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porschefig
Joined: 23 Oct 2003
Posts: 10
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 Posted: Tue Mar 29, 2005 8:24 am Post subject: 924 won't start or idle UPDATE |
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Ok, so in my experience w/ cars prior to Porsche (read: lots of Chevy engines): all an engine needs to start is spark, compression, air, fuel, and that's about it
So, my mind gets numb when my latest 924 doesn't start under its own power even though it has all those things!
the smelly thing will pull start, and the engine will crank over by itself (it HAS started a couple times by itself)
It's really like it only starts when it wants to. And it won't idle, I'm thinking one or many of these? (I'm not even sure if the 924 has all these)
Idle control valve
Fuel Pressure Regulator
Warm up regulator
Coil (or something is heating up and failing)
Also, when we have a spark plug out to test spark, that cylinder fills with gas FAST. Is this just b/c there isn't any back pressure/compression (for lack of better terms) to the fuel injector and it is free to spray at higher than normal pressure? (The engine doesn't seem to run rich)
Last edited by porschefig on Mon Apr 25, 2005 6:52 am; edited 1 time in total |
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numbbers
Joined: 05 Nov 2002
Posts: 1910
Location: Highlands Ranch, Colorado
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| Posted: Tue Mar 29, 2005 10:49 am Post subject: |
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Not enough info in your post to help. The Porsche engine is no different than a chevy V8. Your problem is either spark, fuel, or timing. So, you are probably missing something in your diagnosis. Make sure the spark is bright yellow, or blue. Spray a little either, and see if it tries to start. If it doesn't, their must be a timing problem.
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1980 924 Turbo |
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Tue Mar 29, 2005 11:00 am Post subject: Re: 924 won't start or idle |
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| porschefig wrote: | | Idle control valve |
- that one's called the AAV (auxiliary air valve)
| porschefig wrote: | | Fuel Pressure Regulator |
You'll have 2 pressures- "system pressure" (aka primary pressure) - the regulator for that is built into the fuel distributor. The other is "control pressure" which is regulated by the "control pressure regulator" (aka - WUR "warm-up regulator")
| porschefig wrote: | | Warm up regulator |
Ok, you already knew about that one. You'd need to have access to a CIS fuel pressure tester to troubleshoot the fuel pumps, check valves, WUR, and primary pressure regulator.
| porschefig wrote: | Coil (or something is heating up and failing)
Also, when we have a spark plug out to test spark, that cylinder fills with gas FAST. Is this just b/c there isn't any back pressure/compression (for lack of better terms) to the fuel injector and it is free to spray at higher than normal pressure? (The engine doesn't seem to run rich) |
Check the air:fuel mix anyway, check for vacuum leaks, verify that valve and ignition timings are right and the rest of the usual stuff - plug wire connections, dist cap, rotor, etc.
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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 |
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924guy
Joined: 29 Dec 2003
Posts: 2088
Location: Port St. Lucie, FL
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| Posted: Tue Mar 29, 2005 12:15 pm Post subject: |
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| Quote: | | , and the engine will crank over by itself (it HAS started a couple times by itself) |
there seems to have been a rash of demonic possessions of 924's of late, perhaps you could hook up with a few of the other 924 owners on here and you guys can get a group rate on exorcisms....   
id go through the electrics first, clean all grounds , check for corrosion at the fuse box , etc.. youll have to do it anyhow (they all need this on occasion), and with some of those symptoms, it would be a good place to start. hard to diagnose issues if you dont have good grounds or clean power (ie; no arcing circuits messing up the systems.) youll find grounding terminal junctions in the hatch , under the drivers side dash above the fuse box, and under the hood fore and aft of the powerplant. if it has a wire conecting to the chasis or engine in any manner, clean it.. welcome aboard..
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Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
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dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
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| Posted: Tue Mar 29, 2005 12:35 pm Post subject: |
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If the injector is spraying without the engine running, you have a leaking injector, stuck piston in the fuel distribtor or a bad fuel distributor or a combination of these. How long has the car sat before you tried getting it running?
Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
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Roger
Joined: 06 Jan 2003
Posts: 1235
Location: Cordova, TN
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| Posted: Tue Mar 29, 2005 12:58 pm Post subject: |
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Check fuel supply and spark. Try removing the fuel pump relay and jumpering contacts 30 and 87 on the relay board. This will cause the fuel pump to run continusly and car may start. If this works the repalce the fuel pump relay.
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1981 924 NA
Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs. |
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Roger
Joined: 06 Jan 2003
Posts: 1235
Location: Cordova, TN
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| Posted: Tue Mar 29, 2005 12:59 pm Post subject: |
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Check fuel supply and spark. Try removing the fuel pump relay and jumpering contacts 30 and 87 on the relay board. This will cause the fuel pump to run continusly and car may start. If this works the repalce the fuel pump relay.
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1981 924 NA
Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs. |
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gstv
Joined: 28 Mar 2005
Posts: 17
Location: Santo Domingo/Rep.Dominicana
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| Posted: Tue Mar 29, 2005 1:17 pm Post subject: |
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Hey, I has the same problem last weeks, maybe this can help you.
Thereīs a little problem with the automatic piece of the start motor (I donīt know the exactly name, sorry). My car only started when it wants to, and when the motor was hot,(about 80-90c), the starts motor gets into electric cut.
Maybe this can help you, maybe not, I hope you can fix it,
Regards
Gus
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ī77 924 |
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MunkPuppy
Joined: 02 Jul 2003
Posts: 419
Location: New Westminster, B.C., Canada
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| Posted: Tue Mar 29, 2005 6:14 pm Post subject: |
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| Roger wrote: | | Check fuel supply and spark. Try removing the fuel pump relay and jumpering contacts 30 and 87 on the relay board. This will cause the fuel pump to run continusly and car may start. If this works the repalce the fuel pump relay. |
It has already been established that the fuel is getting into the cylinders, since they are filling up with fuel when he has a plug pulled to check for spark. 
If you want to check for spark, it is worth your while to pull the injectors out, put each into an 8oz pop bottle (preferably the same type), so you can check both the spray patterns and that each injector is putting out the same amount of fuel. Then you are free to check the spark without filling the cylinders with fuel.
And I second the notion to get a CIS pressure tester, and use your hayes manual to properly test your fuel system.
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'80 931 FOR SALE
"It's a shame that stupidity isn't painful"
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Paul
Joined: 02 Nov 2002
Posts: 9491
Location: Southeast Wisconsin
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| Posted: Tue Mar 29, 2005 8:44 pm Post subject: |
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| Change your oil, its probably mostly gasoline now. |
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Roger
Joined: 06 Jan 2003
Posts: 1235
Location: Cordova, TN
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| Posted: Thu Mar 31, 2005 1:05 pm Post subject: |
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| MunkPuppy wrote: | | Roger wrote: | | Check fuel supply and spark. Try removing the fuel pump relay and jumpering contacts 30 and 87 on the relay board. This will cause the fuel pump to run continusly and car may start. If this works the repalce the fuel pump relay. |
It has already been established that the fuel is getting into the cylinders, since they are filling up with fuel when he has a plug pulled to check for spark.
If you want to check for spark, it is worth your while to pull the injectors out, put each into an 8oz pop bottle (preferably the same type), so you can check both the spray patterns and that each injector is putting out the same amount of fuel. Then you are free to check the spark without filling the cylinders with fuel.
It is getting fuel but I am thinking that the return line is blocked causing the high system pressure. A fuel supply test might help determin the problem. It could also be the O-rings inside the fuel distributor. The injector thest you suggest would also be a great idea.
And I second the notion to get a CIS pressure tester, and use your hayes manual to properly test your fuel system. |
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1981 924 NA
Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs. |
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porschefig
Joined: 23 Oct 2003
Posts: 10
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| Posted: Mon Apr 25, 2005 6:54 am Post subject: |
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well, we've got it running a bit more often. We ended up finding that the mixture screw was backed just about ALL the way OUT.
Question: is there like a "starting point" to set the screw at so it will atleast run long enough for us try and figure out the other problems? |
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porschefig
Joined: 23 Oct 2003
Posts: 10
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| Posted: Mon Apr 25, 2005 6:59 am Post subject: |
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and thanks for all the help guys. I'm only home about once every second month so not much work has gotten done on the car. I'll be done with the semester in a few week so...this thread should be uber-helpful  |
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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Roger
Joined: 06 Jan 2003
Posts: 1235
Location: Cordova, TN
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| Posted: Wed Apr 27, 2005 11:02 am Post subject: |
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| porschefig wrote: | well, we've got it running a bit more often. We ended up finding that the mixture screw was backed just about ALL the way OUT.
Question: is there like a "starting point" to set the screw at so it will atleast run long enough for us try and figure out the other problems? |
Turn the mixture screw all the way in then back it out about 8 1/2 turns as a starting point. Thats what I remember when I rebuilt my fuel distributor.
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1981 924 NA
Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs. |
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924 FAQ (Technical)
