Fuel Tank Questions

[ggtsvnv]

Hi,
I have an 87 short bed 2wd, 305 TBI and 4spd auto. When I bought the truck only the R/H (pass. side) tank worked. It has the factory dual tanks and I check the power leads and it was getting power to the selector valve, so I replaced it. Before I replaced it no matter which tank the dash switch was set for, the engine ran and it took the gas from the R/H tank. Now after replacing the selector valve, fuel filter, adding a gas line and tank cleaner (recommended by the guy at NAPA) and filling the L/H tank with fuel, when I change the dash switch to the L/H tank the truck dies. It still runs on the R/H tank but won't run on the left. I cranked the engine over for quiet a while but it would never fire. I know that it is not getting fuel, but does anyone have a suggestions as to what I can check?
Thanks

[nlped]

I had the same issue with my old '87. Turned out that the fuel pump on the "affected" side was not working.

You should be able to hear the fuel pump prime from which ever side is selected via the dash switch. If you don't hear L/H tank pump priming, then it needs the fuel pump. If you actually hear the pump priming, you will need to fab. up a pressure port so you can check the fuel pressure at the TBI. It most likely will be very low from the affected tank. If it is the pump/pressure buy the A/C Delco from Rock Auto...I think it's about $60 shipped. Don't skimp and buy some China junk, or you will be doing it again in 6 months. If I can help with other questions about this please let me know, or I think I posted pics and stuff on "Bob's" build thread that is still referenced in my Sig.

Good Luck!

[ggtsvnv]

Thanks nlped!
May I ask another question? So from what your telling me each fuel tank has its own fuel pump? If so is it in the tank? or somewhere else? Thanks again.

[nlped]

Yes, both tanks have a fuel pump in them. With yours being a TBI truck, the fuel injection uses an in-tank pump in each tank rather than a "draw through" style pump system. The fuel pump is mounted in the fuel sending unit assembly.

If you pull the tank, it is accessible via the top of the tank. Unfortunately, in GM's infinite wisdom, you cannot access it any other way without pulling the Cab or the Bed, which would be a major PITA!. You don't actually have to purchase the entire fuel sending unit/ fuel pump assembly to repair your issue unless the fuel level guage isn't working either. If the guage is working properly, just pull the tank (sucks it has a bunch of gas in it, because it WILL be heavy) and access it that way. It is 8 bolts that hold the tank in, 3 fuel lines ( that are rather easy to access once you take the before mentioned 8 bolts out, but haven't actually lowered it to the ground yet) and the fuel filler neck and vent lines.

Let me know if you have more questions,

Ed

[ggtsvnv]

Ed Thanks for the help.
I have got the 8 bolts out and started lowering the tank but it got to dark to go any further with it. I will attack it again in the morning and get it done.

[USSkoval]

I'm a little late now but...

Sometimes when a fuel pump sits unused for several years, it will just get stuck. You can give the affected fuel tank a couple good whacks on the bottom with a rubber mallet while someone turns the ignition on. Often it will start working again and last for several more years before it finally dies. Sometimes the aftermarket replacement pumps don't even last that long.

[ggtsvnv]

USSkoval,
Thanks for the info. I did buy a new one from NAPA made is the USA so hopefully it will last a few years. I might keep the old one now that you say that just in case and give it a try in the future if one goes out. I decided to replace the sending unit while I was at it. The old one had a wire broken right where it is soldered to the unit, and being I'm not sure if it works I felt the time was now. Don't want to do this job twice. The bummer is no one has the sending unit in stock so I ordered it from LMC.
Thanks for everyone's help.

[nlped]

If you haven't already ordered it, check with RockAuto.com. There pricing was by FAR the best I found when I redid my passenger side system. Just an FYI.