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Discussion Starter #1
I have an intermittent problem on my M5.
Looses its spark,doesnt matter whether its cold,warm,idling,driving.By the time i get it recovered,or towed to somewhere,it starts first time.
I see there are 3 relays next to the fusebox.I know one is for the electric air con fan,not sure what the other 2 are?Also there are 2 relays next to the ecu,but not sure what they are.
If anyone could help,it would be appreciated,as i am scared of going anywhere in it and would like to get it sorted so i can use it now winters over...Thankyou...
 

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The other 2 are for electric fuel pump e main power to dme, chenge both, and treat with some wd40 for electrical purpose the connections, pay attention at the little white connection around the coil, and the plastc 3 wire connection beside the ecu of dme coming out from the mail loom:cheers:
 

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Jimmy,

Before going for the relays, check the fuses very, very carefully.

Make sure all the fuse contacts are clean and gripping the fuses firmly.

I had a problem with No1 fuse (I think) - simply bending the contacts to improve the tension, cleaning them and then replacing the fuse sorted a similar-sounding problem for me (engine would die with no warning - at first it would restart almost immediately and then soon became very hard to restart). Eventually it was doing it every three or four miles.

The fuse conductor itself can also crack - you will need to look hard to see this - perhaps even with a magnifying glass. This condition afflicted another poster on here but in that particular case resulted in loss of central locking, SI board, rev-counter etc.

Once again - E28 fuses are poor - not up to the standard of the rest of the car. At least it's cheap to buy a handful - don't trust the spares in the toolkit, they go poxy, especially if there's a water leak. If not BMW, try GSF or equivalent.

But this is a quick, cheap and simple check/fix - and consequently well worth a try, if only to eliminate a possible cause.

Good luck - hope this helps.

Regards

Mfiver
 

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I second Mfiver on fuses as a quick check; mine died and the RAC estimated two hours to arrival; with only the boot mounted tool kit I couldn't do much so started on the fuses - some were not a pretty sight, and some retaining lugs were slack; five minutes of scraping fuse ends, and off we went. And a new set of fuses went in the fuse box and spares kit
 

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Discussion Starter #5
Just wanted to say Thanks for the replies.They really helped.:cheers:
M5 is fixed now.Turns out it was one of the sensors on the bellhousing,top one i think(engine speed sensor).Replaced both as a matter of course,£58 each.
And thanks to Richard at FritzsBits for his sound advise...cherrsagai
 

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Indeed the E28 has a lot of electrical failure in that department

the DME does need the two sensor on the box in order to function. Unlike the S38, the sensor on the front of the engine has a solely checking function rather than actual input.

Also, bad grounding (there is a small, but very important ground on the LH side under the rear seat) or corrosion inside the fuse box are very common.

Its always easy to measure though, pin #35 of the DME should get power at all times and if not, its either the relays , the sensors like yours or something related to that
 

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The main and fuel pump relays are in the glove box area and can only be found from someone who knows exactly what they are. I think that the # is wrong in "the book". Also, some replacement parts have been streamlined so the replacements might have 6 prong holes when there's only 5 prongs (or something like that). Not a bad idea to replace those 2 relays and keep a set of spares on hand.
 
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