850 non starting self diagnosis

[Merc85]

Well, ive had loads of loads of issues with this dam car now.

Original fault, car broke down , Signal wire to coil had gone bad and wasnt sending signal to coil to spark. Re wired and all was good.

Then when cold the car is hard to start takes ages to crank to throw a spark.
once started car is usually ok.

Performed self diagnoses as still having issues, got it to throw a code, but couldnt read it?? The idle control valve was buzzing with the ignition off??

Started car then turned off, turned to position 2 and read the codes , NON stored??

Started the car and the cel light went out and the buzzing stopped. really confused,

Car is obd 1 with the self code reader under bonnet. made the car do a self test ie runing fan and clicking coil, and injectors. still no fault?

I Have replaced everything on the car ignition wise, and still have a cold starting issue, and its worse when the car is left for a long time. Its electric related as i know there is no spark for at least 10 to 15 cranks when cold.

Any ideas? will be scraping the car soon as cant find the course.

[Thanatos]

I know this is going to be silly but the battery how old is it and what voltage is in it

[Merc85]

Originally Posted by Thanatos

I know this is going to be silly but the battery how old is it and what voltage is in it

Battery is a Big 096/100 and has been tested fine, also tried a New battery also just to double check. car spins over well but coil doesnt output a spark.

Cam sensor and crank sensor also tested fine. Car was scoped by a auto electrician also. no fault found.

Coil has no spark out put when cold for around 10 cranks, car hasnt got a chip key nor imobiliser.

[dinky1]

Are you sure its the coil and not the dizzy? Only reason I ask is because I had similar symptoms to you recently - I could crank it for 10 minutes and still get no starting. When it would eventually start it wasn't firing on all 5 and would cough, splutter, slow down, speed up etc. When I popped the hood I could hear the dizzy clicking - when I looked closer it was sparking all over the place (the plastic was so knackered you could see the spark!).

[Merc85]

Originally Posted by dinky1

Are you sure its the coil and not the dizzy? Only reason I ask is because I had similar symptoms to you recently - I could crank it for 10 minutes and still get no starting. When it would eventually start it wasn't firing on all 5 and would cough, splutter, slow down, speed up etc. When I popped the hood I could hear the dizzy clicking - when I looked closer it was sparking all over the place (the plastic was so knackered you could see the spark!).

Hi,

I ve replaced everything inc cap and rotor, plugs leads, coil n module, ecu, cam and crank sensors plugs, injection relay, fuel pump relays etc etc

[cluckmaster]

HI mate along shot but have you got a loose pulley on cam belt side or a broken locating pin on the dissy/ rotor. I had a very similar problem on a motorcycle it turned out to be a worn wood rough key on the magneto. good luck rob

[Merc85]

Worth a check, will have a look

[cluckmaster]

I know you say it has no spark but what about fuel run back ie injectors draining dry when stood.

[mikealder]

Seen similar with a mates 96 850, in the end changing the electrical portion of the starter switch cured the issue, his was doing the same as yours, no spark/ wouldn't start then randomly the faulty contact in the ignition switch would make letting the ignition fire up and the car would start.

He changed crank sensor, cam sensor and a whole raft of other bits from a spares car that was known to work all to no avail until we nailed it down to the switch - Mike

[Merc85]

Originally Posted by cluckmaster

I know you say it has no spark but what about fuel run back ie injectors draining dry when stood.

Pritty sure its not that as it stinks of fuel after firing ie flooding itself. ran a ht tester out of coil, and there definatly no sparks for the 1st few turns of the engine