Most likely a fuel issue. Check fuel pump supply rate to make sure you are getting enough fuel to fuel distributor. Good idea to change the fuel filter and check the accumulator also. If all that is good then most likely you will need to rebuild the fuel distributor and maybe replace the injectors. I bought rebuilt injectors from Rock Auto and have pleased so far. If the plunger in the FD is sticking you will get very erratic engine behavior. Lots of o-rings in the FD also that don't like ethanol. FD rebuild is not that difficult, just visually intimidating and lots of lines to disconnect. I have rebuilt two of these for 78s I own. If you want to pay someone else then any of main 928 suppliers can help - 928 Intl, 928 Spec, 928 Classics, 928 Rus.

 

Is there a rebuild kit for the fuel distributor?

 

Again think about the engine reving to 3,500 upon start up.....that requires lots of air. The fuel distributor is NOT going to cause the engine to rev.....assuming you start the engine correctly with no foot on the accelerator pedal..

 

I'm definitely going to check all the rubber boots and connections for an air leak.

I am also going to get a fuel pressure tester to begin check for a fuel issue.

 

No doubt that vaccum leaks could be a source of problems also. Check all those.

For FD rebuild http://salvox.com/products.php?43&cP...600525047c3825

Also check 928 Classics for more info.

 

For what it's worth, the only time i've seen a backfire through the intake was when i didn't have the intake runners buttoned down properly, i.e big vacuum leak.

Do a visual check around all the breather hoses, throttle body, intake runners etc and you might find an easy to fix culprit.

 

right with CIS you need to be able to check system pressure and control pressure...
The fuel filter seldom if ever causes a running problem. The fuel accumulator is really only needed during hot restarts otherwise the car runs fine without one.
Once was told that 1/2 of the fuel distributors sent in as "core" actually tested just fine

 

I haven't gotten a fuel pressure test kit yet, but I did some investigating. I wanted to take a look at the fuel filter to see if it appeared to be clogged. I find it is easier to also pull the fuel accumulator when taking the fuel filter out. So I pulled both. Filter appears fine.

So, I spent a few minutes investigating the fuel accumulator as well. My car has a 3-port accumulator and from what I understand I should not have fuel in the "lower" chamber. That is to say, there should not be any fuel on the end with the single port. My third port is capped off and is not connected to anything. When I opened that port, a bunch of fuel poured out. Maybe as much as 10oz.

That's bad, right?

 

My understanding is the fuel accumulator maintains fuel line pressure after the car is shut down to help prevent vapor lock issues. There is a diaphragm and a spring inside and the side with two ports feed into that section. The single port is a vent and I believe is connected (when connected) to the charcoal canister system via a check valve. If you have fuel in that area then the accumulator diaphragm could be leaking and possibly contributing to pressure loss. You can test the accumulator to see if it will hold pressure but you will need to rig up several fittings, a valve, pressure gauge, etc. I tested one of mine using compressed air in this way.

You really just need to check flow rate of pumps and system pressure to determine how much fuel is getting to the fuel distributor.

 

the original fuel accumulators had a small screw and vent on the end and when the diaphragm ruptures it leaked onto the ground. Later version added a return line. So you have a later version fitted with that return port capped. No fuel should be there until the diaphragm ruptures.
But as I said the accumulator has only to do with hot starting......car should start and run fine as it is now. The early accumulators are no longer available.

 

I'm not well versed in CIS, but considering that you describe that you can keep the car running with the accelerator suggests to me that you may have a rich condition or mis-allocated fuel delivery rather than a lean one or fuel starvation for any reason. I'm not sure if a failed diaphragm in the accumulator would cause this condition.

 

Nope.