1987 300E Suddenly Loses Power - PeachParts Mercedes-Benz Forum

ejsharp · #1 06-15-2003, 04:32 PM

While driving my 1987 300E will suddenly and totally lose power as though an off switch were thrown. I coast to the side of the road and wait about 30 seconds and the car will start again. If this is fuel related... What parts are the most likely culprets that might be failing?

If not fuel related then what else migh I check out?

ctaylor738 · #2 06-15-2003, 06:08 PM

That sounds like your fuel pump relay is TU. Assume no misfiring or any warning - just stops?

Why don't you jumper it and see if that cures it?

ejsharp · #3 06-15-2003, 06:30 PM

Thanks Chuck... that sounds like a very likely diagnosis. I had no idea the car has such a relay.

Now I have to find it!

pentoman · #4 06-15-2003, 06:56 PM

Yes this sounds just like the fuel pump relay problem that a number of us have. The relay can corrode inside and cause the exact symptoms you describe.

If you get stuck with it not starting, try opening the hood and tapping the black boxes found to the very very rear, underneath the base of the windshield (often behind largish easily removable black plastic covers).

If you're more DIY, pull the black one that's around the size of a cigarette packet. It has a load of male pins in the bottom (maybe 10-15). This is the blighter. Open it up (easy to do) and look at the connections to the large copper-coloured relays on it. They are often in bad condition. A simple resoldering will solve the problem.

Otherwise, pop to the dealer and get a new one, but if you don't check it as above you won't know its definitely the problem. Then you've got all sorts to start worrying about..

good luck

Russ

ejsharp · #5 06-15-2003, 07:56 PM

Ok Russ... I read you loud and clear. Yes I am a DIY and can solder the contacts if necessary. I just finished pulling out the two relays (behind the cover). One says "Klima" which I assume is Climate Control and the other says "Kickdown". I cleaned up the contact pins with electrical cleaning solvant and put everything back together again. I looked to see if there is a way to open the "Cigarette pack" but it appeared to be fairly well sealed... I did not see any obvious seams to open... but then again that was before I read your post.

I'm not certain I have the right relay so far. I have a suspicion that there are two fuel pump relays and that so far I've discovered only the one called the kickdown.

Can anyone confirm that there is or if there is not a second fuel pump relay on the 300E?

stevebfl · #6 06-15-2003, 07:59 PM

Only one fuel pump relay and it also controls kickdown.

ejsharp · #7 06-15-2003, 08:20 PM

Thanks Steve... you are really most helpful. I'll never forget how you helped me find the bad connection for my door locking system after I had the complete interior of the car torn apart and laying all over the lawn. It was under the carpet... rear passenger side. Water had gotten in before I owned the car and over time coroded the connection.

I went to Miami last week with the car and thought about stopping off at Gainsville to say hi but it was Sunday when I passed by Gainsville so I kept going. I had good reason to stop because the above problem developed when I was in Miami... and then happened again on my way out of Miami on I-95.

Again thanks.

PS. Is it possible to open the kickdoun unit to repair it? I saw a bulleten that said Mercedes was in process of replacing the old relays about the time my car was manufactured.

pentoman · #8 06-16-2003, 06:20 AM

Yes the relay with Kickdown on it is the fuel pump relay, I forgot to mention that.

Mine was very very easy to open, any seal that was there was either broken or very weak, and there were not really any clips to speak of. Try prying at it with something.

If you were prying the right way to open the relay, you would be inserting a knife into the edge of the bottom of the relay (with all the pins on). The knife would be parallel to the pins.

The connections inside are the most important ones to deal with - I remember I looked over it once (wasn't aware of this type of problem beforehand however) and saw nothing. Then I tested around it with a multimeter and only then found the bad solder joint.

good luck

ejsharp · #9 06-16-2003, 11:09 AM

Well Russ it sounds like the "pack" should open. I love projects like this. I'll pull the relay out and have a closer look at it and then go over it with my multimeter once I get it open.