Fuel Pressure Drops after key "on"
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Joined: Jun 2010
Posts: 97
Likes: 2
From: Potomac MD
Fuel Pressure Drops after key "on"
Hey guys,
So i am back at school all settled in, bummer is the vette is back at home! No where safe to keep it in good ole New Haven CT.
The last project I was addressing was the fuel pressure issues. Anyways I installed an electric sending unit on the fuel rail so I can get an accurate guage reading right in the cab. It was a pretty straight forward install and I think is working great.
So here is the problem. When i turn the key to "on" without a crank the pressure jumps to about 50PSI, and then over about 2-3 seconds falls down to damn near 0PSI. So its not holding. Is that normal? The car starts after a few cranks and runs fine....
Thoughts?
So i am back at school all settled in, bummer is the vette is back at home! No where safe to keep it in good ole New Haven CT.
The last project I was addressing was the fuel pressure issues. Anyways I installed an electric sending unit on the fuel rail so I can get an accurate guage reading right in the cab. It was a pretty straight forward install and I think is working great.
So here is the problem. When i turn the key to "on" without a crank the pressure jumps to about 50PSI, and then over about 2-3 seconds falls down to damn near 0PSI. So its not holding. Is that normal? The car starts after a few cranks and runs fine....
Thoughts?
Team Owner
Joined: Jan 2003
Posts: 20,333
Likes: 262
From: Summerland B.C. Canada
Not normal.
Time to pinch the fuel lines above tank to isolate the pressure loss area. Mine was the pulsator, directly above fuel pump. Replaced it with a piece of fuel injection hose and 2 clamps.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Time to pinch the fuel lines above tank to isolate the pressure loss area. Mine was the pulsator, directly above fuel pump. Replaced it with a piece of fuel injection hose and 2 clamps.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Not normal.
Time to pinch the fuel lines above tank to isolate the pressure loss area. Mine was the pulsator, directly above fuel pump. Replaced it with a piece of fuel injection hose and 2 clamps.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Time to pinch the fuel lines above tank to isolate the pressure loss area. Mine was the pulsator, directly above fuel pump. Replaced it with a piece of fuel injection hose and 2 clamps.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Mine was the fuel pump check valve so I replaced the fuel pump...
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
Nope. Jon and I are thinking the thing might be possessed
I can't find any fuel leaking anywhere but the tests keep pointing to injectors. That's why I replaced the diaphram and pump again because I couldn't believe it was the injectors and I still don't think it's the injectors.
Theres a leak somewhere and I'll find it but it's like looking for a needle in a hay stack. I'm planning on replacing the EGR so then I'll have a chance to look more closely at the fuel rail seals. But I checked that before I put everything back together.
If I didn't love this car so much I'ld be trading it for a new camaro.
I can't find any fuel leaking anywhere but the tests keep pointing to injectors. That's why I replaced the diaphram and pump again because I couldn't believe it was the injectors and I still don't think it's the injectors.
Theres a leak somewhere and I'll find it but it's like looking for a needle in a hay stack. I'm planning on replacing the EGR so then I'll have a chance to look more closely at the fuel rail seals. But I checked that before I put everything back together.
If I didn't love this car so much I'ld be trading it for a new camaro.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Nope. Jon and I are thinking the thing might be possessed
I can't find any fuel leaking anywhere but the tests keep pointing to injectors. That's why I replaced the diaphram and pump again because I couldn't believe it was the injectors and I still don't think it's the injectors.
Theres a leak somewhere and I'll find it but it's like looking for a needle in a hay stack. I'm planning on replacing the EGR so then I'll have a chance to look more closely at the fuel rail seals. But I checked that before I put everything back together.
If I didn't love this car so much I'ld be trading it for a new camaro.
I can't find any fuel leaking anywhere but the tests keep pointing to injectors. That's why I replaced the diaphram and pump again because I couldn't believe it was the injectors and I still don't think it's the injectors.
Theres a leak somewhere and I'll find it but it's like looking for a needle in a hay stack. I'm planning on replacing the EGR so then I'll have a chance to look more closely at the fuel rail seals. But I checked that before I put everything back together.
If I didn't love this car so much I'ld be trading it for a new camaro.
Jake
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
Done everything but lift them out and look for leaks. But they're brand new so I doubt they're bad.
Gonna take the plenum off tomorrow so I can get a better looksee at all the connections and the injectors themself.
Probably call Jon and discuss with him.
Gonna take the plenum off tomorrow so I can get a better looksee at all the connections and the injectors themself.
Probably call Jon and discuss with him.
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Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Go ahead and lift them out. With them attached to the fuel rail, turn the ignition key on. The fuel pump will start for about 2 seconds, enough to pressurize the system. If you are losing pressure, and it's not leaking out of the injectors that you are looking at with a dark rag under each injector so you can tell if any are leaking, then it must be the fuel pump if you have replaced the fpr and pinched the line.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Go ahead and lift them out. With them attached to the fuel rail, turn the ignition key on. The fuel pump will start for about 2 seconds, enough to pressurize the system. If you are losing pressure, and it's not leaking out of the injectors that you are looking at with a dark rag under each injector so you can tell if any are leaking, then it must be the fuel pump if you have replaced the fpr and pinched the line.
Jake
Instructor
Joined: Jun 2008
Posts: 138
Likes: 0
From: Bridgewater Ma.
Nope. Jon and I are thinking the thing might be possessed
I can't find any fuel leaking anywhere but the tests keep pointing to injectors. That's why I replaced the diaphram and pump again because I couldn't believe it was the injectors and I still don't think it's the injectors.
Theres a leak somewhere and I'll find it but it's like looking for a needle in a hay stack. I'm planning on replacing the EGR so then I'll have a chance to look more closely at the fuel rail seals. But I checked that before I put everything back together.
If I didn't love this car so much I'ld be trading it for a new camaro.
I can't find any fuel leaking anywhere but the tests keep pointing to injectors. That's why I replaced the diaphram and pump again because I couldn't believe it was the injectors and I still don't think it's the injectors.
Theres a leak somewhere and I'll find it but it's like looking for a needle in a hay stack. I'm planning on replacing the EGR so then I'll have a chance to look more closely at the fuel rail seals. But I checked that before I put everything back together.
If I didn't love this car so much I'ld be trading it for a new camaro.
I also have a 90' with the same issues that you are experiencing with yours. I discovered the problem back in April and I'm just now getting around to trying to fix it. Link to my thread....
http://forums.corvetteforum.com/c4-t...tor-d-c-s.html
I pulled my injectors today and will be returning them to FIC this week for testing.
Go ahead and lift them out. With them attached to the fuel rail, turn the ignition key on. The fuel pump will start for about 2 seconds, enough to pressurize the system. If you are losing pressure, and it's not leaking out of the injectors that you are looking at with a dark rag under each injector so you can tell if any are leaking, then it must be the fuel pump if you have replaced the fpr and pinched the line.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Burning Brakes
Joined: Feb 2001
Posts: 769
Likes: 0
From: Granbury TX
Where is this wire? I have a 91 and my service manual mentions it but never zero's in on it's location or how to use it. Unlike earlier C4's, there is no provision in the ALDL to run the fuel pump. I've been looking for it for years.
