Air in fuel filter

[Okiedokie]

On my 46 coupe I have an Airtex electric fuel pump mounted on the frame just in front of the gas tank. Yesterday I got stuck in a major highway jam due to a trafic accident. Probably three miles creeping along. This was a slowdown after 1 1/2 hours at 70 mph. As the traffic cleared and I accelerated the car began to hesitate and stumble, no question to me it was fuel related. At the next exit I pulled off, even though it has smoothed out for the most part. Time for a break anyway. I open the hood for a look an noticed that air bubbles were appearing in the clear filter I have on it. Wonder how that happens, any ideas? Thanks, Joe

[Carnut]

If you have a fuel filter like in this pic, I'd remove the insides and see if makes any difference.



I replaced one electric fuel pump, installed a MSD Ignition system, Dist, Box, Coil and Wires in an attempt to fix a problem of stalling and dying after running 60mph or so for 20 or 30 mi.

Seems the fine mesh screen in the filter clogged up but wasn't really visible to me. Out of exasperation I removed the filter and fixed my problem.

[Okiedokie]

I will check it, thanks for the reply.

[enjenjo]

Under the conditions you describe, I would suspect vapor lock, particularly if it cleared up soon after you started driving at speed again.

I have had this problem with several cars with carburetors in the last 5 years or so. The oil companies used to reformulate gasoline in the summer to stop this, but since virtually all cars are now fuel injected, they no longer worry about it.

The first thing to check is that the fuel line does not run near the exhaust, particularly with headers. I have had cars with manifolds with no problems, that started doing this when headers are installed. You can insulate the line, but in most cases it doesn't stop[ it, just delays it a bit.

I am not a big fan of that type fuel filter, I have seem at least two of them break, causing engine fires.

Best fix I have found is a return line that allows the fuel to circulate back to the tank when the demand is low, so you are not overheating the fuel in the line causing it to vaporize.

Weatherhead has an in line check valve that is adjust able from about 3 PSI to 10 PSI. Part number is 63x4 for 1/4" or 63x5 for 5/16". You can set them just above your ideal fuel pressure, and they will open, allowing fuel to recirculate back to the tank when idling for long periods. Your return line should be submerged in liquid fuel in the tank to cut down on vaporization in the tank.

You can also use a bypass fuel regulator to do the same thing. There are several brands out there that will do this.

[Okiedokie]

Thanks Joe, that is the second time I have heard the engine fire deal, so I will replace that one for sure. A return line to my Tanks gas tank would be a chore, but maybe worth looking into. Guess I thought the electric ppump would not experience vapor lock. Thanks once again for your input.

[Harry]

It's not the electric fuel pump that causes vapor lock, it's the heat boiling the gas, which creates bubbles in the fuel. Are your fuel lines close to your exhaust?

[enjenjo]

Thanks Joe, that is the second time I have heard the engine fire deal, so I will replace that one for sure. A return line to my Tanks gas tank would be a chore, but maybe worth looking into. Guess I thought the electric ppump would not experience vapor lock. Thanks once again for your input.

The electric pump is better, but not a cure all. In many cases with a mechanical pump, it would have stalled out.

[Okiedokie]

Sorry for the double thread, by the time I had looked the 60 minutes was up. Harry thanks for your replys also. I know that the elec pump wouldn't cause vapor lock, just thought it would help prevent it. No my lines are not by the exhaust. Since this was a first I am contributing it to the three mile creep on a 90 degree humid day. If it occurs again, I will address it again. Thanks guys. Joe

[wayne petty]

one thing...    what type of venting system are your running on the tank.

a few of you will remember my boat voyage back in 2001 or was it 2002.  where the day tank vent was closed and the tank totally full...   and we lost the left engine .. then the right engine.. then he main generator.. mid channel.. a rock lined channel in a 104 foot wooden hulled boat.. when i opened the vent valve i could hear the air rushing in...



empty fuel filters when the engine is running with an electric fuel pump kinda indicates a similar problem...

there are several threads on venting fuel tanks...  through carbon canisters taken from various cars.  this prevents the fuel vapors from filling your garage also...   shutting off the fuel pump and letting the carb run dry also reduced fuel vapors in the garage... but that was not your problem...

if you have one of the fuel pump vacuum testers that are available at any parts store..   you might pick up some of the now available 3/16 fuel line/hose.. and tee it into the suction line at the tank... temp thing... this way you can monitor fuel tank pressures ..   move it to the pressure side of the pump.. as long as your pump does not make over 15 psi... it will work...

the gauge is 4 inches and goes between 30 inches of vacuum and 15 psi..

[Okiedokie]

Filter was not empty, just air bubbles seeping into it. I am going to research the vent/return line. Thanks Wayne.