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zstine04
10-22-2007, 09:19 AM
I have an 87 swb tbi 350 with dual tanks. my left one works the right one doesn't. I can hear the left fuel pump come on. but when i switch it to the right one i hear nuthing. Is it the switch or the fuel pump. or is anything else i can check. any help would be appreciated.

trickedout420
10-22-2007, 02:27 PM
does the truck stay running when switched? i beleive the 2 tanks use 1 fuel pump. check too see if you have clogged lines

zstine04
10-22-2007, 02:45 PM
does the truck stay running when switched? i beleive the 2 tanks use 1 fuel pump. check too see if you have clogged lines


nope it dies instantly

trickedout420
10-22-2007, 04:39 PM
check to see if te valve is actually moving. have someone flip the switch while your under holding it to see if its getting power. then check for plugged lines and i guess check to see if it has a pump

jaredself
10-22-2007, 07:08 PM
My '82 has the same problem but has mechanical fuel pump. I finally got fed up and siphoned out the gas from the right and put it in the left. For sure check the wiring, then the switch, etc.

Porno Joe
10-22-2007, 07:53 PM
an 87 tbi will have a fuel pump in each tank, if you hear nothing when you switch, its probably the fuel pump. I have an 87 LWB 350 tbi and i can hear both pumps running

78 Chevyrado
10-22-2007, 08:27 PM
It has two fuel pumps on tbi. When mine did that, I took the switch apart and cleaned the contacts (They were corroded and filthy as hell) and put new die-electric grease in it and it worked fine ever since.

NovaMan
10-23-2007, 04:07 AM
if you hear nothing when you switch, its probably the fuel pump. I would have thought the opposite.

zstine04
10-23-2007, 07:59 AM
thanks guys i appreciate it. i guess im gonna check the switch before i drop the tank and change the pump.

trickedout420
10-23-2007, 12:16 PM
well thats good i didnt know it used 2 pumps good info to know for next time. i have a fuel cell mounted in my tool box (20 gallon) and have a holley red pumping it up front. works good and the original fuel tank still works thougt about making some sort of duel tank setup for it.

Porno Joe
10-23-2007, 07:09 PM
i dont have my truck with me to look, but on the tbi trucks, doesn't the power to the pump go thru the valve(so that when you switch tanks the power goes to the other pump)? You might want to try cleaning the connections at the valve to if this is the case

Porno Joe
10-23-2007, 07:10 PM
I would have thought the opposite.
Its just like when you turn on the ignition but dont start the truck, you can hear a fuel pump running in the tank, same thing here, if you switch to the tank and the truck dies, turn the truck completely off and then turn the key to "run" and listen for a fuel pump.

zstine04
10-23-2007, 08:54 PM
Its just like when you turn on the ignition but dont start the truck, you can hear a fuel pump running in the tank, same thing here, if you switch to the tank and the truck dies, turn the truck completely off and then turn the key to "run" and listen for a fuel pump.


yep did this and heard nuthing. say i need to check the connection at the valve as well? where might the valve be?

Porno Joe
10-24-2007, 12:13 AM
the valve is on the frame under the pass side door

FordeatinZ71
10-24-2007, 12:28 AM
before determining that "just because the switch is pushed and the pump isn't running its the FP" you have to first get around the switch (like jumper wire the switch...take the switch out, figure out which wires in the plug do what and jump the one that would make the truck think it's using the right fuel tank...a Haynes manual should tell you this) to make sure it's not just the switch not doing its job. if you jump it and it STILL doesn't come on, then you've narrowed it down to either the pump or the wiring...because if i'm not mistaken the valve just changes the fuel flow...the SWITCH is what activates/deactivates the FPs...i think...lol

Porno Joe
10-24-2007, 01:37 AM
...because if i'm not mistaken the valve just changes the fuel flow...the SWITCH is what activates/deactivates the FPs...i think...lol
I believe on the tbi trucks, the power for the in tank fuel pump is routed through the switch and the valve, again i'm not 100% on this.

zstine04
10-24-2007, 09:18 AM
yea that was my next move. i was thinkin last night just to try to hook the right fuel pump up direct. thanks again guys. i gonna try that tonight if it dont rain.

FordeatinZ71
10-24-2007, 09:59 AM
I believe on the tbi trucks, the power for the in tank fuel pump is routed through the switch and the valve, again i'm not 100% on this.

yea, i dunno...the only trucks i've personally owned with dual tanks were carb'd. but i have worked on an '89 V3500 crew with dual tanks that messed up...i just can't remember how it goes...a manual with a wiring diagram should clear things up...

*edit-i looked in my Haynes manual (man those aren't good for crap nowadays are they? i remember back in the day...yea, i'm only 24 but i love old stuff so i collect old manuals/car stuff...when a Chilton's manual was almost the same as a factory service manual...nowadays the manuals SUCK) and it only shows a single tank wiring diagram so i guess you're gonna have to find another source...i'll keep looking

*edit2-nothing found so far...i'll look again later when i have time or hopefully someone else will come up with something! good luck man!

zstine04
10-24-2007, 10:19 AM
thanks. yea i brought my haynes manual with me to work and it does suck. i can't find anything about the switch on the dash nor the valve.

Porno Joe
10-24-2007, 06:30 PM
I have the original wiring diagram that came from GM back in 87, unfortunately its at home and im away at school

jim_in_dorris
10-25-2007, 02:12 AM
Well, just to kick in my $.02, I have an 87 SWB 4x4 305 with dual tanks, and mine does exactly the same thing. I switch to the right tank and its dead instantly. It makes a great anti-theft device. LOL Anyways, my chevy mechanic says that this is a 1 year only setup, 86 chevy dual tank setups were single fuel pump on the motor, and 88 chevys didn't have dual tanks. The switches, the valves and the in tank fuel pump will all need to be checked, and just because you find 1 thing wrong, do not assume that you fixed it as supposedly the switch and valve had a tendency to go out at the same time. P.S. Mines not fixed yet because of the fist sized hole in the right fuel tank, doesn't matter if that side doesn't work, i need to replace the fuel tank, when i do that i will find and fix the problem on mine

zstine04
10-25-2007, 07:50 AM
Well, just to kick in my $.02, I have an 87 SWB 4x4 305 with dual tanks, and mine does exactly the same thing. I switch to the right tank and its dead instantly. It makes a great anti-theft device. LOL Anyways, my chevy mechanic says that this is a 1 year only setup, 86 chevy dual tank setups were single fuel pump on the motor, and 88 chevys didn't have dual tanks. The switches, the valves and the in tank fuel pump will all need to be checked, and just because you find 1 thing wrong, do not assume that you fixed it as supposedly the switch and valve had a tendency to go out at the same time. P.S. Mines not fixed yet because of the fist sized hole in the right fuel tank, doesn't matter if that side doesn't work, i need to replace the fuel tank, when i do that i will find and fix the problem on mine


i like the whole anti theft device. thanks i really hope it ain't the pump. the switch and the valve SHOULD be easy to replace. i guess with it being 20 years old i should replace both swith and vavle. switch shouldn't be much at all how about the vavle anybody got an idea??

FordeatinZ71
10-25-2007, 08:20 AM
switch is $6.99 from Autozone...i'm having trouble finding the selector valve...that might be a dealer item or ebay...unless someone else knows a place for it?

zstine04
10-25-2007, 08:25 AM
switch is $6.99 from Autozone...i'm having trouble finding the selector valve...that might be a dealer item or ebay...unless someone else knows a place for it?

i found the valve for 10 bucks on ebay but it says its for 73-86 carb engines. mine tbi. part # is fv3. dont know if it will work. im gonna call GM and see if i get anywhere.

zstine04
10-25-2007, 08:53 AM
Its a damn good thing i was sitting down with i called chevy on the valve. Gwatney chevy in Jacksonville, Ar told me 192 dollars and sum change for that valve. to hell with that other tank lol. i have had 3 of these trucks. i think i can live with just having one. now that i think about it. i was doin sum searching about the whole dual tank problem and i read where sum body can get this part for 80 dollars from GM. anybody know or remember

ha i found it. the 5th post of this title (fuel tank switching problems) it says its 80 bucks

Porno Joe
10-25-2007, 03:02 PM
because that setup is a one year only as stated, you will have trouble finding a valve.
As im sitting here typing this I am thinking, isnt the power wire for the fuel pump on the sending unit purple? I would switch to the tank and check to see the wire has power. And then I would still probably invest in a switch for the 10 bucks before i drop the tank and spend a decent chuck of change on a pump.

zstine04
10-25-2007, 03:09 PM
yea cuz i bout chit a brick when i talk to them. i found one guy of the 73-87 website and he can get one for right around 100 but still a lot of money to me

Porno Joe
10-25-2007, 03:18 PM
IF you arent really in a hurry to get this fixed, I can check out the wiring diagram when i go home from college for thanksgiving, but thats a few weeks

zstine04
10-25-2007, 03:23 PM
no not in a big hurry. it just kinda bugs the crap out of me. its not my DD but i love driving it. you know anything about lowering them

FordeatinZ71
10-25-2007, 04:25 PM
because that setup is a one year only as stated, you will have trouble finding a valve.
As im sitting here typing this I am thinking, isnt the power wire for the fuel pump on the sending unit purple? I would switch to the tank and check to see the wire has power. And then I would still probably invest in a switch for the 10 bucks before i drop the tank and spend a decent chuck of change on a pump.

EXACTLY what i was saying. don't "troubleguess" it, troubleSHOOT it. don't just assume the valve needs replacing. heck, you might even try taking it off and cleaning it. heck, try even hitting a junkyard and see if you can pick a good one up in there. if you just study a wiring diagram you could figure out what wire (on the valve connection) to jump to make it "switch tanks" and just carry a battery with ya into the junkyard and a piece of wire and jump it before you buy it to see if it "clicks"

Porno Joe
10-25-2007, 05:49 PM
Yeah I know a thing or two about lowering they, what do you wanna know? you can PM me if you want

Also, does your truck have the shield that is supposed to be around the valve? If not, they the FIRST thing to do would be clean it. My truck that I built was not originally a dual tank truck, and let me tell you getting both tanks to work can be a real pain in the ass, I spent months looking for the correct wiring diagram.

dmbradley1978
10-26-2007, 02:16 PM
i have worked on an '89 V3500 crew with dual tanks that messed up

FORDEATINZ71: Tell me all that you deal with on that 89 V3500. I have a 89 Silverado V3500 dually.

FordeatinZ71
10-26-2007, 02:45 PM
well, there wasn't a whole lot to it. his stopped switching over, we used a wiring diagram, figured out what the wires in the plug for the switch did and jumped the appropriate ones to make it switch. when we did that it switched with no problem so we just replaced the switch and that was the end of it...


are you having issues with your tanks? i can help you troubleshoot it if you need me to...

weider1717
06-11-2009, 08:43 PM
well, there wasn't a whole lot to it. his stopped switching over, we used a wiring diagram, figured out what the wires in the plug for the switch did and jumped the appropriate ones to make it switch. when we did that it switched with no problem so we just replaced the switch and that was the end of it...


are you having issues with your tanks? i can help you troubleshoot it if you need me to...

I may need your help then. My 87 does the same thing when I switch to the right tank..it dies instantly.

So the guy that made this post ended up just needing to replace the switch? Because my system is the same as his.

thanks

V30_guthrie
06-12-2009, 01:22 PM
Hi,
This valve switching design is so over kill it routes the fuel supply and return to each tank along with power foe each pump AND each gas gauge. I have been dealing with my '87 for awhile now with this problem. I replaced the coraoded dash switch still no joy. So it must be the valve under the bed. Now the tank switches but not all the time and you have to fuddle with it to get it to switch tanks. So.....kept troubleshooting it...

Finally took it to an electrical shop. He says all the voltages etc...are down at the valve, the valve is bad...( the very valve the GM dealer sold me awhile ). So I go BACK to the delear to check on my warranty...they look it up in the computer, it's been over 2 tears no dice. HE asks me what engine I have "N" code 454 TBI then he says "that's the wrong valve anyway":think: ....:bhb: Turns out the valve for TBI can shuttle the fuel transfer valve but....the valve that goes on a CARB'd 454 can only handle up to around 8 psi...well the intake pump puts out a helluva lot more pressure than that keeping it from shifting. If you try an shift tanks right away ( for about 30 secs ) it'll shift fine until the whole fuel line gets fully pressurized, after that it won't shift until you shut it off and let the pressure bleed down a bit...

Sorry for the long post ...BE SURE you are getting the RIGHT part for your application.

thanks,
Anthony

weider1717
06-13-2009, 09:30 AM
got my switch out..finally