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Join Date: Jan 2006
Location: Gloucester UK
Posts: 5
924S difficult starter

Happy New Year to all 924/944 owners

I have a problem starting an '88 924S, history as follows:

Car was starting and running fine until a couple of months ago then became very difficult to start. This happened when we first bought car a couple of years ago, fixed by changing ref sensors having confirmed they were not reading correct resistance.

Bought 2 new ref sensors, installed same problem, car will ONLY start if really short turns of the key are used, car seems to fire up on over run of cranking.

Suspect then became ignition switch, that was replaced but still same problem

Suspect turned to weak battery bot supplying enough voltage to coil whilst cranking (measured at 9v), new bigger battery bought....same problem

Coil checks out fine ( I have tried spare with same result)

DME relay replaced as a matter of course

When car finally starts I have oil pressure of 4.5 Bar, car idles at 800RPM, pulls strongly throughout rev range and charges battery at 13.5V

Help please, this really is driving me to distraction
Old 01-07-2006, 10:27 AM
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Ornery Bastard
 
Join Date: Sep 2001
Location: Bellevue, WA
Posts: 2,872
At this point, I really don't have anything to suggest other than checking all the connections and the starter itself. If the connections are bad (there are grounds all over the place on these bloody cars) you can have enough voltage drop to muck things up a bit. Also make sure that the starter's not drawing excessive amperage, if it's drawing too much it could theoretically (I think) drop voltage sufficiently to cause problems for other systems like ignition.
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Guards Red 1986 951 <- Seattle car (Gretchen)
White 1976 914 2.0 F.I. <- Prodigal car, traded away then brought back again (Lorelei)
Old 01-07-2006, 10:30 AM
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Thanks for the prompt reply, I did think earthing could be a problem however Voltage at the coil whilst cranking is 11.8V with the new battery but there is no spark until cranking stops, as the engine continues to turn (momentum) I then see a spark hence the car starting with really short turns of the key.

Forgot to mention in 1st post that I do hear the fuel pump whilst cranking
Old 01-07-2006, 10:37 AM
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Ornery Bastard
 
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Location: Bellevue, WA
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Do you have a friend with another 924S that does not have this problem? At this point I'd suggest swapping the DMEs and seeing if that fixes the problem. Typically if the DME can't get a reading from the sensors it shuts down both fuel and spark, so if you're getting fuel but no spark it makes me wonder about something having gone wonky in the DME somewhere.
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Shifting is an art. Learn it, love it, live it.
---------
Silver 1998 Volvo S70 T5 <- Daily (Anja)
Guards Red 1986 951 <- Seattle car (Gretchen)
White 1976 914 2.0 F.I. <- Prodigal car, traded away then brought back again (Lorelei)
Old 01-07-2006, 10:45 AM
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Smile

Unfortunately I don't...is there anyone out there near Gloucester in the UK willing to try a bit of part transfer?
Old 01-07-2006, 11:21 AM
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Is the DME computer in a '88 924S the same as an early 944? and does anyone know if a DME from a BMW work?

Thanks
Old 01-08-2006, 10:50 AM
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Ornery Bastard
 
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BMW definitely won't. The early 944 _might_. Not sure though.
__________________
Shifting is an art. Learn it, love it, live it.
---------
Silver 1998 Volvo S70 T5 <- Daily (Anja)
Guards Red 1986 951 <- Seattle car (Gretchen)
White 1976 914 2.0 F.I. <- Prodigal car, traded away then brought back again (Lorelei)
Old 01-08-2006, 04:04 PM
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The vacuum lines need attention
Get a reading on the AFM specs
Plug wires cap /rotor contacts
Positive battery cable corrosion
Fuel delivery rate....FPR
Clean grounds

Same issue and mine were the vacuum lines.

The 88 DME is not the same as the 87 or early DME. In order to use the early or late DME the correct AFM must be used with the DME. ie....88 DME in an 84 needs the 88 AFM.

You do not want to use an early DME/AFM on a late one.
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Last edited by 924Sman; 01-09-2006 at 02:23 AM..
Old 01-09-2006, 01:07 AM
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The 924S uses the same DME, AFS and idle control valve as the later 944's.

Jumper between the battery (or a known hot connection in the engine comartment) and the positive side of the coil.

Start the car.

If the car starts and runs everytime then you have a problem with the ignition switch wiring. Could be a bad connector at the back of the ignition switch or the white plugs in the engine compartment that feed the coil.

If it still does not start then:

Jumper between Aux fuse #2 and #3 to run the fuel pump AND the jumper to the coil.


Start the car.

This jumper bypasses the fuel pump side (second set of contacts) on the DME/fuel pump relay.

You may be having problems with the power distribution from the battery. The 10 gauge wires take the power into the fuse/relay blocks and buss it to the rest of the system.

I take it your battery is in the back.
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Last edited by SoCal Driver; 01-09-2006 at 07:18 AM..
Old 01-09-2006, 07:16 AM
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Thanks for all the suggestions,
924S Man I'll look at the vacuum lines at the weekend and check out the AFM.

SoCal Driver, I'll try the jumper bypass checks at the same time, I am beginning to wonder if the starter is drawing too much current so will wire the coil with an independent battery
Old 01-10-2006, 09:55 AM
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I suggest doing one at a time. Then you will know which direction you need to go for fixing it.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 01-10-2006, 03:22 PM
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