If it is the relay on the 1991 that would be the M.A.S unit. This does lots more than the fuel pump which makes it a little pricey.If I am correct it does the auto close and sunroof close with the key in door,the AC relay is in it,fuel pump relay and some think else If you have any good CD'S on the 124 you can bypass it to test it.Think it it pin 7 and 8 but please look it up first.
If you do decide to buy one tell me the part number.I should have one here.Also have a bunch of other 124 parts.
Thanks
Rich

__________________
88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car

How would I/My Mechanic be able to tell if it was just the Potentiometer and not just the whole part?

__________________
It's the little things that hold the big picture straight.


1991 300E - Present Car
1988 300CE - Gone but not by choice.

There's an old post here, at least 5 years ago, where someone had their throttle actuator rebuilt. Before sending it off they inspected it very carefully, and did so again when it came back, and concluded that the only thing the rebuilder did was to replace the potentiometer. I don't think there's much else that can go wrong on those old air flow meters.

I think you are going down the wrong road with the potentimeter.It would be cheaper to look for a fuel problem than the meter.The meter would not make the car stall.These cars can run pretty well with no power to the fuel distribator.Try taking out the OVP relay.Hard to start but runs ok when it starts.It won't die on you when driving,maybe a lousy idle.Bypassing the fuel pump relay is not that hard and you can drive it untill you are sure it is not a fuel pump problem.If not you have a crank pickup problem,which would make it die.Try the easy stuff first.Both of those problems are not that hard to verify
Rich

__________________
88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car

I finally got the car fixed awhile ago and I just wanted to close out this post and say thanks for all the help.

As some of you suggested it was the fuel pump. I broke down and finally brought it into a Merc dealership and had them diagnose it. The primary fuel Pump was, for some reason, overheating and shutting off I would then have to rely on the secondary fuel pump but that wouldn't get me too far. So with the Help of Phil i got a great deal on two new fuel pumps $128.00 each through all parts Express and and a new fuel filter (since I was gonna be under there anyways) And my girlfriends dad and I replaced the whole kit and Kaboodle. Car runs great! From the time we chocked the wheels till the time we set it back down it only took 45 minutes.

We took the whole assembly off and replaced the pumps and filters on the bench. It was really slick. Well thanks again.

Now onto the next Project, Those infamous dash lights...

__________________
It's the little things that hold the big picture straight.


1991 300E - Present Car
1988 300CE - Gone but not by choice.

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