1987 Blazer Fuel Problem - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-14-2004, 05:03 PM
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1987 Blazer Fuel Problem

After off-roading, my 1987 Blazer quit and wouldn't start. Turns out the fuel pump isn't operating. If I bypass the fuel pump relay and feed 12V directly to the fuel pump it works fine, but when I connect it back up to the fuel pump relay - no dice.

When I turn the ignition on, the fuel pump relay pulls in, sends 12V to the fuel pump, and then after about a half second turns off. I'm guessing that the engine control module is sensing some sort of fault and disabling the fuel pump.

I know that there's a low oil pressure sensor than can cause the engine control module to turn off the fuel pump - but I think this is only in the running mode.

Anybody got an idea of what else can cause the engine control module to disable the fuel pump?

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post #2 of (permalink) Old 08-20-2004, 09:39 AM
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Re: 1987 Blazer Fuel Problem

post #3 of (permalink) Old 08-21-2004, 12:02 PM
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Re: 1987 Blazer Fuel Problem

I had a simialr fuel pump problem on an 86 Grand Am. I replaced the original equipment ECM with a remanufactured ECM from A1 Cardone for about $62.00. Most 80's type GM fuel injection ECM's will turn on the fuel pump for 3 seconds when the ignition switch is truned to the on position. If the ECM does not see a "reference pulse" from the distributor ignition module, then the ECM will turn off the fuel pump relay. Maybe you could find a good used distributor ignition module to see if maybe your distributor ignition module is bad. I've also seen when a broken wire on the distributor magnetic pickup coil can cause NO "reference pulse". The "reference pulse" is generated when the engine starts cranking at about 400 RPMs. Maybe the starter is not spinning the engie at 400 PRM's.
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