300E sputters, then dies on fwy ... now won't turn over

[pmizell]

Hello gentlemen:

I did a search on this and couldn't find anyone with the symptoms I experienced today.

While driving down freeway, my car starts to miss/stutter badly as if it's misfiring or not getting fuel. It drives like this for about 2 miles before dying altogether. Few erratic cranks later and no start, with dead battery. (car won't turn over)

Battery was strong before the trip, and there were no signs that it was losing gradual charge.

What am I looking at here? Voltage regulator would be my guess; if not then alternator?

Anything else I should look at before I try replacing these parts in that order?

TIA!

~Paul

__________________
'91 300E, 213K miles
(lots 'o problems lately)

[Norm in FL]

Paul, That may be the alternator. The alt. bearings froze up in our 1987 300D and stopped the engine. We were in the dealers shop when it froze but we drove the car 40 mi. to get there. Remove the fan belt and try to restart the eng. Norm in FL

[csnow]

1) Charge the battery. Verify it actually takes a charge and is ok.

2) Next, presuming it starts, take a voltage reading at the battery with all electrical accessories off @ 2000 RPMs. Expect about 13.5 volts.
If it still does not start, it may be a fuel problem. The battery problem may just be a distraction, since the attempted restarts are taxing a marginal battery more than normal use would. [That is exactly what happened to me when my fuel pump failed!]

3) Turn on rear defog, fan on high, and lights on highbeams.
Expect at least 12.5v @2000 rpms.

If tests 2 or 3 fail, replace the regulator and try again.
If still no good, replace (or rebuild) alternator.
[Some folks swear a DIY rebuild is easy, and usually it's just the brushes or the bearing that has gone bad, but I have not tried this myself]

Best rebuilt deal I know of:
http://autoexpress.safeshopper.com/532/2316.htm

This was cheaper than most used quotes, plus a 3 year warranty. You will even get a little rebate back for the core after return shipping charges ($13 shipping for me, $25 core).

[pmizell]

I jumped the car last night and left the battery cables attached and the car ran perfectly. Removed cables, tried to start car and battery had nothing -- almost zero juice. Like I said, I can't conceive that a perfectly good battery would go bad suddenly like that so looks like I'm looking at a bad regulator or alternator.

BTW, alternator made no noises when it started. When bearings go bad, is it audible? I'm going to replace the regulator first thing Tues. It's a shame the dealer wants $71 for this part when it's available at Fastlane for under $10.

I will run down to the local autoparts store and have them check the battery in the meantime just to be sure.

Thanks again y'all

~Paul

___________________
'91 300E, 213K miles

[csnow]

Batteries really can die suddenly, but this is not the most common failure mode.

Bad alt bearings would be audible.

[JCE]

Ditto bad regulator/brush assembly. Bad brushes can result in a repeated heavy drain and under-charge condition on the battery - just happened to mine. What is the voltage on the battery with the engine off? Also, worth checking the battery ground cable for corrosion at attachements. You will also want to check that there is no electrical drain on the battery while the engine is off? The rear dome light switch was accidently left on, and since the rear dome bulb was burned out, we couldn't see that there was a power draw (from the passenger lower door courtesy lights). This and the marginal brushes killed the battery, apparently suddenly, but in actuality over several weeks.

[Mike Murrell]

Paul:

You can check the voltage on the battery with a multi-tester. Set it to the 20 scale - DC. Black probe goes on neg. terminal of battery; red probe goes on pos. terminal of battery. Fresh batteries read 12.60. There are MANY opinions as to what reading indicates the battery is getting tired. I replace mine when they get around 12.25. This test by no means addresses load, but does give good indication as to a batteries ability to accept charge.

You live in a large city. Check with local euro parts suppliers as I did. The $71 dealer Bosch brush can be had for around $30 in your area.

[Mike Murrell]

When did they put diesel engines in 300E's?

[Norm in FL]

Paul, The Battery will not cause a Diesel to stop running. The only way to stop a diesel is to shut off the fuel! Norm in FL