SOLUTION: 79/80 hard starting issue

[spidernut]

If you have a 79/80 carbureted Spider and have the irritating problem with the car not starting after it sits for a while because it is not getting fuel, I am reposting the solution because the last solution was buried in a thread. I keep hearing about this problem in various forums and hearing dozens of inaccurate solutions. Here's how to fix the problem once and for all so you can love your car again.

The primary cause of the problem is the carburetor float bowl emptying when the car sits for any length of time.

1. Ensure that the diaphragms for the accelerator pump (part 85 in the image below), power valve (part 15 in the image below) and auxiliary valve (part 20 in the image below) are not leaking. A leak in any of these will cause the float bowl to empty after the car sits for a while.
- Leaks in the accelerator pump diaphragm are obvious. You will see it leaking when the car is running - especially when you rev up the motor and activate the accelerator pump. The diaphragm is available through just about any parts supplier.
- A leak in the auxiliary pump diaphragm will result in fuel being pulled through the diaphragm into the vacuum line that leads to the auxiliary pump (part number 11 in the linked image). You will not see an external leak if this is happening. If the gasket (outer part) of the diaphragm is leaking, you may or may not see a visible leak. Look for fuel residue on the intake manifold beneath the auxiliary pump to determine if there is an external leak. This diaphragm is no longer available. You'll have to find a good used one. Chris Obert had them recently, but I don't see them on his site any longer. If it is a leak in the gasket part of the diaphragm, you can use a fuel resistant sealant to stop the leak so the float bowl won't empty out. Use a non-hardening fuel resistant sealant designed for this purpose. Use it very sparingly.
- The other possible source of a leak is the power valve diaphragm. Leak symptoms are similar to the auxiliary valve diaphragm. Last I saw, the only vendor who has this part is Midwest-Bayless.

2. Also check the orientation of the auxiliary pump vacuum line. It should point up not down. See the image for reference.

Also look to see if your fuel supply check valve located under the hood is functioning. It should not let fuel bleed back out of your fuel filter and into the gas tank. This will not affect fuel levels in the float bowl. The part is available from Midwest Bayless.http://marketplaceadvisor.channeladviso ... =261868029

While working on the fuel system, consider the following: Replace the fuel vapor check valve located beneath the car near the fuel tank. If you unscrew your gas cap and there is built up air pressure, the valve is bad. This check valve permits built up pressure in the tank to flow to the vapor canister but not in the other direction. This won't cause the starting problem but it can cause your filler pipe hose to burst if too much pressure builds up.

http://marketplaceadvisor.channeladviso ... =251937197

Hope this helps!

[speedracer]

Excellent info!

I've had this problem on my 79 for years now. It's not a problem when I run the car daily, but let her sit for a week or two and I have to pump the pedal a thousand times to get the carb loaded-up and get her fired up. Not the worst problem to have, but it would be nice to get in and fire her right up no matter how long she has sat.

[vandor]

Both of those diaphragms are available from us:

http://www.autoricambi.us/product/FU2-4 ... --1979-80/

http://www.autoricambi.us/product/FU2-4 ... --1979-80/

And also the choke pulloff diaphragm:

http://www.autoricambi.us/product/FU2-4 ... --1975-80/

[spidernut]

The carburetor rebuild kits reference the parts by different names than on the Autoricambi site. I'd recommend using the part names listed in the carb rebuild kits also in the search feature on the site. When I looked for the parts, I could not find them since the names are completely different.

Thanks for the link. I have two other 79s that will need carb rebuilds and I'll definitely be buying them! Thanks for the info!

[bradartigue]

To add: if the above doesn't eliminate the problem then you likely have a weak pump. They will pump fine when cold and when running warm, but don't develop enough pressure. If you have to use starting fluid on a hot engine that was just running fine, and the carb checks out, diagnose the pump pressure warm. Anything less than 3psi and it's too weak.

[Warren]

I solved my problem by installing an electric pump in the trunk and use it for priming the carb; switch under the dash. Will crank up very quickly. Used if it has been sitting for a while. Also an emergency pump if the mechanical pump fails.

[Holshot]

Subscribed for future... Good thread!

[spidernut]

The electronic fuel pump will fix the hard starting issue but will not fix the cause of the problem if you have the problem with your float bowl emptying after sitting any length of time. Many have mistakenly stated that the problem is caused by fuel bleeding back out of the fuel filter due to a poorly designed or faulty check valve. Though this is a very common problem, but there should still be enough fuel in the float bowl to start the car without doing a jig on the gas pedal. The benefit to the electronic fuel pump is that it refills the bowl when the ignition is turned on which alleviates the hard starting issue. Unfortunately, the leak is still present.