1990 GMC Sierra - Page 6 - Answered Questions & Fixed issues

there are lots of issues with the pump it is rare to see the valving in the sector do that

Recheck as there is no code 18

Hello lets start by checking the fuse, panel located left of the drivers knee just up under Te dash the fuse panel has numbered and branded identified gauges/cigarette lighter etc.when you find the gauges fuse remove it and examine should see the loop in the center blown replace with the same amp number such as 15amp.

Hi, if the extra wire goes to the alternator, then yes, it goes on the big post along with the battery wire. This is your charge wire. Please let me know if you have more questions, and thanks for using FixYa.

Generally these controls go bad and nothing works. They are an imported item GM uses of course. The electronics short circuit and go completely dead. Best to find a used one that works for new ones are expensive

Check the reservoir for fluid. If it empty, look around the wheels to see if you have any wetness on the backside. If you don't see a problem here, the booster pump may be bad.

are you looking for the timing marks or the firing order if it is the fire order it is stamped on the intake by the thermostat

you should be able to get them off.

BEST THING TO DO IS REMOVE THERMOSTAT AND REPLACE, IT MOST LIKELY IS STUCK OPEN. THANKS MOTOR62500.

the temp door actuator may not be working, or the door is stuck. see if you can run the temp to cold and hot and see if the motor is trying to move the door. I cant tell you exactly where the door is but I think its on the passenger side.

you mite have blown the emc fuse check all fuses in vehicle & under the hood, that sevice lite has to lite up

Sounds like your looking in the right place but havn't found the bad boy yet. Disconnect the negitive battery cable and connect a test light to thecable and the battery and it should be on. You might also have to remove the fuse for the dome light too so the light will only be on for the problem. Remove the fuses and or relays one at a time till the light goes out ( no draw) put things back till the light comes back on. try to determine if the circuit is supposed to be on ( light draws are OK) or if it's a batterydraining draw. The relay could be commanded on but it should be off with ther key off. The reason the relay getts stuck on is it has tryed to send too much power and has welded it'self on. The blower motor as it weres out will draw more power til it does this so after you find the stuck relay you'll need to replace the blower fan motor too.

The BLACK wire.

The Idle Air Control runs idle speed, it may be stuck or just bad. its located at the left rear corner of the throttle body, make sure its plugged in.

coolant temp sensor most likely aroun t-stat area before you replace it remove first then try to start if workd replace coolnt temp sensor por ecm (singal plug 12 wire yellow and other black around t-stat housing)

All the starters are the same for the V8's in that year on GM motors, They gave you the wrong starter

When you wire it in, run a hot wire directly from the battery to the volt meter (this will give you a more accurate reading) The instructions will come with the volt meter on how to wire it. Just make sure about the hot wire coming directly from the battery.

What I would do first is take off the alternator and go to a parts store and have them test it for free. This will save any additional purchases. Good Luck.

Its at the top of the brake pedal there is a little clip on a pin that slides through it its a pain to get off but when you do you slide the switch off disconnect the connector put the new one in plug the connector back and put the clip on or if its distoryed you can use something called a clevice pin to replace it

Are you just looking at the light at the shift lever? My light wouldn't go on indicating 4WD either. I took the truck to a gravel road moved the lever to 4Hi and stomped on the gas to see if the front wheels would spin, they did. Come to find out it is the switch for the light that's shot. The switch cost $40 but works just fine with out the light on.

I have been sitting here for about ten minutes rereading your problem and the one thing that I am not clear on is does the voltage actually drop or are you taking the gauges reading and assuming that it is accurate? Does the battery drain if you continue to drive the truck to a point that the battery goes flat? If you have a meter that will read volts DC take the truck out and run it till you get the problem happening.Pull over and read the voltage at the battery terminals.It should be between 13.2 and 14.4 volts DC .If it is the gauge has a feed problem,like a bad wire.This bad wire will heat up,after the truck is running for a few minutes,because of the resistance in the wire, and the voltage reading will drop at the gauge ,which in turn will trip the battery
light.I'm trying to think outside the box here with the information posted,hope my speculative ramblings might give you another direction to look at.Good luck and if you get a chance let me know how you make out.