1987 Dual Tanks Valve Switch Problem??

[HGG123]

I'll describe the problem as best I can. The truck is a 305 model (soon to be a 350) with TBI and dual tanks. It quit running the other day and I found a blown fuse for the ECM. It continued to blow fuses until I put a 20 amp in it and it then got me home (only about 4 miles). I then put the proper fuse back in it and it no longer blows the fuse, but is not running properly. It will start, but not run as soon as you press the gas pedal.

When it first happened the I checked the dual tank switch on the dash...in the past I found if it gets bumped in between the rt and left position, the truck will quit running as soon as the fuel in the line is used up. That was not the problem, but I did notice the fuel gauge was no longer changing between the tanks and when I do change the switch, the truck stops running.

I did some research and found the switch valve and sending units run through the ECM and was advised that since the ECM fuse was blown, I probably had a bad ECM. I have changed the ECM and still have the same problem. Now, I am thinking the switch vavle may be the problem, but don't want to change it without being fairly sure (it's $206.00 and I can only find it through Chevy).

Sorry for the length of this post....trying to give as much info as possible. This is my first post here and I have read tons of GREAT info and hoping someone has had a similar problem and can give me some advice. Thanks guys!!

[nn2004]

Have you checked the oil pressure switch? I have an 87, 350 though, and just recently discovered this: there are supposably 2 oil pressure switches. On the rear of the block, at least thats where it is on 350s, there is an oil pressure switch with a gray and and orange wire going to this. If the oil pressure isnt reading right on that switch, it will not allow the fuel pump to run. It's some kind of safety kill switch. It is quite common for these to fail supposably, and since a seperate sensor is used for the gauge, you wont ever know it is reading wrong. To explain the fuse blowing, one of those wires may have broken off the plug and be shorting out on the firewall. *Hopefully* one of these is your problem. The sensor on mine is threaded into a 90 degree fitting going into the block in the far back. The orange and gray wires go directly behind the firewall into the ECM. Hope this helps.

[HGG123]

Thanks.....I give it a try right now.

[383drvr]

I went to the local chevy junkyard and found more tank selector valves than you could shake a stick at. I pulled one for $15 and it fixed my problem, but I knew it was the valve.

Im no expert, but can you try disconnecting the tank switch/valve to see if there is a short in the valve itself?

[HGG123]

Thanks....that's also a good idea. I wasn't sure how avaliable they would be, but I'll be checking it out.

[HGG123]

And...I tried disconnecting the valve switch, it had no effect.

I can hear the fuel pumps change from one tank to the other, but it won't run at all when I switch the tanks and the fuel gauge will only read the tank that it half way runs on......the more I think about it, the more I think about it, the more I want to try a different switch from a junk yard.

We had reformulated gas in our area for about 2 weeks and I saw a spot on the news that said the 'new' gas was causing folks problems with tank guages and sending units.....and I had filled up about 5 minutes before the trouble started, but no one I ask seems to think that has anything to do with my problem. I also emptied that tank and put fresh gas and Techron fuel system cleaner....still no luck.

I looked for a second oil pressure sending unit, but didn't see one and can't find one in my shop manual. Gonna try the switch valve next.

[HGG123]

Turned out to be the tank switch valve. Thanks for the help!!

[landpro00]

Well, mine seems to have the same problem.

Is the fuse that kept blowing on yours located on the bottom left side of the fuse panel and rated at, I think, 10 amps.

Mine would run for a while at first after replacing the fuse, now it blows the fuse as soon as I turn the ignition on.

I have the same symptoms as far as the fuel gauge goes. It stays the same no matter which tank I select.

Anyhelp would be greatly appreciated, THANKS!

PS: Truck is a '88 Crew Cab Dually 1 Ton

[HGG123]

That's the fuse and that sounds just like what mine was doing! I ended up finding a replacment valve at O'Reilly Auto parts. It is a Borge Warner part and it was exactly like the original. It was $61.00.

That solved the problem for me. Hope that helps you.

[Ecnerwal]

I had trouble with the truck stalling whenever I'd hit a bump a few years back. I considered replacing the selector switch (bad contacts - not the greatest switch design for long life, IMO) with another, decided they ("proper replacement fuel switches") would be as poorly designed, and replaced it with a heavy-duty regular toggle switch, which cured mine. But my problem seems a bit different than what you describe, though some aspects were similar (fuse blew sometimes).

[steve k.]

On my truck, PO replaced the electric switchwith a mechanical one because the electric one kept breaking. But to have a working fuel gauge he had to have two separate ones for both tanks. So now i have a machanical switch and two Autometer fuel gauges. I like it.

steve k.

[landpro00]

THANKS ALL!!!

Appreciate the input. Think I'm gonna try a new switch valve, see if the cures it.