Fuel leak at accelerator pump cover. 1978 GTS. Please help.

The diaphragm could be broken/split, or where the diaphragm material serves as the gasket could be leaking. Is it leaking out the edge (maybe tightening the screws would help), or leaking out where the lever goes in to actuate it (needs new diaphragm)? See Fig 13.4 on page 176 of the Haynes Weber Manual.

 

Need to replace the accelerator pump.

 

I would replace all 4 of them.

 

If stored for a long time without starting engine, the fuel in the accelerator pump dries out and rubber becomes like plastic. Then when you operate the throttle, cracks in the rubber diaphragm.
I run my 308 at least once a week to full operating temperature. I drive it.

 

I always wear Nitrile Gloves or Mechanic gloves when working on the 308.
No gashes, cuts, or exposure to gasoline, grease, coolant, or oil.

 

Go here to synch carbs
http://www.birdman308.com/service/sync/carb_synch_tutorial.htm

 

Are you using the stock .55 idle jets?
If so, replace with .65 idle jets.
Today’s gas is not the same gas in the 70’s.

Ignition timing all good?

 

Owner Manual shows .55.
I was able to get very good combustion with .65 and opening idle mixture screws to 3.75 turns.
Idles at 950 rpm.

 

Leak probably caused by old cracked accelerator pump diaphragm. If you look at the design it appears it would leak not only from an edge crack but also a crack in the body of the diaphragm. Its been my experience, however, that they last and last. I changed mine in 1982 and they still work fine even though the car sat for 18 years or so without ever being moved or started. I run .60 idle (.55 is stock) and 130 mains (125 is stock) and it runs great on CA gas. And yes the carbs are a PITA to work on while on the car for anything other than changing jets and float adjustments. I just take mine off to do any major work. They can also leak from the lead plugs located in various places in the carb body. I have managed to stop all the plug leaks by re-pinging them. I also had an annoying leak on the drivers side front (of course) choke housing which had a burr for some reason that was causing the leak. Mine sill have all the original 1978 gaskets and spacers along with the 1982 accelerator pump diaphragms and have no leaks or gas stains.

 

Dane
I have a couple of bent 13mm open end wrenches I use to facilitate removing the carbs. One is bend for the right offset while the other is for the left. With these I can remove any one of the four with no problem. And yes for the purists one of the wrenches is part of the original tool kit.

Barry

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Dane
A plugged or restricted idle jet will cause the cylinder to drop out at idle. You can get all the jets out for inspection or changing without removing the carbs. If you are having trouble with the idle I would check the idle jets to insure they are clean. 140 main jets sounds pretty rich to me. I also run the next size up squinters (accelerator pump nozzles). As I believe it they give crisper throttle response. Probably a carry over from my drag racing days. There are many threads on setting up and syncing the carbs. Just remember there are no absolutes. So don't worry if your stuff doesn't exactly match the parameters espoused in the various threads. For example I don't think mine would even idle with .40 idle jets so you must have different idle screws (I understand there are several with different tapers) then I do. Even with .55 idle jets my idle screws a 4 to 4 1/2 turns out. Anything less and the cylinder drops. One thing I have discovered via lots of messing around is its best to set the final idle mixture after a long enough drive to get everything hot and normalized. If I set mine after bringing it up to temp in the garage it will always change a bit if I reset it after a drive.

 

Dane
Your welcome. I must have missed the part about power loss failures. Keep in mind that the carbed 308s are really simple even though I had a hell of a time with an aftermarket electronic ignition (installation error). If you describe the power failure I'm sure someone on this board can help. This site along with Birdman's is my bible.

Barry