engine and drivetrain Fuel problem???

[richinatlanta]

So, I've only had my car on the road for about 2 or 3 weeks now and love the heck out of it!  (1976 Base).  Here's the problem I've been having lately and need some advice:

 

Occasionally when driving, I'll get about 10 miles down the road and it starts to sputter, like it's the fuel filter.  I'll pull over and change out the fuel filter then she picks right up and runs fine for another 10 miles (sometimes 20 or more) then it'll do it again.  What's odd is that the fuel filter is clean!!!!  

 

Now when I first got her running this seemed normal, as I expected some garbage in the filter (and there was), but now the filter is clean each time. 

 

Could it just be remnants of bad gas I need to burn up still, or a fuel pressure issue? 

[jmr_1602]

I'd first check the mesh screen on the fuel sender in the tank. A lot of them get clogged or they fall off.

Also, mechanical or electronic fuel pump? I had similar issues before, and my elec fuel pump seemed to be working, but under throttle it would cut out.

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[richinatlanta]

jmr_1602,

 

Thanks for the advice.  I'm willing to bet the mesh screen is the problem.  I'll pull it tonight and keep you posted on the results.

[TobyB]

If it keeps doing it after you clean the screen, try just taking the fuel cap off.

 

If there's an air leak in the supply line (not too uncommon) then any negative

pressure in the tank interferes with fuel delivery. 

 

Do you end up cranking a long time after it sits for a few days?

 

t

[richinatlanta]

TobyB, When it sits for a few days it cranks right up.  When it's warm, I have to crank it and pump it a few times.

[jimk]

then any negative pressure in the tank interferes with fuel delivery.

Which may mean the tank vent is non-functional.  After years and years, the line can have condensed fuel/moisture in it and setting at a low point.  Blow it out, but first disconnect both ends and put a rag over the exit or there will be another mess to clean up.  When I was on carb, mine needed cleaning.

[richinatlanta]

This is a great thread!  Lots of excellent advice.  Thank you!

[richinatlanta]

You guys nailed it.  It was the sending unit and the tank vent.  Blew it out, replaced the sending unit and she starts right up like she's fuel injected now!  The sending unit was missing the screen.  I took it apart and it was rusty and had some crud built up in it.  I bought a new fuel pump too but haven't installed it yet.  Want to drive it for a few days and see if any other issues surface.

[Utah02]

I'd first check the mesh screen on the fuel sender in the tank. A lot of them get clogged or they fall off.

Also, mechanical or electronic fuel pump? I had similar issues before, and my elec fuel pump seemed to be working, but under throttle it would cut out.

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I've got this problem. Electric fuel pump and under throttle it cuts out at 4k rpms. What did you do to fix it?

[richinatlanta]

Utah02,

 

I had to replace the fuel sending unit.  My screen was missing and it was in terrible shape.  I also blew out the lines to the vapor canister.  They were full of sludge.

[M3M3]

thanks for getting back and closing out the thread with how you fixed it!