20 Most Recent 1991 GMC Sonoma - Page 9 Questions & Answers

You need to buy a rear differential cover gasket and 80/90 gear oil. Look in the owners manual for the capacity, I think it is 1 1/2 to 2 quarts. There are 8 to 10 13mm bolts to remove. Put a drain pan under the differential. Start removing the bolts from the bottom up. When you get to the last bolt on the top if the oil has not drained yet, loosen the bolt and pry in between the cover and the case with a chisel or flat head screwdriver. Remove the cover after it drains and spray out the inside with brakleen or carb and choke cleaner and wipe it out with a clean rag. Make sure you don't leave any debris inside. Remove the old gasket completely with a razor blade and use emery cloth on both of the gasket surfaces. Put the new gasket on DRY, DO NOT use any silicone or other sealer. Put a couple of bolts in to hold the cover and gasket in place and then start the rest of the bolts by hand. Tighten the bolts in a cross pattern like this- upper left, lower right, upper right, lower left, and so on. DO NOT over tighten the bolts they should be at 13 ft. lbs. and no more or you will destroy the gasket and it will leak. The fill plug is either on the cover or on the upper back left or right of the differential just before the u-joint. Check this before you start the service to make sure you have the right socket. It is large allen i believe. Sorry, it's been a while since I've serviced one of these. Remove the fill plug and fill until the 80/90 starts coming out of the fill hole. To ensure proper filling it is best to put a piece of hose or tube on the nozzle of the 80/90 and insert it into the fill hole. Then squeeze slowly so you don't create air pockets in the process. Let me know if that helps.

My be a bad oil sending unit look by the oil filter it should have a plug unplug and replace with new one some time they will leak when they go bad it is round and it just screws in by the oil filter hope this helps if not sure what it looks like a small inline fuel filter with wires going to it

Well if you are lucky the power supply wire to the ecu is shorted to ground and the fuse saved the computer. It could be the computer. Also it could be something the ecu supply's power to shorted to ground. Get a wiring diagram and a ohm meter and start testing.

Electronic Control Module fuse is more commonly know as your computer for your car. It is just like any other fuse. Just a means of avoiding damage to the module.

Fuel pump is located in the gas tank, your going to have to drop the gas tank, but most tech would rather remove the pick up bed to get to the fuel pump.
Thank you for using fixya and be safe, also would be a good investment to replace the wire harness from the frame to the fuel pump sending unit. #39 is your fuel pump in the sending unit which is located in the gas tank.
http://www.compnine.com/index.php?u=1&year=1991&artnbr=TS03-218&artsfx=NULL&supplgroup=NULL&catcode=53S&modelcode=S&makecode=LG&modelseries=NULL&uid=1&modelid=7076&capuid=1&majorgroup=03&grouptype=B

If you go to the lock smith ... he or she can probably flick the broken bit out in about 3 seconds ... compared to the price of a new switch + putting it in and getting duplicates made ... this might be a good alternative.

Check the fuel pressure,and change the fuel filter ,if this does not help,the pick up coil in the distributor is the most likely cause.

A few feet in front of the gas tank

On the base of the wiper arm there is a lever,using a flat head screw driver pry it outward,then use screw driver to pry on opposite side of where the arm joins the base,to come off even.

Common knowledge of the road speed, mine hasn't worked for 3yrs and for some reason haven't got a ticket since. Install a tachometer.

I have two. A 91 s15 ext cab 5-speed 4x4, 4.3L with a flatbed and 89 s10 ext cab auto 4x4, 4.3L with a box. Make an offer around $500 and thier yours.lol

Does it drip gas after you shut the engine off? It likely isn't the injector but the oring that seals it into the throttle body.

Brake fluid

check with a company called fab-tech they make some pretty good lift kits for 2wd baja rigs. I have bought one of there kits before and made my own. but I like how easy it was to install and function nicely

idle air or egr

no, because they don't have the same connectors

you need to adjust the idle to run higher. its not to hard to do, you just have to locate the idle control. you can find it by looking under the hood while someone presses the gas a couple times, you should see it move. All you have to do is tighten the cable that is connected to it,.. a little at a time until you get the desired idle. careful not to over adjust it, or you will idle to high and waste gas, and over work the enjine on very hot day's or very cold day's.

Replace the hose! You can buy All sizes of vacuum hose at any Auto Parts Store!~!!

How old is your battery??

They generally only have about 3 years of life in them before they run out fo puff...

Check you battery when the car is turned off. Get a Multimetre and check each terminal...A battery without the car starting should have 12.6volts in it...

If you are below that it could mean that your battery is running out of juice.

Also when you get the car started place the multimetre on the battery terminals. If there is anything less than 14.4volts running through it with the car started the alternator may be on the way out and not providing enough charge for your battery.

The third thing to check is your starter motor. Locate the starter motor in the car, when the engine is cold and has not been started for a while give a good hit with a hammer or screw driver and then try to start the car. If it springs straight to life it would seem that you starter solenoid is broken and yu will need to get a replacement.

Good luck.