when did they do this

[fieroking]

on the 6.2 what year did they go from a manual fuel pump to a electric pump ?? and what year did they get rid of the vac pump i have a 82 gmc 4x4 it has dual tanks what normaly goes bad first the selctor switch or the actual tank selctor undre the truck ??

[HammerWerf]

fieroking,

Welcome to the Page. Lots of expirence within these walls. Keep asking questions, and post replys to help others is the way we keep out trucks running.

On my 84, I have replaced the selector valve at least twice in the truck's life. I still have the original switch in the cab.

I have noticed that lack of exercising the valve causes it to fail for me. The valve on my 83CC failed about a year ago, but was so sluggish when I would switch tanks, I quit. Failed valve now.

HammerWerf

[DickWells]

Hammerwerf, I have a question. I've often thought that I'd like more fuel one board, whatever vehicle I might be driving. What's wrong with having a second tank with only a fill pipe and an electric pump, plummed to send fuel to the main tank, once the main tank was low enough to accept it? Easy enough, I would think, to "T" into the main tank fill neck with a small diameter hose from the aux pump. Just hit a switch, while motoring along, and watch the fuel gauge go up. Who cares if it takes a half-hour to transfer?
My Sierra isn't set up to welcome a long, narrow tank on the inside of the frame, but the Suburban looked like you could easilly fit a say, 30+ gallon pickup tank in there on the left side.
Anything wrong with the little 12V pump idea?
Just wondering.
DW:)

[RoverIIa]

My actuator valve failed in the happiest way... the electrics all switched, but the valve itself didn't. So... at about 108 degrees, I got to sit by the side of the road in the dust trying to bypass the valve because the gauge switched to the full tank, and I motored along until I airlocked! It was not the best day of my life.

My FIX:

I replaced the mechanical lift pump with dual electrical pumps, they tee into a single line to the IP, with check valves to make sure I don't pump fuel from tank to tank. The switch (also replaced) now turns off one relay and turns on another to start the other pump. I have often switched tanks under load, and have never had a problem.

The return lines were run into a tee, with no selector valve. As long as both tanks are not nearly empty, there does not seem to be a lot of trouble with pumping fuel through the system into the other tank. I was concerned with that, but for the most part, it does not seem to be happening.

I would NEVER go back to a valve actuated system unless the valve was manual.

Good luck.

-Nate

[arveetek]

on the 6.2 what year did they go from a manual fuel pump to a electric pump ?? and what year did they get rid of the vac pump??

When the body style changed in 1988, they dropped the mechanical fuel lift pump on the lower right side of the block and went to an electric lift pump on the driver's side frame rail. The same year the engines also were upgraded to serpentine belt systems, and the vacuum pump in the rear valley of the engine was moved to a belt-driven pump, and the hole in the valley was covered with a block-off plate with an oil-drive shaft. The injection pumps remained mechanical through 1993.

These changes do not apply to 1988 to 1991 "old body style" crew cabs, Suburbans, and Blazers. These vehicle changes occured in 1992 (except for Suburbans, which dropped the diesel option for two years and reappeared in 1994 with the advent of the electronic DS4 injecion pump).

Casey

[DmaxMaverick]

Hammerwerf, I have a question. I've often thought that I'd like more fuel one board, whatever vehicle I might be driving. What's wrong with having a second tank with only a fill pipe and an electric pump, plummed to send fuel to the main tank, once the main tank was low enough to accept it? Easy enough, I would think, to "T" into the main tank fill neck with a small diameter hose from the aux pump. Just hit a switch, while motoring along, and watch the fuel gauge go up. Who cares if it takes a half-hour to transfer?
My Sierra isn't set up to welcome a long, narrow tank on the inside of the frame, but the Suburban looked like you could easilly fit a say, 30+ gallon pickup tank in there on the left side.
Anything wrong with the little 12V pump idea?
Just wondering.
DW:)

There's nothing wrong with it, and GM agrees, apparently. The newer (GMT800, 99+) GM trucks with dual tanks use a similar system. The transfer is automatically engaged according to the fuel level in the main tank. Fill both tanks, and all the fuel is drawn to the engine from the main tank. The main tank is refilled as necessary from the aux. tank until it's empty. I haven't heard of many issues with this system, and certainly less problems than with the previous dual tank/valve system.

[john8662]

Both my '82 and '86 have the tank switchers.

Question for you guys though...

How FAST are they supposed to swap when healthy?

I've got the mushy-style button in the cab on both trucks. Have to hold it to swap it, not just flip the switch. You can listen, I usually listen to hear whent he motor starts to bind and almost stop, thinking that it's fully swapped.

Is this correct?

I'm, thinking of replacing the one in the '86.

J

[Robyn]

My 86 dually 4x4 has the same setup with the dual tanks. Its a gasser but I think all the tank stuff is the same.
Its always worked. Had the beast since Aug 2000 and just keeps on a tickin.

[HammerWerf]

John,

The switch has to be mashed down to the stop point to activate the selector. The detent is the normal resting position.

Whe my valves were healthy, they would move fast enough to switch while driving on the freeway. I did this more than once, so I could at least do it.

As the selector valve motor slowed down, started to bind, I would listen for the same sounds you are.

When the 83 quit, it was laboring mightly to change position.

The 84 has quit functioning from apparent lack of use. (rubbed perferation in replacement suction line(to fuel pump))

Robyn brings an interesting point to light. Gasoline is a solvent. We all know that diesel is capable of leaving behind a varnish layer. Robyn's 86's valve has worked for her since she bought it in 2000. I've hardly gotten 8 years of use out of my valves.

The only difference between the gasser model and the diesel model are 3 nipples. Return fuel and routing it to the sellected tank.

HammerWerf