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    R12 recharge from high side?

    Pbcasterlin: I have and 87 R1500 262, 98 SL1, 06 Kia Sedona on which I've been managing a/c issues for a number of years. Converted the '87 to R134 about 10 years ago with simple flush (need to rinse out pump of mineral oil and replenish with PAG100), new dryer (134 rated), stock orifice tube...
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    Diagnostics Cable Adapter

    I was not expecting the '87 to communicate in OBDII . . . agreed that it's a modern, more universal protocol. The reader I have was advertised to read legacy protocols . . . it does a scan for a variety of protocols during boot-up. But they didn't offer interface adapters. I've tried several...
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    Diagnostics Cable Adapter

    I'm looking for an adapter cable to plug my modern OBDII code reader into the data port of my 1987 GMC R1500. I've ordered two cables that were supposed to mate with the truck but their connectors were incompatible. Any suggestions? Thanks!
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    Oil Pressure Guage Mystery

    Agreed. If the gage moves at any time it's probably okay. Senders on the other hand live in a pretty harsh environment and have lots of fiddly little moving parts that can impact calibration. If memory serves, circa '87 senders are a pressure sensitive, variable resistor that controls current...
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    What's the best way to drain the gas tank?

    Yeah, external fuel pump with outlet hose long enough to drop into gas tank on my other car. Works good, doesn't spill a drop. Used it on my '87 twice.
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    Asymmetrical braking

    1987 GMC R1500 RWD. Went through the brakes 95% about three years ago. Replaced/refurbished everything except hoses and master cylinder. Began to notice that left front wheel would slide with even moderate braking on wet pavement or loose dirt. Not a big deal normally but this caused me no...
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    I need help with gauge wiring

    I will echo that suggestion. Wiring diagrams are the 'road maps' for the movement of electrical energy from point A to point B. I'm an electrical engineer with 50+ years experience. Nonetheless, folks I would sincerely like to help are often disappointed when I ask, "do you have the wiring...
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    A request for assistance with Fuel transfer valve, switch, and fuel gauge

    I got rid of that monkey-motion transfer valve. I plumbed both pumps to the carburetor via check valves. Either pump will run the engine. Plumbed return line to right tank only. Use simple two-pole, two-position switch to select pump and associated sender. Sticker on fuel gage says 'use right...
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    Diagnostic Data Connector '87 R1500

    Have a modern code reader that functions nicely on most of my vehicles. However, what I think is an OBD1 connector on my 87 GMC R1500 is different. But not to worry, there are numerous offers for a short adapter harness with the appropriate connectors. I've had two such harnesses. The connectors...
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    Dual gas tank switch

    My 87 R1500 came with saddle tanks. Of course, it had the big valve under the bed that switch supply lines, return lines and fuel level senders. I ditched the big valve and plumbed both tanks together through check valves to the TBI carb. The return line is permanently feeding the right tank...
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    Fusible Links vs Maxi Fuse

    In airplanes, the alternator output (b-lead) is always protected. Alternator diode arrays are exceedingly reliable but risk for shorting is not zero. Hence a current limiter (or beefy breaker) is always situated closest to the battery end of that lead. 150A Maxifuse? Didn't know those were...
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    Fusible Links vs Maxi Fuse

    Fusible links are not fuses . . . they are current limiters intended to protect relatively fat wires that carry power to distant distribution points, usually fuse blocks where the power splits out to various appliances and sundry tasks around the vehicle. Fusible links are simply pieces of...
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    Gas gauge wiring question

    There's another option. I have an 87 R1500 with TBI fuel system that came with pretty rusted saddle tanks and a flaky selector valve. Replaced both tanks and pump/sender assemblies. Ditched the selector valve. Plumbed the two pump output lines together with check valves to feed the carburetor...
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    Tying Saddle Tanks with a T?

    I have '87 GMC R1500 with saddle tanks. I put check valves in each pump's output line then Tee'd them together to drive supply line to the carb. Select tank by powering up either pump. Works good, lasts a long time. I think these pumps have check valves but the extra valve doesn't hurt. Was...
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    Upgrading 1987 R10 A/C to R134a parts / questions

    I have an 87 R1500 GMC inherited from my father about 10 years ago with only 35K miles on it but shelled a/c compressor. Replaced with new compressor OILED for R134a after replacing accumulator/dryer and flushing coils/hoses. Flushed the system with acetone by pouring into openings with a...
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    Box fuel tank

    My 87 R1500 has TBI injection and saddle tanks along with a very busy valve with 6 hoses and 5 wires. I recently replaced both tanks (badly rusted and one with bad pump). This system runs about 10 psi fuel pressure to a pressure relief valve at the carb with a return line that takes overflow...
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    Oil Consumption Question

    Have my Dad's last new truck . . . 87 GMC R1500 with 4.3L . . . only 86k miles. Managed to chase down all the hoses, gaskets, etc suffering from old age and the engine is now 'oil tight' no drips on driveway. Part of the refurbishment included replacing cover gaskets . . . while covers were off...
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    LED headlights

    I have converted a number of vehicles to LED with nearly zero problems. Modern LED drop-ins MUST include a built-in constant current power supply. Most have an input voltage range of 10 to 30 volts but in any case, every LED replacement I've purchased off eBay required no special wiring...
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    '87 R1500 4.3L Oil Consumption

    I inherited a one-owner '87 from my father about 12 years ago with only 35K miles. But door hinges were worn out, headliner was down, seat covers trashed. Ran well but had a host of little problems more related to age than mileage. Thankfully, almost zero rust. Over the years, we've 'spruced...

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