I think that the fuel pump relay could be the problem with our 300e cutting out and losing power. I read that the relay is behind the battery. There are three relays there, which one is it?

Fred! Try to locate a relay with "KPR" on it!

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Tore Bjorndalen

1990 300E

Fred,
Since you are a newbie, I say welcome to the group, and I'll be kind, but please see my post on model and year. Up through 1989 MB used a fuel pump relay. Model year 1990 used a MAS unit. Model 1991 moved everything to the main computer. Soooo we need to know the year of your car to be able to help you.

Peter

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Auto Zentral Ltd.

I found it. I had my wife listen near the gas tank as I pulled the relay. It is the first one behind the battery. It is marked KVS Kickd 0025452705. I pulled it apart, there were three or four solder joints that did not look good. I resoldered them. The car ran to the store and back fine. Here is hoping that I fixed it.

Thank you,

Fred P...................

My '91 has a MAS controller just like my '90. '92 went to the main computer maybe? Don't mean to nit-pick...

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2012 E350
2006 Callaway SC560

Brewtoo,

I'm standing by my statement, but MB does have some slop over model changes which is why you must use the last 6 digits of the chassis # when ordering parts. You can't just go by year model. On the one hand you are lucky if your fuel pump relay quits, because you will have to replace the MAS unit and not the main computer. On the other hand if you get codes stored in the MAS unit, you will need a 35 pin breakout box to reset the codes. Codes stay stored in a MAS unit even when it is removed unlike the main computer which can be reset by disconnecting the battery.:p

Peter

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Auto Zentral Ltd.

Peter,

I'm looking at purchasing another Benz. Idealy I would like to get another CE similar to my 89300CE, but since those are somewhat rare around here I may have to find something else in the meantime.

I would like this other Benz to have as many interchangable parts (CIS,KLIMA,relays,etc.) as my CE. I'm thinking 86-89 300E/CE/TE, or 88-89 300SEL. Does that sound about right.

I do like the 90-300E more because of the lower plastic clading on the body but it sounds like it uses a different engine management system. Is this correct?

Thanks
Jorg

Jorg,

You are correct. The 90 300E should have a MAS which incorporates the fuel pump relay, the A/C relay, control of heater current to the oxygen sensor, and talks back and forth with the CIS unit. The 91 model included everything in the CIS unit. As Brewtoo pointed there are slop over year model changes. I believe the 90 model of the 124 chassis had the first convenience system, which I think is really neat. Hold the key in the locking position, and it closes all windows and the sunroof if left open. They never included this system in the 126 chassis. Right now I have 2 300SELs in my stable. One is a 88 and the other is a 90. The 88 has fuel pump relay, and the 90 has a MAS unit. The 90 is hard to work on, because you need a 35 pin breakout box to pull codes stored in the MAS unit. The codes do not go away with the battery disconnected though the CIS codes will. You can retrieve codes on an 88 or 89 at the round plug on the left fender.

Hope the info helps. I'm happy to answer any questions you have.

Peter

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Auto Zentral Ltd.

Peter,

Your 88 has an M103 and your 90 has an M104 correct? I really like the concept of the M103 and wonder how it works in the 126. I'm not into acceleration. Primarily looking at a highway cruiser, 70mph mostly. Does the M103 do well? Is the M104 better suited?
I really, really like the M103 in the CE. Simple, reliable, inexpensive, easy to fix.

Jorg