CIS troubles
 

I am having some troubles with my 78 930 CIS.

It will start if I depress the air meter plate, so I know I have fuel and spark. It sometimes starts and runs for a short period without pushing the air meter plate. It sometimes runs as long as a minute or two, sometimes stumbling others not.

I was guessing the fuel head or the metering plate. Thoughts? The WUR is very recently rebuilt by Larry.

It all started one warm day before going to a ralley. It drove fine, then just putted out and would not restart.

1bc9f3a8.mp4 video by sundevil64 - Photobucket

Fuel pump(s) is where I would first look. Since you can't seem to keep her running long enough to diagnose, try replacing both pump relays (minimal cost, and it's always good to have spares even if that doesn't solve your issue).

Depressing the metering plate is at least causing the pumps (or maybe just one pump) to run. How about unplugging the metering plate switch blue connector (or is it green?). That will result in your pumps running continuously with just the key in the on position and the engine not running. You'll hear the pumps run....pull one relay at a time and see if any difference in the sound that may point you to which pump may not be running. Also, unplug the wire to the overboost sensor and ground it, just to make sure that's not the culprit (a poor or intermittent ground will keep both pumps from running). Gotta be methodical, one thing at a time.

vacuum leak. Intercooler o-rings??

mark houghton- Good suggestions. I did all of those. The overboost was questionable so I replaced it just in case. I actually got it to run at one point to drive down the road then it just stumbled and quit. Both fuel pumps are running. I have not put gauges to it, but I would think that both pumps running would allow it to idle with sufficient fuel.

I suspect the air metering plate and fuel head? I don't now. When I give it gas after it's running it stumbles and shuts down.

LuftWaffle- I checked for vacuum leaks and could not locate. I did find during my search where the charge pipe as not seated well, but I corrected that.

Keep them coming.

Sounds way lean. If thats a warm motor it's probably a vacuum leak somewhere or air leak between the throttle body and air flow meter. There's alot of places that can happen and it's near impossible to find all the possibilities without removing things.

If it's a cold motor and it runs good warmed up it may need the cold start control pressure lowered. A CIS pressure gauge will diagnose that easy. If Larry made the WUR adjustable that will make it alot easier to adjust.

JFairman-Larry did not make the WUR adjustable and I think you are right I may have to start taking the intake stuff off and doing some investigating. Fortunately, I have some of the gaskets including one for the air meter. Is the air meter hard to take apart?

Does the metering plate move freely? Sometimes it gums up and doesn't modulate as it should... bad/old/contaminated gas causes that.

Yes with a little consistent resistance. I don't have a way to measure the amount of force it take to depress the metering plate, but it isn't much. A few ounces maybe.

Test
 

Sounds to be lean, have you tried adjusting the metering plate or fuel air mixture at the throttle body?

The metering plate and whinning sound just like it should...

metering plate
 

thanks for the confirming the sound.

I have, but I may need to start from a base line and readjust. I've heard it's very sensitive. I am starting to think I need to remove the air metering assembly, clean, put a new gasket in, and recalibrate.

Check that charge pipe again, my car had similar behavior when charge pipe not sealed correctly.

Spend the money and buy or borrow a set of fuel pressure gauges.. You're pissing in the wind until you know your fuel pressures.. It may be as simple as an adjustment on the throttle body screw,, just richen it up..
The other thing to consider is you're in Texas and it's July ,, our CIS machines HATE hot weather

Before dismantling things, do indeed check your control pressures. Could be your WUR is acting up. Seems your metering plate is moving freely, so put that out of your mind for now. If your control pressure is too high, then the metering plate arm won't deflect as far as it should, thus causing a lean condition already mentioned.
Yes, you could for a short term diagnostic adjust the mixture screw downwards to richen up the mixture, but don't turn it more than a degree or two. Since depressing the plate keeps her running, then adjusting that screw will have a similar affect. But it won't solve control pressure issues.
You'll get there, sooner or later, with an "ah-ha!" moment.

Spend the money and buy or borrow a set of fuel pressure gauges.. You're pissing in the wind until you know your fuel pressures.. It may be as simple as an adjustment on the throttle body screw,, just richen it up..
The other thing to consider is you're in Texas and it's July ,, our CIS machines HATE hot weather

I've got gauges, it's time I don't have. I'll put gauges on it after my next trip.

Was this car being serviced in AZ by chance?

cis
 

No. It's in Austin, but if I was still in AZ I would have some options for good shops for this car. Although I will be there in the very near future, but the car will not.

I wanted to update the thread. I finally found a good shop in Austin that was able to help me out. In looking back at all the thoughts of what might be wrong it seemed many of them were correct. The problems were multiple, an intermitent working fuel pump, air leaks at the charge pipe, overly rich, fuel adjustment, and another unrelated problem was too much play in the distributor. The fuel pump was replaced, the charge pipe was better secured, the mixture was adjusted using a CO meter, and the distributor received a machined shim of .073" and a new inductor coil. I had to make a few minor adjustments and tonight I put the first real amount of mileage on the car and drove it pretty hard and it went well. Hopefully the days of tow trucks are over for little bit.

Thank you all.

John

Just curious
could you share the name of the shop in Austin?
I was not aware of any

stefan

Congrats... now drive it hard and enjoy it AGAIN!!!!!!