Fuel Pressure Question
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
Fuel Pressure Question
Originally I posted a thread about fuel odor that I was getting only at the back of the car. Thought that the gas cap was a problem so I switched it but wasnt' quite confident that was the problem.
I was told to check the fuel pressure at the fuel rail and see if it held pressure overnight. After about 2 hours it dropped. Any thoughts?
I was told to check the fuel pressure at the fuel rail and see if it held pressure overnight. After about 2 hours it dropped. Any thoughts?
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
Originally I posted a thread about fuel odor that I was getting only at the back of the car. Thought that the gas cap was a problem so I switched it but wasnt' quite confident that was the problem.
I was told to check the fuel pressure at the fuel rail and see if it held pressure overnight. After about 2 hours it dropped. Any thoughts?
I was told to check the fuel pressure at the fuel rail and see if it held pressure overnight. After about 2 hours it dropped. Any thoughts?
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
After two hours is dropped to WHAT pressure??
I recently ran a pressure test on mine (1985). Started at 38 PSI, at one hour it was 27 PSI, two hrs 22 PSI and 23 hours down to 6 PSI. This kind of drop is not bad.
John
I recently ran a pressure test on mine (1985). Started at 38 PSI, at one hour it was 27 PSI, two hrs 22 PSI and 23 hours down to 6 PSI. This kind of drop is not bad.
John
Team Owner
Joined: Jan 2003
Posts: 20,315
Likes: 245
From: Summerland B.C. Canada
Mine would lose pressure within a few minutes, but still ran good. The pressure loss was due to a leak at the pulse dampener(directly above pump. I replaced it with a piece of injection hose and 2 clamps.
Diagnose where the pressure loss is, then fix it.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Diagnose where the pressure loss is, then fix it.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
So a slow pressure drop after shut down is normal? OK. As I mentioned, the gas smell only came from the fuel tank area. There aren't any signs of fluid leakage...just an odor. I replaced the gas cap, drove for about 20 minutes and no problem. It seems that the longer I drive the more the pressure builds up(no on the fuel rail, only when opening the gas tank).
Melting Slicks
Joined: Feb 2005
Posts: 2,135
Likes: 0
From: Sebastian Florida
St. Jude Donor '06
A Clogged canister is your most likely problem, I have seen it once and it had a strong gas smell.
You said it held for 2 hours and dropped, did it drop to 0 or what???
You need to give more details, otherwise we are just guessing at the problem.
You said it held for 2 hours and dropped, did it drop to 0 or what???
You need to give more details, otherwise we are just guessing at the problem.
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Race Director
Joined: Aug 2000
Posts: 14,130
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Cruise-In II Veteran
If there are no fuel leaks,its prob the vapor recovery system.There are a few very small rubber hoses on the driver side tank on that side of the car.
They connect to a metal line that runs under the drivers rocker panel area and vent the vapors to the cannister up front under the headlight.Remove the gas door lid assembly and look inside there at the top of the tank inside there...youll see the small valve with the hoses coming off it.
My former 86,the rubber hoses rotted away and also the metal line under the car was rusted inside.Its a very small line,very easily clogged.
I found the metal line was clogged after I used the airhose blowgun to try and blow air through it while a friend was up front feeling if air would come through,and it would not.
The cannister up front was also failing.The gas odor was pretty strong back there and I went under the car and used my nose to track it down.
I replaced the small rubber vapor hoses in back of the car at the tank,put a new metal line under the car,and replaced the hoses and cannister up front.No more gas smell.No more high pressure in the gas tank either.
They connect to a metal line that runs under the drivers rocker panel area and vent the vapors to the cannister up front under the headlight.Remove the gas door lid assembly and look inside there at the top of the tank inside there...youll see the small valve with the hoses coming off it.
My former 86,the rubber hoses rotted away and also the metal line under the car was rusted inside.Its a very small line,very easily clogged.
I found the metal line was clogged after I used the airhose blowgun to try and blow air through it while a friend was up front feeling if air would come through,and it would not.
The cannister up front was also failing.The gas odor was pretty strong back there and I went under the car and used my nose to track it down.
I replaced the small rubber vapor hoses in back of the car at the tank,put a new metal line under the car,and replaced the hoses and cannister up front.No more gas smell.No more high pressure in the gas tank either.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
The hard lines on my 86' rusted out. The section from the tank to the fuel filter was replaced.
The lines looked fine under the car, but once it turned up to go to the tank, the rust began, especially around the retaining clamps.
I also smelled raw fuel around the gas tank.
The lines looked fine under the car, but once it turned up to go to the tank, the rust began, especially around the retaining clamps.
I also smelled raw fuel around the gas tank.
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
Mike, when you say lose pressure, do you mean down to 0psi? If so, and the car is running fine, you probably have the problem agent86 had with his fuel lines. I'll let him comment on that. He has a nice trouble shooting guide that should help you out, it sure helped me!
edit, he already did comment on that, check post number 5 in this thread.
edit, he already did comment on that, check post number 5 in this thread.
