1996,NO Start,High fuel Pressure
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
1996,NO Start,High fuel Pressure
HAPPY THANKSGIVING TO ALL. I have a 1996 Grand Sport That will not start after changing fuel pump. It was changed due to no start condition and no fuel pressure. Pump was 9 mos old and rusted lead snapped off. (SEE PIC) New pump and sending unit installed but needed a lot of cranking to start but ran so poorly that it couldn't be driven, Now it doesn't start. Fuel pressure regulator is original . I don't see any fuel when i remove vacuum line. Te fuel pressures are wild and does not stay at 40 See video. Now not starting. Only 2 codes set Random Misfire and Low voltage 02 sensor Bank 2:1
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
If the pump looked like that, I'd be suspicious of the whole fuel system, especially the injectors. Have you tested them? It looks like you have quite the fuel pressure dropoff the moment the pump stops, which doesn't seem right unless it's leaking from somewhere, like an injector or the FPR.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Your fuel pressure is too HIGH. It is 80psi while the pump is running. It should be about 45. If it is 80, that will probably make it flood. Try holding your foot to the floor and crank it. WOT during cranking enters "clear flood mode" by disabling the injectors. If it starts, the high pressure is flooding it.
Is it possible that the return line to the tank is restricted with rust? The line is made of steel, and is smaller in diameter than the supply line. It could also be the pressure regulator.
I don't worry about the pressure reading when the pump isn't running. The engine doesn't care what the pressure is when it is shut down. The drop-off means little if it won't run. Fix the high pressure. and go from there.
Is it possible that the return line to the tank is restricted with rust? The line is made of steel, and is smaller in diameter than the supply line. It could also be the pressure regulator.
I don't worry about the pressure reading when the pump isn't running. The engine doesn't care what the pressure is when it is shut down. The drop-off means little if it won't run. Fix the high pressure. and go from there.
Great catch! Since the fuel pressure regulator can be responsible for both the fuel pressure being too high and the fuel pressure dropping off when the car's shut off, it may be a really good idea to give it a close eye.
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
If the pump looked like that, I'd be suspicious of the whole fuel system, especially the injectors. Have you tested them? It looks like you have quite the fuel pressure dropoff the moment the pump stops, which doesn't seem right unless it's leaking from somewhere, like an injector or the FPR.
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
Oh wow, I was so focused on what it did when he turned the pump off that I ignored the needle spike while it was running. Yikes, yeah, if it's actually that high of a fuel pressure, the PCM won't be able to compensate at all--it thinks you have half that pressure, and so even if the injectors are working properly, they'd be pulsing at too high a duty cycle for that amount of fuel.
Great catch! Since the fuel pressure regulator can be responsible for both the fuel pressure being too high and the fuel pressure dropping off when the car's shut off, it may be a really good idea to give it a close eye.
Great catch! Since the fuel pressure regulator can be responsible for both the fuel pressure being too high and the fuel pressure dropping off when the car's shut off, it may be a really good idea to give it a close eye.
the 80 psi was with out running. With the ke in accessory, it spiked to 80 then down to 40 the after 10 min 5psi. Then I cranked engine. The regulator is original and looks corroded on the outside.No fuel dripping I just ordered one..When I installed pump I was super careful and confident it is properly installed.
Last edited by rhandle; Nov 26, 2020 at 12:45 AM.
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
If the pump looked like that, I'd be suspicious of the whole fuel system, especially the injectors. Have you tested them? It looks like you have quite the fuel pressure dropoff the moment the pump stops, which doesn't seem right unless it's leaking from somewhere, like an injector or the FPR.
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
Oh wow, I was so focused on what it did when he turned the pump off that I ignored the needle spike while it was running. Yikes, yeah, if it's actually that high of a fuel pressure, the PCM won't be able to compensate at all--it thinks you have half that pressure, and so even if the injectors are working properly, they'd be pulsing at too high a duty cycle for that amount of fuel.
Great catch! Since the fuel pressure regulator can be responsible for both the fuel pressure being too high and the fuel pressure dropping off when the car's shut off, it may be a really good idea to give it a close eye.
Great catch! Since the fuel pressure regulator can be responsible for both the fuel pressure being too high and the fuel pressure dropping off when the car's shut off, it may be a really good idea to give it a close eye.
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
A restriction after the fuel rail raise the fue pressure. That is what the fuel pressure regulator does. It could be a restriction in the fuel return line. You could temporarily disconnect the fuel return line after the regulator and run a hose to a bucket to see if that fix the problem.
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Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
I tried again to start the engine with the pedal down and she did fire. Very rich exhaust smell. I rechecked the FPR . Although there was no fuel dripping out of the vacuum line,it did seem wet and smelling the FPR it smelled STRONGLY like gasoline. Is that a bad FPR then? New FPR coming Saturday
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
Took the sending unit out for inspection. All is well installed. No twisted fuel lines. There is no rust and fuel looks good in tank . Also inspected fuel lines and all appears well. Is there any chance a blockage in the FPR is causing a high pressure. I drained the fuel rais and the fuel was the color of ****. Any ideas? Also if there was a block in the return line would the pressure drop to zero so quickly or stay at 80 psi? If there is a block wouldn’t it stay blocked?
Last edited by rhandle; Nov 26, 2020 at 12:43 PM.
Pro
Joined: Aug 2020
Posts: 647
Likes: 126
From: Liliha Bakery stuffing my face with coco puffs!
A restriction after the fuel rail raise the fue pressure. That is what the fuel pressure regulator does. It could be a restriction in the fuel return line. You could temporarily disconnect the fuel return line after the regulator and run a hose to a bucket to see if that fix the problem.
Last edited by stew86MCSS396; Nov 28, 2020 at 04:33 PM.
Pro
Joined: Aug 2020
Posts: 647
Likes: 126
From: Liliha Bakery stuffing my face with coco puffs!
Took the sending unit out for inspection. All is well installed. No twisted fuel lines. There is no rust and fuel looks good in tank . Also inspected fuel lines and all appears well. Is there any chance a blockage in the FPR is causing a high pressure. I drained the fuel rais and the fuel was the color of ****. Any ideas? Also if there was a block in the return line would the pressure drop to zero so quickly or stay at 80 psi? If there is a block wouldn’t it stay blocked?
Thread Starter
Burning Brakes
Joined: Jun 2007
Posts: 765
Likes: 49
From: West Palm Beach,Florida
Replacing FPR with ac delco OEM. Does anyone know what O ring do i need for the fpr /fuel line connection? Mine didn't come with one. I heard that they are hard to source and ******** buy the FPR take the o ring then return the fpr minus its o ring. I want the EXACT o ring . don't want a garage fire. Also What type of rubber fuel line do i need if i want to replace the both fuel lines at the rear of my Vette.They are both beat up from replacing the fuel pump a few times