1988 gmc k2500
 

I have a 1988 K2500 that doesn’t get much use. I bought it a few years ago from a shady used car dealer. They had the truck on their lot, but had to meet me at a grocery store parking lot. I thought it would be a good donor for a frame swap for an older truck, and stick shifts are rare around here. I use it for work around the house, getting a load of gravel, or making a dump run.
I have had it for about six years. When I got it, it had an intermittent starting issue. I found that if I push on the fuse block, it would allow it to start. The ECM fuse is shared with the Temperature sender, oil sender, and fuel pump. If the engine overheats, or looses oil pressure, the circuit draws excessive current and blows the fuse, shutting off the system. It looks like a new radiator, so it may have overheated. The fuse was 30A, should be 20A, and the fuse socket had lost it’s tension-the fuse was loose. I picked up a used fuse block and replaced several loose fuse sockets to fix that.
The speedometer was broken, so I also picked up a gauge cluster. The gauge cluster in the truck was broken at the odometer, so it was probably rolled back. The new to me gauge cluster works, but I’ll never know how many miles are on this truck. It mostly sits. A couple years ago, I was having difficulty starting. It would try to start, and eventually go. I looked at the injectors, replaced one, but it still had problems. I measured the resistance of the temperature sender cold, ran the engine awhile and measured it again hot. It did change, but the range was shifted from what it should have been. I replaced the temp sender and it starts right up now.
At some point I did a brake job, pads and rotors turned, shoes and drums turned on the back. The right front rotor got hot on a trip back from the hardware store, so I replace the caliper. That was easy enough, so I replaced the driver side too.
This spring I decided to start driving it. I got a load of gravel and the right front rotor got hot, I was smelling burning brake pad on the way home. I’m working through this problem now.I’m ready to start the frame swap project, so I want to fix this first. I’m also ready to continue on projects around the house, so I needed a replacement truck.

Re: 1988 gmc k2500
 

You may want to replace the rubber hose going from the hard line to the caliper. They're pretty notorious for separating on the inside and letting fluid go to the caliper, but not back.

Re: 1988 gmc k2500
 

Thanks for the tip Mingoman, I have read about that in my on-line search, and it’s even listed in the manual as one of the culprits. I’m trying not to throw parts at this, instead learning how systems work and troubleshooting to determine the fix.

I was going to put the two trucks in the same thread, but decided it might get even more confusing. Here’s my new truck:
http://67-72chevytrucks.com/vboard/s...d.php?t=786384

I have been reading on-line and in manuals about the brake system.
I tested the master and booster first because it was easy following this procedure:
With the engine stopped, press the brake pedal several times to deplete the vacuum reservoir, then press the pedal hard and hold it for15 seconds . If the pedal sinks, either the master cylinder is bypassing internally, or the brake system (master cylinder, lines, modulator, proportioning valve, calipers, or wheel cylinders) is leaking.
Start the engine with the brake pedal pressed. If the pedal sinks slightly, the vacuum booster is operating normally. If the pedal height does not vary, the booster or check valve is faulty.
With the engine running, press the brake pedal lightly. If the brake pedal sinks more than 10 mm (3/8 inch) in 3 minutes , the master cylinder is faulty. A slight change in pedal height when the A/C compressor cycles on and off is normal. (The A/C compressor load changes the vacuum available to the booster.) Leak Test
Press the brake pedal with the engine running, then stop the engine. If the pedal height does not vary while pressed for30 seconds , the vacuum booster is OK. If the pedal rises, the booster is faulty.
Turn the engine off and wait 30 seconds . Press the brake pedal several times using normal pressure. When the pedal is first pressed, it should be low. On consecutive applications, the pedal height should gradually rise. If the pedal position does not vary, check the booster check valve.
That all checks good.

There is a long hill that I was riding the brakes down when I got the gravel before, I thought maybe that caused the burning. I went for another load of gravel, and changed my technique. When I got home and found the wheels hot, I jacked up the front and put it on jack stands. I rushed around gathering the jackstands, droplight and wrench. I finally opened the bleeder on each side and the fluid did not squirt out. I also tried to turn the wheels with the bleeder open and it was difficult.
This weekend I took off the calipers and lubed the pins, but they looked new. I also compressed the pads. When I bled the brakes before, I didn’t do anything with the distribution block, or the isolation/dump valve. I read some more and found something about clearance between caliper and bracket. I had to hammer and pry to get the calipers off and on, so there was no clearance. I read about different kinds of calipers, floating and fixed, these are floating. I tried to file the edge of the caliper, but the file wasn’t even getting the paint off. I dug out my grinder, but couldn’t find a grinding wheel. I put 80 grit sandpaper and it worked great, took off enough and not too much. I put some sil-glyde on the edge, and the calipers went on easy. I pumped the brake pedal up and the wheels spin now. I’m still unloading gravel, but I’ll get it on the road next week.

Re: 1988 gmc k2500
 

I went for a drive around town this week. The brake issue seems to be resolved. Sometimes when I'm driving the truck starts to shake violently, usually around 40mph. I think it may be a wheel bouncing. Awhile ago I picked up a set of 8 lug rims with tires for my '47 truck for $100. those tires had good tread, so I had them mounted on this truck's rims. I don't know if they were balanced then. When I drove it this week, I may have hit a pot hole as I was getting up to speed, but it started shaking, wheel hop? I plan on replacing the shocks first. I think if a wheel was out of balance it would be consistent, but I later got it up to 50mph with no shakes. The shocks look crusty too. I can take off pretty hard without issue, it shakes while I'm already moving. I've read about axle wrap and pinion angle causing wheel hop, I don't think that's going on here. I did grab the driveshaft and it didn't seem loose, I do need to hit every zerk with the grease gun though.

Re: 1988 gmc k2500
 

I replaced the shocks. When I took out the first one, it collapsed. The rest were toast as well. I had known about the test that you push down on a corner of the vehicle to test the shocks. When I did this test there wasn’t much movement with the old shocks, I jump on the end of the bumper and the truck goes down and returns. With new shocks, it goes up and down a few times before settling. I didn’t know it should do that, now I know.
The ride is better, but still shakes when I hit a pothole. The maypop tires are load range D and I had 30lbs in them. I aired up to 60 and that helped some. They may need to be ballanced, but I’ll probably get new tires instead.
Truck is running good and strong, it’s fun to drive…Last time I went out on errands, the idle would not kick down. Actually it did that a week before and after I got home, I started it up and let it idle awhile and it did go down. This time I made several stops, but it stayed high.
I compiled a list of things to check including the IAC and vacuum leaks, but I have been focused on another issue. My knuckles hit the dashboard when I was shifting. I started a thread about that when it happened before:
http://67-72chevytrucks.com/vboard/s...d.php?t=694423

Re: 1988 gmc k2500
 

I put some helicoils in the top of the transmission, now the stick doesn’t flop around so bad. For the high idle, I tried to test the AIC. I checked the signal at the connector with volt meter and saw pulsing. I shorted the ALDL pins A and B, turned the key, and disconnected the AIC after a minute. I pulled the short, and started the engine, but the idle remained high. I sprayed starting fluid around looking for vacuum leaks. I replaced the AIC, but the idle remained high. I took the truck to a repair shop. They replaced the AIC, said the one I put in was bad. It’s running good now and I’m ready to start the frame swap.

Re: 1988 gmc k2500
 

Here is a picture of the ’88 k2500 with ’47 Paneltruck sheetmetal, on the trailer. It was quite a load for the ’90 k1500, but it made it home safely. I had a shop do the frame swap and now I’ll take on the rest of the project myself.

Re: 1988 gmc k2500
 

I have been posting about this in my build thread in the ’47 to ’59 section, but there are things that are specific to this ’88 to ’98 section.
Progress has been slow and steady. About a year after I brought the truck home from the shop, I got around to repairing the heater hose connection that snapped off on the manifold.

Half a year after that I was ready to start the engine. It wouldn’t start. Tried dumping gas in but no go. I got a new battery but still wouldn’t start. I started looking at the fuel delivery. I put a test light on the fuel pump wire. Turn the key on, light comes on and then goes off after a moment. That part was working, but was the pump running? I disconnected the ground from the fuel tank and placed a current meter in series between the ground and frame. My meter goes up to 2 Amps. I turned the key on and the meter went to OL for a moment. Looks like the fuel pump is drawing current. Lastly I unscrewed the fuel line from the throttle body, it was wet. Awhile ago I was troubleshooting a garden tiller. I needed a way to check for spark. I looked for spark checkers on-line and found two kinds available. I was not impressed with the reviews on either, so I made my own. I took a switch that contains a neon bulb, and wired that to a spark plug. Not for the spark plug itself, but for the terminal of the spark plug. I connected one spark plug wire to my tester and placed the light in the hole for the cowl vent drain so I could see it while cranking. No spark. Look under the distributor cap to find a rusted mess.

The ignition coil ohmed out good, the Pickup coil tested bad. I put in a new distributor and the ’88 k2500 came to life. The truck was in a paint/body shop for awhile. They liked to remove paint with a disk and didn’t cover anything up. I suspect the magnet attracted the metal dust and with some humidity the rusting was accelerated. Ran fine when parked…

I was able to drive the truck a short distance to it’s current location. I have been starting it occasionally just to keep it running. I had hooked up a laptop with WinALDL to the ALDL port and found the battery was not charging and there was a vacuum leak. I had disconnected the gauge cluster, turns out the battery wasn’t charging with the cluster disconnected. I hooked up the cluster and replaced the battery and it started right up and ran o.k. The vacuum leak was a hose to the charcoal cannister was disconnected.

I’m getting closer to finishing the build so I’m looking forward to getting on the road. I tried to start recently, but the battery was dead. Charged it up and the truck started, I let it idle for awhile and then it shut down. It was hard to start after that. Up until this point when I start it the battery light would be on for a moment and then go off. I thought that was normal. Now the battery light stays on. I checked the running voltage and it was close to 12v. I checked for codes and got 33, MAP error.
Took the alternator to the parts store and they confirmed it was not charging. I got a new alternator and saw it had the 6 rib pulley. The parts guy said to swap it over, o.k. I spent half a day trying to figure out how to do that, went to several other parts stores looking for the special tool. In the end I figured it out with the tools that I already have. I have the hex bit set, so hex bit in the alternator shaft, Deep socket over that, 3/8” extension through the 1/2” socket and it was easy. Now the battery light comes on while cranking but turns off while cranking too. I let the truck idle for awhile, it did not die, but the throttle seemed less responsive. It was hard to start, I had to try to start it several times before it ran. I checked for trouble codes again, but nothing was set. I’m not sure if the code 33 was thrown from the no charge, or for the MAP sensor. I tried the MAP sensor from my other truck, but it was still hard to start and the throttle seemed less responsive.

I went to the parts yard and got a handful of obsolete junk for $5.00 including an EGR valve and module, Fuel pressure regulator spring and diaphragm, connectors for the fuel line to throttle body, and the thing I actually need, the Injector connectors. Most of the trucks in the yard were too new and had the top ends removed, or nothing left. It looked like they were low on stock, there was an empty row. There was one TBI truck, and that had some things I was looking for. I thought this other stuff might be useful some day.

I was planning on testing the fuel pressure, so I picked up a gauge. I was about to head to the hardware store to get some fittings to T into the fuel line when I decided to start the truck one more time. I had also purchased a MAP sensor and fuel filter. I installed those and then it would not start. I didn’t know what to do, so I though the most obvious solution was probably the right solution. I put some gas in the tank. It fired right up and runs strong and smooth. I’m happy it’s running good, I’m kicking myself for thinking something was bad when it was just out of gas.

Re: 1988 gmc k2500
 

Nice truck

Re: 1988 gmc k2500
 

One of my favorite color schemes with the best color interior imo

Re: 1988 gmc k2500
 

Thanks! I sold most of the body parts during the frame swap, only the cab remains. Everything mechanical is still the 1988 k2500.