sfuller1965

Hi,
This is my first post and rather than bore you all I have searched the site to try and find an answer to my problem but alas no joy so here goes.

Car will only start if you give it short turns on the ignition switch, continual cranking will not start the car. If you do the usual spark check you'll only see a spark on the overrun, not whilst cranking.

Car is an '88 924S owned for the last two years, shortly after I bought it I had a similar problem fixed by replacing the flywheel sensors. This time around I have repalced the DME relay, Coil, Sensors...again but the car still refuses to start easily.

I do wander if the actual ignition switch is at fault?..Any suggestions greatfully received....

Chris_924s

Welcome to Rennlist, Nice choice on the 924S.
Make sure the speed/ ref sensors are plugged in correctly (Does the tach bounce while cranking? )
Have you tried a new coil, plugs or a noid light on the injectors yet?

sfuller1965

Hi,
Thanks for the reply, yep, both sensors as they should be....would the car even start if they were the wrong way round?

It is an odd problem as I can start the car but only after releasing the ignition key from the cranking mode which is why I wandered if the actual ignition switch could be at fault.

Coil replaced, spark plugs about 3 months old (as is the rotor arm and distributor cap....what a pain to get that on!)

I know fuel is getting there because you can smell it, get the occasional back fire when car does finally start (fuel in exhaust?)

One thing I should have mentioned, the car will always start from a push start (no engine cranking involved) and battery is about 6 months old.

Chris_924s

sounds like a bad key/ ignition cylinder. If the speed ref sensors were switched ther would be a no start- but the tach wouldnt bounce and a push start wouldn't happen.

Dammit- i gave one away a few months back-

cjeckert

Thats what happened to me when my ignition cylinder crapped out, contact cleaner fixed it temporarily untill i was able to get a new one. Good choice on the 924S

Rip It

Sounds like no 12vdc going to the ignition system with your key in the start position. That voltage, on say a chevy, comes from the starter solenoid terminal marked "S" . On a porsche it may come from another connection point ? Anyway that's why u can push start it because u are bypassing the start circuit and only using the run circuit.

sfuller1965

All,
Thanks for the feedback and the reference to Clarkes with all their repair guides.

I'll attempt the fix this weekend....why do these problems always occur when the weather turns bad?

ike229

924S = goodness

89magic98

He didn't say the engine doesn't crank, he said that spark goes away when he's cranking for any length of time. The car runs fine once it starts, right? And the car can be push started, right?

Sometimes my 924s will turn over with hardly any cranking at all.

My bet - the bellhousing ground to the negative cable is bad. When cranking for any length of time, it's not able to sink all the current through the ground, and raises up the potential of the engine just enough to knock out the dme (not get 12v supply to it).

Want to test my theory? Get a jumper cable. Connect one end to the negative terminal of the battery. Connect the other end of the same cable to the metal bracket piece on the back of the cam tower (where you loop the chain through when using an engine hoist). Effectively, this is giving another ground to the engine. Then see if the car starts. If so, it's corrosion at the ground at the bellhousing. Follow the negative battery cable to where it bolts to the bellhousing, both bolts and connectors need to be cleaned.

This exact same problem happened to me.

sfuller1965

Attempted ignition fix this weekend...- degrees outside so I opted for the quick fix of contact cleaner, appeared to work and I noticed the Rev counter bouncing before car fired up (a couple of seconds), left the car until the following morning....back to same old problem and whilst cranking Rev counter didn't bounce until you release key, singular bounce, went back to short turns on the key and sure enough car started....does this confirm ignition switch to be the faulty item?

WolfeMacleod

Hey, that just happened to me today. Turned the key and BAM! started immediately. I normally have to crank it about 2 seconds. It was wierd.
924S also.

89magic98

Did you try my suggestion with the jumper cable connected between the negative of the battery and the engine block?

To be honest, I don't understand how the ignition switch would be the source of the problem, given the problem you described.

Chris_924s

Kevin has a very good point- what condition are your grounds and battery cables in? Have they been recently cleaned and protected with dielectric grease?

FWIW I will normally crank once and she'll fire right up.

sfuller1965

89magic98, no i Haven't tried your suggestion yet, I will do this coming weekend.

Chris_924s, mine was much like yours, pretty much an instant start no matter what the weather.

Would the poor earth stop the tacho bouncing whilst cranking the engine?

sfuller1965

bump