First, Check fuse on top of OVP..

Then give OVP a few good taps w/KO... try to start the car.........

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A Dalton

Your gonna love this...OVP guts.






Please forgive hack work on OVP case, I had to do it...Any way to jump OVP? I'm sure its toast, but I would just like to make sure lol.

It's junk..
You mentioned you have a '95/124....so, just stick that one in there as a quicky test ..they are the same..

Also, you want to check the drains in the corners of the fenders , where they meet the doors...you have a water drain problem.
Also check that the plastic panel was seated in it's grove/guter...if it is not , the water goes right into the OVP from the windshield rain.
That is why the FP relay has a rain cap. Some guys put a platic zip-lock over the OVP for that reason.

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A Dalton

Mr Dalton, I can't thank you enough for your help tonight. Once I got on the right relay, seems to have rolled right along. Car still doesn't start, but I'm sure after the ovp and new fuel pump relay it will. I will swap the ovp out of my 95 and see what happens. I will post updates sometime tomorrow. Until then !!!!!THANK YOU SIR!!!!!

just be aware that the test I had you do on the FP relay did not verify the relay as BAD..all I had you do was to jumper the LOAD side of that relay in order to test the Fuel Pumps and Power.
The relay needs 12v power to the coil terminals [ 85/86] in order to turn the relay ON [ pull in the contacts that you jumpered] ..but the reason they did not pull in is b/c they are fed that 12v suppy from the ECU, which could not feed the relay b/c of a bad OVP signal to the ECU..so, don't condemn the K27 FP relay b/c we did not test the relay, we simply jumpered its contactor set..

You can bench test that relay by simply bringing 12v to 85/86 coil terminals and see if it clicks the contactor set ON/OFF...which can be checked at the same time by checking cont. w/ohm meter across 30/87....
It is just a simple 4 prong On/OFF relay with a built-in fuse for the load side.
The schematic of it's internals are right on the case.

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A Dalton

Yes, I understand we didn't test the control side of the fp relay. I am condeming it since inside it looks similar to the ovp relay (pics above). Thank you.

Alright! Replaced OVP and FP relay, car runs woohooo!!!! Cleaned the drains and the whole area, plus all the contacts. Mr Dalton thank you very much... Problem solved!

Very Good

A Dalton
BenzMeister.

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A Dalton

I have the exact same problem as discussed on a different forum (Pump Relay or Wiring Problems - Benzworld.org - Mercedes-Benz Discussion Forum).
It appears I'm only getting 0.77 volts to pin # 86 of the Fuel Pumps Relay. If I jumper #30 to #87, the Pumps come on but the car still will not start. I have read conflicting information regarding the OVP by stating the car will start without it and just run poorly or not start at all depending on if the engine is CIS or HFM. I, too, haven't been able to find a wiring diagram that reflects my engine that I believe is a 3.2 liter, 217 HP, DOHC in a US version 1993 300E.