Top 20 1991 GMC Sierra - Page 9 Questions & Answers

The hot coolant is being blocked by a faulty thermostat. This is an inexpensive part and easy to change. Go to any auto parts store and tell them you need a thermostat. They will even assist you in installing it. Joe

there should be a hole for a crank either next to the licence plate or between the bumper and the bed

the rods in back of the handle probably came off.

on some GMC models there is a valve that opens when you turn on the heat inside. It is called a heater control / actuator valve, it works off engine vacuum thru hoses connected under the dash, and going to the top of the valve. Now junk and crud and old rust will get in the valve and restrict it's flow. You will have to pull the valve off and clean it, but it is best to replace it, seeing it is hard to get all the junk out of it.
It looks like a L shape pipe with a hose on top & bottom, black plastic,and a smaller line on top mounted close to the wheel well about even with the exhaust manifold on the pass side. Drain the coolant, remove the valve and see if this is the cause, lots of gunk in the one hose. It is not real hard not real easy to replace this valve. Now if your truck does not have this valve check the pipe that the hose hooks to on top of the engine, remove the hose and see if a small screw driver will go down inside or if it is stopped up. .

Your issue is either with the coil or the distributor. You must first determine if you ALWAYS have consistant fire from the coil. If not, then that is your problem...If you do, then the breakdown is with the distributor. Make sure your connections from the coil to the distributor are perfect. You have a simple problem to solve...it is right in front of you. The fact that you can mess with the rotor and get sporatic fire, may indicate a proor connection from the rotor to the cap..even though they are both new...stay with it, you are all over the solution to your issue. Good Luck! I hope you find this to be very helpful!

get the oil pressure sender and gauge checked most likley cause is incorrect reading not sudden high oil pressure

It turns over but will not fire up? If this is your problen how long has it been since a fuel filter was replaced?

Best thing to do is replace wheel cylinder, they run about $10.00 - $15.00.

My mistake,I forgot to post the attatchment.Let me know if this is what you were looking for.Take care .

Do you have power to the injectors? One of the wires to the injector will come on for a couple seconds as soon as you turn the key to the on position.The computer controls the ground side. If you do not get power to one of them start looking for an open circuit. The same power source will also go to your ignition coil and ignition module. If you do not have power on the pink wire to the coil apply a temporary fused battery power source to it and give it a try, this will also power up the injectors.
Check it out and let me know.

Yes this will work.

check resistors 

disconnect neg battery terminal -remove steering wheel will need a puller some auto stores let u borrow these tools -remove turn signal switch not necessary to totally remove switch pull far enough rearward to slip over shaft but dont pull harness out of column --turn key to run -remove the lock retaining screws dont drop into column -remove lock -screw torque is 40 inch lbs for reg column 22 for adjustable column

idle my be offset or a hose my be off as well

Sounds like air filter needs to be changed or fuel pressure regulator is bad.If you need to hold the pedal down that means the engine needs more than the usual amount of air to start because there maybe to much fuel pouring into the engine.Black smoke is indication of too much fuel mixing with the air (rich).Also check for leaking fuel injectors

this is a tilt column and you need a special tool to push the lock ring down and remove the c clip on the shaft without hurting yourself.

6-7k

head gasket or valve cover gasket

The follwing is a cut and paste from a service bulletin:

Bulletin No.: 461202

Date: May, 1994

SUBJECT:
A/C CONTROL HEAD FLASHES OR ERRATIC OPERATION OF A/C CONTROLS (POLISH
TERMINALS)

MODELS:
1988-94 CHEVROLET AND GMC TRUCK C/K MODELS
1990-94 CHEVROLET AND GMC TRUCK TOPKICK/KODIAK MODELS WITH C60 OR C69 AIR
CONDITIONING

CONDITION:

A/C Control Head flashes, performs erratically or malfunctions.

CAUSE:

Light surface corrosion on the Control Head terminals.

CORRECTION:

Remove the A/C Control Head and while holding the unit with the terminal
cavity down (toward the floor) so no particles will fall inside on the
circuit boards, polish the terminals on both sides of the cavity with a lead
pencil pink eraser. Do not use an ink eraser or other abrasive such as a
small wire brush or sandpaper, etc. Doing so will remove the terminal
coating and degrade the contact surface.

Performing this procedure, in many cases, will make replacing the Control
Head unnecessary. Using this procedure in conjunction with the A/C circuit
diagnosis found in the Electrical Diagnosis Manual and especially before
replacing a Control Head for any reason is recommended.

After polishing the Control Head terminals, but before reconnecting, check
for proper terminal contact as described in the applicable electrical
diagnosis manual. If contact is good, apply dielectric grease (P/N 12345579)
to the harness connector terminals. Please do not apply grease to the
Control Head.

check o ring on distributer