Electrical diagnosis needed. - PeachParts Mercedes-Benz Forum

JBoggs · #1 09-16-2002, 07:42 PM

The other day went to start and nothing, dead. Sheesh, opened the trunk and to my surprise the negative cable has worked it's way loose. I re-attached, cranks right up, no prob.

This a.m., I'm driving to work, and the thing quits (right in the middle of traffic),I pull over turn the key and it's starts back up again, no prob. Check the battery cable, tight as can be.

86 560sl, only had it a few weeks, high mileage, but great condition. It almost has to be in that cable I'm thinking but it appears to be in perfect shape, not loose, nearly new battery.

Any way to do an intermiitent diagnosis? I can't remember if all the electrics went or not, doesn't seem like the radio went off but it all happened pretty quickly.

Thanks.

J. Boggs

engatwork · #2 09-16-2002, 07:52 PM

You did not say what time of day you were driving to work but the first thing I would test would be the alternator.

mbdoc · #3 09-17-2002, 08:11 AM

A loose battery cable wouldn't cause the car to stall & then RE-START! Would think that a fuel pump relay was at fault OR possibly a bad over-voltage relay. This can be very hard to diagnosis untill it happens all of the time.
Even a bad coil or ignition control unit could be at fault.
Many times the flywheel crank sensor can also cause this type of problem as well!

sleepwalker · #4 09-17-2002, 08:22 AM

M.B.DOC was right! He knows that model very well. Take his advise and say goodbye to stalling. Check that fuel pump relay or fuel system.

Sleepwalker
Technical Advisor
Mecedes-Benz

JBoggs · #5 09-17-2002, 10:12 AM

It happened to my wife last night pulling out of the driveway-she said that the radio never went off so it must be something under the hood. It ran fine for me this morning. I'm going to check for a loose coil wire or something else loose later on today.

Thanks again.

J. Boggs