Auto electrician ?

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blade7

Original Poster:

11,311 posts

215 months

Saturday 21st June 2014
quotequote all
I had an issue with my 944 recently, after an hour or so driving I stopped for fuel and afterwards only got a few hundred yards before the car coasted to a halt. Tried a couple of things but it wouldn't restart so had to call the RAC. The guy checked for a spark first by putting the coil lead to earth while I turned the engine over, must have been a spark as he reconnected the lead, told me to try again, and it fired straight up. I drove home without issue and the strange thing is the car was running better than before and the air fuel ratio was spot on whereas before it had been a little rich. So what did shorting the coil lead do ?

paintman

7,669 posts

189 months

Saturday 21st June 2014
quotequote all
Your breakdown symptoms suggest an electrical issue.
Breaking & remaking the connection likely corrected a connectivity issue.

blade7

Original Poster:

11,311 posts

215 months

Saturday 21st June 2014
quotequote all
The RAC guy struggled to remove the coil lead so that connection looked good, going by the fact the AFR improved to where it had originally been 4 or 5 months ago where was the poor connection likely to be ?

ch427

8,857 posts

232 months

Saturday 21st June 2014
quotequote all
The coil lead he disconnected.

blade7

Original Poster:

11,311 posts

215 months

Saturday 21st June 2014
quotequote all
ch427 said:
The coil lead he disconnected.
I watched him disconnect the coil lead, it was fully in.

imagineifyeswill

1,224 posts

165 months

Saturday 21st June 2014
quotequote all
Whilst working 24 hour emergency breakdown services in the mid nineties, over the space of a couple of years I had a spate of Sierras and Cavaliers failing to start, I used to connect a test lamp to -lt on coil and short to earth, vehicle would then start fine, according to a friend seriously into electronics it was caused by a problem with the firing points on the electronic pick ups in the distributor.

ch427

8,857 posts

232 months

Sunday 22nd June 2014
quotequote all
blade7 said:
I watched him disconnect the coil lead, it was fully in.
You said it was difficult to remove, maybe it had some light corrosion on it?

blade7

Original Poster:

11,311 posts

215 months

Sunday 22nd June 2014
quotequote all
ch427 said:
blade7 said:
I watched him disconnect the coil lead, it was fully in.
You said it was difficult to remove, maybe it had some light corrosion on it?
No it was hard to remove because the leads rubber boot was tight on the distributor and the plug leads are very close. The leads/distributor/rotor arm are in good condition, I replaced them a couple of thousand miles ago.

ch427

8,857 posts

232 months

Sunday 22nd June 2014
quotequote all
Fair enough, worth pulling the coil end of the lead out too and checking that but its a strange one.
Sometimes the heat can get to a standard oil filled coil if its breaking down but thats all i can think of.

blade7

Original Poster:

11,311 posts

215 months

Sunday 22nd June 2014
quotequote all
Removed the distributor cap and disconnected all the leads today and everything looks good, the car starts straight up, idles fine and the AFR is spot on. Wait and see I guess.

paintman

7,669 posts

189 months

Sunday 22nd June 2014
quotequote all
I've sorted a lot of problems just by disconecting, cleaning & reconnecting connections. Hence my comment.
Pleasures of classic cars & boatsrolleyes Most useful bits of my diagnostic kit are several lengths of cable with a crocodile clip at each end!

blade7

Original Poster:

11,311 posts

215 months

Thursday 17th July 2014
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Around 15 years ago was the last time I had to call the RAC when my 93 Audi 2.6 wouldn't restart, they tried various things the last was disconnecting the battery leads and touching them together, it worked. I believe this either resets the ECU and or discharges the capacitors. My 944 hasn't died since but a couple of times the AFR went rich and the engine stumbled for a couple of minutes. I temporarily disconnected the battery leads and connected them with a fused wire and all seems fine at the moment...