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No power to 500sl fuel pump

10K views 22 replies 4 participants last post by  unavita 
#1 ·
To all

The fuel pump on the 83 AMG 500 sl has died. After listening to it whine for a bit, it finally gave up. Luckily I made back to the house on my last outing.

After replacing the fuel pump and filter the car would not start. When turning the key in the ignition I do not here the pump pressurize as I usually do. I attached a test light to the electrical terminals at the pump to see if I was getting power to the pump but it did not light. Alas I had no power to the pump. Given the age of things I replaced the fuel pump relay behind the glove box. The motor cranks but still no power to the fuel pump. Does anyone know if there are any other pump relays or fuses that govern this circuit. What am I missing?
Thanks in advance

regards
fjs60
 
#3 ·
Rowdie

I was thinking that was a possibility. The dash lights have never been strong so I really did not notice anything out of the ordinary. Whenever I do turn the key the car cranks right over. The reason I mention if there is anything else I recall reading in an old post something about an over voltage protection relay with a fuse? I also do not know where to look for such an item if it indeed has anything to do with the fuel pump. thanks

fjs560
 
#5 ·
Funny. I was just going to do an update on my 500sl. I replaced the fuel pump, filter and accumulator. I think I may need a fuel pressure thingy... can't think right now...
Anyway, I dumped some 100 octane down the air intake. She fired right up and ran for about 2 minutes.
Tomorrow I will try and jump the pins. Then I will check the ignition. I have the same problem as listed here! Not getting power to the fuel pump.
 
#11 · (Edited)
Here is the wiring diagram for the fuelpump for my 85 500SL.

I would try the following:
1: Verify the fuelpump and ignition is OK by connecting 12V directly to the fuelpump

2: Check that the fuelpump relay wiring to the fuelpump is ok by bridging the FP relay

3: If the starter does not run, the ignition switch, the neutral safety switch or the connection to the strarter solenoid are faulty. The solenoid is very exposed and was badly corroded on my car.
 

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#12 · (Edited)
Great guideline!
I'd already bridged the FP while it was still on the car. I got a new one with filter and accumulator. I ended up getting the old FP to work also.
I managed to get the car running by putting 100 octane right in the intake. It ran for about 5 minutes and blue a lot of white smoke. I'm guessing there is an intake manifold leak since the compression tests turned out better than hoped. 175-185 on all cylinders. I'm going to bridge the relay (upper towards firewall I believe). I did see a relay is missing: lowest towards passenger door. Aux fan I believe. The car has an external electric fan that runs full time.
 
#14 ·
Rowdie

just getting around to pulling the instrument cluster. Is there any trick to getting enough slack in the harness to get the cluster out far enough to disconnect the tach. right now I cannot even get my hands behind it. any thoughts? Once that's out I can tackle the ignition switch.

regards

fjs 560
 
#17 ·
Rowdie

I have the cluster out . is there any tabs on the electrical plug that goes to the ignition starter switch in order pull it off? I do not see or feel any but it does not want to budge. Once I have that out I can access the three screws to separate the electrical switch from the steering lock housing and then replace it.
Any thoughts. Thanks
 
#22 ·
To all

As a follow up I replaced the ignition switch (superseded pn 202 545 01 04) but that was not the problem, but given that it was original it made sense to do so and eliminate that variable. Ultimately it was a bad Over Voltage Protection relay ( it rattled when I shook it). The superseded part number is 201 540 08 45 . Once that was replaced I had power to the fuel pump and it fired right up. I used Jon Siggson at MB Classic center @ 949-598-4843 for my parts. He was very helpful .
 
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