Benzmac, M.B. Doc or Stevebfl, can you help? - PeachParts Mercedes-Benz Forum

MB FRAU · #1 05-29-2002, 10:40 AM

1993 400E

Could you please take a look at the following. I'm reposting hoping that someone can give me some feedback!

Our '93 400E has begun having some very intermittent starting/stalling problems. A couple of weeks ago I drove home (about 10 miles) and things were running fine. Within an hour of arriving home I went out to move the car and it would turnover and catch for just a second and then die. This happened numerous times. After a couple of hours had passed I went out and it started like normal and continued run fine until about a week later when it stalled on my husband as he was going through the parking garage at work. It started right back up, though. Over the weekend, I went out to move it for a wash job (it finely quit raining). It started for a few seconds and then died...but started fine on the second try.

It had it's 60,000 service about 10 months ago which included the rotor.

I have read through a lot of the posts and need some help/clarification.

1. Does this car have a fuel pump relay? If so, where exactly would it be located on this car? I ask because the local MB shop says "no", that it is somehow built into the Mass Air Controller and yet the our service CD indicates that it does have a relay (k27). There is a relay under the back seat (passenger side) with a part # 001 542 96 19. What is this relay for?

2. My understanding is that this car does not have a OVP. And that the Base Module replaces the OVP on this model. Is this true? And does the base module seem to have the same problems as the OVP?

3. Would running diagnostics give us codes for faulty relays and modules? Independent shop says, "no".

By the way, the wiring harness was replaced just over two years ago.

Any suggestions/ideas or specific answers to my questions would be greatly appreciated. This is such a fun car to drive but don't have a lot of confidence in it these days.

MB FRAU

brookspw · #2 05-29-2002, 12:12 PM

I don't have any answers, but I sure do enjoy hearing the ladies talk like that!

brookspw

Benzwood · #3 06-18-2002, 01:11 PM

Part #001 542 96 19 says "Auxiliary Fan, Stage II Relay".

I'm interested in the answer to the Fuel Pump Relay question too -- I have a '92 300E with the identical problem and can't find that relay??

I've replaced the fuel filter (didn't fix) and will be replacing the OVP relay to see if that helps.

My OVP relay is to the rear of the battery, under the plastic protective flap, my guess is yours is too.

Amuso · #4 06-18-2002, 01:34 PM

The location of the fuel pump (and OVP and A/C) relay is here...

And it looks like this

It's the "6 zyl. 6350, min KVS, kickd." - if you have a 6 cylinder. Might say something else otherwise.

OVP is the little metal one with fuse on top.

And the last one is the A/C relay.

Amuso · #5 06-18-2002, 01:35 PM

And while on the subject... What are the other two huge boxes for? I assume one is the engine control management module.. but that leaves one unaccounted for? And which one of the two is for the engine?

Benzwood · #6 06-18-2002, 02:25 PM

It appears that my '92 (and presumably MB FRAU's '93) doesn't have the Fuel Pump and A/C relays, at least not in the same place (see below, inspired by your photo).

I do have a few more mystery control boxes, though.

From what I can tell, your two control boxes are the KE Control Unit and possibly the ABS Control Unit. If you've got the part numbers for them I could look 'em up.

Amuso · #7 06-18-2002, 03:22 PM

That is very interesting. I will check the partnumbers and have them for you tomorrow.

stevebfl · #8 06-18-2002, 04:09 PM

The biggest problem here is that many components are talked about as if they all existed on all 124 cars. As it turns out the OVP function was taken over by the MAS (not mass air flow). MAS was a combination OVP, KLIMA and FPR (fuel pump relay). The v8s changed everything. A whole new electrical center is setting where the battery used to and all the controllers including the base module which is an even more sophisticated OVR/Klima/FPR/air pump relay/etc. See illustration.

The relay under the seat is the fuel pump relay, I think. Which is the same relay as the aux fan relay one stage or the other, which is located in the fuse panel relay center.

stevebfl · #9 06-18-2002, 04:28 PM

As for the MAS try this picture which isn't too good when blown up.

Benzwood · #10 06-18-2002, 04:52 PM

Thanks for the info, my car has an MAS as pictured, but I've got a separate OVP relay, which you mentioned was also part of the MAS?

In any case that explains the missing Fuel Pump relay -- glad I didn't let the shop "replace" it.

Is the MAS prone to the same bad Fuel Pump relay symptoms as mentioned in the orginal post? Would that be a logical next step for replacement if a new fuel filter and new OVP doesn't do the trick?

Amuso · #11 06-20-2002, 10:32 AM

Thanks Steve,
That clears up quite a bit. I'll be sure to make a note of that on my W124 site.

Anyways here are the partnumbers I pulled from my car for the mysterious big boxes

0 280 800 216, this one says jettronic so that was self-expl.
0 265 101 016, the box behind it...
004 545 46 32, wondering what it is called..

I would test that "aux.fan" relay which Steve thinks is the fuel pump relay under the seat.

Wish I had full schematics for these cars - when is payday?

Benzwood · #12 06-20-2002, 02:00 PM

Amuso, agh, I'm out of town and don't have access to the part numbers, or I'd finally be able to contribute back to the forum. If you can wait 10 days I'll get them.

An update on my problem... I finished installing a variety of shiny new parts prior to my road trip, including a brand new OVP relay and set off happily down the road, and...

1/2 mile from my house the car did its usual "sudden death" thing again.

Same symptoms as the original poster. Mine seems to do it only when the car is cold, and generally within the first 5 minutes, though with no consistency.

So far I've replaced the fuel filter and the OVP relay, and as mentioned I don't have a fuel pump relay. Should I swap out the MAS that performs that function?? Looks like an expensive box...

Amuso · #13 06-20-2002, 02:54 PM

No problem! No hurry.

Have you tried to see if your pump stops prior to engine stalls? I stood outside my 300E while somebody started it. Listened to the pump hiss from the rear wheel - and sure enough - it would stop briefly for a second maybe once, twice and then completely...followed by engine stall 2-3 seconds later.

This was my faulty relay indications.

On fixes... well don't have any good ones. I would have tried to locate the relay that turns on the pump and "hot wired" it to the ignition II position to buy some time. That's how I did it on my car. Until I can troubleshoot any missing tacho-signal and/or replace the pump relay. I might continue to use this "hack" as I don't need the high-rev cutout feature, or the cold-start valve thing.... right now. I might build and post schematics for an replacement fuel pump relay with cold-start features later

Benzwood · #14 07-02-2002, 05:21 AM

Finally back in town... Amuso, your 004 545 46 32 is an Ignition Control Box (replaced by 005 545 87 32).

The other part numbers you listed don't seem to be the standard format... but the only control units I see listed for your car are the KE Control Unit and ABS Control Unit. So if you've got ABS brakes that should be that mystery unit.

Another update on my sudden-death problem... I ended up replacing my MAS control unit during my trip, not for the sudden death problem but due to my A/C going out. Both the A/C and fuel pump relay functions are handled by the MAS so I'll see if that fixes the sudden-death thing too.

As feared, it wasn't a cheap part -- $350.

Amuso · #15 07-02-2002, 12:23 PM

Thanks! Yeah I found the ABS unit in the Parts Shop here actually, so now I have an idea of what all these boxes do.

I hope the sudden death is gone for you now. Mine's been doing fine since I modified it too. $3.99 at AutoZone for a relay

*knock on wood*

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