No gas in clear fuel filter but car runs great, why??? [Archive] - Team Camaro Tech

: No gas in clear fuel filter but car runs great, why???

Erik Beckett
Apr 19th, 05, 06:42 PM
After getting my new 383 dialed in and running really good, I just cant figure out the fuel system on this car. I have a Holley 110 mechanical fuel pump running into -6 hose to a NAPA Gold clear filter right up to the carb. Sometimes the filter is full at idle but most of the time the filter only has about 1/4" of fuel in it and the fuel pressure guage reads zero but the car runs great. Sometimes it is full and reads about 7-8 at idle but for the most part always reads zero pressure. I have the stock lines going into the stock tank with an SS cap on the back. Should I be worried about this or since its running fine its obviously getting fuel. I will be taking it to the track sometimes and dont want any problems. This car should run low 12's to high 11's.

Any suggestions? I can get pics of setop if needed.

Thanks, Erik

Apr 20th, 05, 08:43 AM
Some thoughts pop into my head,
1. Gas cap a vented one? An unvented cap will create a vacuum in the tank and after awhile, no fuel.
2. Pump not primed?
3. Leak in fuel line from tank forward? A pinhole in the steel line, a dry rotted fuel hose at the tank sending unit, or right behind the pass rear wheel.
4. Sending unit sock at pickup is broken and restricting the line?
5. Fuel line close to an exhaust component and causing fuel to evaporate?

I take a long, 6-8 foot, clear vinyl hose and place it over the pump inlet tubing and dump it into a gas can. The long length so I can see the hose and delivery from the rear of the car. I remove the gas cap and insert an air nozzle covered by a rag into the fill tube. I pressurize the tank and watch the flow from the vinyl hose. It should be coming out very good. I give the tank about a 3-5 second shot of air, don't worry, you're not going to damage anything with short squirts of air.

If no leaks are found, you could do a vacuum check on the pump to see if it does draw a vacuum on its inlet side with a vacuum gauge. It should at least develop 10 in/Hg. of vacuum.

You might even hook your Mighty Vac gun to the fuel line and see how easy/hard it is to suck fuel from the tank.

Fuel filter should be full. It could be due to evaporization. You might try a different brand and hopefully get a 'summer' mixture. Winter mixtures don't do well in warmer climates.

Joe Harrison
Apr 20th, 05, 01:57 PM
Mine does the same thing with and edelbrock carb and stock fuel system. I know I don't have any leaks and don't have restriction at the fuel pick-up in the tank. Never been able to figure it out. I don't have a fuel pressure gauge on it to see what's happing so no info there. I have had 4 different fuel filters and they all do the same thing. I have thought maybe a weak fuel pump? Sometimes it's full and sometimes you don't see much fuel in it at all?


Apr 20th, 05, 10:05 PM
If your carb is getting too hot, the fuel will expand as vapor and push the fuel back too. I solved that problem on mine by putting a spacer between the carb and manifold.

Erik Beckett
Apr 21st, 05, 04:50 AM
I know i dont have any fuel leaks anywhere and i cant imagine the gas is evaporating because it will do it even when the motor isnt warmed up yet. I have a feeling it has to do with pressurizing the system. I know my last car did the same thing as well. I have a feeling alot of cars are like this but they dont run a clear filter to actually see it happen. I will try to pressurize the tank and see what happens.

Any other thoughts?

Thanks, Erik

Apr 21st, 05, 09:02 AM
As seen in my sig, I have a MCSS. Now has a carb and mech fuel pump with a clear filter at the carb inlet. Its always full of gas.

You can "tee in" a vacuum gauge on the fuel pump inler side to see what the pump is sucking. You can even run the gauge up to the w/shield and duct tape it on to view while driving.

Is the filter full when first startup of the day, when everything is at ambient temperature?

Apr 21st, 05, 10:24 AM
Both my cars have the same issue, clear filter, sometimes full, sometimes almost empty, always run great. I gave up on trying to figure it out. Didn't ever check the pressure though. One has a Carter high vol pump, the other I've removed the sock, replaced the pump, the rubber lines and cap. There seems to be no pattern to it. The '69 had been sitting for awhile and last night I hit the switch and it barely fired and the filter went from empty to full in a blink. Other times it's idling almost empty. I found some old post on this sometime back but never a clear resolve. I've decided it must have something to do with which way the wind is blowing.

Joe Harrison
Apr 21st, 05, 02:00 PM
Mine is the same as posts above. It never seems to be the same, I do run an e-brock carb anyone else running one with the same problem?


Erik Beckett
Apr 21st, 05, 04:18 PM
Well, today I installed an Autometer fuel pressure gauge and it works now. But I still dont understand why the fuel filter would not fill up to even half way. I am getting a steady 7.5 on the gauge so that makes me feel better.

Thanks, Erik

Apr 21st, 05, 05:01 PM
Joe, both mine are Holleys