911 starting problem

mango · 01-30-2005, 01:42 PM

Hi chaps,
Have a bit of a problem with my '86 3.2 911. after the car failed to crank I diagnosed a faulty starter. After standing for two weeks I replaced the starter and it now cranks fine, unfortunately it fires whilst cranking but dies as soon as the key is released. seems to be a lot of smoke/fuel smell after cranking (no leaks though).
Followed advice from another post and bypassed dme supply to fuel pump and although pump runs it still wont start - any suggestions?
Thanks in advance

curiousone940 · curiousone940's Garage

Start with the basics.....gotta have fuel, air and fire. Pull a plug, connect the wire, ground it to the engine and have someone crank while you watch for a healthy blue-flamed spark. Also, check the plug for evidence of unburned fuel. If you're not getting a spark at the plug, then replace the DME relay with a known good one; check the rotor and cap for proper contact on the points or a possible arcing/grounding condition due to a cracked cap, bad wires, etc. When is the last time you changed the fuel filter???

mango · 02-01-2005, 12:33 PM

Thanks for the advice. I have checked aLL THE ABOVE AND THEY SEEM FINE. iT'S BACKFIRING EVERY SO OFTEN THROUGH THE INTAKE (i REMOVED THE AIRBOX NOW) THE TIME IT RAN FOR A FEW SECONDS WAS EITHER WHEN I TRY TO START IT AFTER BACKFIRE OR JUST AS THE BATTERY DIED - Grrrrr!

I'm stumped - may have to call for professional help - shame 'cos I always prefer to fix 'em myself - any further suggestions?

Cheers

midlife · 02-01-2005, 03:10 PM

Since it started with the starter change out, could it be ground connections? Maybe debri from the bad starter on the speed and reference sensors.

mango · 02-01-2005, 03:21 PM

I'l have a look at the sensors tomorrow - are they on the flywheel?

I see from wiring diagram there may be 4? connections to starter motor, I only have 3 (main battery +ive and smaller red wire both on solenoid supply post and yellow wire on solenoid activation connection) have I 'lost' a connection?

midlife · 02-02-2005, 07:53 AM

The sensors are at the flywheel and look like this:

It's just a guess, but I've had metal shavings stuck to the end of the sensor cause a no-start.

Just make sure you get the same sensor back in the right hole, and don't lose any shims that may be there.

Good luck.