Blowing ECM 20A fuses

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Blowing ECM 20A fuses

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Chevrolet Forums >> Chevy Trucks, Vans & SUV's >> Astro >> Blowing ECM 20A fuses

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Blowing ECM 20A fuses - 5/7/2008 11:25:27 PM

99safari

Posts: 1
Joined: 5/7/2008
Status: offline

This is for a 1999 GMC Safari with a 4.3 L (same as Astro):

1. Was running fine during the day.
2. Vehicle parked for about 1 hour turned off.
3. Turned on ignition key (run position), gas gauge reading fine.
4. Attempted to start the vehicle, cranks, no start. Cannot hear fuel pump.
5. Gas gauge going to the 3:00 position, pegged to the right, looks invalid.
6. Stopped cranking.
7. 20A ECM-1 fuse under the hood is blown.
8. Took a spare 20A from the under dash & replaced.
9. Turned on ignition key (run position), gas gauge reading fine for about 30 seconds
without cranking. I do not hear the fuel pump go thru the 2 second pump up.
10. As soon as I crank the car, gas gauge pegs to the 3:00 position.
11. 20A ECM-1 fuse is blown for the 2nd time.
12. The last 20A ECM-1 fuse blows for the 3rd time, after cranking starts.

After a while of cooling down, replace the 20A ECM-1, WORKS!

This problem is incredibly intermittent, but when it happens, it fails, but somehow clears after a while.

The dealer has done the following:
1. Replaced cylinder #1 injector, says it was shorted, now it's doing the same thing after 9 months.
2. Repaired the crankshaft position sensor wire, says it was frayed, I inspected, no trouble found.

I looked in my service manual and the ECM-1 fuse under the hood feeds
all fuel injectors, crankshaft position sensor, the VCM, ignition control module,
and ignition coil. Based on what I see, the fuel pump is not working and the
ECM-1 fuse blows once cranking starts. It appears the VCM is not powered hence
it cannot turn on the fuel pump relay.

I have asked the dealer to verify all the 0.8 PNK wires and the ground terminals.
Only thing left is a possible short to ground internally to the electronic ignition
control module. The dealer has been in touch with GM technical support for 3
days.

I just don't understand why GM did not fuse the injectors separately in order
to help isolate such a key component.

Any help greatly appreciated!

HELP!