So I picked up a 1994 s10 Blazer Tahoe 4.3 vin w and need some help. Im going to replace the radiator and engine cooling lines along with the cooler gasket to the block. Any tips? The volt gauge reads 18 volts but the battery and alt show 15 volts. I heard about a ground wire to the back of the cluster but I cant seem to see what people are saying. Any pics? the gas gauge is off too and was told that might also be the problem. I was told that the fuel pump was changed but not the sending unit. Can a bad o2 sensor cause a rough idle for the first 10 sec on a cold start up?

 

Yeah flush that badboy out real good with CLR and let it run with the chemical in for about 15 minutes before you dump it and flush with water. Then put in your new rad and hoses.

Might wanna do the fuel pressure test too, these engines are notorious for internal fuel leaks with all kinds of symptoms ranging from yours when problems are starting, to horrible milage/rough running, to no starting at all... The tool is about 40 bucks or less online.

So the dash gauge is reading 18 volts? You mean its pinned to the max? Do it fluctuate? Have you read the output with a voltmeter at the alternator? It should be 14.3 to 14.4 normally. And 12 volts at the battery when not running.

The gas gauge is pinned to max too? Try looking for where the ground broke off behind your rear licence plate. Its a little wire exposed to the environment. Goes from on top of the gastank, to a nut on the crossmember behing the plate. Another thing to consider is that your tank has a huge top half and small bottom half, thats a design problem, not a malfunction, and it is like that for all of us. I have a new sending unit and all in mine, and I can get 500km to a tank. Thats 350 till half, then 150 till empty... Its just how it is and we cant change it.

Says you have a Tahoe LT, that means a digital dash cluster. Dont even bother trying to get that one out and clean a ground, there is none, there is a plug on the back that you could check for rust and stuff I guess, but its a hard job to get it out, and theres not much you can adjust on it.

 

Sorry if I was a little unclear I posted that while I was tired. Its not an L.T. So it has the analog gauges. The volt gauge pegs but drops a volt under a load (lights on) ill double check the actually voltage with a better meter when I can. As for the gas gauge when full it shows 7/8 of a tank and is empty at 1/8 of a tank. Ill look into the ground strap that you mentioned. So run CLR in with the coolant for 15 mins then flush it and install the new radiator. And part number on the fuel pressure tool to use?

 

Its a "Fuel injection pressure tester" they are univeral to many makes and models. Its about 50 bucks.

Yup, you got the CLR right.

You probably have a bad voltage regulator inside the alternator. You can but a rebuild kit for the alternator for about 40 bucks. It will have the regulator (gotta solder it in), 2 bearings, and another electircal component cant remember the name. You remove the alternator and crack it open to change the parts. You should test the output voltage between the battery and alternator with your voltmeter. It its more than 14.6 when running I would change that regulator.

As for the fuel, I would guess there is crud built up on the sending unit interfering with its ability to move all the way up and down. But check out the grounds anyways and refasten them and see if you can make a difference. A sending unit is about 50 bucks as well and takes about 2 to 4 hours to change out depending on the speed at which a person works.

 

Okay so I got the radiator, oil cooler line to the radiator, and belt replaced today. Fired it up and got it up to operating temp. while i was waiting for it to come up I was doing some leak check and saw none so I decide to double check the voltage at the alt and it was 14.55 with nothing but the blower motor and stereo on. After all looked good I took it around the block with the blower on high and wow it was pumping out the hot air and didnt smell of coolant like it did before. Got home and was cleaning up the drive way when I noticed it starting dripping coolant in the center popped the hood and it looks like the water pump seal failed. Im glad its not a 2.8l.

 

Been a while since your last post...but any updates on the volt gauge? Same issue here. Votage when engine running is the correct 14-15V, just the gauge is showing very high, basically pegged to the max.