Stop me if you have heard this one before.... - PeachParts Mercedes-Benz Forum

smittysworld · #1 02-18-2004, 05:39 PM

First let me say I have enjoyed reading thru your forum for the past few days. It has given me quite a bit of insight to the recent problem I've been having with my '84 230E (123).

It's my first Merc, inspired by my father's '72 220D which he bought back in the late '70 and it still a "fine automobile" today. (Although I'm sure he squandered my college money to keep it serviced -- diesels eh!).

Anyway back to my newly aquired '84 230E....

It's been relative trouble free now for the 1st 4 months of my ownership until last month. I experienced the usual dead battery/dead alternator scenerio that any car owner has probably experienced. Amazingly (or not), it took me less than 20 mins to swap the out the alternator. That's the part about Mercs I really like! Once you know what's wrong, basic tools and logical mechanical apitude gets the job right and in good time.

Then last week...

It died completely...no warning...I had been out running an errand, it was running great, stop at the store was in and out in 15mins, jump in to start it, fine, started right up, no hesitation, went 100yards down the road, then just died. And it wouldn't start back up. The batt power was good, starter turned and the engine would fire straight up then died after 10 secs as though it was out of fuel. Engine was not overheated, temp gauge read around 90c. Tried to restart it for about a half hour, still no joy. I had to call out a recovery, 2 hours later arrived home courtesy of a ride back on a platform recovery truck. After rolling the car off into the street in front of the house, I jump back in to turn it over and whola...started right up as though nothing had happened. I parked it up into the drive, let it idle a bit, let the temp get up to about 90c (which seems normal for a warm standing idle, I've yet to see it go much hotter...) then as it did before, died as though it ran out of fuel. Fuel gauge okay, over 1/4 of a tank, but it would start up, run 10-15 secs then die. By this time, late at night, decided to leave until morning.

Next morning, started up fine, ran great for the 10 min trip to work. 8 hours later, started up fine, ran great for the 10 min trip back home. After arriving home, decided to let it idle for 15-20 mins to get the temp back up to around 90c, and sure enough, engine chugged to a halt without a notion to run after several restarts.

Now it seems to me if it was the fuel pump/fuel filter/ignition/coil/distributor/cap/rotor/spark plugs/wires, this problem would be continuous. Being so intermittant I was left scratching my head and turning to anyone who had any sensable advice, which has led me to your forum. And after 2 heavy nights of meticulous research, I myself have come to the conclusion that it may be the fuel control relay. Now I haven't deemed it my final conclusion but from all of the horror stories I've read in this forum, I feel it's work checking out.

Now if I could just find the little bugger!!!

If it's being sujected to various ranges of temperature which is affecting it's operation, I figure it must be somewhere in the engine compartment. But I can find any relays??? Fuse panel yes, easy-pezy, relays---what relays???

So anyone who has had clocked any mechanical repair time on the ole 123 chassis can assist me in finding this fuel control relay, please, please reply to this thread as soon as possible.

In the mean time I am desperately waiting for a "certain online book seller" to send me a copy of the Mercedes W123 Owners Workshop Manual which I'm sure will answer all the question I so long to ask about my 1st baby!

Cap'n Carageous · #2 02-19-2004, 08:23 AM

First off, I don't know a thing about your engine, but you may be on the right track. My 89 300e pulled the same stunt a couple of times. I replaced the fuel relay and it got better but would still do it. I ended up replacing one of the fuel pumps because it was drawing too many amps. That cured that problem. Good luck!!

psfred · #3 02-19-2004, 09:45 AM

Relay or fuel pump -- my 75 Audi Fox did the same thing, had to borrow tools and replace the fuel pump in the parking lot one day.

Relay is, I believe, near the fuse box, but I don't know which one it is on that car. When you find it, jumper it and see if it runs that way -- if not, fuel pump, if so, new relay.

Peter

kott · #4 02-19-2004, 04:25 PM

In a GM world, that sounds like a coil getting warm, opening up, and failing. Works again after it cools off.... but nevers works well for long. 10 minutes may not cause it to fail, but a few extra moments idling in the driveway might finish it off.

RKreutzer · #5 02-19-2004, 06:25 PM

Hi there,

if you go to the top of the page and click on FastLane, you can check their online catalogue and if you are lucky there is a picture which will help you to find the part.
On a 126 it looks like this and is close to the windshield in the middle. Yours looks about half the size on FastLane. Unfortunately, I don't know where it is on your car.
Good luck
Reinhard Kreutzer

smittysworld · #6 02-20-2004, 02:17 AM

Thanks for the tips and replies.

I have found the fuel control relay, for 123 chassis it's located inside, left under the dashboard, right above the hood/bonnet release lever. Just 3 screws holding up the footwell/dashboard panel. Talk about getting lucky, I wouldn't of ever found it if it wasn't for hearing a clicking sound coming from underneath the dash when I turn the key into position 2.

Now I've pulled this relay out and it looked brand new. Reseated to make sure it was fully plugged in and tried to restart. No joy, still would not run. When plugged in and the engine was about to die, you could hear it clicking quite madly. Figuring I had nothing to lose, I removed the cover to reveal the inner bits. The unit was sealed well but the plastic cover was easy to remove. The board and componets look as brand new, all the solder joints are bright and solid.

I've since put the relay back into it's socket with out the cover (hey no danger to anyone or weather elements since it's inside in a sealed compartment.) and the engine has behaved well. I have yet to make a multi-stop trip but I have run it up to operating temp (80-90c) with out any problem. It managed to get me to work yesterday and back with no problem.

I'm not sure if I have done anything yet to fix this problem but today's my day off this week and I will have more time to test things out. I'll give it a typical drive out and see if tries to strand me somewhere.

More to follow....

124Addict · #7 02-20-2004, 06:33 AM

I agree with Kott, I'm sure it's your ignition coil. But to be sure, I advise you to feel the coil before and after your engine dies. If the coil becomes warmer than usual then it is the culprit.

smittysworld · #8 02-22-2004, 07:55 AM

I seemed to have cured it. It's been running great now for two days. I haven't replaced the fuel control relay, the original is still plugged in with out the plastic cover. The relay assembly does generate a bit of warmth when the engine is running but I can't see an overheating problem. The plastic cover doesn't seemed to have suffered any damage from heat. If they (MB) had used an aluminum cover, it might have help to dissipate any excess heat.

Another theory might be that just by unplugging the relay from the socket might have dissipated any surge voltage that may have been trapped in the relay system. It's more that just a relay, yes it has 2 relay coils, but the circuit system also contains a transitor, IC chip, and various resistors and capacitors. A power off reset may have clear any logic malfunction the circuit may have been experiencing.

Nevertheless, I'm closing my investigation for now and look forward to participating in this forum on a regular basis. A big thanks to everyone who has posted a reply for your help and support.

RKreutzer · #9 02-22-2004, 09:16 AM

Mine wasn't running the pumps for 1 - 2 seconds when I turned the key to just before the start position. Took it out and just cleaned the prongs with dielectric grease. Had a bit of dirt in the socket like a christmas tree needle.
Has worked ever since. My experience would confirm your theory.
Good luck with the relay to both of us...

stevebfl · #10 02-22-2004, 09:57 AM

Typically the fuel pump relay is one of the notorious cracked solder joint problems. Since there are about as many relays as there are engine/chassis/year combinations we don't stock them, which leads to many just being fixed by resoldering.

The old long coils used on these cars very seldom fail. The short square ones like used on later cars fail all the time.

xp190 · #11 02-22-2004, 02:48 PM

Had the same problem wit my w201, it would die after a few minutes of driving and refused to restart until it cooled. The Fuel pump relay was overheating causing one of the switches to move out of operating range. Resoldering it worked, but only for a while since the IC board had a huge burn mark on it. Replaced it and the problem was fixed.

There is an easy way to test this by jumping the fuel pump relay, I don't remember the pins exactly, but the manual will tell you what to do.

xp

jammer · #12 02-23-2004, 07:38 AM

Back in my college days I had a 108 '70 280 SE (still one of my favorite models) that had similar problem. It would start, but dies and wouldn't start again unless you let it cool down for a few minutes. If I remember right, a mechanic changed the fuel pump for me and the problem was solved.