No Start/No Tacho Bounce/Speed-Ref Sensors?

[scam75]

Morning All

Was greeted with a no start, no tacho bounce this morning in sub zero temps. Nice. Had noticed last week a no start incident, isolated, failed to notice tacho as it fired up next try. Anyway it wasn't having it this morning. So opened the bonnet to wiggle the speed/ref sensor bracket. Noticed bracket was loose, floating about, anyway starts first time after a wiggle. Noticed I needed a splash of oil, so switched off, topped up oil, secured and tightened 10mm bolt holding bracket, started first time, no dramas.

So firstly, does a turbo have a speed and a reference sensor, sure I read it just has one? The bracket seemed to have one plug going into it from O/S and then a couple leaving it from the N/S. Not really got a clue what they all are. Secondly, can this cause an engine cut-out whilst driving or will it just prevent a start when playing up? Thirdly, what advice? Obviously the bracket is no longer floating about so that will help. Is it worth unplugging it and spraying in some contact cleaner or is it likely to fall apart as I've read previously? The car had a new speed or ref sensor (not sure) about 10 years ago just before I bought it I noticed from the history.

Anyway, thanks all in advance!

Stuart

 

[PSH]

Hi Stuart

I think it's only the 16v cars that have one sensor..I'm sure someone will correct me if I have this wrong.
!: yes, turbos have two, speed and reference as you mentioned, certainly my '86' does.
2: yes, the engine can falter and cut if they come loose during driving, it happened to me once on the M25...lol
3: I'm a little confused by your description?... the bracket should have both sensor cables going through it, It's shaped to do so, so a multi-plug for each sensor on either side of the bracket. I'm not sure what you mean when saying you have one plug from the O/S and two from the other? that sounds like one is disconnected?.. can you take a picture to help?

Cheers

Pete

 

[robwright]

Turbo has both sensors mate and they both connect through the bracket. There is another round one for a coding plug I think? It can fail in the way that it will still run but then not start after a stop. Happened to me once but was accompanied by rough running under load. Just a partial connection. I have both of plugs trussed up with cable ties either side now. Not that pretty but doesn't look too bad an is good insurance against them ever coming apart again, which they never have.

 

[robwright]

Hi Stuart

I think it's only the 16v cars that have one sensor..I'm sure someone will correct me if I have this wrong.
!: yes, turbos have two, speed and reference as you mentioned, certainly my '86' does.
2: yes, the engine can falter and cut if they come loose during driving, it happened to me once on the M25...lol
3: I'm a little confused by your description?... the bracket should have both sensor cables going through it, It's shaped to do so, so a multi-plug for each sensor on either side of the bracket. I'm not sure what you mean when saying you have one plug from the O/S and two from the other? that sounds like one is disconnected?.. can you take a picture to help?

Cheers

Pete

My thoughts exactly Pete sounds like you have one missing.

 

[scam75]

Thanks guys. I shall go down to the car park just now and take a picture and feed back to you. The wiring all looked pretty good to me, nice and clean anyway!

I did notice the round plug.

Stuart

 

[scam75]

Ok chaps, turns out I do have 2 sensors and all the wiring is where it should be! Both plugs are fully home with the metal clips engaged, both sides of both plugs and the wiring look in tip top condition. I did not attempt to unplug them. Clearly the floating bracket would not have been helping so I think I'll leave it be just now, now the bracket is secure, and see if it happens again. If so I'll unplug them carefully and apply some contact cleaner and see how we go. Not much else to do is there?

Stuart

 

[pse_SC]

Stuart, could you possibly take a picture of the relevant connections/sensors and their location.
Would like to check these out on my Turbo, please?

Hope your car is OK again now...

 

[scam75]

This is where the loom joins on to the sensor plugs. Usual fault area, of course unless the sensors themselves are goosed. Located between rear of engine and bulkhead.

Stuart

 

[Frenchy]

Thinks me has that problem also, as afaik the DME pulls in on flywheel pulses, mine was running fine but I still have a cooling issue with the fans not kicking in.
I was checking my compression readings out and all where okay, removed the plugs and DME whilst taking readings replaced everything and the car would not start, noticed no fuel pressure showing on my fuel rail mounted gauge and no tachometer bounce when cranking, need to get a good look this weekend.
Got me some sexy Michelin Pilot Sport Cup 2 tyres to go on today via flea bay []

 

[scam75]

Never good Jim. It ran faultless back and from work today so see how we go. The loom bends an inch or so behind the plugs. Might be a starting point if it goes tits up as quite common for the AFM connector on the loom to cause issues where it bends.

Stuart

 

[vitesse]

Put up with the Bosch connector "wiggle " procedure for some time on my red track 924S car until the reliability factor was bugging me if I was far from home so replaced them even though multimeter checks gave the correct readings.

Advice I received when discussing with Independants was that it is usually down to:-
1/Duff sensor(s)
2/ Duff plugs
3/ Duff cables mainly due to breakdown in the structure caused by heat,flexure,vibration & any combination of all 3.

No 3/-the most likely.

 

[PSH]

No 3/-the most likely.

I would concur with this...I replaced all my engine loom with new harnesses from LR many years ago that's sheaved in 1200 F heat resistant material, hopefully, this is now protecting the wiring properly.

Pete

 

[scam75]

Thanks guys. Makes sense. It will undoubtedly have another episode at some point, as good as they are self fixing they ain't!

Stuart

 

[944Turbo]

Thanks guys. Makes sense. It will undoubtedly have another episode at some point, as good as they are self fixing they ain't!

Stuart

Well if you have tightened the bracket it is probably fixed - crosses fingers

 

[Frenchy]

Mines, not looking good at the moment, quick shufty this evening no fuel and no spark so DME not pulling in, the DME checked and is okay, flywheel sensor plugs disconnected and seem fine......bugger ![&:]

 

[scam75]

Immobiliser? If I crank my car with the alarm on by mistake, it turns over but nothing else? Just a thought.

 

[Frenchy]

Good shout but don't think it will be that as my immoboliser will not allow ignition, it is quite a simple thing with a coil around the steering column and the dongle in the key ring activates it, thinking flywheel sensor.

 

[scam75]

No worries. My alarm/immobiliser (one unit), allows ignition lights and cranking but won't start. So it must cut off the DME. No tacho bounce or fuel.

Could easily be a flywheel sensor. From what I can gather some start after wiggling can last for years, but this would be loom/plug failure. Dare say if the sensor itself goes tits up then you would go from alive to dead in the blink of an eye. I would probably renew both sensors and see where you get to.

Stuart

 

[PSH]

my 'Toad' alarm immobiliser won't allow the engine to crank either, can't remember if the dashboard lights come on or not?

 

[scam75]

Yeah mine can catch you out if you've inadvertently pressed the key fob. A quick look for the red led in the console and door buttons flashing reveals your error. However I had find all that out myself!!

Stuart