'98 3500 dual tank, slow fill front tank at the pump and intermittent transfer from rear tank.

[big bird]

Just a followup on this issue.

I have been all the way through the breather line. No check valves anywhere and 98 3500s didn't have the evap system.

It's a really long breather and fill line that is mostly horizontal. Transfer pump fill and return are factory routed into it as well. Those are the lines on the right side of the picture going to the double tee section. $57 for that piece of plastic from the dealership. Jerks.

Using a carefully calibrated piece of broom handle and c-clamp, I raised the breather line. It is now even or above the fill line all the way.

Replaced transfer pump.

Back tank now transfers just fine. Filling the front tank is still real slow but not quite as bad as was before. Instead of putting in gas with an eyedropper, I can fill it at turkey baster speeds.

It's not fixed, but may be about as good as I care to get it. For it to be better, I think fill and breather would have to be shortened, and the transfer lines given a dedicated tank inlet. Maybe a separate breather line with a ball valve on the side of the truck would help.

I think it's just bad engineering.

You must be registered for see images attach

 

[termite]

You must be registered for see images attach

You must be registered for see images attach

Have you checked to see that the tank is lower than the filler neck? I drove an 2007 K 2500 that had a after marker flat bed installed and the the filler tube was almost horizontal, it to forever to fill the tank unless you could find a filling station that had a lot that was on a bit of an angle so that the fuel would not pool up in the filler line causing the pump to continually shut off.

I'd be awful tempted to throw a few blocks of wood in the rig to pull that side up on at the gas station. The filler neck looks really flat and maybe a slight belly at the elbow (may just be artifact of the camera angle).

 

[tpass]

same setup in my rig... I recently rebuilt the rear tank with a new sender, transfer lines and a lift pump.

I may have a lot more space between my frame and flatbed, so there was no issue with flat hose angles like yours, I think you are on the right track with the angles.

I also didn't even try to bring my rear tank filler nozzle out the side of the bed, I just put a short hose and new nozzle basically on the top of the tank.

 

[someotherguy]

and 98 3500s didn't have the evap system.

Oh but they do... yours might not have it, but only because someone removed it.

Richard

 

[big bird]

Oh but they do... yours might not have it, but only because someone removed it.

Richard

I'm too tired to try and find the source, but I distinctly remember reading that the 3500s were exempt that year. It may just be the cab and chassis ones, don't remember. I got a diagram of the tank system from the dealership, and it shows exactly what I have, no evap system.

 

[Road Trip]

...Broke the plastic Tee getting it apart, don't really want to JB Weld it. Going to try and order one. Local parts store didn't even have it in their system.

...Those are the lines on the right side of the picture going to the double tee section. $57 for that piece of plastic from the dealership. Jerks.

Don't know if you are already aware of the Nemigaparts.com GM parts website, but I learned about it in here
thanks to postings by @df2x4. The parts diagrams are not only detailed, but they cross-reference the exploded
diagram # to the actual part number below.

And once you have the GM part number, you can now scour the internet for NOS OEM parts...and if you are lucky
you can avoid paying the stealership list price. (!)

Check this out. I went to the site and looked up a '98 dual tank plumbing diagram:

You must be registered for see images attach

Part #29 looks like the twin tee that you are referencing. So down the parts list I go, and here's what I found for #29:

You must be registered for see images attach

I followed their link, and it looks like the part is no longer available?
So I took the number "15991369", added the word 'tee' to it, Googled it and stumbled across the following:

You must be registered for see images attach

The point I'm trying to illustrate is that the Factory Service Manuals are a great reference for
how to go about troubleshooting and repair of our GMT400s. However, on purpose they don't
list the actual part numbers we need in order to find all the unique bits that keep these vehicles
on the road. But this website is an excellent part # database -- and once we have the part number
this improves our specific internet searches a lot. (NEMIGAPARTS.COM 'Chevrolet' jumping off point)

Obviously I'm a little late to this twin tee discussion, but maybe you can take advantage of
this database in the future if/when your truck needs something and you'd like to take
advantage of their diagrams and OEM part numbers.

PS: I like @termite's idea of a couple of carrying a couple pieces of wood to run up on
in order to tip the truck just enough to improve the fill rate. Whatever it takes / cheat to win, etc.

Safe travels --

 

[someotherguy]

I'm too tired to try and find the source, but I distinctly remember reading that the 3500s were exempt that year. It may just be the cab and chassis ones, don't remember. I got a diagram of the tank system from the dealership, and it shows exactly what I have, no evap system.

Fair enough! In the past I operated a '98 3500HD 7.4 but fortunately never spent much time under the hood; company truck that was always at the shop where it was someone else's job to work on it. My personal '98 3500 7.4 was a regular (non-C&C) dually crew cab pickup and it absolutely had the EVAP system. I don't doubt what you're saying on the C&C models.

Richard