Losing fuel pressure

CManT1914

CManT1914

New Member
Feb 5, 2004
3,172
2
0
Killeen, Texas
#1
I just put everything back together after readjusting my rockers. When I turn the key on, the pressure shoots up to 30psi or so, but then it slowly drops down to 15 or so. I checked all the lines going to the fuel rails and AFPR, but none are leaking. Any ideas? Oh, and I haven't yet messed with my AFPR, I just put it on the other day and haven't adjusted it.
 
#2
Shoots up and then drops...sounds like the regulator to me. Do you have a Haynes/Chiltons manual? They describe a test procedure involving pinching the feed and then the return line; you might want to try this.
 
#4
Does it drop while the car is running or just with the key on?

Might me a bad injector bleeding off pressure if the car is not running. Then again, if you didn't adjust the FPR, that could be the issue as will. I doubt that though. I just installed mine as well. Here is what mine does.

Mine shoots up to about 43psi key on, then drops to about 40-41 at start up, then after a minute of warm up sits between 37-39 which I am told is normal.

With just the key on it will sit at about 42psi all day. Even with the key off actually.

Should the gauge read with the car off? Kinda hard to hook it up wrong, just curious..........
 
#5
LoudToy958 said:
Does it drop while the car is running or just with the key on?

Might me a bad injector bleeding off pressure if the car is not running. Then again, if you didn't adjust the FPR, that could be the issue as will. I doubt that though. I just installed mine as well. Here is what mine does.

Mine shoots up to about 43psi key on, then drops to about 40-41 at start up, then after a minute of warm up sits between 37-39 which I am told is normal.

With just the key on it will sit at about 42psi all day. Even with the key off actually.

Should the gauge read with the car off? Kinda hard to hook it up wrong, just curious..........
Click to expand...

It onlys bleeds off when KOEO, when the engine's running, at idle it's sitting around 41 or so (to high), then with the vacuum line pulled, it shot up to around 50, ran for a bit, then died. When I pulled my plugs yesterday to do a compression check, I could smell gas in the combustion chambers, and they were all black and sooty like it was running way to rich.

The good news is, the motor runs a lot better since I relashed the rockers and put everything back together. I'm gonna go get lunch in a minute, and grab a new pulley installer for my p/s. Mine bent. Then I'll hook up the regular belt since the short belt squeals like a pig. Then I gotta burp the coolant system, then I might try driving it. I'm scared to drive it though, I don't wanna mess anything up. :(
 
#6
When you turn the koeo the pump primes. How old is your pump? I know when the pumps are starting to go and with the key off they start to lose pressure if there is a problem. A good pump will prime and should hold the pressure and shouldn't drop very fast. But that's if there isn't any leaks.
 
#8
94gts said:
my regulator will do the same thing when you turn the key, the pressure drops off. but i have no running issues with the car :shrug:
Click to expand...

Yea as far as I know mine runs all right.....

EXCEPT IT KEEPS SURGING AND DYING!!! :fuss:

No but seriously it holds pressure when its running. But it's at 40psi at idle and 50 under load, too much huh?
 
#9
CManT1914 said:
Yea as far as I know mine runs all right.....

EXCEPT IT KEEPS SURGING AND DYING!!! :fuss:

No but seriously it holds pressure when its running. But it's at 40psi at idle and 50 under load, too much huh?
Click to expand...


yea 50 under load is way too much. take the vacum line off the regulator then set the fpr guage to say 43(with the line off this is what it will be under load).

the surging and dyng mite be vacum related. thats what my cars issue was. after the heads and intake it wouldn't idle for anything. turns out i had the vacum lines all outta wack
 
#10
94gts said:
yea 50 under load is way too much. take the vacum line off the regulator then set the fpr guage to say 43(with the line off this is what it will be under load).

the surging and dyng mite be vacum related. thats what my cars issue was. after the heads and intake it wouldn't idle for anything. turns out i had the vacum lines all outta wack
Click to expand...

Here's a stupid question, but it's been a long time since I had to adjust my fuel pressure. With the vacuum line off of the AFPR do you plug the vacuum line while adjusting the fuel pressure or just let it hang?
Tim
 
#11
18mustangs said:
Here's a stupid question, but it's been a long time since I had to adjust my fuel pressure. With the vacuum line off of the AFPR do you plug the vacuum line while adjusting the fuel pressure or just let it hang?
Tim
Click to expand...
Yeah, cap the vac line. Technically it arguably makes a difference.

FWIW, some aftermarket regulators bleed off pressure very quickly when the car is off (which is not bad - no need to keep high pressure in those lines 24/7).

Good luck Chis. :nice:
 
#12
HISSIN50 said:
Yeah, cap the vac line. Technically it arguably makes a difference.

FWIW, some aftermarket regulators bleed off pressure very quickly when the car is off (which is not bad - no need to keep high pressure in those lines 24/7).

Good luck Chis. :nice:
Click to expand...

Thanks for clearing that up. My Aeromotive holds pressure well, but if it sits over night it zeros out.
Tim
 
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