968 Intermittent Starting Issues - Any Thoughts Please?

Fraser · Jul 25, 2013

As the title says really. Car starts fine, then doesn't. ECU checked, old alarm taken off, current alarm checked, DME relay swapped out, swapped back. All sensors checked, apparently (crank etc).

Usually when the engine is cranking, the rev counter needle flicks up and down. When it isn't going to start, it doesn't (or oscillates less).

Any thoughts (other than turning it off and turning it back on again) would be welcome - thanks in advance.

Fraser.

vitesse · Jul 25, 2013

Certainly sounds like crank sensors-have you tried wiggling the connectors/wires--they embrittle with heat & age & apparently weaken the signal & I can't explain why wiggling them seems to work (for a while) but it it did with the red 924S until made unnecessary by replacing the 2 sensors.

Fred Hindle · Jul 25, 2013

ORIGINAL: VITESSE

Certainly sounds like crank sensors-have you tried wiggling the connectors/wires--they embrittle with heat & age & apparently weaken the signal & I can't explain why wiggling them seems to work (for a while) but it it did with the red 924S until made unnecessary by replacing the 2 sensors.

The sensors are probably the most expensive items on your Fleabay 924S now.[8|]

Cheers,

Fraser · Jul 25, 2013

Thanks for the post. The electrician has apparently checked both the sensors, and they appear to be OK. That said, when the car was running he wasn't getting any signal from the sensor (or none that he could measure). I thought a crank sensor as well initally - it's a bit of a puzzle. I'll jiggle them when I get home (that said, I'll probably get home, turn keys, start on the button - famous last words!).

Thanks again,

Fraser.

Fraser · Jul 25, 2013

ORIGINAL: Fred Hindle

The sensors are probably the most expensive items on your Fleabay 924S now.[8|]

Cheers,

I've been warned to expect open wallet surgery if it's one of the sensors - a bit of a mission to get to.

vitesse · Jul 25, 2013

The 2 were under £60 & mine gave readings when I checked them with a multimeter--I presume those on a 968 are the same-I haven't checked of course.

Now had I bought them from Porsche, then Fred you would probably have been right.[

]

Fraser · Jul 26, 2013

ORIGINAL: VITESSE

The 2 were under £60 & mine gave readings when I checked them with a multimeter--I presume those on a 968 are the same-I haven't checked of course.

[]

Thanks for the further input - that looks like the first thing to rule out then. Best I get them changed.

vitesse · Jul 26, 2013

Just to clarify,I bought them from GFS for that money,negotiated through my teeth to get the best price & fitted them myself-I think they are over £150 ea from an OPC.

I suggest you check it all out before letting someone loose with your money-buy them yourself for them to fit--on my 924S,one of them fits inside a aluminium metal thinwalled can which prevents interference,this can then fits into the engine casing over the flywheel-can be quite difficult to get out.

vitesse · Jul 26, 2013

Have checked the Porsche parts list -shows the 968 having only 1 of the pulse senders but exactly the same part no as the 924S,944--ie 944 606 115 00-so could cost you under £30 & is probably easier to replace because of the lessons learnt with the earlier models--ie the can doesn't oxidise & jam in the housing--what is a sticking point (pun intended -)is the rubber "O" ring round the can--makes it harder to remove once in the housing mainly because you are not pushing down against it rather pulling up & more difficult to grip the top to really exert the force without risking something breaking--which makes things rather difficult.

Fraser · Jul 30, 2013

Many thanks for checking, and the feedback - and tips on removal / fitting. They combined the speed and reference sensors - good news it's only 1 bit to purchase and fit.

Sadly it appears the 968 pulse sender is made from unobtainium, covered in a gold / platinum alloy and packed with diamonds. That or Porsche parts are just quite dear in this area - Porsche quoting £161 plus vat, happily I've managed to source one a bit cheaper (still Bosch).

I will keep you posted, and thanks again.

Best,
Fraser.

vitesse · Jul 30, 2013

Make sure they keep the one they take out as a thin washer can then be stuck to the end of it -allowing the setting gap to be adjusted on the bracket to give the correct clearance when the new one is inserted---(once the O-ring is removed & the old can cleaned it slides in & removes easily)-see Clarkes Garage for how it's done for 944's.

The ones I got from GFS were Valeo-a brand used commonly by Porsche & so I've kept my old one with the washer for any future use in the Valeo box..

Hope it goes well & solves the problem.

Fraser · Aug 8, 2013

Hope it goes well & solves the problem.

Many thanks for your input and and wishes (I owe you an ice cream if you're at the Gold Cup later this month).

By way of an update - no solution yet, but great progress as a result of help from the garage over the road from my home and an auto electrician they recommended.

They swapped out the crank sensor and initially it looked like the problem was fixed, then it came back. So the old crank sensor went back on.

One of the techies noticed if he tapped the coil the car would start, so they tried a different coil - same story - initial fix then the problem returned.

I should point out they stuck a new battery on the car to rule that out too.

Additionally I should mention the garage didn't charge me for any of the work above apart from the cost of the battery.

So as my car has a Toad alarm / immobiliser fitted the garage recommended an auto electrician to me - he's the "go to" bloke for fitting Toad Alarms. He's been fitting Toad alarms for 15 years and they seldom go wrong.

He (John) spent some time with the car this morning - noticed the same thing that when there's no oscillation on the rev counter when cranking, it ain't gonna start.

John traced a clicking noise back to the glove compartment area, from there to the fuse box, and found some corrosion in the fuse box by pulling and reinserting relays. Annoyingly I know how the corrosion arose. Sitting in the car in the rain I could hear water running down the passenger side of the car - I asked the mechanic who regularly serviced it to look at it - he forgot - and I finished up tracing the problem myself (blocked drains under the bonnet).

Currently the car starts on the button. Electric John said if it doesn't, turn off, turn igintion back on and wait (up to 10 seconds) for the tacho to flick once, then turn ignition to crank - it'll start every time.

I'll take the car into work tomorrow, confident it'll get me there and back (however if you see me kerbside with hazard lights on do stop and say hello).

Best,

Fraser.