OK....this could be something really stupid and simple or the start of another 924 *magical mystery tour* through vw electricals (gag!). My '78 924 (yes same one still FULL of *surprises*) has been running faultlessly for 2 years...until two days ago. She started, but didn't run. wait 12 seconds, try again ignition and then...no running. Wait again,try, and then she started and ran perfect like there was no problem. The rest of the day whether hot or cold, fine fine fine. No hesitation, no hunting, no misses. Yesterday perfect as well, then today rolled her out of the garage, and ignition (starter works, and there IS gas and spark), starts but doesn't run. Four more tries and then finally all was well for the rest of the day. Could this be something to do with the ignition switch itself? or is there a relay (somewhere) that tells the car to (freekin) run AFTER the starter has done its thing, or is this a possible fuel pressure leakdown (disgusting little hard to get at fuel pump check valve)?

~ jeanette

 

Yeah, I'd be a little suspicious of the ignition switch... they all go, eventually. Easy to check, just reach under the dash, unplug the ignition switch, and hotwire the car. If it runs fine, you've just isolated the bad component!

 

I, too, would start with the ignition first.

The check valve is more of a nasty job than a difficult one- I once saw a similar problem to yours fixed by replacing the valve. Once removed, the check valve is easy to "check" - the spring in the valve wears out and won't close to maintain pressure in the line. Once started (and running) the fuel pump will generally be strong enough to maintain adequate pressure even with a faulty valve.

You may also check your idle... I know, seems too easy... but cold start problems could be an indicator of idle adjustment problem.

Keep us posted & good luck!

 

Thanks, and so far, after flying out ...then sneaking out ...to the garage and suddenly *test* starting her, she is behaving like a little choir girl, starting and running perfectly. I know better...she is waiting until am a zillion miles from anything ...on a triple holiday when not even a two truck is running <---(yes...we have done this before on BOTH memorial day and labor days).
Methinks ignition as well right now as the problem can happen after running hard, or after sitting for a day.... cold or warm ...no matter. So maybe (I hope) the check valve stuff will be ruled out ..for now. I DREAD (and dread having any one else) going after anything attached to fuel lines, as they are so old.
If this problem happens when she is hot then for sure I will rule out check valve as there will not have been enough time for a leak down in fuel pressure.
Idle is steady once she starts running, so the fuel and spark seems ruled out as well.
Next time I will start her in heels as though I am going somewhere *important*...with THIS car that should be enough to trigger her evil side...

jeanette
78 924
80 931S

 

Jeanette,

Two other possibilites are 1) bad resistor/connection for the ignition wire going to the #15 post of the coil or 2) Corroded fuel pump fuse or relay. Since your problem is intermittant and temperature dependent, the most likely area is one of the electical components. May also want to check your grounds.

Dennis

 

I often (in some cars, like my racecar) carry, in the glovebox, a special connector of wire I made up - 10ga wire, 3 male spade connectors - just in case this happens. I can unplug the ign switch and hotwire it with the little bits of wire very easily. Just have to use big-gauge wire to handle the current involved (if I want to make it all the way home without overheating the wire).

 

Uh huh...well right now I have so many spares (IE: spare fuses, spare fan relay, spare fan switch, spare light bulbs, spare micro tools, spare flasher relay, spare spark plugs, in the glove box that there is barely room for the registration much less gloves.
Rear "saddlebags" have tools manuals water, oil, grease, coveralls...of course everything and anything but what I really need when I can't get the car to start.... THAT would be an angel...(good or bad... I'm not picky.... we make deals and seal them AFTER I get home).
I am not QUITE up there with Der Maestro tripping around with a spare engine block in the passenger footwell of a 356.
Oh well, Methinks Dennis is correct....I am prepping myself for another go-around with the wacked out electrical wiring/ connectors.
Time to find a divining chicken...
jeanette