BMW engine in Triumph stalling problem.

[andyborris]

I have a BMW M52 engine in my Triumph.

It has developed a odd fault. Car starts easily, drives and idles well, but as soon as the temperature reaches 40*C, it stalls and won't restart till it's stone cold.

Then it starts easily, drives and idles well till the temperature reaches 40*C again!

I can't find anything that might give me a clue to this problem, I first thought the air ICV was not working, but it appears fine (although I haven't checked the ohms yet). And I think that a problem with the ICV, is more likely to cause rough running, rather then a total stop?

I admit I'm stumped, I can't see how a coolant temperature sensor would stall the engine and when the engine stops, it's like it's just been switched off. No pre-warning by poor running. Today, for example, just ticking over in the garage, it hit 40*C and just stopped.

The only other symptom, the plugs were very (very!) sooty.

Any suggestions?

Thanks

[steveg]

Sooty plugs would suggest it's running rich but you would think it would gradually run worse then stop if it was a temperature sensor. That would be like leaving the choke out !

Is it just running out of spark, a relay or coil pack gradually getting warm the failing ? My knowledge of Injected cars is limited but had an old Panda that drove fine until it got a bit hot, then it gradually died and that was the coil.

[Rob M]

Typing your symptoms into google brought up this....
www.bmwland.co.uk/forums/viewtopic.php?f=5&t=50637&start=0
or
en.allexperts.com/q/BMW-772/1989-BMW-325i-Engine.htm
Seems like its not uncommon and may need a bit of methodical "suck it and see".
Best of luck.

[bmw2101]

probably crank sensor,


cant you get it plugged in somewhere and read the fault codes?

[taurus]

I've had a CTS fail where the car ran fine with no sign of flooding or bogging down, then it just cut out. So for the price of the part I'd whack a replacement CTS in there. They also do it and never show a fault code, which is annoying.

[andyborris]

Thanks everyone.

I was thinking CTS too, it be sending a overheat signal. the gauge is mechanical. Guess it's going to be a suck it and see thing, one sensor at a time.

[andyborris]

Just a thought, when I installed the engine, I had a component mismatch.

A early wiring loom won't work with a late crank sensor, so I fitted the early crank sensor in place of the one on the engine. But the early sensor is 2mm shorter (further from the trigger wheel) and is (I think!) 5V not 12V.

It has, however, been fine. Obviously the car wouldn't start without a crank reading, so if it is the crank sensor, it must just be a age/wear failure?

Andy

[steveg]

You can tell on some cars if the crank sensor has failed as the rev counter doesn't move whilst cranking.

[momanatorz]

Hi what ECU are you running? Presuming it's the Siemens which is factory for the M52.
You need to run the correct sensors, the older crank sensor won't be helping. It's for the Bosch ECU

[momanatorz]

Has it still got the OBD port? plug it in and see what comes up

[dodgerover]

Could it be running in limp home or base settings mode upto 40 degrees if it not picking up a decent signal from one of the sensors, I had a 2.5 omega that would run (badly) with the crank sensor disconnected!

[andyborris]

It is the Siemens ECU, but the car has run fine like this for over a year (around 5000 miles) now and still runs quick, till the temp reaches 40*C!

I'd like to plug it in, but the nearest garage with a OBD reader is over 40*C away, it'll take a long time to get there!

I'm going to try unplugging sensors to see what happens, starting with the CTS, I'll know when it hits 40*C from the mech gauge.....thanks for all the suggestions, you've got the brain working again!

[ejenner]

I've got the BMW diagnostics gear so if you can get to Bromley in Kent then I can connect it up for you.

[andyborris]

Mar 30, 2014 19:00:40 GMT ejenner said:

I've got the BMW diagnostics gear so if you can get to Bromley in Kent then I can connect it up for you.

You're my new best friend ... not sure the car will make it from Herne Bay though, runs for about 15 mins, then needs 4+ hours to cool down!

I'm going to have a go at unplugging sensors, if this doesn't point me in the right direction I'll give you a call and maybe trailer it over...thanks for the offer, much appreciated.

[ejenner]

I don't get notifications off the board so contact me through one of my websites in the signature.

[andyborris]

Tried disconnecting various sensors, started with the coolant, car took a bit longer to "catch" and run, but as ever, run well once started.

Cut out after about 5 mins and wouldn't restart.
Reconnected the coolant sensor and tried with the Idle Air Valve uplugged, car started run for about 1 min and stopped. Likewise with the crank sensor unplugged.
Then it refused to start any more, no matter what I unplugged or plugged back in and I tried them all!

I wonder what the symptoms of failing Coil on Plugs are? Could they be failing as they warm, perhaps the above restarts with sensors unplugged, only happened because the coils cooled with I was fiddling with the sensor plugs (space is tight!)?

And how likely is it, that all 6 coils will fail together?

It does sound like I'm not getting a spark when the engine won't restart, it's just spinning, normally you can hear the engine trying to "catch".

And it's always taken 2 turns of the engine to fire

[steveg]

Can you re-set the ECU by disconnecting the battery, might be worth doing that to start with as it might have stored a few fault codes.
Check to see if there is a spark either by taking a plug out and earthing it on something or by using a timing light. At least then you will know whats going on.

Unplugging things might have finished off a bad connection somewhere, might be a good place to start. I hope I didn't give you a red herring with the mention of failing coils. I didn't know they had more then one.

I tried to fix a relatives Fiesta recently. Various garages had diagnosed various sensors and I gave up in the end. It turned out to be a blocked vent pipe somewhere. Car would start and run fine for a minute or so then just die. Just goes to show simple mechanical things can still stop cars not just iffy electrics.

Hope someone can suggest something more helpful.

[andyborris]

All suggestions are welcome, so thanks.

Not sure if you can reset the ECU by disconnecting the battery, I use a master switch anyway when the car is garaged and this isolates the battery.

The air intake system has been simplified, all the fume recirculating gubbins has been removed and it all now vents to air, so no fault codes from blocked filters. And again, it's been running like this for over a year now and to put it all in perspective, it's now a 130+ mph car.

The ECU has been modified to cope with the engines new home, no speed sensor, ABS, EWS etc.

I also believe that the engine stops, (it just like switching it off, no fuss or warning!) are now happening quicker, perhaps whatever that's causing it is getting worse.....

[v8ian]

Sounds very similar to my e39 problem, turned out to be a duff cam sensor, sometimes they pick up a bit of rubbish on them, or get corrosion around where they bolt in and the corrosion moves the sensor away, engine get warm, sensor moves out of range,

[andyborris]

Tried unplugging the cam sensor after the engine had died for the 3rd time tonight, no luck, assuming it'd run with it unplugged? It run pretty well with the crank sensor unplugged for about a minute, so I'm guessing yes?!

I've ordered a spark testing kit, so I'll check that when it arrives and tomorrow I'll try it with the cam sensor unplugged first.

I am leaning towards a total failure of the coils as they warm though.....