66 Lemans fuel issue

[algtrader]

Dear Lemans forum guys,

I have a difficult issue going on with my 66 Lemans I could definitely use your advice.

The engine starts but fails to stay running. I have a glass fuel filter right before the Holley carburator and I can see that there is hardly any fuel in the filter when this problem happens.

Here's some pictures of the fuel filter:


Now here's the catch.... I would wait until the next morning. Pour a cup of gasoline into the carburator, start the car and voila!... the engine would start and keep running! I would check the glass fuel filter and it will show almost full of fuel.

The car would be driveable with no problems. Then I would park the car in the driveway and after 30 minutes, I would check the fuel filter and it would have almost no fuel in it.

Here's what I have done so far troubleshooting:
1. Check the car has gas - yes. Half a tank full.
2. Replaced the fuel tank sending unit with a new one.
3. Check the fuel line between fuel pump and fuel tank for clogs.
4. I haven't replaced the fuel pump because the symptoms don't point to that part being the problem.

Thanks for allowing me to consult with you.

Regards,

Al

 

[melsg5]

1. If there is no fuel in the gas filter after letting the car sit for 1/2 an hour with the engine off at the very least the one way valve in the pump is shot.
2. Have you done a fuel pressure test?
3. Do you have the original vented gas cap?

 

[algtrader]

1. If there is no fuel in the gas filter after letting the car sit for 1/2 an hour with the engine off at the very least the one way valve in the pump is shot.
2. Have you done a fuel pressure test?
3. Do you have the original vented gas cap?

Hi melsg5,

Thank your for the quick reply.

1. The one -way valve in the fuel pump is shot - is that why the fuel is flowing back to the fuel line from the fuel filter?
2. How do you perform a fuel pressure test?
3. I believe I have the original vented gas cap - the fuel tank has a inverted U-shape 1/4" stainless steel located where you put the fuel nozzle for venting gas fumes. Is this what you were referring to? Why?

Once again, thanks melsg5!

 

[melsg5]

1. Yes
2. Rent or buy a gauge and connect a "T" fitting right before going into the carburetor.
3. If you have a non-vented cap you will starve the engine for fuel and could collapse the gas tank.

______________________________

 

[cammerjeff]

Do what melsg5 said, plus PLEASE replace that glass fuel filter with a see thru 1 piece plastic one, Fram makes a good one. I have seen several engine fires over the years caused by leaking or broken old school glass filters!!!!!!!

 

[melsg5]

even better on the gas filter, drop the whole see thru concept and install a metal filter

 

[algtrader]

Update

Do what melsg5 said, plus PLEASE replace that glass fuel filter with a see thru 1 piece plastic one, Fram makes a good one. I have seen several engine fires over the years caused by leaking or broken old school glass filters!!!!!!!

Hi cammerjeff and melsg5

OK will do - I will replace the filter with a plastic or metal fuel filter. I've been told enough times and you guys have convinced me.

Update as of 12/18/16: I still have not successfully diagnosed my starting issue. I ordered a fuel pump from RockAuto and their came with only two nozzles - mine has 3: an inlet, outlet and relief connections. I emailed a picture to Ames Performance who said they can get it for me.

Nevertheless, it does not look like a fuel issue - I poured gasoline into the carb and started the engine - it would start but not stay running. I will need to go step by step using the Trouble Diagnosis guide in the Service Manual. But any advice would be great.

Also I noticed everytime I have this problem, I see the big radiator hose collapsed (see picture) . This is scaring me sh**t since it looks like there's a vacuum problem somewhere. Any deas on what this issue is?

As always thank you for the help!

 

[melsg5]

why would you say it's not the pump if it starts when you pour gas in and then stops?
anything unusual about your radiator cap? is it the correct cap, vented, no gasket where it meets the outside of the neck, only the round gasket in the center?

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[cammerjeff]

I still think you have a bad Fuel Pump

As for the upper Radiator hose collapsing, if it does it when the engine is cooling down, it is most likely a radiator cap not venting properly, and needs to be replaced.

If it is doing it any other time I have no idea.

 

[algtrader]

Update

It's about time! I finally resolved my starting issue.

The culprit was a loose exterior resistor wire to the ignition coil.

I will still replace the fuel pump since it has a lot of miles on it.

Thanks to everyone who helped!