924Board.org

[markp]

Gentlemen,

I'm having cold start problems. I've been reading through the various cold start problem topics, but I can't seem to find an answer to my problem. The car is '79 924N/A from Europe.

When I turn the key to ignition, the engine seems to be running. When I turn the key back, the engine will stop. If I try to start it again I hear a few coughs and mostly the starter motor running (I do smell gasoline, so I guess theres flow to the cylinders). When I keep this up for 5-10 minutes, I can get the engine running, though very unstable. It idles around 500 rpm and when I hit the throttle, it will only go down in rpm.. The car is very shaky as well. I keep the engine going at this state for say, 5 minutes, then turn it of and wait 5 minutes. When I start the engine at this point, it will normally idle and I can drive the car. If I drive it for an hour or so, and start again 4 hours later, it will run. The first few seconds it will idle at about 500 rpm and the car is shaky. After that, it runs pretty smooth, but at idling it will shake a bit. Around 1500-2000 rpm the power output seems unstable, shaky accelerating.

The things I checked:

The battery seems to give a normal voltage, a little bit more than 12V.
I replaced the spark plugs and the spark plug wires. The rotor and distribution cap are nicely cleaned (no cracks also).
The auxiliary air valve was checked by putting it in a freezer, after an hour it was mostly opened. The resistance on the connector was about 50 Ohm, may be too much? When cold it should be a better conductor.. The connector to the AAV gives it a steady 12V.
The thermo time switch gave a voltage of 12V to the cold start valve for a few seconds, when cold.
The ignition coil had a primary resistance of 3 Ohm, according to Haynes this should be around 1-1.3 Ohm. The secondary resistance is 9.6 Ohm, which should be 5.5-8 kOhm. Can the ignition coil create cold start problems? Whilst it will start when somewhat hot.

I also checked the rubber boots and tubes for leaks, but can't seem to find any. So could be I missed something there, because to me it could be an air leak.

I hope you guys can give me some advice.. Because I'd really like a good cold start!

Thanks in advance,

Mark

[Ozzie]

You did not mention the WUR
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[markp]

I checked the resistance, seemed ok. But I'm not sure if it works.. Have to do a pressure test to make sure if the WUR works, right?

[markp]

Cleaned the WUR, gave it a bit more room to get some fuel. Won't start now either..

[Smoothie]

Common CIS scenario:
Previous owner doesn't fix vacuum leaks, and adjust A:F mix to compensate.
Soooo - you may have vac leaks + incorrect A:F setting + incorrect fuel pressures (control (WUR) and primary). -And/or a number of other things like clogged fuel filter, junk in the fuel tank and pump/s, etc. -But leave the A:F alone until everything else has been checked/repaired.

Check vacuum line routing (may as well replace all lines & elbows at the same time), firing order (1-3-4-2), valve timing (timing belt installation), etc.

Shouldn't be cranking the starter for 5 minutes. For a warm/hot start [,and stubborn cold start] try this -
before even inserting the key, press and hold the throttle to the floor, now insert key and crank the starter, continuing to hold the throttle down. If this is going to help, it will start within a few revolutions.. Let off the throttle only after it starts, then blip the throttle as needed to keep it going.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[markp]

I also checked the spray on the cold start valve, was a nice spray. I ordered some new (used) elbows, and I'm going to buy new tubes.

I'm rechecking the AAR, because I have a feeling it doesn't open entirely, only for like one fourth whilst it is pretty cold. It's in the freezer now, how long will it take for it to open entirely? Btw, wouldn't the car start with a broken AAR if I'd floor it during a cold start? Because that doesn't work as well.

I might as well replace the fuel filter, it's not that expensive.

[staticsan]

[markp]

Alright.. I'll check the whole CIS for cracks. Is it any use to reinstall the tubes and tighten them some more, so there are no leaks at the transitions?

[markp]

Checked the system from air mass meter to the inlet valve. No cracks whatsoever. The tube from the aav to the inlet has a crack in it, but I taped it. I can only get a replacement at the Porsche dealer..

Starting with the pedal pressed a bit doesn't seem to work either.

[staticsan]

I had another read of your OP and I'm sorry, but I'm out of ideas. My '924 had starting problems, which I've gotten fixed, but not of that calibre. :-/

About the only thing I can add is that my father had the bright idea of checking for vacuum leaks with his hand whilst it was running, which showed a slight one from an over-tightened join on one of the rubber boots.

Wade.

[markp]

It won't run anymore, so can't check it that way..

[joejax]

Have you checked your timing? Line it all up, then when you try to start it bump the distrib either way to see if it will catch.

Mine has had a similar issue to yours, had to bump dist clockwise a little to get to start, I hit it with a timing light and it doesn't seem right. But it runs OK for now.

Also have some wiring issues with the idle stabilizer gizmo, the little black box with 2 wiring plugs to it, bad connections there made for bad start and run.
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I got nothin'
Uhhh...you got any pics?

[markp]

-edit- never mind what I wrote first. I'll bump the distributor later this day and see what happens. I will also check the fuel system, to see if it supplies enough fuel.

I keep having this feeling that I found the problem, but still haven't found it. Quite frustrating.

[markp]

[joejax]

Cool, I think we're getting closer. Just to be clear, bump means to turn slightly. Sounds like other problems exist though; vac leaks, A/F mix, etc.

I've had to adjust idle, timing, and air/fuel mix then go back and keep adjusting each one to get it running OK. Timing light on flywheel is not quite right yet. I believe I'm getting close though.

I have researched the A/F mixture settings, I am adjusting with the counting turns and watching how it runs method. This can be a real pain, but without costly smog devices, it's the best I can do.

Seems to be running OK at this time, power seems like it should be more, but I have nothing to compare to a 30 year old 4 cylinder, so it's not too bad I guess.
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I got nothin'
Uhhh...you got any pics?