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Old 07-30-2013, 02:42 PM   #1
 
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Default 1990 Suburban ECM-1 fuse blows, again & again :-(
I can't find my problem, and I'm going crazy. 1990 V2500, normally run perfect. :-)

On the road last month, and it died. get it home, check fuses... ECM 1 blown. replace..turn key to On position... blows again. sometimes blows on crank.

Before the blow, I could hear fuel pump relay click but no fuel pump prime. I changed the relay and fuel injector relay anyway. still blows.

I have also changed, distrib & cap, rotor, coil. 3 months ago I changed all sensors.

I have traced wiring, everything seems OK. Did the process of elimination with sensors, fuel pump, etc. unplug/plug in... still blows.

What am I missing?

HELP! :-) please Thank you!
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Old 07-30-2013, 03:01 PM   #2
 
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I can look in my wiring diagram and see what is on that fuse. From there, I would isolate anything that is tied to that circuit, and start checking for shorts to ground with a meter.
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Old 07-30-2013, 03:18 PM   #3
 
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It goes to the ECM. I would start by unplugging the ECM and cleaning the grounds. The wire that we're looking for is pink/black and goes to the Electronic Spark Control; the gauges; the ECM, the fuel injectors; fuel pump relay.

Does the check engine light come on?

Chengny will know more, I have the wiring diagram available for download though if you'd like.


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Old 07-30-2013, 03:44 PM   #4
 
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Originally Posted by RetroC10Sport View Post
It goes to the ECM. I would start by unplugging the ECM and cleaning the grounds. The wire that we're looking for is pink/black and goes to the Electronic Spark Control; the gauges; the ECM, the fuel injectors; fuel pump relay.

Does the check engine light come on?

Chengny will know more, I have the wiring diagram available for download though if you'd like.
Thanks everyone for the replies.

Truck isn't throwing any codes... I will check pink/black & ECM...
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Old 07-30-2013, 07:04 PM   #5
 
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Default 1990 Suburban ECM-1 fuse blows, again & again :-(



Posted from hell


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Old 08-01-2013, 04:45 PM   #6
 
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LMAO...

I have everything unplugged ECM, electronic spark control, map, IAC, etc...

and the damn fuse still blows!

now, I'm going to pull the dash & gauges...

But, could it be in the steering column, lock cylinder?
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Old 08-01-2013, 05:06 PM   #7
 
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No, not in the lock cylinder as there's no wiring for it, the ignition switch is down the column a little ways.

You've likely got a pinched wire somewhere or something is shorting out. I my 1991 S10 Blazer, the gages fuse kept blowing because somehow the speedometer wiring got pinched in the transfer case shifter.

1990 Suburban wiring diagram - right click and save as.


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Old 08-01-2013, 05:17 PM   #8
 
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If you have a voltmeter with a diode tester, many have a beep to show a short. You can put the vm in that mode then probe the feed to each of the items on that fuse until it beeps. If you don't get any shorts, try to slowly move the wires around. Since it's intermittent, you may have to prod it a little to find the short.
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Old 08-01-2013, 05:26 PM   #9
 
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Originally Posted by RetroC10Sport View Post
No, not in the lock cylinder as there's no wiring for it, the ignition switch is down the column a little ways.

You've likely got a pinched wire somewhere or something is shorting out. I my 1991 S10 Blazer, the gages fuse kept blowing because somehow the speedometer wiring got pinched in the transfer case shifter.

1990 Suburban wiring diagram - right click and save as.
Holy Heck! Thank you so much for the diagrams!

You made my day!
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Old 08-01-2013, 05:27 PM   #10
 
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You're very welcome.


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Old 08-01-2013, 05:32 PM   #11
 
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Originally Posted by RetroC10Sport View Post
No, not in the lock cylinder as there's no wiring for it, the ignition switch is down the column a little ways.

You've likely got a pinched wire somewhere or something is shorting out. I my 1991 S10 Blazer, the gages fuse kept blowing because somehow the speedometer wiring got pinched in the transfer case shifter.

1990 Suburban wiring diagram - right click and save as.
Unplug the downshift relay as well...I am assuming you have a TH400 3speed trans. its the relay next to the fuel pump relay on the firewall.
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Old 08-01-2013, 09:10 PM   #12
 
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Originally Posted by Jims86 View Post
Unplug the downshift relay as well...I am assuming you have a TH400 3speed trans. its the relay next to the fuel pump relay on the firewall.
:-( The only relays on the firewall are the fuel pump & fuel injector relays.

Would the downshift be somewhere else?
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Old 08-01-2013, 10:13 PM   #13
 
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If it has a 700r4 OD trans, it won't have one.


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Old 08-02-2013, 12:46 AM   #14
 
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Originally Posted by CWGRL View Post
:-( The only relays on the firewall are the fuel pump & fuel injector relays.

Would the downshift be somewhere else?
there is no fuel injector relay. just the fuel pump relay, then if it has a similar relay next to it, thats the downshift relay. it has a red, orange, tan/blk, and a purple wire going to it.

Originally Posted by RetroC10Sport View Post
If it has a 700r4 OD trans, it won't have one.
its a v2500....if its a 4l80e, we need to make sure we are looking at the right diagrams.

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Old 08-02-2013, 12:49 AM   #15
 
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Originally Posted by Jims86 View Post
there is no fuel injector relay. just the fuel pump relay, then if it has a similar relay next to it, thats the downshift relay.



its a v2500
Damn interchange is showing that the V2500 could have a 700r4, but the factory info says otherwise.



See your edit. 4L80E did not come out until 1991. Let me look at the compnine info I have and see what it says, could have been a late year option.

Compnine says no 4 speed auto R or V 2500s. So I get schooled as well!


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