi - 5:06 (the pressure goes up from the fuel heating up in the rail from a hot engine, with no where to go since i had clamps on it.)
88psi - 5:30
80psi - 5:38
0psi - 9:19

There was a gap in time b/c I went out for dinner with my GF.

#2 - cold engine, turned on to prime system then clamped off the fuel feed and return lines

40psi - 9:36am
31psi - 9:58
30psi - 10:18
30psi - 10:40
27psi - 11:10
30psi - 11:30
40psi - 11:57
42psi - 12:08pm
52psi - 12:40
60psi - 1:14
70psi - 1:48
51psi - 3:33
42psi - 4:41
40psi - 5:30
31psi - 7:06
25psi - 8:42
22psi - 10:12
0psi - 7:53 am next morning

i think the pressure increased as the temperature of the day increased. The fact it held 90psi and also held pressure for over 12 hours - makes me think my injectors are not leaking. Would you all agree?

 

its still a tough call. but you dont have one hanging open.