dual tanks with late model EFI?
 

Any issues with using the dual-tank setup with a high-pressure late model EFI system? My 87 has a stock tbi 454, and sometimes dirty thoughts of a 6.0 keep creeping in. I've seen my share of guys putting TPI on their trucks, but never noticed if any of those used dual tanks. I understand that I'd have to upgrade the fuel pumps, fuel lines, etc, but wasn't sure if (or how) I could retain the dual tank switch-over business. Can that equipment handle 55+lbs of fuel pressure? If not, what are my options for retaining dual tanks?

Re: dual tanks with late model EFI?
 

A short answer is no, but it can be worked around. The transfer switch is low pressure design - and can only only handle 13 to 20 PSI needed for TBI operation. For TPI or any other port injection system operating at 3-bars (43 PSI) transfer switch will not fare well.
A simple solution is to build a small surge tank between fuel supply transfer switch and new high pressure fuel pump rated for TPI or 6.0 L operation. A purpose of a surge tank is to act as a buffer between TBI in tank pumps and provide uninterrupted fuel source to high pressure TPI pump. In another words OE, in tank TBI pumps act as fuel lift pumps, delivering fuel into surge tank. Excess, overflow fuel from the surge tank is returned back to selected main tank. TPI pump takes fuel from the surge tank, via fuel filter, and return line from TPI rail dumps excess fuel back into surge tank. See attached diagram and a photo of my surge tank:

//RF

Re: dual tanks with late model EFI?
 

How about a dual tanks setup W/O the intank fuel pumps. Will an aftermarket pump work well enough to pull from the selector valve and send the pressure to a EFI system? I have an 84 with dual tanks and would like to go to an electric pump system.

Re: dual tanks with late model EFI?
 

Wow... more complicated than I thought.

Maybe I'll just eliminate a tank, or make it like a late model truck where one tank feeds the other.

Re: dual tanks with late model EFI?
 

In my TBI conversion I used external lift pump to pull fuel through the tank selector valve. Generally, lift pump works best when it is placed at lowest fuel level expected in the tank. So, placement of the fuel pump is somewhat critical.

Back to original post - for TPI conversion you can probably get external TPI rated fuel pump (for example Walbro GSL-392), remove TBI in tank fuel pumps by installing a jumper (fuel immersion rated) hose in their place. This way external TPI pump can lift fuel through the selector valve and it is not subject to fuel pump (output) pressure! Just be aware that external fuel pumps are nosier and can overheat under extreme conditions. Since you already have EFI tanks fuel starvation is minimized, thus surge tank is not really required. I should have read your post a bit closer.

//RF

Re: dual tanks with late model EFI?
 

Glock did this with a high pressure switching valve on his 5.3 swap into Fred. He just posted a link to the stuff he used a short while ago.

http://67-72chevytrucks.com/vboard/s...350986&page=46
posts 1143 & 1144

What about just a low pressure external transfer pump coming from the passenger side tank into the driver side tank and only running one in-tank fuel pump.

Set up the return line to go into the passenger side tank and wire up the transfer pump to operate when you hit half tank on the primary & stop when 3/4 full it could keep the fuel in the secondary tank fresh.

Not sure how to wire that up to work but it could be as simple as a micro switch on the sending unit float arm of the primary tank.

You would need a second switch on the secondary tank to keep the pump from trying to work when the tank was dry or low on fuel.

Re: dual tanks with late model EFI?
 

This thread:

http://67-72chevytrucks.com/vboard/s...d.php?t=353149

has a great discussion on dual tanks and high pressure EFI.

Basic rundown:
87 tanks with baffles for fuel pump
87 Fuel senders for in tank pumps
AC Delco EP 241 pumps
JC Whitney Motor Operated Dual Tank Valve (outwardly identical to original dual tank valves, but rated for higher pressure)
Corvette fuel regulator/filter
87 Tank switch inside the cab
Fuel pump relays and fuel pump/fuel tank switching valve wiring harness from an 87

Surge tank system above would be my second choice and both will work just fine.

Re: dual tanks with late model EFI?
 

JC Whitney has the worst price for this valve. The Pollack # 42-159 Light Truck 6-Port Motor Driven Valve is well known. I pulled the data sheet for this valve:

http://pollak.thomasnet.com/Asset/IS-41_b.pdf

Read application notes - not to exceed 65 PSI! They must have upgraded this design since the last time I have looked at it. The valves that I have used in the past stated not be used with systems over 30 PSI! Go figure!

//RF

Re: dual tanks with late model EFI?
 

Good call. I didn't look for this valve other places when I bought it. JC Whitney has the 42-300P kit for $82.99 and carparts.com has it for $65.59.

The 42-300P kit is a 42-159 valve plus the switch, pigtail, and switch bezel. I don't see the actual 42-159 valve by itself after a quick google search. Are there other places with even better prices?

Re: dual tanks with late model EFI?
 

[QUOT=ElGracho;3715902]Good call. I didn't look for this valve other places when I bought it. JC Whitney has the 42-300P kit for $82.99 and carparts.com has it for $65.59.

The 42-300P kit is a 42-159 valve plus the switch, pigtail, and switch bezel. I don't see the actual 42-159 valve by itself after a quick google search. Are there other places with even better prices?[/QUOTE]

Try Autozone - Search for FV-5. It is very common for a manufacturer to provide OE parts to a range of marketing / aftermarket companies under a different part numbers. Essentially, it is the same part, in a different box and part number. POLLAK 42-159 aka (AC DELCO 4029228, STANDARD FV5, Wells FSV2 and possibly others) Also there are couple ebay listings for Pollack 42-159.

Price: 59.99
Part Number: FSV2
Weight: 0.674 lbs
OEM Brand: STANDARD_MOTOR
Quantity Per Car: 1
OEM Number: 12336291


//RF

Re: dual tanks with late model EFI?
 

Once again you come up with great answers for us all, great info RF.

Thanks again.

I really like the idea of having a fully function backup fuel system in the secondary fuel tank. You never know when a fuel pump will go out or where you will be when it happens.

Re: dual tanks with late model EFI?
 

I know this is a super old thread nonetheless I'm about to install the Pollak 6 port high pressure valve PN 42-159 to satisfy the return and high pressure requirements of on my 5.3L, with this said my question is why would I need to change out the wiring harness as the pig tail looks to be identical to the original?

Also, does anyone have wiring instruction for the in-tank pumps, I've installed them on 87' sending units but not sure how to wire up the pigtails ?

Thanks in advance!

Popeye

Re: dual tanks with late model EFI?
 

Wait I thought the 6 port was for Diesel and 3 port for gas? Would AC Delco ACDelco U7000 work as well?

Re: dual tanks with late model EFI?
 

I put a msd atomic in my 86 with dual tanks, no problems, the transfer valve is good to 65 psi in the later model trucks, the earlier years it wouldnt work , really wasnt difficult to do every thing works fine my truck had steel lines i used the recomended fuel hose thst came with the msd kit, and changed all the short hoses that go from the sending units to the tansfer valve, the hardest part to figure out was mounting msd pumps on chevy sending unots pyt that wasnt to hard

Re: dual tanks with late model EFI?
 

Wal-bro is a good in-tank pump swap as well. The 2-wire connector is for pump power and fuel level sender.

Re: dual tanks with late model EFI?
 

Look up the Specs on the Delco U7000. It's likely the same valve but not necessarily. In 2004 my U7000 was a Pollack 42-159. Delco has been sourcing China, Southeast Asia, and Indian parts of late so all bets are off.

Three port valves are for fuel systems with no return line Period. I'm not sure any of the gasoline engine squares after 1980 were manufactured without a return line.
Diesels MUST have a return line. The DB2 Injection pumps on the AMG 6.2L & Oldsmobile 350N & 350DX diesels control cold injection timing advance by restricting flow from the Injection pump to the fuel return line via the HPCA (Housing Pressure Cold Advance) solenoid. Without a return line the DB2 Injection pumps would inject fuel for an ignition point 3° advanced at all times.

Swapping a 73-80 over to motorized valve isn't rocket science. Get a complete 1981-1991 NL2 dual tank harness with the switch and the valve then install it.
ON all years... The NL2 dual tank harness is separate from the main engine harness. This meant that the assembly folks didn't have to pick a different harness for the dual tank trucks... just be sure the hole was present in the dash, add on the NL2 harness etc and continue. The single-tank fuel sender wire connects to the fuel gauge output wire on the NL2 harness, usually on the RH frame rail, and the NL2 sender connectors plug into the proper senders.

Three comments on hoses.
-In order of preference use German Fuel Injection hose clamps or constant tension band clamps or Oetiker hose clamps on your fuel hoses.
-Be sure the hose in the tank is SAE J30R10 fuel submersible hose inside the tank. If it doesn't state SAE J30R10 then get 6" or a foot of the real thing. You don't want to have drop the tank because the hose failed.
-Be sure to use SAE J30R9 "Fuel Injection" hose between the senders and the engine connections. J30R10 isn't rated for use in the open air and J30R7 wasn't rated for the fuel pressure when it was still approved as liquid fuel line.

More on SAE hoses and clamps here.http://67-72chevytrucks.com/vboard/s...d.php?t=696742

If you're doing in-tank pumps you'll need the 1987-1991 R/V series TBI fuel tanks and TBI NL2 harness with the correct connections to the fuel pump. The TBI senders have 2 position Weatherpack disconnects that have Pump Power and Sender wires. The TBI sender and Fuel pumps complete the circuits using the tank to frame ground.
If you're running in-tank pumps use the 1987-1991 TBI tank switch.

This is the NL2 schematic for a 1989 RV 10-30 with TBI. The 1987-1991 Diesels do not have the in-tank pump power wire provision. You can see the part numbers for the Weatherpack shells and the extra power wires teed off the Gray and Tan D & E wires at the valve.
http://johnnynightstick.s3.amazonaws...ght_Trucks.jpg

It's worth noting that a pump shutoff provision should be added for safety. GM TBI systems used an oil pressure switch, relay, and the ECM to shutdown the fuel pump. You'll need to dig into the 5.3L PCM schematic for the fuel pump relay output wiring. It's safer to do this. You don't want the fuel pump to run after the engine shuts down in an accident.

Re: dual tanks with late model EFI?
 

If you want a complete kit w/wiring, relays, etc. all plug n play I've get them. $319 for a complete kit w/65 psi Pollak valve and 87-up TBI dash selector switch. Shown here is a stock replacement harness kit for $239. Next image is for LSx stand alone.

Re: dual tanks with late model EFI?
 

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Re: dual tanks with late model EFI?
 

I'm just going to feed one tank with the other. Depending what ECM/PCM you are using it may run the jockey pump natively and combine the fuel senders to a combined fuel gauge reading.

I'm doing a diesel swap but some of the gas PCM/ECMs can do it depending how you configure them. Many late model vans and such or cab and chassis have dual tanks stock.

Re: dual tanks with late model EFI?
 

That's worthwhile information.
Do you have any details on how it works or links to share?

Re: dual tanks with late model EFI?
 

I've done quite a few Cummins fuel setups that way.

Re: dual tanks with late model EFI?
 

I'll make a build thread soon for my duramax swap. For late model diesels, this is the only way to go as they require large fuel supply lines and flow- more than the switch will handle. Duramax vans usually had dual tanks, one primary and one secondary that would jockey pump into the primary. They still have two fills. Duramax are not tank in pump, only have the pump on the motor. I'm going to run an aftermarket lift pump but even so it isn't required. Really the only tank modifications is to get a sender with a 1/2" feed and 3/8 return...which is easy to do by using a stock sender and adding in the 1/2" feed and using the 3/8" line as the return.

This is similar to some LS cars. Any newer style dual tank setup is this way, just have to find one. Again looking at vans and cab and chassis is the way to go. Or older 2007 and prior GM medium duty trucks. Find the application and lookup the wiring diagrams/parts list.

The voltage to gallons capacity map can be configured in the tune to use stock square senders. The duramax(LML anyways) can even configure the output voltage to the gauge. I'm not sure if other PCMs can do this or if you need to modify the gauge- but you can also lie on the volts to gallons map to get the fuel gauge correct- it'll just be off if you check with a code scanner.

Re: dual tanks with late model EFI?
 

can anyone elaborate on the 1987-1991 R/V series TBI fuel tank VS a newer tank?

I'm not sure which tanks I have, and I'm not sure how to determine which is which. If I use an 87 TBI fuel sender with in-tank pump as my jockey pump, do I require a later tank?

Can an earlier tank be modified to mimic the later?

Thanks.

Re: dual tanks with late model EFI?
 

Since liquid seeks its own level and my 1984 C10 dual tanks sit at the same level; why couldn’t I pipe a manifold from near the bottom of both tanks. Say 1 inch or bigger braded line or rigid steel or aluminum either welded or attached with a tig in bulkhead. An AN line between the tank tops to prevent vapor locking, and just use one internal or external 58psi pump to deliver fuel to the rail. Eliminate switches and other pumps all together. The one sending unit doesn’t care if it’s 3/4 of 20 gal. or 40 gal. Run the manifold pipe in a steel tube welded to a cross member for duribility. I had 55 gal. drums that caught water from my downspout. Fill one drum and they all fill equally. Pull water from one they still keep the same level. Other than protecting the manifold pipe or line, this in theory sounds like it would work. Save coin on valves, switches, sending units, etc. Just a thought. Open to why not.
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Re: dual tanks with late model EFI?
 

I thought about this idea on my crew cab , but it would be the lowest thing hanging down . not sure if you have an issue if you could ever stop the fuel flow to the ground.