Fuel Pump/Pressure Problem
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
A little late but did you try to apply a test light to the FP fuse the same time you turned the key, should light up if relay is good? BTW guys, nice education on the check valve, toilet, and whatever. If ever in doubt I'll check back to this thread just to refreshen. 
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Racer
Joined: Sep 2005
Posts: 297
Likes: 0
From: Wauseon Ohio
no it did not light up. The problem was it would not start. Id crank it over and it wouldnt start. I thought i smelled gas so i pulled out a spark plug and it was dry. So i did what i thought was just jumping the fuel pump right from the fuse box, and it started up. That i decided was my relay. I recently put in a new cold start valve, so that should work, but to make sure i tested it and it works well. Now the fuel pressure was low, vaccum was good. I adjust the FPR and nothing happens to the pressure, this could be happening because the FPR has no pressure to work with. We'll see. What would it mean if i clamped off the fuel return line and the pressure came back up?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by Biff Buyer
no it did not light up. The problem was it would not start. Id crank it over and it wouldnt start. I thought i smelled gas so i pulled out a spark plug and it was dry. So i did what i thought was just jumping the fuel pump right from the fuse box, and it started up. That i decided was my relay. I recently put in a new cold start valve, so that should work, but to make sure i tested it and it works well. Now the fuel pressure was low, vaccum was good. I adjust the FPR and nothing happens to the pressure, this could be happening because the FPR has no pressure to work with. We'll see. What would it mean if i clamped off the fuel return line and the pressure came back up?
When I was testing my pump, when I clamped off the return line my pressure shot up to about 70psi quickly.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Bad pressure regulator. I still think you may have a blown fusible link.And for my friend-and I'm sincere, the purpose of the check valve on my boat tank was to prevent fuel from siphoning into the bilge area
if a fuel line were to fail.
if a fuel line were to fail.
Last edited by rick lambert; Apr 15, 2006 at 12:05 PM.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by Biff Buyer
What would it mean if i clamped off the fuel return line and the pressure came back up?
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Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by rick lambert
And for my friend-and I'm sincere, the purpose of the check valve on my boat tank was to prevent fuel from siphoning into the bilge area
if a fuel line were to fail.
if a fuel line were to fail.
Back to: "Funny about fuel pumps, I know on another post CFI-EFI stated that the only time a check valve leaks is when the engine isn't running. Never had one apart-I just wonder about that". Just like the faucet valve in your kitchen sink, even if it drips when turned off, it doesn't leak when you have the water turned on.
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Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by CFI-EFI
There has to be more to this boat fuel system than you are explaining. A check valve is simply a back flow preventer. If the valve is installed to prevent fuel from flowing from the tank to the engine, what does the engine run on???
Back to: "Funny about fuel pumps, I know on another post CFI-EFI stated that the only time a check valve leaks is when the engine isn't running. Never had one apart-I just wonder about that". Just like the faucet valve in your kitchen sink, even if it drips when turned off, it doesn't leak when you have the water turned on.
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Back to: "Funny about fuel pumps, I know on another post CFI-EFI stated that the only time a check valve leaks is when the engine isn't running. Never had one apart-I just wonder about that". Just like the faucet valve in your kitchen sink, even if it drips when turned off, it doesn't leak when you have the water turned on.
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with CFI. The check valve on the corvette fuel system should be and is a one way valve when working properly to let fuel flow one way when pumping and close when fuel has stopped flowing. In other words it keeps fuel from backing up when pump is shut off. I would say both you guys are correct in your own way.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
First-sounds like we agree about the regulator? Back to the boat, this was an older boat with mechanical fuel pumps on the engine-the way I see it the pumps actually by their action allowed the check valve to open allowing the fuel from the tank through the now open check valve
to flow-once again, if the fuel line ruptured-the check valve stopped any chance of fuel siphoning from the tank into the bilge area.
to flow-once again, if the fuel line ruptured-the check valve stopped any chance of fuel siphoning from the tank into the bilge area.
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Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by rick lambert
...if the fuel line ruptured-the check valve stopped any chance of fuel siphoning from the tank into the bilge area.
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Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
I also think, from your description, your AFPR may be bad being that adjusting it does nothing and it could be leaking. You intend to replace the FP anyway , do to high mileage, and this should eliminate one of the suspected problems. If not, I would check the AFPR. IMO You either have a weak pump or a leak in the system with 28psi. Where abouts on the car did you smell the raw gas? And also did you check the power at the fuel pump harness (I believe it is a tan wire)?
Last edited by RRT vette; Apr 15, 2006 at 02:06 PM.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
He may have smelled raw gas at the pressure regulator-he can pull the vac line off that and see if it's wet.Could explain his pressure problem.
Because of his power problem I did make a suggestion regarding the fusible link. 12 volts comes from the power tower behind the battery through a fusible link-at a point this branches off, running to the fp relay and the other branch if you will runs to the oil pressure switch.
This is from my FSM for an 87-not sure if it's identical for an 85.
Because of his power problem I did make a suggestion regarding the fusible link. 12 volts comes from the power tower behind the battery through a fusible link-at a point this branches off, running to the fp relay and the other branch if you will runs to the oil pressure switch.
This is from my FSM for an 87-not sure if it's identical for an 85.
Thread Starter
Racer
Joined: Sep 2005
Posts: 297
Likes: 0
From: Wauseon Ohio
i just put a new AFPR on it and a new diaphram couple of months ago. I installed my new fuel pump and relay and it runs great now. Tomorrow ill put the pressure gauge on it to fine tune it, but for now, it ran alot better than what it did with the stock pump and relay. And it starts up right away everytime. thanks guys. If anything else comes up while im still working this out, ill let ya know.
-Matt-
-Matt-
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by Biff Buyer
i just put a new AFPR on it and a new diaphram couple of months ago. I installed my new fuel pump and relay and it runs great now.
-Matt-
-Matt-
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