Question about 1987 Chevrolet Blazer

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Blowing ECM-B fuses

Blows the ECM fuses every few days or short distances. Engine will crank but won't start. When fuses blow the engine shuts down. When we put a new 25 amp fuse in, it will start right up.

Thanks I have a 1987 K5 Blazer, and my ECM B fuse is blowing constantly. It was fine until I used it to pull a 1998 Chevy 3500 Silverado out of the snow, and as soon as I put a little strain on the motor the fuse popped, over and over again. Now it will blow thew fuse at random, even a 30 gauge fuse. The fuse will blow in both 2WD and 4WD. It will blow with a lot of strain on the engine and even near idle. I think it is a faulty ground, If I am wrong please tell me, and tell me where to look first for this short, if it is a short at all.

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The ECM-B fuse is a 20 amp fuse, and you should NEVER put a larger fuse in to try to overcome any problem. The oil pressure switch is a secondary concern; there is an idiot light or oil pressure guage in the dash to alert you to oil pressure problems. Under heavy load, such as towing, your engine requires more fuel, and if your fuel pump is going/has gone bad, it cannot supply the demand.
The problem is almost certainly a fuel pump wire harness short, caused by a dying fuel pump. I have both had this problem myself, and repaired it on three other vehicles. On my vehicle, the wire harness had welded itself together when the fuel pump locked up, and the wire harness caught on fire.
The fuel pump is in the gas tank (of course my tank was full), and the tank has to be dropped to access it. The wire harness is modular, with plugs at both ends, and can be bought from the Chevrolet or GMC dealer.
If you put an incorrectly-rated fuse anywhere in your vehicle's electrical system, the WORST place to do it is where you have--the fuel pump circuit. Fuses blow for a reason, and the manufacturer's engineers properly size the fuses for the application at hand. Please don't do that again.
This can be a very dangerous problem and repair, and no, it is not cheap.
Do not attempt to operate this vehicle until you have had the problem properly corrected. Good luck.

Posted on Feb 14, 2010

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The first thing you should do is to locate the oil pressure switch/sending unit.

It's a single wire terminal with plastic connect sensor from the engine block.


This oil switch is about $30.


This switch serves two functions.

1) provide oil pressure reading

2) disable the fuel pump relay in event of oil pressure loss.

===

When this switch is failing to provide the correct pressure to the ECU. The wiring harness can overheat and eventually create a short.

ECM B blow is because the harness is grounding/shorting.

===

DO NOT drive the truck until you change the oil pressure switch.

After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.


Please post up day on the comment window/page.

I will follow up on it later.


Good luck.

Posted on Aug 03, 2009

  • Vincent_G
    Vincent_G Aug 03, 2009

    The first thing you should do is to locate the oil pressure switch/sending unit.

    This switch serves two functions.

    1) provide oil pressure reading

    2) disable the fuel pump relay in event of oil pressure loss.

    ===

    When
    this switch is failing to provide the correct pressure to the ECU. The
    wiring harness can overheat and eventually create a short.

    ECM fuse blow is because the harness is grounding/shorting.

    ===

    DO NOT drive the truck until you change the oil pressure switch.

    After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.


    Please post up day on the comment window/page.

    I will follow up on it later.


    Good luck.

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I HAD A 1999 CHEVY SURBURAN THAT WAS DOING THE SAME THING.IT WAS THE WIRES IN THE GAS TANK TO THE PUMP.THEY WOULD GET HOT AND SHORT TOGETHER.DROVE ME CRAZY.

Posted on Feb 02, 2010

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Blowing ECM-B fuses


The first thing you should do is to locate the oil pressure switch/sending unit.


This switch serves two functions.

1) provide oil pressure reading

2) disable the fuel pump relay in event of oil pressure loss.

===

When this switch is failing to provide the correct pressure to the ECU. The wiring harness can overheat and eventually create a short.

ECM B blow is because the harness is grounding/shorting.

===

DO NOT drive the truck until you change the oil pressure switch.

After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.


Please post up day on the comment window/page.

I will follow up on it later.


Good luck.

Aug 24, 2008 | 2000 GMC Savana

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