fuel system question
Thread Starter
Advanced
Joined: Jun 2008
Posts: 51
Likes: 0
From: Manchester NH
fuel system question
92 coupe auto
Im having hard starting issues
I put a fuel pressure tester on the fuel rail test port. I turned the key to the on position and I could hear the fuel pump energize for 2 seconds and then the gauge went to 43 psi and then a 1/4 second later I heard "pssss" (sounded like air coming out of a balloon) for about a second and the gauge dropped to zero. I tried it a few times and the same thing happened. At first I thought it was the gauge not being properly seated on the test port. But then I removed the gauge and the same thing happened, the pump energized and then I heard the sound. The haynes manual says if the pressure doesnt stay steady and drops below spec to check the fuel filter(changed 2 weeks ago) the fuel lines (the car runs great once it fires) and if those check out to change the fuel pump (I hear the pump energize every time). My question is what keeps the fuel pressure steady after the fuel pump shuts off after 2 secs. Is it the easy answer...change the fuel pump?
Im having hard starting issues
I put a fuel pressure tester on the fuel rail test port. I turned the key to the on position and I could hear the fuel pump energize for 2 seconds and then the gauge went to 43 psi and then a 1/4 second later I heard "pssss" (sounded like air coming out of a balloon) for about a second and the gauge dropped to zero. I tried it a few times and the same thing happened. At first I thought it was the gauge not being properly seated on the test port. But then I removed the gauge and the same thing happened, the pump energized and then I heard the sound. The haynes manual says if the pressure doesnt stay steady and drops below spec to check the fuel filter(changed 2 weeks ago) the fuel lines (the car runs great once it fires) and if those check out to change the fuel pump (I hear the pump energize every time). My question is what keeps the fuel pressure steady after the fuel pump shuts off after 2 secs. Is it the easy answer...change the fuel pump?
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
Your fuel pressure regulator hold the pressure until the car starts.
If the pressure drop to zero right away, one of 2 (or both) things are wrong:
The diaphragm / bladder in the regulator is ruptured, and gas is escaping into the vacuum supply to the regulator. Motor may bog down under acceleration from fuel gettin' sucked in where it ain't supposed to go. Pull the vacuum tube that goes to the FPR, and see if you can get gas out - NOT just a smell.
Another thing ( ...
There's a few more things too that I'm realizin' here - check valve in fuel feed line, among others...
You need the fuel delivery diagnostic procedure...
DON'T buy a fuel pump at this point...
If the pressure drop to zero right away, one of 2 (or both) things are wrong:
The diaphragm / bladder in the regulator is ruptured, and gas is escaping into the vacuum supply to the regulator. Motor may bog down under acceleration from fuel gettin' sucked in where it ain't supposed to go. Pull the vacuum tube that goes to the FPR, and see if you can get gas out - NOT just a smell.
Another thing ( ...
There's a few more things too that I'm realizin' here - check valve in fuel feed line, among others...
You need the fuel delivery diagnostic procedure...
DON'T buy a fuel pump at this point...
Burning Brakes
Joined: Apr 2006
Posts: 765
Likes: 0
From: Houston Texas
"The diaphragm / bladder in the regulator is ruptured, and gas is escaping into the vacuum supply to the regulator. Motor may bog down under acceleration from fuel gettin' sucked in where it ain't supposed to go. Pull the vacuum tube that goes to the FPR, and see if you can get gas out - NOT just a smell."
Also check to make sure there is no gas in the oil pan. It can get sucked down into the pan.
If one or more injectors have failed completely (leaking), it would not hold pressure at the regulator test port and you would have flooding of those cylinders and no fuel pressure to the other cylinders causing a hard start situation.
Also check to make sure there is no gas in the oil pan. It can get sucked down into the pan.
If one or more injectors have failed completely (leaking), it would not hold pressure at the regulator test port and you would have flooding of those cylinders and no fuel pressure to the other cylinders causing a hard start situation.
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
Good point E&C - I was tryin' to remember that very thread.
Apparently a bad injector WILL let pressure drop to zero right away. jm22 - see FICINJECTORS' diagnostic thread for injectors video.
Apparently a bad injector WILL let pressure drop to zero right away. jm22 - see FICINJECTORS' diagnostic thread for injectors video.
Thread Starter
Advanced
Joined: Jun 2008
Posts: 51
Likes: 0
From: Manchester NH
I forgot to mention something
If i turn the key and crank for half a second then turn off then crank again the car fire right up 90 percent of the time. So what im trying to say is:
crank (1/2 second), off, crank (1 second), fires right up and runs great
Its think im catching the fuel pump right when its primed the rail before whatever is causing the problem to make the fuel pressure drop
crank (1/2 second), off, crank (1 second), fires right up and runs great
Its think im catching the fuel pump right when its primed the rail before whatever is causing the problem to make the fuel pressure drop
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
Better check the oil for gas in it you are dumping a lot of gas somwhere and if it is getting into the cylinders you WILL have a major problem. In fact I would not drive it till you solve the issue and change the oil.If you are hearing that Psssst sound at the intake I doubt it will be the check valve in the tank and both suggestions above are valid.
Last edited by Redeasysport; Aug 5, 2008 at 03:28 PM.
