While doing some work on my 1985 drive shaft, I broke the fuel canister/filter mounted on the rail on drivers side. The salvage yard didn't have the same year but I pulled one from an 89, not an exact match but close so I mounted it. The old one had 2 fuel line ports coming in and 2 ports going out, the 89 has 4 ports coming in (2 had been capped off) and 2 going out. After installing and reattaching the fuel lines, the truck started and ran fine, but started having issues soon thereafter. It will run good for several miles, then act like it is running out of gas and die, then will not start. After towing it home and sitting for a while it will start and run fine for a while, then quit the same way. I replaced the filter in the canister and pulled the fuel pump relay and cleaned the prongs (there was some corrosion) but still having the problem. This might be unrelated to the canister, but I can't help thinking it has something to do with it. What is the purpose really of the canister/filter on these trucks other than filter the fuel?

 

The 4 port unit is called a Single Function Reservoir and is found on single fuel tank trucks. It's purpose is to provide a reserve of fuel for high load, WOT or extreme tilt where the low pressure in-tank pumps might suck air or not be able to keep up with the demand to the high pressure pump. There is a filter as well but that was removed on later versions.

The 6 port version called a Dual Function Reservoir also incorporates a non electric dual tank switching valve. The DFR is operated by fuel pressure from the selected in-tank pump. Both in-tank pumps must be operational in order for the valve to operate correctly. If not then you can get problems like fuel being returned to the wrong tank from the EFI return or problems like you are having.

I suppose that a DFR could be operated as a SFR if the correct ports where blocked off and all the internal parts are all present and functional?

If not and you don't want to put out the $ for the correct part then you would be better off putting an in-line filter back there on the supply line and splicing the return line through.

See my web site for pictures of the inside of the DFR etc.

 

I appreciate the response, thanks. This has been a mystery to me because the original reservoir had 4 ports yet I had the duel tanks. Finding the exact replacement at the salvage yards has not yielded anything, but I think I found an OEM from Amazon. Through my own research and posts like yours, I've decided this has to be the source of my issues. I'll post with my results after I install the new one. Thanks.

 

What engine? EFI or carb. What I described was for EFI 5.0L (302).

 

It's the EFI 302

 

Maybe some confusion? Or a PO has messed with stuff.
The EFI with dual tanks must have 6 port DFR (4 in - 2 out). 1 supply and 1 return to eash tank, 1 supply and 1 return to the engine.
An EFI with 1 tank uses the 4 port SFR (2 in - 2 out)

 

We are the original owners, first my dad then me, and the one that broke was the original. The other fuel pump between the tanks and the reservoir has 4 lines coming into it and 2 leaving, which lead to the reservoir, but definitely just 2 lines coming into the res. which probably means this model uses the SFR. I should have been more clear about that but my understanding is evolving here.

 

We are talking about the same thing. 2 ports on the front side leading to the engine bay and 4 ports on the back side going to the tanks = 6 port = DFR
Actually all the 3/8" lines are fuel flowing from the selected tank to the engine and all the 5/16" lines are excess fuel from the EFI system flowing from the engine back into the selected tank.

 

Here is what I installed. It's a 4 port reservoir that is the same as the original. It has taken care of the problem, no more issues.