Hey guys,
I just picked up a 1998 W126 420SEL and the car is dead. I bought it as kind of a project, just play around car and she's in need of some love.

It cranks fine but won't turn over and the person I bought it from said the dealer told him 'probably the fuel pump'. Well, I figured I would start there and found the fuel pump under the car (convenient by the way) and put the car ignition on and listened. No humming at all. I tapped the fuel pump a couple times with a small hammer and nothing. So I decided to get the old voltmeter out, and pulled the rubber protectors off the power/ground leads and tested the voltage with the ignition on.There is nothing, not one millivolt, just dead. My first thought after searching on here a bit was Fuel Pump Relay. Just kind of wanted to get some input from the experts so to speak. What do you guys think?

Also can anyone point me to a schematic for the fuse box under bonnet? I don't have any manuals for this car.

Thanks a ton and have a good one!

 

Hey thanks a ton for the response. Do you happen to have a diagram of the pins you are speaking of?As I look down into the relay socket am I just count left to right on top then left to right on the bottom to get the pin count? I just want to be sure I jumper wire the correct 2 pins because I have seen a ton of different types of relays. For instance, my relay only has 9 pins total, so I can't count to 10? Perhaps if someone has a schematic of that socket that shows what the different pinouts are?

Thanks again gang and happy motoring!

 

Well, I stopped at the MB dealer here and they actually helped me. You were right yhwh12, it was the fuel pump relay,thanks for being so helpful
The head mechanic came out and showed me what pins to jumper. I went home, jumpered them and wham! she started right up, only 2 cranks.

Fuel pumps are extremely LOUD and old. I looked at them and they are probably original, as is the fuel filter I think, judging by the caked on rust/oxidation of the clamps and holding brackets. Get ready to fall over, the car has 241,000 mileson it and I think they're all original Yikes! So the carruns and I tried to drive it, but she just has no power and has a nice lumpy idle. Lumpiness goes away if you give it gas in "Park". So, I was going to go ahead and get her new fuel pumps and filter but I would like to try and make some 'progress' on my project, so I am looking for your opinions again so I spend my project money in the right places. I know the same symptoms can be found if the Distributor Cap/Rotor/Plugs/Wires are shot. Going to pull off the Cap and inspect in there tomorrow, but I am thinking plugs probably aren't a bad idea no matter what since they can foul easily and they are more than likely older-than-dirt. So tell me gang, how bad do you guys think these pumps are? I mean they're LOUD, you can sit in the car and hear them with the engine running and radio on lol. If they are indeed shot has anyone tried these?

http://cgi.ebay.com/ebaymotors/ws/eB...;rd=1&rd=1

Doesn't look bad...nice hardware, seems like a good solid case, but the story can be vastly different when you actually get them. So give me opinions or if you have experience with this vendor/pumps let me know how they are working out for you. Looking for the best deal on pumps because the pumpscould cost me more than car did, I got it for $650
Thanks for all the help gang!