Page 1 of 2 12 LastLast
Results 1 to 15 of 26

Thread: 1991 Chevy C/K wiring diagrams?

  1. #1
    Electronic Ignition!
    Join Date
    Nov 2014
    Age
    52
    Posts
    11

    1991 Chevy C/K wiring diagrams?

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

  2. #2
    Fuel Injected! BLG355's Avatar
    Join Date
    Feb 2014
    Location
    Elizabethtown, PA
    Age
    41
    Posts
    220
    Does this help?


    BLG
    My Build: 95 K1500, 355ci w/ OEM roller setup - zero decked, Eagle steel crank, Scat bushed H-beam rods, Speed Pro 2V flat top pistons - Rotating assembly balanced. Dart 165cc Iron Eagle S/S heads - 72cc chambers - 1.94 / 1.50 valves. Isky roller cam - 204/209 dur @ .050 - .480/.496 lift with Comp Magnum 1.6 rockers, Edelbrock 3704 intake - Bored to 52mm - 454 throttle body, Delco EP381 fuel pump @ 18 psi running through 80# 454 injectors. Hedman Headers into 3" Dynomax exhaust.

  3. #3
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    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).

  4. #4
    Electronic Ignition!
    Join Date
    Nov 2014
    Age
    52
    Posts
    11
    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.

  5. #5
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    Ahhh... I'll try to dig it up later today. Do you have C100 / bulkhead for the 82?

  6. #6
    Fuel Injected!
    Join Date
    May 2011
    Location
    Pocono's PA.
    Age
    50
    Posts
    370
    This is what I have for the 1991 1500 C/K , hope it helps.


    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  7. #7
    Electronic Ignition!
    Join Date
    Nov 2014
    Age
    52
    Posts
    11
    Quote Originally Posted by Nasty-Z View Post
    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.
    Last edited by Galane; 11-05-2014 at 06:02 AM.

  8. #8
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    The books change format over the years. You train and learn to use the new format when it comes out and you're good. They changed them again, substantially in '96. Suddenly GM manuals looked a lot like Ford books. It's a mess each time they get changed. Now it's in electronic format whaich is a completely new way to find (or not find) the info.

    The circuit numbers are in the wiring diagrams that are in the electrical manual. The images posted here are from the service manual. The electrical manuals have much more detail than the simple pictorial schematics including wire sizes, colors, splices, and (usually) connector pinouts. You probably noticed this looking at the dealer's book. If my memory hasn't gone completely, connector pinouts were placed in one section and listed by connector number starting at LF of vehicle. Except for ecm connectors, of course, which are in section 6E of the service manual.

    I'm still waiting for my service information provider to send the image of C100. I'll probably hit them up for the circuit listing when it comes in.

  9. #9
    Fuel Injected!
    Join Date
    May 2011
    Location
    Pocono's PA.
    Age
    50
    Posts
    370
    This what you are all looking for ?

    This may be for the later '96-98 Vortec stuff now that I look at it , I can check the files tonight if need be .

    TOM
    Last edited by Nasty-Z; 11-05-2014 at 05:44 PM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  10. #10
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    The 1991 wiring diagrams break out C100 into about 14 pages of circuits. I can get specific diagrams if needed. These are (or should be) related to the instrument cluster.

    Please let me know if this helps.

  11. #11
    Electronic Ignition!
    Join Date
    Nov 2014
    Age
    52
    Posts
    11
    Quote Originally Posted by Nasty-Z View Post
    This what you are all looking for ?

    This may be for the later '96-98 Vortec stuff now that I look at it , I can check the files tonight if need be .

    TOM
    Looks different. The 91 connector is pretty similar to the 82 connector, has a "claw" on one side to hold other plugs but there are more contacts in the 91's connector.

    Can I connect the old oil pressure gauge in parallel with the sensor at the rear of the engine, by the distributor, or will I need a separate sensor? I'm planning on upgrading the idiot light cluster to the gauge one that has oil pressure, temp and amp gauges. The 91 engine already has separate temp sensors for the computer (front crossover on intake) and gauge (left head). Will have to change connectors on the temp wire to use the 91 sensor.

    Looking at the 1980's diagram I found showing all three clusters, looks like all the wiring is in the connector, just change clusters and make sure to have the right switches or sensors for oil pressure and coolant temp.

  12. #12
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    The original configuration for '91 placed the OP switch above the oil filter on the LF side of the block and a switch (for the fuel pump) at the top of the block. Later configurations came with a combination switch/sender. Either sender works with the guages, provided the range is correct (0-40 psi or 0-80 psi.)

  13. #13
    Electronic Ignition!
    Join Date
    Nov 2014
    Age
    52
    Posts
    11
    This has the big plastic sensor with three wires in a 90 degree fitting atop a tall pipe by the distributor. I replaced it because it was leaking oil.

  14. #14
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    Yes... but are all three wires used? There's no use for a pressure reading for anything other than the gauge. So if all three wires are used, two would be for the fuel pump circuit and I would suspect the third triggers a warning light on the dash. I don't remember that being the case but hey... it's been a *few* years since I worked on these trucks. Now if that's the case then you could replace that sender with an actual pressure sensor / switch combination and connect the gauge directly to the circuit formerly used for a warning light.

    But ultimately, if you have the room it won't hurt anything to Tee the gauge sender and that unit to the same point in the block.

  15. #15
    Electronic Ignition!
    Join Date
    Nov 2014
    Age
    52
    Posts
    11
    I got the cluster out of the 91. It has oil pressure, amp and temp gauges.

Similar Threads

  1. ECU Swap On 1991 TBI 454 / 4L80E
    By X-cabsquarebody in forum GM EFI Systems
    Replies: 35
    Last Post: 12-28-2017, 11:54 PM
  2. 1991 454/4L60E loping idle, no power, codes
    By EDZIP in forum GM EFI Systems
    Replies: 13
    Last Post: 09-24-2014, 11:48 PM
  3. 90 chevy sb lt1 wiring onfo
    By hoffmb0612 in forum GM EFI Systems
    Replies: 0
    Last Post: 01-08-2014, 10:38 AM
  4. 1991 TBI Setup Need tech HELP!
    By Trentec in forum GM EFI Systems
    Replies: 18
    Last Post: 10-02-2013, 03:32 AM
  5. 2000 GMT-800 Wiring Diagrams
    By Caleditor in forum OBDII Tuning
    Replies: 0
    Last Post: 09-09-2013, 07:52 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •