If I remember right, the W108/109 cars have three round-looking relays on the passenger side of the firewall. One of them is the fuel pump relay. Swap them around to see if you get voltage at the pump.

 

If I remember right, the W108/109 cars have three round-looking relays on the passenger side of the firewall. One of them is the fuel pump relay. Swap them around to see if you get voltage at the pump.

(I believe you did not remember correctly, and) they are on the right side behind headlamp.

 

From what I can tell, I have 1 relay that is mounted on the passenger side of the engine compartment behind the battery. I believe that is suppose to be the fuel pump relay. It is rectangular and has 5 pins (1 pin plugs into a empty slot). However, the part number on it is Bosch 332-202-001, but what I have found on-line for a replacement fuel pump relay calls for a Bosch 332-008-002 (also rectangular).

The 3 relays that are mounted side-by side in the engine compartment in front of the glove compartment have the outer 2 being round. The part number is 000-542-97-19. The middle one is square. It's part number is 001-542-02.

Could someone have substituted a different relay for my fuel pump, that might have worked but just had an extra pin function that wasn't used?

 

Still need help with relay & wiring

I'm trying the picture attachment feature for the first time. Sorry to cut off a lot of the photo, but the upload feature had a file size limitation. In the lower left is the rectangular relay that was mounted to the passenger firewall. At the top of the photo are 3 more relays.

Does anyone know which relay should operate the fuel pump? I tried running a wire from the positive wire at the fuel pump back to these relays, but could not find zero resistance to any of the wires using a mutimeter.

I'm going to post another relay question as a separate thread. I hope someone out there has some insight they can provide. This is frustrating!

 

It is not a fuel pump relay. It is deemed a "change-over relay' and seems to be for A/C, electric windows, seat belt warning, and/or turn signal. Mercedes number is 000 542 5919.

 

Thank you for your input! I could not see how this could provide the 12V to the fuel pump. Any idea which relay might give voltage to the pump? Since none of the wires off of any of the other relays I checked showed continuity to the (+) at the pump, there must either be another device between the relay and the pump, or there is another relay/fuse somewhere that I haven't seen, or there is a break in the wire between the relay and the pump. Any suggestions?? And, do you know if there is a schematic/photo anywhere out there in the vast Internet that I can buy that shows the electrical layout for this vehicle?

 

Fuel Pump Relay: MB P/N: 000 542 8719; Bosch P/N: 0 332 008 002

 

Ron,

I trust ya, but where in the heck is this thing suppose to be??? The only relay I can find that is rectangular in shape is the one that was mounted behind the battery, but it's Bosch number is 332-202-001.

 

That's all I got -- do with it what you will.

 

my relay like ron has pictured is attached with another similar relay to the inner fender beside the battery, not behind it where you have the window fuses, etc.

One week ago I realized that I was not hearing the fuel pump energize and that simple item could be my non-start problem. I initally assumed all kinds of nasty, dire events. Instaed, all I did was spin the fuel pump fuse (left driver knee area) to clean off corrosion and -- VOILA-- a working, running 108! Do not remember the fuse number, hopefully, you still have the index inside the fuse box cover.

It would be nice if this is it....

 

Nothing like a happy ending!

 

Nothing like a happy ending!

on happy endings -- thanx for the recent parts ron. ordered sat, received tue!!

 

Where or where has my fuel pump relay gone??

I think KPB said he had TWO rectangular relays on his passenger side fender well. Does anyone else know if there should be 2 relays? Also, where everyone says the fuel pump relay should be, mounted to the passenger side front fender well, I have a different 5 pin relay (Bosch 332 202 001). The wall on my car only has vibration mounts for one relay behind the battery.

I'm still VERY confused and frustrated. I have tested and confirmed continuity across the #4 fuse, as well as the others, in the driver's floorboard. I tested the one rectangular relay on a separate battery and it works like it should. However, it is being plugged into a holder that, in either direction you install it, the 87 pin goes into an empty plastic hole. Only 87A goes into a metal sleeve. And, doing a voltage check from ground to the pins, in both the off and run positions, I get zero volts. So, I'm not sure what or when or how this relay controls anything at the moment. Going to the relay holder is a brown wire to #5, a blue with white stripe to #3, a purple with white stripe to #4, and a big blue and a small blue to #2 (the small blue's wire shows corrosion). If I was going to jumper across the relay, like nutz4benz suggested, I'm not even sure what I would try to jumper. I unhooked the positive wire at the fuel pump, and connected it to a wire I ran all the way back to the battery area, but could not find continuity anywhere. Does anyone have ANY suggestions to continue my troubleshooting? Thanks!!

 

Where or where has my fuel pump relay gone??

View attachment 105148
I think KPB said he had TWO rectangular relays on his passenger side fender well. Does anyone else know if there should be 2 relays? Also, where everyone says the fuel pump relay should be, mounted to the passenger side front fender well, I have a different 5 pin relay (Bosch 332 202 001). The wall on my car only has vibration mounts for one relay behind the battery.

I'm still VERY confused and frustrated. I have tested and confirmed continuity across the #4 fuse, as well as the others, in the driver's floorboard. I tested the one rectangular relay on a separate battery and it works like it should. However, it is being plugged into a holder that, in either direction you install it, the 87 pin goes into an empty plastic hole. Only 87A goes into a metal sleeve. And, doing a voltage check from ground to the pins, in both the off and run positions, I get zero volts. So, I'm not sure what or when or how this relay controls anything at the moment. Going to the relay holder is a brown wire to #5, a blue with white stripe to #3, a purple with white stripe to #4, and a big blue and a small blue to #2 (the small blue's wire shows corrosion). If I was going to jumper across the relay, like nutz4benz suggested, I'm not even sure what I would try to jumper. I unhooked the positive wire at the fuel pump, and connected it to a wire I ran all the way back to the battery area, but could not find continuity anywhere. Does anyone have ANY suggestions to continue my troubleshooting? Thanks!!

It's a four pin relay

 

GermanStar, you were right- that is what the fuel pump relay looks like. And, in hindsight, your diagram is kind of helpful. I FINALLY found the sucker! It is located just behind the front right headlight. There are a couple of relays on a plate (what looks like your #485) just behind the ecu. I had tested those for continuity back to the fuel pump wire earlier, with no success. BUT, if you put a mirror under that plate, you see 2 more rectangular relays. The fuel pump relay is not on the side or near the windshield. What a hassle!! I have no idea how to get that plate out without a special shaped wrench and a lot of knuckle-busting, but fortunately someone had been in that area before (or Mercedes realized it would be a real hassle in the future) and there was only one screw holding the relay in. Unplugged the relay, and found the continuity I was looking for.

Wish me luck as I jumper or switch the relay, and continue trying to get fuel to my engine once again.

Thanks guys for the input!!

 

I'm glad you found it -- good luck! :thumbsup:

 

Fuel Pump Relay location

To try to help others who may ever encounter this problem, I'm going to try to attach a photo (the beer bottle was not just due to the great amout of frustration, but also was serving the function of catching fuel when the pump ever did start working). The round and square relays mount on top of a plate behind the ECU which is just behind the right headlight. UNDER that plate is where the rectangular relay (there are actually two) is located. You can't see them without almost looking upside down or using a lighted mirror. I almost swore that they were not anywhere on this car. They are in a terrible location! Good luck ever getting that plate out (2 bolts and a screw that are also very hard to get to). I won't be putting the relays back in that location.

 

Fuel Pump Relay

Floyd, which is the fuel pump relay is it the left or right on the plate? There is a relay below the two relays as well.
Thanks.

 

For those having trouble locating the fuel pump relay, here's a picture from an M-B training manual: