Diesel gurus

[Freak]

I have a old 6.2 GMC that I use to haul junk with. Under normal driving everthing is fine but if I have to get down on the throttle the water in fuel light comes on. What needs to be done?

[PHX ATC]

How long has it been since you've changed your fuel filter?
I'm not sure about this type engine, but there might be some "wicks" (sensors) in the fuel filter canister/housing that detect the water in the fuel. Those might need to be cleaned. A lint free rag (baby diaper) would clean them as well as you could. Don't use paper towels as that might leave lint in there.
Is there a dump that would allow fuel to dump out of the fuel filter canister/housing? If so, it might be a little lever to allow the water/fuel mixture to dump out of there.
I bet it's something simple, like your fuel filter needs to be changed.
I'm not a guru on Chevy diesels, especially the old 6.2, but I'm sure someone in here would have some other ideas.
Jordy, any ideas?

[Jordy]

Fuel filter would be the first place I looked. I'm not sure what setup you have on your 6.2, but on the 6.5 I had, there was a brass t-valve mounted up by the thermostat housing that was a water drain for the fuel filter housing. Seems that once you had it running, you could crack the valve and it would drain the bottom of the housing, and any water that might be in there. Other than that, I'd start with the fuel filter.
Worst case, and this happened to me once, is a bad load of fuel that was full of water. Ended up having to drop the fuel tank and drain it as every time I fired the truck up the water in fuel light would come on, drain the water out of the filter and it would be good for a while, then same thing... got old when I had to do it 14 times to get home.
If it's only doing it under load, I'm guessing you don't have it that bad.

[PHX ATC]

I knew you'd save the day.

[Freak]

Thanks peeps. I will do the mentioned above. I picked up the truck recently from a widow. It was her husbands truck. Once he died she kept the oil changed but rarely drove it. My guess is condensation in one of the tanks. It runs well for a non turbo and only has 48k org miles. 85 GMC 2500. One more question. I have heard that on these old diesels you need to prime the fuel filter when you install a new one. If that is correct what is the best way?

[Jordy]

Thanks peeps. I will do the mentioned above. I picked up the truck recently from a widow. It was her husbands truck. Once he died she kept the oil changed but rarely drove it. My guess is condensation in one of the tanks. It runs well for a non turbo and only has 48k org miles. 85 GMC 2500. One more question. I have heard that on these old diesels you need to prime the fuel filter when you install a new one. If that is correct what is the best way?
If it's the canister filter that sits in the middle of the intake manifold by the fire wall, every time I changed my filter, I'd fill the housing up with ATF, and then slowly install the filter, letting it soak the oil up. There was a bleed screw on the top of the filter, right in the middle. Open that up and crank it over. Mine fired up right away every time. I don't think there was alot of difference between the 6.2 and the 6.5 from what I remember.
Both the 6.2 and the 6.5 were great engines at the time. Banks and ATS both made a turbo for them that would really bring them to life. I sold my 6.5 with almost 250K miles on it.

[PHX ATC]

What he said.
I had a 6.5TD and had to remove the plastic cover thingy (6.2 no havey I think), pull the bleed screw off and have somebody crank it until the fuel spewed out. A bit messy, but have a towel/rag handy and you'll have it primed and bled in no time.
BTW, that was on the side of a road, right after I ran it out of fuel. BAD, VERY VERY BAD. I suck.

[Freak]

Thanks - what is the ATF for?

[Jordy]

Thanks - what is the ATF for?
It will clean your injectors out, especially if it's been sitting for a while. I did it every time I changed my fuel filter out on my 6.5 and we used to do it with all the equipment at a construction company I worked for. We had an old 621 Cat water pull and it would start loading up and running bad, new fuel filter full of ATF and she'd be fine for another couple hundred hours.

[Freak]

I'll do it - thanks Jordy.