2000 Chev 3500 Factory Inline Rear Tank Fuel Pump

[67JimmyMO]

I was hoping someone could explain to me how the inline fuel pump between the front and rear fuel tanks works on a 2000 Chev 3500 chassis/cab.

It is the 159.5" wheelbase with 454 Vortec.

There is no switch on the dash to switch between tanks so I guess that the inline pump is triggered automatically somehow, and then transfers fuel from the back tank to the front tank?

Also wondering what tank the fuel gauge is reading, I am assuming that it reads the level of the front tank?

A little background...when I purchased the truck in 2015 the previous owner told me to consider the truck empty when the fuel gauge read 1/4 full, and I have always done that. Well last week I ran out of gas with the gauge reading 3/8 full. I poured 5 gallons into the front tank and got it going again, but when I got to the gas station the rear tank was totally full.

I have attached a pic of the truck and a link to the inline pump, thanks for any info you can give me on this.

https://www.ebay.com/itm/BRAND-NEW-F...53.m1438.l2649

[95 S_Trucker]

This should be posted in the 88-98 section

The front tank has a high pressure pump that supplies fuel to the engine. There is a balance module that gets inputs from the sending unit of each tank. The balance module used that info to operate the transfer pump that pumps fuel from the rear tank to the front tank. The balance module also sends the computed fuel level to the fuel gauge.

You could have a sending unit problem, a module/wiring problem, or a bad transfer pump.

My 96 had this system. I had to remove the rear tank when I put the rollback bed on it.

I have some diagrams somewhere. I will post them when I find them.

[67JimmyMO]

Thanks for the reply 95 S_Trucker, that fills in a lot of the blanks. I have never had a truck with 2 tanks that didn't have some way of (manually) switching between tanks.

I did some testing this morning and found that the little transfer pump did run when I put 12V directly to it. It sounded a kinda noisy though. Also, just to add a little more info to the thread I did replace the high pressure fuel pump in the front tank a couple of years ago, probably put 2000 miles on the truck since then.

Had no clue about the existence of a "balance module"...and would sure appreciate looking at any diagrams you come up with.

Wasn't really sure where to post this so I just went by the year, 2000 model in the 99-06 forum.

Thanks again!

[95 S_Trucker]

They are noisy pumps. They kind of click. I still haven't found those diagrams, but I'm still looking.

The module is located in front of the front tank.

[67JimmyMO]

I will definitely look for that module when I get back home, that might be my issue. Do you know if that is a dealer-only part or if there is any aftermarket availability? Will do some Googling and see what turns up.

Hope you can find those diagrams, luckily I know someone smart enough to read them if I can't figure them out.

At least the truck is running as-is and I don't use it much so there's no big crisis, thanks for your help.

[95 S_Trucker]

This link has a wiring diagram in it:

http://67-72chevytrucks.com/vboard/s...d.php?t=674993

[67JimmyMO]

Originally Posted by 95 S_Trucker

This link has a wiring diagram in it:

http://67-72chevytrucks.com/vboard/s...d.php?t=674993

Excellent, thank you.