jettboi

I have a 1995 XLT with dual fuel tanks that I just got a couple of months ago. I'm having some trouble with the rear fuel tank. It seems like when the rear fuel tank is engaged, the engine isn't getting any gas even though I know there's gas in there. I've tried once when the truck was in idle but not moving and once when the truck wasn't on. Both times the engine sputters heavily and seems like it's going to die. I have to confess both times I've chickened out after 5 seconds and gone back to the front fuel tank because I was afraid of doing engine damage. I have three possible theories as to why this is happening:

1. I have a disconnected rear fuel tank or a clogged/broken hose
2. The rear tank wasn't used for so long that it's not "primed" so to speak to run the engine
3. Even though I put in new gas until the pump clicked off, the tank already had plenty of old and/or dirty gas in it that's pissing off the engine.

So here are my questions:

1) If theory #2 is correct, how do I get the gas flowing again? Sit in idle and rev the engine alot?
2) If I'm wrong about theory #2 and the trouble is in fact theory #1, how much engine damage will I do if I keep making the engine try to work without gas?
3) How long does it take for gas to go bad?

Thanks,
Jesse

aliens8mycow

If you have the front tank selected, and turn the key to 'on' (not starting the truck), you will hear the front fuel pump prime for 2 seconds.

If you turn the truck off and switch to the rear tank - when you turn the key on, do you hear the rear pump prime?

jettboi

Funny enough I just got back from getting my oil changed and asked the guy to take a look. He didn't hear the fuel pump prime when he did the very thing you suggested. He had a theory that it was possibly the switch itself.

aliens8mycow

I'm no expert here, but you can pull the lower dash panel and check the switch if you have a continuity tester or voltage meter. I doubt it's the switch, though.

These trucks are notorious for fuel pump failure. If your rear tank has been left inactive for a long time, the check valve may not 'check' any longer, allowing return fuel from the front tank to go to the rear tank. My truck is doing this from the rear to front right now. (it's always nice to watch gas run out of the filler cap of a tank that you don't even use)

If you find the switch good, it's probably the pump. You say the rear tank is full - if you are switched to that tank, does the gas guage show full? If not, the sender is probably bad too. The pump and sender are both in the tank, and you have to drop the tank to get them out (or remove the bed). If the tank is all nasty from having old gas in it for years, that's another $100 well spent to just replace the whole tank while you're at it.

str8dogg

I concur. If there is no whine to the rear tank like the front, it is more probable the fuel pump, provided it is engaged as you say. You mentioned that you just go the truck but didn't quite say whether or not it was running before you got it, or whether or not the rear tank was used. If you think it has not been used in 6 months or more, I would also say the gas is bad as well and mixing new gas with it won't work. Remember your lawnmower, it is recomended to use up the gas in the mower and tank when you will put it down for the season (which is usually about 3-6 months), same philosophy. Once gas looses it "bite" it will cause the vehicle to sputter and shake something fierce. Try using 5 year old gas sored in a metal VW tank!!!

aliens8mycow

Yeah - if it's been in that tank for awhile, everything it is in contact with has been varnished. I'd assume the pump is rotten and the tank is rusty too, which is why I recommended doing a complete replacement.

bassmac

I had the same problem with my 93 side/ front tank. Only difference is it happened to me after years of ownership while driving accross the great state of Texas(in the middle of nowhere). When I got home and tested it by turning on the key with that tank selected, I also did not hear the pump engage. I dropped the tank, replaced the pump, and haven't had any problems since.