I already started discussing this problem in another thread, but to avoid threadjacking that one, and hopefully to get a faster response, I thought it would be better to start my own thread.

Just as the title says...I replaced my fuel pumps, and started the car...it ran perfect, so I got back underneath just to make sure nothing was leaking. I spotted a slight drip at one of the fittings, so I left the car running and (like an idiot) tried tightening the loose fitting. There was a spark, and the engine died. Now it won't start at all, and I don't hear the pumps running like I did before.

I tried my known good fuel pump relay, and OVP from my 87 560SEL, but the car still won't start, no change. What could the problem be? At first I thought maybe a fuse, but I can't find any fuse for the fuel pump at all.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

If I remember correctly, there isn't a fuse for the fuel pump circuit. I did the exact thing once, and I blew the fuel pump relay. Try jumping pins 7 and 8 on the fuel pump relay connector to see if the pumps come on. If it does, then you blew your relay, if it doesn't pull a diagram to see where else the circuit goes...

Fuses?

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-Justin

91 560 SEC AMG - other dogs dd
01 Honda S2000 - dogs dd
07 MB ML320 CDI - dd
16 Lexus IS250 - wifes dd

it's automatic.

I checked all the fuses in the engine bay...they all look fine.

I also tried the fuel pump relay from my 87 560SEL (immediately to the left of the OVP), which looks like an aftermarket one, and the pins are slightly different, but the car didn't start. Maybe I need a different one?

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

There isn't a fuse involved. The pump can be jumped by crossing pin holes matching the circuit designations 30 and 87 on the relay. They should be next to one another at the center of the socket.

As to the relay you tried, what is the MB number on it. The FP relay looks about identical to the Klima relay for teh AC.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I don't think there is an MB part number on the relay I tried, it's an aftermarket unit.

This is the exact one:


The one in my SEC is a genuine Mercedes relay. I looked up the relay's for both of my car's on all parts express, and they show the same part number...

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

They have the same part number but a different pin configuration??

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Yes, the pins look a little bit different.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Post a picture of the other relay or MB part #.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Ok, I just jumpered pins 30 & 87, and the fuel pumps started running. So the relay is definitely bad. It's MB part No. 002 545 16 05.

What I don't understand is why the relay from my 87 wouldn't work?

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Does the 87 one have that part number? If so then the issue may be the control circuit. Do both relays work in your 87?

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Jumping 30 and 87 by-passes the relays pump contacts and verifies pump, but if there is not 12v feed to the relays coil side, that would be a possible fuse, as that should be a fused circuit.

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A Dalton

Ok, I just realized that I was trying to use the relay labelled AC Compressor, as they are in opposite locations on both of my cars...UGH! Well, I tried the proper FP relay in the SEC, and it started! So that was the problem.

Unfortunately tho, my car still has the same problem that I thought replacing the fuel pumps would fix. What a waste of time and effort.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles