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  1. chengny

    Changing the heater core anything I should do while its out? And is this spot on the coil ok

    The 1980 Light Truck Service Manual. Look for it here: http://67-72chevytrucks.com/vboard/showthread.php?t=545416
  2. chengny

    1986 K20 ALCL connector location

    An "M" engine code in the VIN indicates that the truck came equipped with a heavy duty emissions package (H5D/FED). It probably doesn't even have a typical ECM - one that would generate any real DTC's. Look on the firewall - if you see one of these - that is all you got for computer control...
  3. chengny

    Changing the heater core anything I should do while its out? And is this spot on the coil ok

    Duh - I should have realized it was AC equipped (at least at some point in time). Heat only air handlers do not use vacuum lines - they are totally cable controlled. Below is some info to help you get started: BTW - is the AC type control panel still installed? Without that, I'm afraid you...
  4. chengny

    Piston Ring Gap Placement

    Yes, but that is correct - but only for the compression rings.
  5. chengny

    87 305 tbi crank/ no start issue

    The following would suggest that the common lead (from the gauge to the Pollak valve) has an open after turning the truck off and on a few times, the fuel gauge went to past full and is stuck there, no matter which tank I select. Read the attached documents and do the diagnostic procedure -...
  6. chengny

    Piston Ring Gap Placement

    From Federal Mogul (or maybe Sealed Power):
  7. chengny

    Changing the heater core anything I should do while its out? And is this spot on the coil ok

    With AC or heat only?
  8. chengny

    Burb rear bumper impact trim

    Look around on the Truck-lite website. They stock a huge selection of lenses, housings, connectors, lamps, etc...
  9. chengny

    Absolute factory clearance & steering

    The links down at the solenoid are 14 and 16 AWG. Thee one up at the FW JB is a 16. The dwg below doesn't show your exact model year but the links are the same. The correct fusible link is 4 sizes smaller than the wiring it is intended to protect. I am only aware of 3 links - the ones shown below.
  10. chengny

    Wiper Issues

    Keep in mind that the WSW motor always has power on both the HI & LO speed windings. It is only when a path to ground is created (through the switch) that the wipers can operate. The ground leg from the control switch is ultimately connected to the common ground buss block - located above the...
  11. chengny

    Park brake release

    Maybe consider releasing the actuating cable/rod from the e-brake operator (also remove the screws securing the handle assembly to the dash) and then, with it on the bench, try to free it up. If you find that it is already free to move, that would suggest the problem is in the operating...
  12. chengny

    Speedometer in reverse

    Maybe a little bit, but because the hairspring is tightly wound when at 0 MPH - and the pointer is connected to the hairspring - it prevents reverse rotation.
  13. chengny

    Reverse light issue

    Look along the inside of the LH frame rail and you will find a hard plastic tube that runs like this: Obviously, yours wont be wire tied to the top of the cross member, but it will terminate with a 4 pin socket like this: It (the socket half of the plug) should be somewhere behind the...
  14. chengny

    Horn button on 1991 suburban

    See the post below.
  15. chengny

    Choke issues

    You are alright as you are now. The IGN sockets are actually protected by the B/U LPS fuse. See the wiring dwg below:
  16. chengny

    Cranks, no fuel, no spark

    Yeah, since you already know that code 42 is being thrown (and the engine won't start anyway), I would move on to step 2.
  17. chengny

    1986 C20 454 cooling questions

    Yeah, but after 35 years, the watersides of the radiator will almost certainly be coated with deposits. It doesn't take much of a deposit film to hinder heat transfer. I don't know if you're up for it, but consider the de-scaling procedure detailed below - it would be a shame to scrap an OEM HD...
  18. chengny

    Cranks, no fuel, no spark

    Code 42 diagnostic from the 1987 GMC Light Duty Truck Fuel and Emissions Including Driveability manual:
  19. chengny

    Weird Starting Issue After Putting It Back Together

    Heard that sound many times. With the timing set too far BTDC, when the engine fires, it kicks back (i.e. rotates backwards). The flex plate/ring gear momentarily drives the starter pinion in reverse and the overrunning clutch disengages from the ring gear teeth. But since you are still leaning...
  20. chengny

    Gauge swap.

    Gas gauge accurate when stopped, but bounces while driving. Probably loos connection somewhere. Old one worked fine. There is a pulsation dampener (a resistor actually) that bridges the two opposing coils. It's function is to control the rate of movement of the ray (needle) when the sender is...
  21. chengny

    Gauge swap.

    QUESTIONS: Why big swing on speedo readings? Are there different temp sending units? 1. On the increase in speed - as indicated by the pointer: It's anybody's guess why that is happening. Maybe the strength of the magnet in the speed cup was increased over the years, maybe your original...
  22. chengny

    Choke issues

    The choke fuse feeds the line side of the oil pressure switch (on PNK/WHT 350) - nothing else is directly connected to that fuse. However the load side of the pressure switch supplies two branch circuits; DK BLU 931 (goes to the negative leg of the CHOKE light) and LT BLU 78 (supplies the coil...
  23. chengny

    Weird Starting Issue After Putting It Back Together

    If by "turn it", you mean the distributor - then no, that is not going to help. You have already tried that and even rotating the distributor as far as possible - till it hits something - you were unable to bring the timing into proper range. Put the distributor back in its normally indexed...
  24. chengny

    Wiper Issue

    I'm guessing that the truck equipped with intermittent wipers? If so, I would try a new pulse module. Rotating the knob backwards to the MIST position runs the motor the same as rotating it forward to the LO position - except that it is a momentary connection and will spring back to OFF when...
  25. chengny

    Weird Starting Issue After Putting It Back Together

    I don't know how that could have gotten fd up though. I didnt take off the cap or do anything to it but remove the whole thing to change the intake manifold and then put it back just how it was. When you dropped it back down - despite your best efforts to position it exactly as it was before...

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