gmc w4 is the bane of my existence

[solidshark91493]

Hi, not sure if this is a good place to go or post this. We have a 94 gmc w4 (2500?). This thing has been a royal pita since we bought it. Engine has had issues, transmission had to be rebuilt you name it. Now that namely is because of the previous owners. 
This however presents an issue for me as I have to fix the thing. I cannot find parts or info on these trucks to save my life. We have a 96 also thats techically an isuzu. Same thing. 
Its like GMC (and isuzu technically) want to pretend these things never existed. Dealers pretty much tell us they cant help us and they have no idea what the things are or what parts they need. 

I have the vin: 4KDB4B1A9RJ001182 
Ive checked numerous places but every one tells me this vin is incorrect and doesnt exist. Same thing on our isuzu model. 
9th vin number doesnt check out with the algorithm. Ive checked many times and thats indeed what the number is.

Im trying to get as much info about them as I can as this thing is insanely sluggish and runs poorly after a new alternator, plugs, wires, you name it. I was thinking maybe the timing could be adjusted? maybe the timing chain is going bad too, not sure its got over 179k miles. 
I believe its a stock gm 350. Its paired with a 4L80-E transmission. 

Any advice would be so helpful. Thanks.
Nick.

[Jsdirt]

If the fuel pressure is good and the pump is putting out good volume and the injectors are both spraying a good pattern (use a timing light to see them better), then I'd focus on the distributor - cap, rotor, wires, timing, ignitor unit, pickup, etc.. Also make sure the distributor isn't completely worn out, since it sounds like it was neglected by the prior owners - check the shaft with rotor removed for excessive play.

 

Always start with the simple stuff first before diving into the engine. Those 350's will run 400k-plus miles with good care. Sounds like the previous owners didn't like maintenance, so timing chain issues are possible there, too.

[solidshark91493]

7 minutes ago, Jsdirt said:

If the fuel pressure is good and the pump is putting out good volume and the injectors are both spraying a good pattern (use a timing light to see them better), then I'd focus on the distributor - cap, rotor, wires, timing, ignitor unit, pickup, etc.. Also make sure the distributor isn't completely worn out, since it sounds like it was neglected by the prior owners - check the shaft with rotor removed for excessive play.

 

Always start with the simple stuff first before diving into the engine. Those 350's will run 400k-plus miles with good care. Sounds like the previous owners didn't like maintenance, so timing chain issues are possible there, too.

Awesome. I will write those things down and look into them.
The tank is on the right side (under the dump bed) And it has a single wire on top that doesnt appear to go to anything. The fuel gauge also doesnt work so we are thinking the pump will need to be replaced. (Hence trying to find the info on what to buy to replace it with). 
Odd thing is its mostly super sluggish on startup but runs generally fine after its warm. 


An insight on the genius we bought it from.. All of a sudden it wouldnt shift out of 2nd gear. Found out the transmission was almost out of fluid and put itself in limp mode. Ended up needing to rebuild it because of this. 
It ran out of fluid because the guy for whatever reason removed the plug from the trans pan and tried to weld it shut. He wasnt successful and it leaked like a sieve. 

[Jsdirt]

Yikes.

 

Those transmissions won't go into "limp mode" since they're not computer controlled. They either work or they don't. There's an electrical connection for the lockup converter, and usually a mechanical cable connection to the throttle body called a "TV cable" - SUPER important. If this cable is adjusted incorrectly, you can burn a transmission up in less than 50 feet. That controls line pressure, shift points, kick down, etc. - basically everything. Running it low on fluid will also burn them up fairly quickly.

 

That single wire is probably for the fuel gauge. Don't replace the pump unless it's down on pressure and volume. No need to replace a pump just for the gauge. Parts today are garbage, so you're better off with whatever is in there. Fuel pressure should increase slightly on a snap throttle. If it decreases, it's days are numbered, IF the regulator is working correctly. It should increase pressure when the vacuum line is pulled off the regulator (if it's set up that way - my memory is fuzzy on that). Do that test first.

[Snowcamo]

Rockauto.com for parts.