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Ames63

Off topic question of a german nature

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Helping my brother with his 1990 740 GL, we thought it was the fuel pump(btw his volvo has only one fuel pump, not two), so we replaced it. I tested the old fuel pump and it is working just fine. We replaced the fuel pump relay, the fuel filter and (FPR)fuel pressure regulator. Still not fuel is getting into the combustion chamber. We did spray starter fluid into the intake and the car started and ran for a few seconds(`10 sec). So we know it is a fuel delivery issue. We know that if we remove the FPR and cycle the electronics the fuel pump pushes out fuel. I suspect we initially we misdiagnoised the problem, but we suspect either the FPR was the problem or for some reason the injectiors are not opening up. Since fuel will not flow pass the new FPR, is there away to prime the system to start flow pass the FPR or is there a way to determine if the injectors(all of them) are not functioning or have we misdiagnoised the problem again?

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Borrow a fuel injector "noid" tester from an auto parts store and verify that your injectors are being fired by the engine computer. Think Autozone and Advance have them to lend.

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Assuming this is electronic FI, betcha the injectors are not rattling. Could be a bad crank sensor.

Service manual should have a procedure for "Cranks but Does Not Run". Can be a bit AR but will find the problem.

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check the self-diagnostic code readout, if your 740 has one it is on the cross-brace left-rear corner of the engine compartment. A little black box with a removeable cover, and a probe attached to a wire. Plug the wire into socket #6, hold button down for 1 second, then wait for code(s) to flash, read service manual to discern code description(S), then diagnose (decide) what is causing the code to be set. The trouble code does not always point to the defective part, rather to the part, or system being affected by the problem.

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