20 Most Recent 1991 GMC C1500 - Page 4 Questions & Answers

check fuel pump for proper pressure....Also very common is a bad o2 sensor not allowing enough fuel.

Check all wiring.

Mine did same (not same car)... turned out to be a bad elec conection.

If my memory serves me right, I'm pretty sure the only way to change the tail shaft is to tear the transmission apart. Depending on how much extra length you have you might be able to rig up some kind of spacer, but keep in mind that it will be supporting a lot of weight. You are probably better off finding the right transmission and re selling the one you have.

Replace brake hoses,they have an inner core that has ruptured and the outside rubber core is keeping pressure on the caliper with you foot off the brake. This will fix it! A common problem for this vehicle.

might be something going on with the brake pedal switch or something with the wire to the taillight assembly. here's how you can figure it out: find the brake pedal switch, you are going to have to stand on your head and get up under the dash, you will see a switch that has a two wire plug on a part that is attached to the brake pedal. unplug it and see what happens. if unplugging it makes the lights go out you have a bad brake pedal switch. it's a pretty easy part to replace. if unplugging it makes no difference then your brake lights have what is called short to hot, they are getting power from somewhere other than this switch. to find it you are going to have to start back at the taillight assembly and follow the wires back. looked at wiring diagram, looks like wire you want to follow back there is brown. you are looking for a place where that wire is against another wire and the insulation is worn off and it is getting power from another wire. might have to pull wires out of the wiring loom to find it. hope that helps

I did 15a and electrical for over 30 for chevrolet and seen some pretty weird stuff.To me you still have a ground problem.your idea of checking the brake light switch is a good start.both rear lamps flashing to me means the hazards are shorting across the turn and brake light circuits,because hazards stop flashing when brakes are applied.The brakes light switches in the 90's were really weird because they also incorporated the abs system.Good luck,let me know what happens.Thanks

your fuel injectors may be clogged or your fuel sending unit may be operating for a while then cut off causing the fuel supply to the fuel injectors to not feed anymore fuel to the engine. check those out then write me back. [email protected] thanks.

Check out this website, they have your bolt an much more. Good luck Curt
http://www.lmctruck.com/icatalog/cd/full.aspx?page=25

It sounds like you may have an intake leaking. You've replaced the major components so now you need to look for a possible vacuum leaking. The intake gaskets is the easiest part to check. Get a can of brake clean. While the engine is running, spray the brake clean on the top center of the engine. The engine may idle up or idle down or may smooth out. Try this and see what you come up with. If this does not solve you problem, let me know and I will help you figure it out.

Gravity bleeding doesnt usually work real well.

Get a clear jar of some type, and a piece of 1/4 inch vacuum hose about 18 inches long. Put about 2 inches of new brake fluid in the container.

Start at the passenger rear wheel, losen the bleeder, slide the hose tightly over the open bleeder, the other end in the jar where you can see the hose end.
Fill master cylinder reservoir.

Pump brake no more than 4 times, watching the hose end in the jar for bubbles. After 4 pumps, check reservoir, refill. Pump 4 more times. Watch for bubbles. Check reservoir, pump 4 more times. If you see bubbles at any time, then keep going through the above steps until you stop seeing bubbles.

Go to rear wheel, tighten bleeder. Go to driver rear wheel, and do the same thing, although this time it won't take but 4-6 pumps to purge any air.

Go to passenger front, repeat.
Go to driver front, repeat.

Do not recycle any of the fluid.

at the raditor top hose end-engine side.

It should be a white or purple wire at the coil, or you can get it at the ecm plug on the passenger side of the firewall.

Theres a vacume dash pot under the battery box. It pulls a cable that engages the front diff. Put the vacume line and you'll have lights and four wheel drive. (it happened to my blazzer)

you need to get your viles checked that is the promblem..you may have a rod knocking as well

It should be 3/8 allen wrench to remove pads & 13 or 9/16 metric to get off calipers. I have a GMC Suburban & I have to have both metric & standard to work on it.

it sounds like you may have a vacuum issue, obtain a diagram and be sure that all the lines are in the proper places and none are cracked, another possibilty is your MAPS, the black smoke is probably fuel so that means that the engine is getting too much fuel during load

the last one i bought did,it came with everything except the cap and wires,good luck.

Might be caused by tranny filter being dirty

it's the connector tape on main harness it could be Inside isolator

Hi, P0122 code i think reads as "low input" on the fault text, if thats so, the fault is most likely with the wiring to/from the tps, low input codes would usually relate to a short on the wiring so check for any chaffing or corrosion on wires and multiplug connectors, ideally you need to check voltages at the tps connector.