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A fix for an ECU with broken fuel pump relay control
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Posted by walt [Email] (#2707) [Profile/Gallery] (more from walt) on Thu, 5 Apr 2012 21:22:25 Share Post by Email
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Had the common problem with LH 2.4 ECU (Bosch 0 280 000 580) in a 1990 C900 non/turbo not grounding the fuel pump relay coil to run fuel pump. Some people may replace ECU, repair ECU, use an 8-valve fuel pump relay, or simply run wire from ignition 15 circuit to fuel pump (which isn't safe after a collision which leaves driver unconscious and unable to switch off ignition). I opted for a relay control circuit found on a Volvo forum. Ran the fuel pump relay coil 85 terminal violet wire over to fuse/relay box and installed a fuel pump relay "missing pulse relay control" circuit as described in link below with a few modifications. Wire-wrapped it on a 1x1.5-inch circuit board, and epoxied it to the base of gutted generic auto relay, and installed it in vacant relay socket. Got ground, ignition supply (15-green/white), and ignition tachometer signal from EZK (blue) from the TSI socket in fuse/relay box. Now car is running more safely, because circuit turns off pump once engine stops running even if ignition switch stays in RUN position. Circuit also runs pump for 2 seconds when energized then turns pump off.

posted by 72.49.19...

missing pulse detector circuit for fuel pump control

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