Fuel System operation
Thread Starter
Drifting
Joined: May 2020
Posts: 1,663
Likes: 702
From: Baton Rouge, Louisiana, metro area
Fuel System operation
General question that is straining my already weak brain.
1991 Corvette. Stock.
Testing the fuel pump and general system.
I connected a straight fuel line to outside the car.
I plugged the Return Line and Charcoal Vent ports. I left the Vent on the fuel manifold open to the atmosphere. Tightened the gas cap.
I ran the pump for about two minutes. The gas is pumping fine.
I turned the pump off.
It now wants to continually siphon at low volume. I have tried draining the line, taking the cap off, ensuring the vent is open, back-blowing through the fuel line. The gas still siphons out.
I finally went with “flow” and just put the line on the capped off Return line on the pump manifold. I will just let it siphon back into the tank until I figure out this mystery.
Please educate me on how to stop the siphon flow without actually lifting the pump itself out of the fuel.
1991 Corvette. Stock.
Testing the fuel pump and general system.
I connected a straight fuel line to outside the car.
I plugged the Return Line and Charcoal Vent ports. I left the Vent on the fuel manifold open to the atmosphere. Tightened the gas cap.
I ran the pump for about two minutes. The gas is pumping fine.
I turned the pump off.
It now wants to continually siphon at low volume. I have tried draining the line, taking the cap off, ensuring the vent is open, back-blowing through the fuel line. The gas still siphons out.
I finally went with “flow” and just put the line on the capped off Return line on the pump manifold. I will just let it siphon back into the tank until I figure out this mystery.
Please educate me on how to stop the siphon flow without actually lifting the pump itself out of the fuel.
Drifting
Joined: Jan 2005
Posts: 1,353
Likes: 324
From: San Antonio Tx
You could remove the fuel cap and then blow back through the line until all or the fuel is out of the line. That would break the siphon. I recommend using an air compressor. Gas tastes nasty.
Thread Starter
Drifting
Joined: May 2020
Posts: 1,663
Likes: 702
From: Baton Rouge, Louisiana, metro area
Thanks for the response.
I tried that at first ( yea, the hose tasted nasty), however, the line is connected to the fuel pump and would not blow back through the pump.
I am thinking there is a check valve in the pump to keep the fuel system primed between operation. Feeding it back into the Fuel Return line worked.
I ordered a good quality brass gasoline rated shut off valve that I will install on the end of the fuel line to use temporarily while I am doing this work.
I tried that at first ( yea, the hose tasted nasty), however, the line is connected to the fuel pump and would not blow back through the pump.
I am thinking there is a check valve in the pump to keep the fuel system primed between operation. Feeding it back into the Fuel Return line worked.
I ordered a good quality brass gasoline rated shut off valve that I will install on the end of the fuel line to use temporarily while I am doing this work.
Pro
Joined: Aug 2023
Posts: 520
Likes: 585
From: CenTex
If it helps, I use silicone caps to stop the flow. I have a variety pack of them and they do a good enough job. They also make silicone plugs which should work better because you won't need to push the nut back on the line for the cap to fit, just push the plug in the line, and it would be a tighter fit.
The cap set I bought...
What I would use instead, I didn't see the set of caps and plugs when I got mine...
The cap set I bought...
What I would use instead, I didn't see the set of caps and plugs when I got mine...
