'79 Spider Restarting Problem

[bonsaiwino]

Hi guys, I have a '79 Spider (carbed). Here's the problem: after letting the car sit for at least 48 hrs. between starts, the car won't restart unless I put either some fuel or starting fluid down the carb. After taking off the top of the carb, I saw that there was no fuel left in the carb. I've hung the carb over my bench & poured a little fuel in it, but it doesn't appear to be leaking. I took the accel. pump & power valve apart, but the diaphragms aren't split & leaking. What gives? Could the fuel be evaporating that quickly (overnight)? How to remedy this situation? Thanks everyone, Don

[spidernut]

This is an extremely common problem, so don't be discouraged. The fuel can leak from several bad diaphragms, and also have a mysterious leak that can never be found...believe me, I've tried on my current carb. If you crank the engine long enough (which I do not recommend since it is really hard on the starter), it will bring up the fuel pressure and fill the float bowl again.

What typically occurs is that there are several diaphragms that can leak leaving the float bowl empty. First check the accelerator pump diaphragm, then the power valve diaphragm, then the auxiliary pump diaphragm. If any of them are leaking, the float bowl will empty. It is also important to ensure the gasket at the top of the float bowl is good.

I've bench tested several ADHA carbs with no diaphragm leaks and still had the float bowl empty with no sign of leaking. It can be infuriating. The easy fix is to replace the manual fuel pump with a low pressure electronic fuel pump.

Also, don't forget to check the inline check valve in the fuel supply line under the hood. There's also a vapor recovery check valve near the gas tank that should be checked regularly. If it is bad, you'll build up excessive pressure in the tank and can blow out the side of the fuel filler pipe that is made of rubber (it happened to me).

Hope that helps.