Question about 1992 BMW 3 Series
Hi, what I recommend is interrogating the relay socket. In this way, you can determine what signals are getting to the relay and isolate the problem. It is also a simple matter to jump the relay to test the pump itself. If the relay is mounted in the open, you can easily see the wire colors for the terminals. Otherwise, you have to do a little extra work to identify the terminals. You will need a 12 volt test light to interrogate the relay socket. First, find the fuel pump relay. It may be in the relay box under the hood. Pull the relay out and connect your test light clip to chassis ground. Probe the terminals in the relay socket--there should be 2 hot terminals when the key is on. If only one hot terminal, suspect the DME relay. Note which terminals are hot. Next, switch your test light clip to battery positive. Probe the terminals again. With the key on, there should be one terminal that lights the light brightly and one that lights it dimly. If there is no terminal that lights the light brightly, the DME controller is not turning the pump relay on for some reason. If there is no terminal that lights the light dimly, the pump has an open circuit or the 15 amp fuse is bad (F18). If you do have a terminal that light the light dimly, that is your pump wire. Run a small jumper or use a large paper clip to connect one of the hot terminals to that terminal to apply voltage to the pump. If the pump only hums but does not pump, replace the pump. If all of the signals at the socket are correct, try swapping the relay with a similar one to see if the pump will come on when the key is on. Please let me know if you have questions and do let me know the outcome of your tests so that I can provide repair advice.
Posted on May 27, 2011
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Posted on Jan 02, 2017
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