1990 tbi ecm shorting

[BennyPorras]

I have a 1990 Silverado tbi. I was able to figure out that the ecm had a short where pin 16 connects to the circuit board. I added some solder when I went to connect it. It shorted instantly. On this pin it has the injector light blue wire and a orange wire that runs to a fusible link, fuel pump relay, and oil pressure switch.
I tried putting fuses on both the light blue and orange wires. And still short. I haven’t had the chance to try another ecm. But any ideas on what would cause this. I have not been able to find any shorts in these wires so far.

 

[PlayingWithTBI]

I was able to figure out that the ecm had a short where pin 16 connects to the circuit board. I added some solder when I went to connect it. It shorted instantly. On this pin it has the injector light blue wire and a orange wire that runs to a fusible link, fuel pump relay, and oil pressure switch.

Which ECM do you have, a 1227747? Which pin 16, maybe D16? There's 4 different sets of pins on 2 connectors from A - D. There shouldn't be 2 different colored wires going to a single pin. Here's some info on the 7747 ECM

1227747 ECM Information $42

1227747 ECM Information $42 This ECM was used in 1987 to 1991 C/K Truck, Van, 4.3L, 5.7L, 5.0L & 7.4L engines. $42 Mask Click here for details on how to read error codes known as Check Engine Light (CEL) or Service Engine Soon (SES) can be found in this thread. *Work in progress*

www.gearhead-efi.com

Here's a schematic from my 88 ECM. The Orange wire should go to the Oil Pressure Switch, Fuel Pump Relay, Pins B1, and C16.

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Another

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[BennyPorras]

I have the same ecm on the 32 pin connector I have a short that seems to be coming from either d16 or c16. this short is happening in the actual circuit board of the ecm.

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[PlayingWithTBI]

Is the short inside the ECM itself? Did you Ohm out pins D16 and C16?

 

[Schurkey]

What are the symptoms? How does the truck run?

I have a 1990 Silverado tbi. I was able to figure out that the ecm had a short where pin 16 connects to the circuit board. I added some solder when I went to connect it. It shorted instantly. On this pin it has the injector light blue wire and a orange wire that runs to a fusible link, fuel pump relay, and oil pressure switch.
I tried putting fuses on both the light blue and orange wires. And still short. I haven’t had the chance to try another ecm. But any ideas on what would cause this. I have not been able to find any shorts in these wires so far.

You're popping fuses you added to the "light blue" and "orange" wires?

If you have a short-circuit to ground, most folks would call that a "grounded" circuit, not "short".

Is this melting the solder in the place you've circled on the photo of the circuit board?

First Guess: Failed ECM. Try another.

 

[BennyPorras]

Is the short inside the ECM itself? Did you Ohm out pins D16 and C16?

I have not ohm the pins yet.

 

[BennyPorras]

What are the symptoms? How does the truck run?


You're popping fuses you added to the "light blue" and "orange" wires?

If you have a short-circuit to ground, most folks would call that a "grounded" circuit, not "short".

Is this melting the solder in the place you've circled on the photo of the circuit board?

First Guess: Failed ECM. Try another.

The fuses are not popping at all. Yes the soldering is melting where I circled.
I thought it would be the ecm I just did not want to plug in another ecm just for the same thing to happen to it.
The truck cranks but does not send any power to the fuel system. where the wires (Dk green wht) pins to A1 and (Light Blue) pins to D16. I can't remember if the orange wire has any power to it. I need to check again.

 

[Schurkey]

I have no idea about A1. Not on the schematic or circuit descriptions posted above, although there's a dark green/white stripe wire from the ECM to the fuel pump relay is. But that's at C2, not A1.

D16 is a ground for the fuel injectors. The injectors get power via the injector fuse, they're "hot" any time the key is in "Run" or "Start".

If there's too much current for the ECM to handle...so that it's melting solder...I'd think that injector windings would have to be shorted. If the insulation on the wires melted, the resistance would go way down, and the current would go way up. But that SHOULD pop the 5-amp injector fuse. That brings us back to why there's an orange wire connected to D16 when that's not on the schematic.

Did someone slap a higher-value fuse into the injector fuse position? Is your '90 wired differently than that '88 schematic? Did someone cram an orange wire where it doesn't belong? According to the schematic, there's an orange wire like you describe connected to C16, but not D16.

 

[BennyPorras]

I have no idea about A1. Not on the schematic or circuit descriptions posted above, although there's a dark green/white stripe wire from the ECM to the fuel pump relay is. But that's at C2, not A1.

D16 is a ground for the fuel injectors. The injectors get power via the injector fuse, they're "hot" any time the key is in "Run" or "Start".

If there's too much current for the ECM to handle...so that it's melting solder...I'd think that injector windings would have to be shorted. If the insulation on the wires melted, the resistance would go way down, and the current would go way up. But that SHOULD pop the 5-amp injector fuse. That brings us back to why there's an orange wire connected to D16 when that's not on the schematic.

Did someone slap a higher-value fuse into the injector fuse position? Is your '90 wired differently than that '88 schematic? Did someone cram an orange wire where it doesn't belong? According to the schematic, there's an orange wire like you describe connected to C16, but not D16.

The dark green wire is a1. There is another orange on b1. But that’s on the 24 pin. The short is coming from the 32 pin. D16 is the injector (light blue) the orange is c16 (org 440). The fuse panel has a not blown 10 amp fuse for the injectors.

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[Schurkey]

There's only one wire connected to D16. The blue wire that's supposed to be there.

One of the illustrations above says "5-amp", the other says "10-amp" fuse for the injectors. I missed that before. And D16 is the ground for only one injector, not both.

I guess it's time to find the schematics and circuit description for YOUR vehicle.