Mercedes-benz r129 fuel pump replacement – sl500, 500sl, 300sl, sl320, 600sl, sl600 (1990 – 2002) – pelican parts technical article 1 electricity unit in kwh


With the metal line out of the way slide the lower fuel pump out of the mounting bracket. Installation is the reverse of the removal procedures. Install the lower pump first and then the metal line that connects the fuel pump to the fuel filter and the fuel pressure regulator. Position the black plastic spacer and install the upper pump and connect the line with the rubber end to the lower pump and the metal banjo fitting on the upper pump. Install the banjo cap fasteners on both the upper and lower fuel pumps and tighten the hose clamp on the other side of the lower pump. Tighten the fasteners that clamp the bracket onto the fuel pumps. With the fuel pump assembly together position it under the car and attach the electrical wiring as you took it off. Lift the fuel pump assembly and attach the four rubber hangars that suspend the fuel pumps assembly under the body of the car. Install and tighten the large feed line from the fuel tank and the fuel output line on the filter. Turn on the ignition and crank the engine. Verify you do not have any fuel leaks before you take the car off of the jack stands. Once on the ground verify the car starts.

Comments: UK 1995 R129 SL500 no start after a long period of flat battery. no fuel getting to injector rail, no power to pump. cap removed off green relay in boot all looks new. exact same relay under bonnet. swapped them over for a test no change. engine cranks over but doesnt even try to start. had intermittent rough running before it was dormant for 6 months. still to bridge relay terminals t rule that out but do you have any other suggestions for what could be stopping power to the fuel pump? excellent website extremely useful with my 202s, 124s, 123 and 129!

Comments: have 91 sl500 starts good idles for few mins then surges and stalls, will start up right away runs surges then stalls replaced fuel filter thinking now it’s the pumps. noticed in 93 they change to 1 pump can i covert my car to 1 pump, how do i test them thks

Comments: ’94 SL320, I couldn’t get the support screws back in and after 20 minutes of frustration and broken plastic, I said, "screw it," and got some zip-ties and fed them through the screw holes. worked great, holds great, and was done in 60 seconds!

Comments: My 1994 S500 Coupe will not start execpt when I prime the engine. I am not getting any electrical current to the fuel pump. Is there a enertia switch or wath could it be. I have current to the fuel pump relay and fuse. from the relay to the pump dead.

Comments: 94 SL500. Runs great until it gets warmed up. Then it got really rough and wouldn’t idle. Just turned over 100k miles. Replaced distributors and plugs. Now it’s not rough but when it gets heated up, on the highway at 60 MPH, 2k rpm, nothing happens when you step on the gas. Fuel consumption pegs high 30mpg with the accelerator floored but no response in power. Downshift to 3rd, stays at 60MPH, but rpm goes to 3k. I was going to start replacing fuel system parts, but thought I’d check in first.

Followup from the Pelican Staff: Sounds like a sensor issue to me. I can’t help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Once you figure out what is missing, it will be easier to diagnose.

Comments: I have a SL500. It would act like it was missing when starting. Tried to start several times and would finally start and run. Eventually the car wouldn’t start. I replaced the fuel filter and it will start but has no power when you put it in gear and feels like it is out of time even though it has 1200 rpm.

Comments: I have a 1995 SL600 that had a dead battery. Put a new battery in and it doesn’t start. I don’t hear the fuel. Tested for voltage at the pump, but don’t seem to have any. Thought about jumping 12v directly to it, but not sure how to do it and don’t want to damage anything. I can hear the fuel relay clicking. Is there anything between the relay and pump that would keep it from getting power?

Comments: This is an excellent write up that I just stumbled upon while looking up other information. I was looking for this back in June ’14 and was unable to find any information on where these were even located let alone the step-by-step. Thank you. Now only if the 17mm fitting that connects the output line of the fuel filter was not completely rusted solid I would have been ahead of the game. Nothing can be easy.