sudden engine failure

[eva09]

We have a 1985 735i that has twice completely shut down while driving, once on the freeway. Since these occurances we haven't driven it (except around our neighborhood where it has been fine for the last couple of weeks) safety being the issue. Have talked to several mechanics but a concrete solution has yet to be found - still don't feel comfortable taking it on the freeway. Has anyone else experienced this problem and found a solution?
thanks!
eva

[libertylover]

Hmmmmm. "Completely shut down", as if you turned off the ignition? After you pulled over, did it restart right away or what? How long since you changed the fuel filters?

[eva09]

Originally Posted by libertylover

Hmmmmm. "Completely shut down", as if you turned off the ignition? After you pulled over, did it restart right away or what? How long since you changed the fuel filters?

Hi,
Yes it completely shut down as if the ignition was turned off. I pulled over and it started right up again. On the freeway it turned off completely again and, while passing through the various lanes of traffic trying to get over, was able to start again by turning the key off and then on.
Any ideas?
eva

[libertylover]

I used to have a Mazda that would shut off like that for perhaps 1/2 second. Maddening!

Momentarily shut down an '85 735? Here's a few thoughts:

1) Fuel level in the tank. My brother used to have a van that ran like absolute crap if the fuel level dropped much below 1/2 tank. At 1/4 tank it would hardly run at all. About 6 months ago I saw an explanation for this saying it had to do with excessive water vapor in the tank. So...

2) Fuel filter - I suppose if the fuel filter is pretty clogged it might starve the engine for gas momentarily. Change it if you haven't done so recently.

3) Distributor cap, rotor, and wiring. First, make sure all of your ignition wires are in good shape and well connected, especially the one from the coil to the distributor. Check for a crack in the distributor cap-look HARD, it might be tiny.

4) There's a Main DME (Digital Motor Electronics) Relay and a fuel pump relay that could be a problem, and the fuel pump itself.

What I would do: I'd replace the fuel filter, the distributor cap, and the rotor then I'd see what happens before I did anything else. That won't cost much. I'd also replace the ignition wiring if it's old and cracked, but buy good ones, not cheap ones. If the problem persists, then it's probably somewhere in the electronics. Good luck.

BTW, I never did fix the Mazda. :-(