Won't start after sitting

[bradartigue]

When the accelerator pump is old it allows fuel to leak from the bowl into the venturi; overnight it will drain your carb into your motor.

If this symptom exists but the engine does NOT buck on acceleration, is this still the sign of a bad accellerator pump? Hoses and lines to the tank are new and tight so no air is being sucked in from anywhere.

Yes. Oddly enough the acceleration pump doesn't really have much to do with what we call acceleration. It is more in the transition between operating modes.

[gchocevar]

Hi there,

I have the same problem with my 79 spider. Rebuilt the carb, Put a new check valve in before the carb inlet, same problem I can let it sit for two days and it will fire right up. Give it week or two and you have to pump the heck out it for about 30 seconds.

I was thinking about putting in an electric fuel pump below the gas tank. Climbing under the car I spotted what looks like another original check valve. Can the fuel from the fuel line get pumped back to the fuel tank if this check valve was opened?

Greg

[bradartigue]

The factory original check valves likely don't work any longer...the ones in the engine compartment, if still plastic, are a hazard.

[valmontej]

I have the same problem but it can't be because of an older accelerator pump or leaking diaphragm. The carb is a new Empi 32/36 I just bought from Mark. So it must be a check valve? Where are these valves anyway and what do they look like?

[bradartigue]

These problems are likely nothing more than negative pressure in the fuel tank. Do you have a fuel return line? Is your vapor recovery system working? Is tank still vented or did you cap it all off?

A good, new, metal check valve can help. though slow leaks back into the tank don't usually have enough force to close the valve.

For cars without fuel return get a fuel filter that has a return line and use it. This normalizes pressure in the tank, especially when your vapor recovery is off.

Finally this may be simply a weak mechanical fuel pump -how old is it?

[valmontej]

Thanks Brad. I haven't been on this board for years! Since 2015 I think. Anyway I still have the problem and it's spring time again so I'll be going through this hard routine again. You mentioned the fuel pump - I believe it's the original! Can you believe that?!!

I bought the car in 2010 from the original owner and he's never replaced that pump. Hehe.

I've thought about installing an online electric pump to be turned on only to help prime the bowl in the carb and turning it off soon as it starts. I'll check out the other items you mentioned before I do anything like that. This car just sits for months on end and it looks like the handbrake calipers have seized and won't release! Anyway, I'm off getting it ready for my first spring drive. Thanks again!