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87 740 Jetronic fuel pump relay grounding transistor is bad?'s

Me again.. I discovered that I have two Bosch Jetronics ECU's 0 280 000

544 & 0 280 000 541 who's fuel pump relay's (ecu transistors) will not energize and make contact. I discovered this by switching a third, working ECU 0 280 000 511 from my 85 740 to my newly aquired 87 740 turbo and the fuel pump relay energized, made contact and started without a problem.

I read that there is potentially volvo aftermarketer's or independant's that sell a kit that allows you to fix the "transistor" problem onesself. Is anyone knowledgable of this? I called Bergerone Volvo here in New Orleans and a mechanic acted like he never heard of such a thing. If not, I am potentially interested in selling, trading, exchanging these two computers for a good ecu. Also, I read that it's possible to ground or overide the fuel pump relay. Is anyone knowledgable of this and if so, could you please elaborate. As well, could someone please tell me where this transistor is located in the ecu?

BTW: If I manually close the fuel pump relay both ecu's will start and run the auto. Thanks for any HELP!! :(( SO SAD:((((

Reply to
Shade(y
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What you do is take a fuel pump relay from a K-Jetronic car and use it to turn on your existing fuel pump relay (Volvo pn 3523639), which only turns the fuel pump on when there is spark. You need to tap into 2 wires at your computer, and run a third to either the ignition coil or tachometer, and ground 2 more terminals on the new relay.

Connect the following: Terminal 31 on the new relay to ground. (This is for the circuit inside the new relay.) Terminal 30 on the new relay to ground. (This is the current path for your existing relay.) Terminal 31b on the new relay to the red-white wire on the coil or tachometer for engine running signal. Terminal 15 on the new relay to a switched power wire on your computer (usually blue or blue-green). Terminal 87b on the new relay to the black-yellow wire on your computer. (This is the power path for your existing relay, and the wire that the computer no longer grounds.)

Reply to
Mike F

The usual problem is just a cold solder joint in the ECU, worst case is a blown transistor.

Reply to
James Sweet

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