1987 V10 with carb and dual tanks will not stay running

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Broken85

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I thought I read a few posts back that you replaced the switch already. Did you purchase a switch for a 1987 specifically??? You’re saying that you are only getting power to the switch valve when you hold the switch in. This sounds like you may have installed a pre 87’ switch????

From 81ish-86, the switches were momentary. They only needed to be pressed for a few seconds, long enough for the pollak valve to switch over. In 87 with the TBIs they went to a persistent switch to send power to each pump.

It takes a grinder to modify the lug of an 87 switch to work with a pre 87 wiring, but a pre-87 switch will plug into an 87 harness without any problem.
 

Broken85

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With the key on I have power to the tank selector switch through the tan/white wire. When I depress the switch to the left tank I get power to the tan wire. It does not stay hot, only when I depress the switch. When I let up on the switch the power stops. The gray wire for the passenger side tank does the same thing. Should the wire to the dri ers tank stay hot when the selector is on the left tank?
See my post above.
 

Shoote

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I did replace the tank selector switch. It said it was good for C K V and R trucks. I am guessing it is not because I took Ricko's advice and jumped the switch. When I did both fuel pumps worked. I have ordered another switch for 1987 to 1991 Chevy trucks. How can I make this switch work on a 1987? What needs a grinder?
 

Ricko1966

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I did replace the tank selector switch. It said it was good for C K V and R trucks. I am guessing it is not because I took Ricko's advice and jumped the switch. When I did both fuel pumps worked. I have ordered another switch for 1987 to 1991 Chevy trucks. How can I make this switch work on a 1987? What needs a grinder?
The early switch will not work on an 87.
 

mtbadbob

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The '87 TBI tank switches have to stay switched to the tank you're running off of. It cannot be the rocker-type that stays centered when not being touched. I learned this on my '87 V20 when I sorted all the BS wiring the clown had done to my truck before I got ahold of it. I also got my auxilary tank back in service. The right switch should work!
 

Shoote

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I ordered the same switch I installed in my 85 GMC for the 87 Chevy. Both are running a carb so I thought it would work. You are right, it does not work. I just installed the switch for 87 to 91 and I have both fuel pumps running. I will take a test drive later and post a pic. Thanks to all of you who helped me figure this out!! This is a great site and resource for square body owners.
 

Ricko1966

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Dammit I wish we had known you changed switches on page 1. This was a real head scratcher. I'm glad it's going.
 
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Shoote

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I swapped out the switch about halfway through the the diagnostic process.
 

Ricko1966

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I swapped out the switch about halfway through the the diagnostic process.
Anyway glad it's fixed. And another good example of why just swapping parts without running tests complicates things. Not bagging on you. Just writing it so it gets seen. I'm always telling people don't just start swapping parts because you might create a second problem making the whole process harder to diagnose. I've written it before on here. I've changed ABCDE and F and it still doesn't run. What do you think is wrong? Well it could be ABCDE or F or something else entirely but now we have 6 more things to verify are the right part and work correctly. I don't count on a new part being good right out of the box anymore,too many poor quality parts and too many incorrect parts.
 
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Grit dog

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Anyway glad it's fixed. And another goid example of why just swapping parts without running tests complicates things. Not bagging on you. Just writing it so it gets seen. I'm always telling people don't just start swapping parts because you might create a second problem making the whole process harder to diagnose. I've written it before on here. I've changed ABCDE and F and it still doesn't run. What do you think is wrong? Well it could be ABCDE or F or something else entirely but now we have 6 more things to verify are the right part and work correctly. I don't count on a new part being good right out of the box anymore,too many poor quality parts and too many incorrect parts.
It’s sometimes hard to explain to people that a question needs to be supported by as much info as possible. It’s hard enough to play internet diagnostics. Even harder when you’re spoon fed info or “I forgot I….” or the odd person who knows they f ed something up so they don’t tell the whole story, trying to get the fix without admitting a mistake.
Classic one recently on a boat forum. Guy has a (LS inboard closed loop cooling) that ran 2 weeks ago and now won’t crank, but by crank he means won’t fire, and has 3 batteries but can’t provide state of charge or how they’re linked together. After going through a bunch of back n forth, with him just not answering follow in questions completely or at all, a mobile “mechanic” tells him it’s a bad starter and a second “mechanic” says bad battery (has 3 batteries and not able to check/swap/combine them?)
Then after a couple of us go down that rabbit hole with the same spotty input from the guy with the issue, another mechanic (that’s 3 now in person and us internet mechanics) suggests he has water in the cylinders and hydro locked it since he apparently admitted to leaving the garden hose on for a “while” when it started and died a few times and wouldn’t start again.
At the end of it, the solution was he was out of gas and forgot the previous owner told him the gas gauge sticks sometimes. And he changes the subject to how hard it is to load in the wind and how he bolted bunk boards to the side of his wakeboat trailer (that has guide poles already like all comp boat trailers)
And when we suggest those will likely rip the very expensive raised letters decals off the side of his boat and to just start with the trailer shallower he says already installed will see how it goes…..
This boat is 12 years old but worth probably $60-70k if it’s in great shape and that’s what transpired online.
It’s like half the world is Facebook retarded….
 

AuroraGirl

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It’s sometimes hard to explain to people that a question needs to be supported by as much info as possible. It’s hard enough to play internet diagnostics. Even harder when you’re spoon fed info or “I forgot I….” or the odd person who knows they f ed something up so they don’t tell the whole story, trying to get the fix without admitting a mistake.
Classic one recently on a boat forum. Guy has a (LS inboard closed loop cooling) that ran 2 weeks ago and now won’t crank, but by crank he means won’t fire, and has 3 batteries but can’t provide state of charge or how they’re linked together. After going through a bunch of back n forth, with him just not answering follow in questions completely or at all, a mobile “mechanic” tells him it’s a bad starter and a second “mechanic” says bad battery (has 3 batteries and not able to check/swap/combine them?)
Then after a couple of us go down that rabbit hole with the same spotty input from the guy with the issue, another mechanic (that’s 3 now in person and us internet mechanics) suggests he has water in the cylinders and hydro locked it since he apparently admitted to leaving the garden hose on for a “while” when it started and died a few times and wouldn’t start again.
At the end of it, the solution was he was out of gas and forgot the previous owner told him the gas gauge sticks sometimes. And he changes the subject to how hard it is to load in the wind and how he bolted bunk boards to the side of his wakeboat trailer (that has guide poles already like all comp boat trailers)
And when we suggest those will likely rip the very expensive raised letters decals off the side of his boat and to just start with the trailer shallower he says already installed will see how it goes…..
This boat is 12 years old but worth probably $60-70k if it’s in great shape and that’s what transpired online.
It’s like half the world is Facebook retarded….
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Shoote

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I agree, but I did not change the switch until about halfway through the process. It is out of the garage and running. First time in over a month. Thanks again to all who helped.
 

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Ricko1966

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I agree, but I did not change the switch until about halfway through the process. It is out of the garage and running. First time in over a month. Thanks again to all who helped.
Yea,but halfway through the process you didn't test the switch,or install the correct switch testing the old switch instead of just replacing it would have made your life easier.
 

Shoote

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the old switch was bad when I tested it. My mistake was installing the same switch that my 85 takes, thinking they are both carbs so the same switch should work. They dont.
 

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