Engine Shut Down on my '87 300E
 

Last week a friend and I took a drive out to Roslyn Harbor Long Island, about 35 miles away. On the way back before coming to a complete stop at a traffic light, all my idiot lights came on and I realized the engine had shut off. I shifted to neutral and turned the key, the car restarted with no problem and we continued on our way, back to the city. The next day, I gassed up at a mobil w/ the usual 93 octane, came to a halt at a stop sign and the engine quit again (no sputtering or knocking)just a complete shutoff without warning. I again restarted (this time after a couple of tries) and drove across the Manhattan Bridge. I continued on a couple of blocks and again the engine shutoff. (this time it would restart only after about a 5 minute rest)I then drove another couple of blocks and it shutoff again. This time I noticed a little condensation at the bottom of the windshield so I added a little water. I drove all over Manhattan until the engine was hot and the problem seemed to be corrected. The next day the car was very difficult to start, but when it did it purred like a kitten (as always) and then promptly shutoff, without restarting at all.
would anyone know if this is electrical or mechanical or what could cause this problem....
Thanks jsails46

"Classic" signs of fuel pump failure.

Could be the pump(s) or the relay.
Smells like a pump.
Don't wait until you are stranded.

This is how I spent my 'quality time' this past weekend.

Hint:
Take the plastic splash shield off right away. If a pump seizes (after dark, in the rain), you may be able to revive it temporarily by striking it with something. Easy enough, but the shield gets in the way! Pack a tarp to lye on, a pair of gloves, and carry a flashlight.

Also a classic sign of a failing idle air valve, or one of the components in the "failure chain" telling the computer to shut the valve down. Possible culprits are the decel switch or the throttle position switch or the air flow sensor.

If you are not intimately familiar with this problem, best take the car to a good shop because this problem can drive you crazy.

Faulty Relay?
 

What about the Fuel Pump Relay? I read (on some other site) a fellows almost identical problem was traced to a faulty Fuel Pump Relay. Is this likley?


Thanks again,

jsails46

Chuck is right about the stalling problem driving you crazy. I have the same exact problem on my '88 260e and recently replaced the airflow sensor pot. The car ran fine for a couple weeks then one night started stalling again. Every time I would come to a stop the lights came on the dash and I had to restart it. Besides the intermittent stalling, the car runs and idles smooth as silk.

I cleaned the idle control valve and tested the decel switch (through about 100 cycles) and both seem to be okay.I had ruled out the fuel pump and pump relay as the cause because the problem only occurs when at idle or coming to a stop - never while driving. I would think a fuel pump problem could occur at any speed. Or am I wrong?

From Steve Brotherton article:
A failing OVP will cause stalling.
Read his "Evaluating ........" article in the DIY section.
Random stalling may be caused by many things, but failing OVP is a major one.

I did not mean to imply that this could ONLY be a fuel problem, just that the symptoms match well.

Certainly could be the relay.
You can jump terminals 7 & 8 at the relay connector, then feel the pump(s) to see if they operate.

The difficulty is that you would need to catch it in a failure state for this to be meaningful.

Is it starting now, or does it continue to be intermittent?

Normally a failing OVP provides a clue by turning on the ABS light on the dash. But it is smart to replace it on principle because sooner or later it will fail.

Maybe was the OVP relay
 

The day after I had the stalling problem I swapped OVP relays with my wife's "92 300e and my car has not stalled since. Maybe it was the OVP relay. I was not getting an ABS light or any other symptoms and my wife's car is still running fine with my old OVP (I was really hoping it would stall so I would know the problem for sure). Maybe the OVP is bad and her car is just more tolerant.

John

Hence the maddening aspect of this problem ...
 

My car stalled and the ABS light came on. I barely made it to the restaurant, where we were celebrating my wife's birthday. When we came out, it went into limp-home mode with a high idle. Got home, replaced the OVP relay. ABS light went out and stalling problem got better for a couple of days. Then back to same old tricks.

I heard from my MB service advisor, they (MB) found that the Overload Protection Relay was the real culprit. That along wth the diagnostics and some other egine adjustments now has my car ready for pick up.... after I settle the matter of the bill $545.33.

If I have no further unexpected problems this year, it will be worth the cost.


jsails46

Cutting out problems
 

My general advice for problems of this nature on older cars (15 years/100k miles or more)

Change the Dist cap, Overload Protection relay, voltage regulator on alternator and A/c relay (and keep changing them every 15 years)

Total cost around $200. Peace of mind? Invaluable! If you still need diagnostics after this, you're pretty unlucky!

BTW the ABS light on the dash is often a classic case of low voltage, (lazy diode/bad regulator in Alternator)

Vivian

Thanks
 

Jsails, thanks for the follow-up post. I guess after 15 years I should break down and get a new OVP relay.

John