Baffling Fuel Pressure issue not pump,filter
Thread Starter
Intermediate
Joined: Apr 2019
Posts: 49
Likes: 16
From: New Yorkistan
Baffling Fuel Pressure issue not pump,filter
Quick story, I bought a 91 C4 from Copart for a ride while I await my C8. The car drove on the trailer (with a new battery). When I got home I noted the water pump was bad and changed that. Car hasn't had fuel pressure since even with a pressure gage facing me in the driver seat. Changed out with new AC delco stuff both fuel pump and fuel filter the old one rattled when I pulled it out. Odd issue now is that I have plenty of pressure at the fuel lines by the pump but near none at the schrader valve in the front. Pulled the hose off the regulator and no fuel coming out there and the pressure at the rear lines lasts overnight with more pressure on the supply side than the regulator side. I have a new AC delco pressure regulator I am about to install but have a feeling it won't do anything. BTW injectors all Ohm out okay and the car runs great on fuel pumped directly into the throttle body.
Could it be something I did when doing the water pump? Or maybe a plugged fuel line?
Thanks,
John
Could it be something I did when doing the water pump? Or maybe a plugged fuel line?
Thanks,
John
Thread Starter
Intermediate
Joined: Apr 2019
Posts: 49
Likes: 16
From: New Yorkistan
I have ordered the Factory Service Manuals for the car so hopefully they will go into detail about how the line can be replaced. I might just temporarily run a new line from the tank to ensure the issue is the line.
Thread Starter
Intermediate
Joined: Apr 2019
Posts: 49
Likes: 16
From: New Yorkistan
Awesome Idea. Brand new filter on there already. I will also pull off the fuel line and try shooting air through that side to see what happens. Thanks for the idea!
Safety Car
Joined: May 2001
Posts: 4,757
Likes: 1,647
From: Fairfax Virginia
Check your Fuel Pressure Regulator to be sure that your regulator is not the cause of your problems. You can remove the vacuum hose from it and take a sniff, if you smell gasoline then it is likely that your diaphragm is damaged. They are not too bad to install. If the regulator is bad it will do all sorts of strange things.
Just be aware that the fuel "supply" and "return" lines can both rust shut internally. This has been made easier with Ethanol in our gasoline. I would try to clear it by blowing through it. I used carburetor cleaner first hoping it would break up the blockage. I got fuel through at pressure but insufficient volume to allow the Corvette to run 25 mph. I ended up replacing the fuel "supply" hose as it was the culprit.
The best way of testing the system is to remove the fuel filler cover and access the three wires going in to the pump and level sender. The Big wire was the Fuel pump HOT, the middle wire was for the fuel level sending unit and the last was a ground wire. I applied power to the Fuel pump motor and had the filter detached and a hose taking the fuel to a safe container. This will tell you that the pump is working properly which is important!
Just be aware that the fuel "supply" and "return" lines can both rust shut internally. This has been made easier with Ethanol in our gasoline. I would try to clear it by blowing through it. I used carburetor cleaner first hoping it would break up the blockage. I got fuel through at pressure but insufficient volume to allow the Corvette to run 25 mph. I ended up replacing the fuel "supply" hose as it was the culprit.
The best way of testing the system is to remove the fuel filler cover and access the three wires going in to the pump and level sender. The Big wire was the Fuel pump HOT, the middle wire was for the fuel level sending unit and the last was a ground wire. I applied power to the Fuel pump motor and had the filter detached and a hose taking the fuel to a safe container. This will tell you that the pump is working properly which is important!
