1991 Chevy C/K wiring diagrams?

**Galane** · 11-03-2014

I'm looking for engine compartment harness diagrams for 1991 Chevy and GMC C/K truck, with the bulkhead connector and circuit number list.

**BLG355** · 11-03-2014

Does this help?

BLG

**1project2many** · 11-03-2014

When that body style truck was equipped with EFI the harness was routed through the firewall just above and to the passenger side of the distributor using a rubber grommet. If you have a harness from the older square body truck there are very few connections with the main harness.

In the next generation trucks the harness is routed under the heater box on the passenger side. There is no connector where the harness passes through the firewall. Instead, there's a plastic "pass through" interface which is filled with sealant (ugly stuff to cut or remove) and bolted to the firewall. Some years have a narrow, rectangular pass through connector and some (I believe the later years) use a larger squared part.

If you are looking for diagrams for C100, the bulkhead connector on the driver's firewall, I can obtain them. It helps to know truck model the harness came from (C/K 1500/2500/3500).

**Galane** · 11-04-2014

1991 two wheel drive C3500. 350 V8, 700R4. It had air conditioning but did not have cruise control.

I'm planning on upgrading the gauge cluster from the simple idiot light one it has to the one with oil, amp and temp gauges.

**1project2many** · 11-04-2014

Ahhh... I'll try to dig it up later today. Do you have C100 / bulkhead for the 82?

**Nasty-Z** · 11-04-2014

This is what I have for the 1991 1500 C/K , hope it helps.

TOM

**Galane** · 11-05-2014

Originally Posted by Nasty-Z

This is what I have for the 1991 1500 C/K , hope it helps.

TOM

Those may help. Thanks.

Looking more and more like I should just cut the bleeping thing off at the inside of the ECM bulkhead plug and start from there. I went to a GM dealer's service department today and they dug out a 1991 C/K wiring diagram book. I got a copy of the image of the bulkhead connector with all the circuit numbers in the boxes.

Fat lot of good that does since the book does not have a nice listing of what all the circuit numbers are, like the 1980's books have on the first few pages. One must peruse the book for ages and make many notes just to track down what goes where.

Far too logical for all those wiring books to devote a few pages to connector diagrams with complete circuit number lists right by each diagram. Nooo, couldn't have that!

Compiling such data would be in the best interests of the automotive hacking community.

**Racerx** · 04-21-2015

Originally Posted by 1project2many

When that body style truck was equipped with EFI the harness was routed through the firewall just above and to the passenger side of the distributor using a rubber grommet. If you have a harness from the older square body truck there are very few connections with the main harness.

In the next generation trucks the harness is routed under the heater box on the passenger side. There is no connector where the harness passes through the firewall. Instead, there's a plastic "pass through" interface which is filled with sealant (ugly stuff to cut or remove) and bolted to the firewall. Some years have a narrow, rectangular pass through connector and some (I believe the later years) use a larger squared part.

If you are looking for diagrams for C100, the bulkhead connector on the driver's firewall, I can obtain them. It helps to know truck model the harness came from (C/K 1500/2500/3500).

Hi, im from spain. i have a big problem since an american car in europe its an import hard to find parts and not much people knows how to fix them. I have a 89 C1500 stepside single cab 5.7 tbi. i bought about 1.5 year. engine start smoking so i take apart but at the end engine and accessories where in bad condition so i found a really nice 92 blazer k15 at a yunkyard. I've bought the engine complete with wire harness and dash harness including gauges.(unfortunately somebody cut the bulkhead connector the one that came from engine) what I did.... cut the c100 connector on 89 wire harness and weld on blazer engine harness. since i have no information what i did was copy blazer bulkhead in cab pinout and weld on engine side by same color . after weld i try to fire up but nothing came so I've check and found the fuel pump doesn't work so i make it run straight to a positive and the truck fire up perfect but nothing electric work like gauges lights a/c radio nothing. i was looking for a bulkhead pinout for 89 c1500 and 92 k15 blazer but i cant get any info. i really will appreciate if can get some help... thank you in advance. Gonzalo

**turbopowered68** · 10-17-2015

Originally Posted by 1project2many

When that body style truck was equipped with EFI the harness was routed through the firewall just above and to the passenger side of the distributor using a rubber grommet. If you have a harness from the older square body truck there are very few connections with the main harness.

In the next generation trucks the harness is routed under the heater box on the passenger side. There is no connector where the harness passes through the firewall. Instead, there's a plastic "pass through" interface which is filled with sealant (ugly stuff to cut or remove) and bolted to the firewall. Some years have a narrow, rectangular pass through connector and some (I believe the later years) use a larger squared part.

If you are looking for diagrams for C100, the bulkhead connector on the driver's firewall, I can obtain them. It helps to know truck model the harness came from (C/K 1500/2500/3500).

I am in NEED of the C100 bulkhead connector for an 1987 G20 tbi engine.
Do The ones you get come with labeled leads?
Thanks
David