924Board.org

[Funk1974]

I've had this 1977.5 924na for about a year. It had a number of electrical issues when I got it and I've gone through and replaced about everything (electrical) but the control unit. It ran well before it was parked for the winter. I went to start it recently and it started right away. It idled for a while and warmed up. I pushed the accelerator and it revved freely up to at least 5000rpm. I put it in gear from idle and it coughed and died. It was difficult to start again. It starts then idles well. If I can get it to stay running in gear until it reaches above 1500 rpm, it drives fine until I need to accelerate from idle again. Half the time it stalls.

The timing is set correctly. The mechanical/vacuum advance works correctly. There is plenty of spark. There is no restriction in the air intake/filter. This leads me to focus on fuel delivery as the culprit. I cannot find air leaks in the fuel system. The injectors were serviced right before I bought the car, so they aren't suspect quite yet. I assume it may be the fuel pump or the in tank pump. Maybe some ice or rust got into the system and caused damage. If this is the case, why does the car run fine above 1500rpm? How can I find which pump is the culprit if it is one of the pumps? If it isn't a pump, what other causes do these symptoms suggest?

Thanks for any help
_________________
1977.5 NA, Automatic, Diamond Silver metallic
1979 engine
265 60 r 14 BFG TAs
MB Quart, JL audio, Alpine stereo

[ideola]

It doesn't sound like a pump malfunction to me, although I'm not sure what it could be. Also, I don't know what you mean when you say "control unit"...to what are you referring?

A couple of things to look into regardless...
1. Vacuum leaks. Check everything. Check for leaks at the intake gaskets, throttle body gaskets, ALL of the soft vacuum lines, and the large rubber-to-plastic-to-rubber boots coming off the air metering unit.
2. Clogged fuel filter. When's the last time it was changed? Is it on in the correct orientation? I know it's an NA, and hard to screw up, but on a CIS system, if the filter is on backwards (a common mistake on the 931), it will impede flow and cause intermittent running problems. So your filter might need replacing.
3. Regarding the water in gas issue you questioned, why not get a container of dry gas and a container of techron, and run them through the system. Certainly won't hurt anything, and techron is amazing stuff.
4. Have you performed a CIS pressure test? If not, I would definitely check that next. If you need a CIS tester, you can get one here. A proper CIS test can isolate or rule out any issues with the CIS components, and may also identify a fuel delivery problem. Haynes has an adequate troubleshooting regimen if you have the proper tester.
5. Fuel injection pattern. I know you're assuming they're good, but troubleshooting 101 says you always challenge every assumption, particularly things that were recently changed in the system. Follow the Haynes test to check for flow and spray pattern so you can conclusively rule them out.

HTH. I'm sure you'll get some other helpful advice as well, so stay tuned, and good luck!
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erstwhile owner of just about every 924 variant ever made

[Funk1974]

Haynes calls it a "transistorized ignition control unit". Its the silver box that the ignition system plugs into.

Filter orientation and techron through the system are on the list of things to try. I do hope it isn't the pump(s). If I can adjust something and be back on the road, that would be great. The CIS tester I read about in a few other posts and is something I may buy just to have because it's only $50 or so if i remember.
_________________
1977.5 NA, Automatic, Diamond Silver metallic
1979 engine
265 60 r 14 BFG TAs
MB Quart, JL audio, Alpine stereo

[ideola]

[Funk1974]

techron solved it. I still don't know what was the problem, but techron did it.

Thanks again
_________________
1977.5 NA, Automatic, Diamond Silver metallic
1979 engine
265 60 r 14 BFG TAs
MB Quart, JL audio, Alpine stereo