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986 3.2s wont start

Ok a bit of a recap and starting from the top .. you got the car started , i assume no obvious misfires .. car ran ok ?

Ignore the comprsion checks .. they are low , several cyls very low which would give you a running fault , misfires etc , you dont seem to have that .

Compresion check needs fuel pump fuse out and even so you can still get bore wash from residual fuel injected and as you know .. throttle open is best .

Rule of thumb , even running then all cyls ok reguardless of compresion check , no lumpyness then its ok basically .

Crank sensor .. usual fault is engine stops when it gets warm , will restart after 10 mins or so .

With car in the non starting position you need a noid light on any injector to see if you have switching .. ie crank sensor fault .

Spark , a little harder but a spare coil and plug , connect it , ground the plug and crank .. do you have spark .

Fuel pressure , the pump can get blocked , more so on 997 but even so , theres a filter in the base , it can get restricted , check is with gauges im afraid , no other way .

Fault code check .. this is the first thing i do to be honest .

Single plug replacement is usually a sign of a mechanic diagnosing a fault , replace a coil or a plug .

I very much doubt it but unplug the maf sensor and start it .. if faulty then it will reset to defaults and run ok .

Exhaust in coolant ..

If compression gasses get into the coolant via a crack then you will have a serious over pressurisation of the coolant system , the cap when released will shoot out coolant even when cold after a few mins of running , a " sniff test " , chemical test will prove that very quickly , but ..

unless coolant gets into a single cyl then it wont cause running issues .

Plugs all the same " colour " then you dont have coolant in cyls .. black = over fueling .

Heavy buildup = oil leakage into cyls ..

White or pinkage can indicate coolant .

Remember .. you bought a project , you have the info .. play and fix .. dont give up , its fun when you fix it ..

Also .. i do this every day lol .

Thats all i got for now but keep at it :)
 
Only just spotted this thread, I had a similar problem with a crank sensor, after a rebuild some years ago the engine wouldn't start. I bought a new crank sensor as this showed up faulty on the diagnostics and it still didn't start so I started unplugging the main engine wiring harness and cleaned, plugged back up. The car then started and I didn't have an issue for a while until I started getting an issue where it would not rev above 3500 rpm when pushing on, this was really annoying and I couldn't find the problem.

It eventually got better and would falter less than it did but when I rebuilt the engine again a couple of years later it was fine until I was in France and it stalled on me twice within a couple of days which I though was unusual, then one day in Switzerland a day later it failed to start, my Durametric reader said crank sensor so off it went to Porsche Bern, they fitted a new sensor but it still didn't run. After they did some continuity testing through the engine wiring loom they found the crank sensor wiring to the engine wiring harness plug was broken inside the sheathing. They ran a new wire across the engine and it fired up and I have never had a problem since.

The wire must have been breaking down for a few of years, it runs really tight over the engine where the AOS sits. Worth doing a full continuity test from crank sensor to ECU although this may not be conclusive. Also clean up all the terminals on the ECU and harness plugs for dry joints. IIRC you should be getting 5 volts at the sensor plug and also check the Ohms of the sensor.
 
Thanks again guys for all the comments and ideas.

So to confirm the car does seem to run very well whilst its actually running and there are no signs of missfire and no noticeable loss of performance. On its first start, I would say it was lumpy for about 5 seconds but cleared instantly and I would expect this given it hadnt started for about 2 months and probably had loads of fuel in there from previous attempts. It was very smokey at first but cleared very quickly to the point of no smoke whatsoever - again all that I would expect from a cold start from a Porsche. I would certainly expect a real noticeable performance drop to warrant low compression to the point of not starting so I agree with you all that its unlikely this is a low compression issue. I only did the comp test once as I was getting so much dirt in my eyes that I decided to knock it on the head for the day after the first round of checks. Unfortunately the Boxster is one of many things I'm working on at the moment and sadly its probably at the bottom of the list.

Whilst I did buy it as a project, if I'm honest I was expecting a water pump or a thermostat and certainly not this non-start issue. If I'd have known I wouldnt have taken it on as my time is so limited. I love a good project - especially the satisfaction of taking a good car that needs some attention and making it great. Given the time I know I could do it with the Boxster - its a case of whether I can find enough time to get this running properly.

Due to the relatively low cost, I will replace all 6 spark plugs anyway - seems silly having a mix especially when they are all showing their age. Nothing really stands out on the plugs out of the ordinary that would suggest anything other than normal operation. They are certainly not black and there are no real odd colours - they all look the same. when I replace them, I'll put a picture up of the old ones.

The engine doesnt cut out when it gets warm and has never done so. Once its running, its running well. Still no fault codes at all showing although granted this isnt using Durametric. I may have to see if somebody local with it can pop over and see if anything shows up.

Based on the comments on pressurisation, the car can certainly run longer than a few minutes without the coolant shooting out when removing the cap and the car will still take the normal sort of time to get up to full temperature - a good 10 mins or so when cold. I know it seems unlikely but is it possible for exhaust gases to escape into the coolant jacket without coolant getting into the cylinders? There is no sign of coolant getting into the cylinders. I did another block test also this weekend and I need to upload the picture of the fluid as it again feels inconclusive. I think the blue liquid has changed colour a bit - its certainly lost some of its blue but I wouldn't say its an obvious green or yellow colour. It seems more clear.

I think my next step will be new plugs, full coolant flush (its awful) followed by careful filling of some new stuff making sure to eliminate all air in the system and then assuming it starts, try and test it out and see what happens. I think we all seem to be in agreement that the over heat issue and the non-start issue are unconnected. I think I might also pull the fuel pump to just check its condition as well as its pre-filter. Probably worth a new fuel filter anyway as there is no record of when this was last changed - good preventative maintenance if nothing else.
 
I'd agree with what you are saying, however if there's a crack allowing exhaust gas into the coolant then it's normally a very clear cut thing and not a marginal 'maybe' due to the pressures involved.

The other thing I'd be checking if it was me would be the live outputs of the coolant temperature sender into the DME, does it tie in with real world and change during a normal cold start upto normal running temperature?

If this is faulty then difficult starting is a strong possibility (the DME doesn't know that the engine is cold and doesn't enrichen the start up mixture)
 
So its been a long while since I updated this - work has prevented any real progress. Hoping to get a few hours this weekend.

Anyway a couple of pictures - firstly the old plugs. In terms of colour I cant really see anything out of the ordinary however the one odd plug looks like its missing a tip. I only spotted this in the photo and have more than likely thrown the actual plugs away now. All new ones are fitted and the engine seems to currently be starting fine and sounds fine - no obvious missing.



Next picture is the result of another attempt at a block test. To me the fluid has definitely changed colour as you can see between the neat fluid and the 'tested' fluid however again its not that clear cut. Its not the clear 'blue' or 'green' that the instructions state. I still think the coolant reservoir stinks of fuel when the cars running so I'm still thinking the worst here.



Due to the mix of different coolants, I have also now emptied and flushed the system disconnecting everything, refilled with water and a flushing agent, run the engine up and then drained and flushed fully again.

I just need to pick up some coolant this weekend, fill, bleed and hope for the best. If it still has an issue, I think there clearly must be an exhaust gas leak into the coolant - there is no other option. I will have to get somebody else to test it to be 100% sure and if its confirmed I will pull the engine, do the head-gaskets and have the heads pressure tested.

Does anybody know of any good mobile specialists in the Hertfordshire area who could get to come out to diagnose once and for all if I don't have success this weekend? I'd rather not take it to a local independent who isn't a specialist in these engines. Any suggestions would be greatly received.
 
Another little update. So over the weekend I had a little bit of time and took the Boxster for a bit of a test. I drove it for a good 15 mins or so on the hottest day of the year - it got up to temperature gradually and then held there in the correct spot. This was encouraging.

When I parked up with it still running, I checked in the boot and there was no steam escaping and no nasty sounds or smells, in fact I could hear the coolant circulating at the top of the coolant tank which says to me there was no excess pressure. Heaters are nice and hot so no air locks there and I kept the bleed valve open to try and squeeze any last bits of air out.

I'm cautiously optimistic as I feel if there were exhaust gases escaping into the coolant, I would have known about it by now. I need to give it a slightly longer test now.

On the negative side however, the starting issue occurred again when I had stopped it for about 30 mins. First start was absolutely fine however upon starting up again it took a good amount of effort for it to start. Once started however it ran like a dream.

Its very annoying as I still cant rely on the car at the minute and being so intermittent, its not easy working it out. I think now I really need to get someone with the full Porsche software to plug in and see what the various sensors are doing. Still has a 'crank sensor' feel to it. The fact that it has now been hard to start when warm as well, rules out it being a temperature sensor issue. I obviously have a spare known working crank sensor but I cant get the original one out. Its really stuck in there.

The only other thing I can think of is one of those annoying things that often gets over looked and that's a dodgy old battery. Might stick my 996 one in and see if it makes a difference.
 
You can test the crank sensor with a multi meter to see if you are getting voltage supplied (I think you should be getting 5 Volts??) and the ohms reading (can't remember the figures) when hot and cold, this will give a you a clue as to whether the sensor is at fault before you have to butcher it off.
 
Resistance should be between 0.8 and 1.0 KOhms at around 20 degrees C so cold engine. Its worth me checking that to see. I've ordered some service parts for it anyway as I feel a little more confident know the coolant issue looks like it may be solved. It will have a new air filter and fuel filter to go along with the new plugs. Am hoping to do a bit more diagnosing on the dodgy start issue at the weekend.
 
Crank sensors dont always throw up a fault code for intermitant non start faults but hot and left or just getting hot is when they tend to fail .

Its a weak signal basically and a good scope is the best way of checking but its dificult to get it in the non start position when checking it .

Resistance check is certainly worth doing but may not prove its actually faulty .

Changeing when its seized in .. well .. gearbox out is the best option , its the same sensor as abs and drilling is pretty much out , the magnet snaps drill bits .. ive spent 3 hours drilling one out on a 928 before and i had access to that .. its a mare of a job .

Assumeing no fault codes on a non start then fuel pump / pressure is the next thing as the car doesn,t know this so cant generate a code for it .
 
Time for a small update - not that I have done a great deal. I did however take it for another 20 minute drive and no overheating and no sign of steam escaping which is positive. This is obviously my main concern as the starting issue will be relatively simple and will get sorted. If the cooling issue isn't fixed then obviously its an engine out job which I really don't have time for. There was a little coolant dripping down afterwards however which was clearly coming from the drain tube at the back. Checking in the boot however, it definitely wasn't coming from the filler cap (brand new 04 cap fitted as a precaution already) yet the top of the bleed valve was a little damp. I changed the seals on this recently and upon double checking the screws were fairly loose so I guess they have loosened as the seals settled so I tightened them up and hopefully that's all it was.

My brothers E46 M3 has spat its dummy out and needs a new HG (as a minimum) so annoyingly this has moved ahead in the list of things to do however I plan to keep working at the starting issue.

Again the issue is still there but at the moment it does still start every time eventually. When I first went to start it, it started right up on the button. Next few times throughout the day - it took some encouragement. When it nearly starts but doesn't quite manage it, I get quite a loud squeal which I'm fairly sure is coming from the starter. I know this is fairly common and at 90k miles its probably relatively worn. I didn't consider this could be the issue and to be honest I still don't really but regardless I'd like to sort this out as its a nice simple job and I can clean and check all the cables at the same time. I'll pop the motor out and take it to my local auto electricians for a rebuild. I guess it deserves it at 90k miles.

I also replaced the cabin filter which looks like it was probably the original - absolutely filthy. Also did the fuel filter which again looked really old.

I'm waiting on a new air filter and drive belt to arrive as well. I'm basically changing all the serviceable's so I know exactly where I stand with the car. I must say when its running - it feels like new - really impressed.

Eventually this is going to be a great car - I do feel like I'm slowly getting there with every hour I find to work on it.

I think I'm confident enough now with the cooling system to drive it to a specialist to check the crank sensor.
 

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