Starting mystery - posible faulty sensor?

I have just tried starting the car after it had been left for 6 weeks. I had to charge the battery, connected it up, turned it over and nothing? The engine spun over fine, but there was nothing not even a cough or a splutter. The only thing that I noticed was when I was turning the key off, that there was a slight hint that it was trying to catch.
I left it for 15 mins and tried it again.......exactly the same.
Fortunately I live on a hill, so I bump started it and eventually it started. I drove the car around the block and it seemed normal.
I parked it up for 15 mins, tried it again expecting it to be OK, but nothing. It was the same turning over quickly, but not a hint of it starting.

I run it down the hill again, but this time it didn't want to start. It fired eventually, but then cut out.

I removed 5 of the plugs ( these were new NGK fitted only 2 months ago) and they seemed normal, not flooded or anything. I checked to see if there was petrol getting to the manifolds that was OK. I spun the engine over to clear out the bores and surprisingly it tried to start on one cylinder!!! I couldn't believe it. I re-fitted the plugs, and it fired up as normal
I ran it around the block again and it was normal. I parked it up for 15 mins, tried it again and it was exactly the same symptoms again - nothing.
I took the 2 plugs out of the left bank and tried starting it.
It started on the 3 plugs straight away - put the other plugs back in and it started straight away.
I ran it again and this time kept it going and warmed it through. It has been OK ever since.

I normally use the car daily and in the 12 years that I have had it, I have experienced similar symptoms only on 2-3 previous occasions,

I know that it has been standing in some of the worst weather that we have seen for a long time, but I am mystified why it will try and start on either 1 or 3 cylinders, but will not fire at all with them all connected?

Could it be a sensor? I am sure that it is either a sensor or possibly ignition, but it doesn't explain why once it starts that it runs perfectly.

I appreciate if anyone can throw some light on it, even if it is only to explain why this could happen. It is not logical.
I am not sure if it is possibly connected, but I have been seeing an occasional diagnostic light flash only when the car is cold or perhaps sometimes when the engine is under load when accelerating. It is not always, but it has been more noticeable lately - maybe the issues are connected.
I have also found that if it has been left for the weekend and I start it on the Monday, that there is a slight misfire only under load, but it clears once it has warmed up. It doesn't re-appear for the remainder of the week?

I Look forward to your comments

Thanks,
Jeff

Jeff

i have a very similar problem. if its left a week or two it will start then miss on load and if you keep driving for say 10-12 miles it will clear its throat- but if it stops you wont get it started at all!!

if you leave it months it just wont start - backfires etc

the only cure i have found is to remove the cao and you will find condensation on the rotor arm dry it re assemble and it will work perfectly.

i have thought of changing the rotor and cap but if it was faulty why would it work perfectly when you drive it every day?

i have had gtas and this never happened even after say 6 months not started

it doesnt appear to be a sensor either

is it just a design fault?

regards

dermot

Could be the ignition (Renix) unit on the rhs of the engine bay. Mine started to break down and sometimes it would run fine but other times it started to run very rough. This occured during driving and also when starting. Replaced the Renix unit and it's been fine.

Was also going to suggest the flywheel sensor. However, this normally only causes problems when the engine is hot, and the protective sheath on the sensor starts to breakdown.

If you can find a spare Renix I'd try swapping it over.

Jeff

It would be helpful to know if your Alp is a Turbo, or Atmo.

John

If your car is turbo engined, i would say a distributor cap fault esp if the car has been laid up for a while.

The car is a turbo and I am interested in your views relating to the starting problems. I can understand how you can relate it to the distributer cap... but this was changed together with the rotor arm early in the year, so I doubt if it is a faulty cap, but it could be condensation?

I am wondering about the leads? I know these take a hammering with the heat of the turbo, and I know that they have not been change for about 8 years? They were changed then because I was getting a misfire under load, which after a diagnostic check, temp sensor change, and new plugs immediately went away when the leads were changed.
I am thinking that they are probably due a change, but are not convinced that they are the root of the issue? I am going to spray the leads in the night with water and see if they show up anything. When I did this before it was like Star wars!!

I used originals before - what are the recomendations... Magnecor?

I am still getting the occassional flash on the diagnostic lights which happens a couple of times only when cold (never stays on), which makes me suspect the temp/cold start sensor, this showed up on the diagnostic when I had the issue before but although changing it never made any difference?? It obviously means something is degrading because it has only done this recently, so it must mean the start of something? I am suspecting this because it is mainly occuring when it is cold.

Any suggestions where you can pick these sensors up cheaper - the Simon list price is now 65 euro plus the dreaded


Keep the suggestions coming in...please!!

Doubt it would be the leads, a GTA will start on 3 cylinders quite easily. It would have to be nearly all leads faulty not to start

Id say either rotor arm/cap or coolant temp sensor/map sensor.

Easy way to know, disconnect EVERY sensor, coolant, air and map(pipe only) This sets the coolant temp to a default of 66c, the air temp to 33c and the map sensor will read atmospheric, ie start very rich. If it then starts you know it was a sensor/lean fuel enrichment problem, if it still doesnt start, then it can only be trigger or spark related.

Oh, it could be a physical problem, ie fuel pressure/supply.

Again check for this by taking off the boost pipe into the V6 plenum, and squirting in Easy Start or the like into the plenum with the throttle open while cranking.

I am going to spray the leads in the night with water and see if they show up anything. When I did this before it was like Star wars!!

Jeff, who on earth told you that this was a good idea The Star Wars vision was hardly surprising. I would expect that to happen even with an engin in 100% condition If there is a problem with EHT flashover, you will see it in the dark in normal atmosphere, if you do not see any flash over in the leads in normal conditions, there is no problem. Seeing as you have an intermittent warning light, in the first instant I would check all the connectors involved in the ignition system, all the sensor connectors, and the ones on the ignition power unit. Unplug each of them in turn, spray them with Electrolube switch cleaner, or similar, and connect and disconnect a couple of times to scratch clean the pins/sockets before finally reconnecting them. I would do this before anything else, as I am sure you are aware these French connectors are not the most reliable, especally if the car has not been used for a while.
Good luck

John

capity capity cap

John,

I wasn't atlking about dousing the engine with a hosepipe!! I tried it with a misting spray last night and I am pleased to say that there was no tracking at all!!
If the insulation is good and not breaking down, that is what I would expect to see. If there is tracking evident, then it is an indictation that the lead insulation is not doing what it is supposed to be doing ie.sending the energy to the spark plug, the same applies to the dis cap.

The car has been working fine since the original starting problem, apart from the occasional diagnostic light flash when cold,

Dave, Thanks for the info on the sensors. It is good to know what the ECU defaults to when they fail. I will certainly keep that in mind if it happens again, which I am sure it will. The next time it does I will be certain to diconnect some of the sensors to see if that changes something.

Thanks Guys for the replies.

Jeff

I wasn't talking about dousing the engine with a hosepipe!!

Jeff, I take your point, its just that you scared the hell out of me when you stated that you were "going to spray the leads with water" . However the main point of my reply to you was to check all connectors, as this fault appears to be intermittent. In my opinion it is most unlikely that a sensor will be intermittent in its self, it would normally work or not work, however with the known dodgy nature of the electrical connections in these cars, it is always worth checking them first. I have always held the view that quite often when a sensor is changed, and the fault dissapears, the fault in fact was cleared by just deconnecting and reconnecting the the wiring to the sensor, and the fault was due to a poor connection, and a good sensor is thrown away. I have been known to pop the apparant faulty sensor back in just to check that it was in fact faulty, not on these cars I might add, but in my working life

John

making sure the leads are clean in any case I spray mine up with WD40 wipe them down with a clean rag; keeps moisture out cleans them too

And looks better under the rear hatch 3 jobs done in one


si21