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Strange starting issue. Help required please!

berni29

Well-known member
Joined
24 Oct 2009
Messages
3,045
Hi Guys and girls

Very long time no post. I hope everyone is well. I'm still living abroad, and my brother who is looking after my 993 is stumped on a starting issue the car has developed. He and I rebuilt the top of the engine ourselves, and have had most of the car apart at one time or another so are not total noobs with it. It was also mapped by Wayne a while back.

We also have the durametric, but no help there.

The problem goes like this.....

Car starts immediately, on the button from cold and runs well. Not perfectly but well. Turn off the car when its warm or even after a few minutes and no start. Can smell fuel. If it does start it will rev to 2,000 and stay there blip throttle and it comes down a bit but not drivable.

Leave it a while, the hotter the longer, then its ok again.

We know its not the DME. Changed it and jumping the terminals does not help.

O2 sensor is new and it passed the MOT afterwards, so its not that.

Fuel pump is running seemingly fine. Plus can smell fuel.

MAF has been cleaned, but could be faulty. Car runs well if you do not switch it off though. Have not pulled the MAF plug yet when its in a non start state but will try that next time.

Battery is good plus earths. The engine spins very fast when not starting, so its not the 200 rpm no start limit or whatever it is.

Have not checked starter motor earths yet.

Have not checked CHT sensor, but Motronic on the durametric shows no faults. And believe me when the car wants to throw faults then they do appear. Usually cryptic ones.

So any help much appreciated. The answer is out there somewhere.

If he gets stuck in another petrol station I think that will be it. Plus more importantly I am back in the UK next week and want to drive it without having to keep the engine running all the time.

Failing that the car is in SE London (Beckenham) and may have to go to a specialist (suggestions please). We hate to admit defeat though, and specialists love to fix things via an expensive just replace everything strategy. The car has done 200k miles and its just not that sort of situation/relationship.

Thanks again in advance

Berni
 
Hi,

I'd put my money on the crank position sensor as you have already guessed. Breaking down with heat and metal expansion. The gap needs to be a specific value.

Regards
GR
 
Had very similar issue with 993 C2 race car last year and it was as has been said already faulty crank position sensor. Air gap set up is important, crank sensor faults dont always show up on durametric. Definitely first port of call.
 
Hi I hope I can help, my car would sometimes struggle to restart at a petrol station when it was hot. This usually happened after I had done some miles and the engine was really hot, this also included a smell of petrol. I had my Injectors tested and cleaned which made the running of the engine so much better. It's a stab in the dark, but it may help?

good luck

A
 
+1 Crank sensor. Works by electro-magnetic induction if the coil has a break in the wire it will work until warmed and expanded then fail 'til it cools down.
Seems to be age related they only last 20yrs or so.
 
Brooklands in Swanley is not too far from you. Sorted the misfire on my car when the distributor caps/rotor arms needed replacing.
 
Chaps,
does anyone have details of the CPS?, location on the engine and replacement item costs etc?, is this a 'whilst you're in there' item that you should replace if the engine is out of the car?.

Trev
 
Hello Guys!

Thank you so much for taking the time to reply and for the guidance. Will order a CPS today, and hopefully my brother can do the swap ASAP. He's knackered his back and I think this one will require some bending/keyhole surgery so he may not want to.

Will report back.

If my engine was out I would at the the very least remove the sensor, clean up any corrosion and debris, and check wire condition. Careful with the retaining bolt they love to snap.

Thanks again.
 
Hi Guys

We changed the crank position impulse sensor and it's not that.

The car starts on the button, then switch off and will not start. You can smell fuel and there is a spark.

Any further ideas welcome!

All the best
 
I seem to remember reading an article, I think in Porsche & 911 World this summer, where an older 911 (not 993) had what sounded like a very similar problem. In that case it was down to - I think - the fuel regulator where a membrane had failed. It stops hot fuel being forced through somewhere as the heat increases the pressure.

Anyway, I don't even know if there is such a component on a 993. Just thought I'd mention it.
 
Hi

Thanks will give him a ring.

A spot more information, sometimes the car will start and Rev to 2k rpm, whereupon if you touch the throttle it dies.

Tsk again

Berni
 
Sounds like a tough one. I'd be inclined to thoroughly check the ignition side of things. Suddenly cutting out sounds like ignition to me.

If you can borrow items the coils and ignition amps would be a check point. Do you have a Durametric or the like to read live info before the engine cuts out?

Regards
GR
 

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