Duel Tank Question

[TruckCo]

I recently purchased a 87 C10 with dual tanks. Truck had a frame off restoration a few years ago and has an edelbrock Multi port fuel injection system. The owner said both tanks work. I had a few questions about the dual tanks regarding this matter.

When the switch is on LH and I turn the key on the fuel gauge registers, and I can hear a "strong" initial pump sound coming from the tank I believe for a few seconds then shuts off. When I switch the selector over with the truck off but key on, I don't hear anything actuate, and the fuel gauge stays where its at.

If I shut the key off, switch to RH and turn the key on, the gas gauge will spike past full, and I will hear a momentary "brr" , different sound of the pump (may be weaker or aftermarket) I assume these trucks have separate fuel tanks.

Its winter out so I haven't driven it yet but is this all normal and can anyone point me in the right direction if something is wrong in terms of the gauge or the selectors not working or does this sound normal? I assume if one tanks not working the truck will die instantly unlike a carburetor which kinda scares me cus at least you have bowl float fuel to safely pull over etc.

Also, I thought these trucks had seperate fuel pumps inside each tank. When I laid underneath, there is a fuel filter and a seperate pump next to eachother on the passengar side frame rail? So would this do both tanks as well?

I am a little lost. Any help would be appreciated.

 

[Grit dog]

On the upside you prolly have twice or 3x as many fuel pumps as you need.
Regarding the pump prime cycle not happening switching tanks with key on shouldn’t trigger the second tank pump if it’s like the relay I bought to control my electric pump.
Presume it runs fine on both tanks, and if one is running off an in tank pump then the other tank has to be running off of one of the other 3 pumps (assuming there’s even a pump in the rh tank)

Need to figure out what the rh side is running off of and a general knowledge of these fuel systems.
OE 1987 first year of TBI engines were the first year with in tank pumps. You obviously have aftermarket efi but it will and does run off a TBI pump apparently.
Bottom line, 3 primary ways to supply fuel.
1. In tank OE type pumps in each tank.
2. Separate aftermarket pumps
3. 1 aftermarket pump.
Find out what you have and what’s running what.
If it works it works but sounds like a cluster that needs cleaned up.

 

[TruckCo]

Grit Dog thank you so much. The truck had a frame off resto and everything is super clean, super straight, so im wondering and assuming that all work done was in good intent.

My plan, if this sounds like a good idea, is the LH tank is reading directly 1/2 tank of fuel. I will fill the RH side full, switch to RH. If the RH gauge levels out and goes down, sweet. If the LH tank continues to go down, i know the tanks arent switching. If when I switch to RH and the truck dies, then i know its a supply issue.

 

[Rumbledawg]

edelbrock fuel injection systems are some of the best aftermarket ones going. there super reliable. being one of the best also means comes with a hefty price tag. to help keep costs down for the avg. gearhead, they use an external fuel pump, as you have noted.
yes, your single pump will run either tank. i'm not quite getting what you describe as the pump is mounted in front of your selector valve, so it should make no diff which tank your on when starting.
i have the pro-flo system on my truck with dual tanks, i can rummage around in the shop for the owners manual and installation guide , it has a very good troubleshooting section and goes into great detail how to properly run dual tanks with their system.
my pump is also mounted on the pass frame rail just in front of the selector and it does not matter which tank i'm on, the pump always primes for about 3-4 seconds before firing

 

[TruckCo]

grit and rumble i can take a photo of it in the am. I appreciate the responses.

 

[SquareRoot]

I have an 85 that I upgraded to Edelbrock Pf4. I replaced all of the wiring for the fuel system. What your describing sounds like it wasn't done right. You should have an in-tank pump (ep381) in each tank. All the factory wiring remains the same except: you need a two way toggle switch to control the fuel pump power that comes from the Pf4. The output ground from the Pf4 is the common input to a relay that determines which pump gets a fused 12volts

 

[Rumbledawg]

the older pro-flo's (1,2,3) use external pumps.
i'm assuming he wasn't running a pf4 as he says the resto is a few yrs old. if it is a 1, 2, or 3, it is wired correctly.
after thinking about what he has said, i would be checking the selector valve for obstructions, fuel out the weep hole, or just a bad selector, might as well check his fuel lines for any kinks, obstructions, etc as well.
like i said, the pump is mounted forward of the selector, so it should make no diff at all which tank he is on.

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[TruckCo]

You guys rock! I still am not home to take a photo as I work 24 hour shifts. The two different pump sounds are odd to me and throwing me off. Are the tank switches all the same? I notice they have very specific years for those switches and they stop at 1986. Rumble dawg that filter/pump from the photo looks spot on. So that pump would replace the tank pumps? Or is that a “pony pump” to help with the injection.

 

[SquareRoot]

If it's a PF-4, you will be monitoring and tuning with an app on your phone or tablet.

 

[TruckCo]

Here you guys go. Wondering if I have pumps in the actual tanks which i dont think so. Also looks like Im “missing” a relay unless the EFIs are seperate.

 

[TruckCo]

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Heres also a few more of what I believe is the tank selector actuator. I assume the lines there are all returns or something. Theres on copper with rubber and one metal one.

 

[Grit dog]

There are 3? different types of tank selector valves and 2 kinds of switches.
But they were all the same style from early 80s? on I believe.
In your case you’d be replacing same with same if needed.
Do you really have 2 external pumps or just the pump/filter in the pic?
Could have 1 tank running off a tank pump and one from the external.
Could have in tank pumping to the Edelbrock pump too. I think. Not sure if OE pumps will let fuel pull thru them if they’re dead.
Different noise doesn’t necessarily mean anything. But could be internal vs external pumps. 2 different in tank pumps could each sound different too.
Mfg, quality etc. Replaced a dead original pump in our boat. GM high pressure in tank pump. The aftermarket one sounds totally different.

Figure out which pumps run which tank(s). That’s first order of diagnosis

 

[Rumbledawg]

it is possible your truck was factory fi being an '87 and having in tank pumps, but i seriously doubt there is in tank pumps now. if you had in tank pumps, installing the pro flo external pump would be unnecessary. your pump is a Walbro and their extremely reliable, and have more than enough juice. one thing you do not want to do is run your tanks low, i never let mine get below a 1/4 tank. any fuel slosh or starvation will kill your pump as it is not submerged in gas like a tank pump. that was how i killed my pump the other year.
when i installed mine, i put the fuel pump relay on top of the outside of my glovebox (a pretty common spot) maybe check there. if your pump is priming up as you say, doubt your fuel pump relay is bad.
kinda hard to tell from your pics what pro-flo you have, but i'm going to guess it looks like a pro-flo 2.
can you get a pic of the MAP sensor (mounted to the throttle body on pass side at the rear of the throttle body) also, do you have an ignition amplifier or not
if your selector valve is bad, you will need an '80's up 6 port valve. 2 lines for fuel to engine, 2 return lines and 2 vent lines. they can be a bitch to change unless you got long limber fingers, i unbolted my box and shoved it back a couple feet to change out mine.
also what kind of controller do you have? does it look like this?

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when you start the truck, wait the couple seconds for the pump to prime before firing the motor. switching tanks with the motor off key on, you shouldn't hear the pump as it will have already primed when you first turned the key on. take it for a drive and then throw the selector switch, if your truck keeps on running fine, then your selector valve is good.
TBH, everything i see in your pics looks fine, i know every now and then my pump will sound a little different, depends on how cold out it is, battery state of charge, etc...
i just replaced my pump 2021 after 18 yrs service from the other pump, they ARE pretty durable

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[TruckCo]

everyone has been so amazingly helpful! I will try to get more pics. I dont have a controller with the truck. Unless its hidden somewhere.

 

[calredneck]

From 81 to 87 if your gauge switches the valve is working