Fuel Pump Relay in 1995 E320 Wagon

12262 Views 7 Replies 4 Participants Last post by parad0x_i, Apr 17, 2009

batmanandbobbin

Discussion Starter · Apr 9, 2009

Hi--

My fuel pump is sometimes not turning on when I turn the key before starting the engine. The pump sounds fine when it runs, but it sounds like the fuel pump relay is dying. I used to have this problem on volvos that I drove and it was easy to replace the fuel pump relay in the older volvos.

My question is: where is the fuel pump relay on my car? The service CD's show that it is in the rear compartment of the sedans, but I don't see a location for the wagons. I've read a lot of posts claiming that the fuel pump relay is under the rear seat, behind the battery, or that the fuel pump relay is part of the OVP and that there is no separate relay.

The service CD's show a distinctly separate device called the fuel pump relay, so I believe that there must be one somewhere. Can anyone advise on where to find the relay in my '95 E320 Wagon?

--James

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augapfel

· #7 · Apr 13, 2009

On every EFI car I've ever worked on, the fuel pump runs for a few seconds as soon as the key is turned to run. This is to ensure that the EFI system is adequately pressurized for the injectors to spray prperly.
The pump keeps running so long as the engine is cranking. If the key is released from cranking and the engine hasn't started, the pump is shut off after ablut 2 seconds. If the ECU loses the crankshaft position signal while the engine is running, the fuel pump is shut off. This last one is to prevent the pump from emptying the tank following a crash where a fuel line has ruptured.
Can't help with location since my experience (at least in that area) is with the early 124s. Under the hood, near the battery is my best guess, though.

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