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96 740iL - Fuel Pump and Wiring Problems

11014 Views 3 Replies 2 Participants Last post by  randyw419
To start off this is my 1rst BMW. Its a 1996 740 iL with 160k miles and needs a lot of work. I considered replacing the engine but that may not solve the problems Im having. I put a new battery in but there is acid in the tray. They previous owner put what Im assuming is a stereo system and blew the alternator. Anyways it fires up with starting fluid and dies. Ive put together the engine part by part. Anyhow I disconnect the hose at the fuel rail and dirty old pump out. I put new fuel and replaced the filter. The filter had no pressure so when I checked the pump it isnt switching on. Keyed on position 2 only 1 wire has 12v and that a constant in any position. I found 3 relays in the engine compartment, 3 above the battery in the trunck, and this is where I have a major problem. In the cabin I have no center console components such as a rdio, climate control ect. I have found 3 more relays, 1 tall black relay, there is a plug hanging down with no resistor. Its inline with 2 thin gauge wires. Whats worse I have 2 wires with eyelets that are attached to nothing. 1 is red/blue. Right now Im just trying to figure out why I the fuel pump isnt kicking on. I also heard that it might have an inertia switch. Im over my head right now, but this car just grows on me and I hate to get rid of it. Any suggestions on any of these issues?
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Have you checked the fuel pump relay for corroded pins? Can you hear the fuel pump engaging? The fuel pump relay is shown in the video min 1:10

If you don't hear the fuel pump engaging probably the fuel pump is bad. With a voltmeter, if u check, do you have continuity between the pins? You could jump the fuel pum from the fuel pum relay...
I would remove the fuel pump and check the fuel pump sump for sandy corrosion, If the car was sitting for a while without being started for sure it has a lot of dirt around.
Ill check it out tonight to see if its working.
Sounds like the relay is working so Im going to jump the termals to see if pump comes on. I also found the two hanging wires at the other relay location under the passenger side dash are from a relay. Just have to find which one goes where and screw them in.
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