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Discussion Starter · #1 ·
Going to be doing a 4bt in my 1995 f150 in the next month or so. What I'm trying to figure out is how I want to do the fuel system. It would be nice to keep both tanks, but on the other hand it would also be nice to just use the 4bt lift pump with a hose into one tank. Everyone else who has done a 4bt in a 1992-1996 ford, what did you go with? I will also considering doing a fuel selector valve like the diesels had on the obs trucks. Not sure how hard that would be to wire up to my current system. Any ideas?
 

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If you want to keep both tanks that should be no problem. You will need a diesel selector valve that has both the suction and return ports. Electrical connection should be the same as the gas selector valve. OEM units are tough to find but I believe there are universal fit aftermarket replacements. You will probably need to modify or change your in tank pickups. If your truck has in tank fuel pumps and filter socks those need to go away. You can buy diesel tank pickups now. They are being reproduced. Those have the return line port for a diesel. You will also need the Ford filter screen that was used on the diesels. Those can still be found and I can look up the part # if you need it. The tank fill port on diesel trucks was a bit larger to accommodate the large nozzles at truck stops. The ones at service stations for auto diesels would fit but if you went to the big truck pump you'd need to modify that inlet.
 

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Discussion Starter · #3 ·
I also have a 1997 7.3 I will compare it to. Right now the gasser is just 2 in tank pumps with a switch for each tank and no intermediate selector valve. I'll have to see how I can splice it in.
 

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I also have a 1997 7.3 I will compare it to. Right now the gasser is just 2 in tank pumps with a switch for each tank and no intermediate selector valve. I'll have to see how I can splice it in.
Figure out how to switch your return line - Returning diesel to a tank that is full is not going to end well.

And a repeat of the above advice on the fuel sock.

And is the fuel pressure from the in-tank electric pump compatible with the 4bt injection pump? NOTE the difference between the VE pump and the P pump. I don't remember the specifications - BUT - recently sent my 1986 Bosch VE pump out for a much needed re-seal (re-$eal) and rebuild.

Russ
 

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If you have a '97 7.3 it would have the system you'd want to copy. As Russ pointed out, those in tank pumps are high pressure and not compatible with a VE injection pump as well as the fuel sock issue. Also, don't know if those have the return line setup. Here's a link to the selector valve for $59.99. Amazon.com: JDMSPEED New 6 Port Fuel Tank Selector Valve Replacement for Ford Super Duty F250 F350 Diesel 6C3Z9189A: Industrial & Scientific One issue might be the wiring harness to tie to your control switch. If you could find one of these vintage trucks in a salvage yard you could get the parts you need. Your local Ford dealer may have a schematic of the layout to help you there. Here's a company that has the replacement pickup units and filter screens. A little over $200 to equip both tanks. Have to pay attention to the year model because pre 1994 units are different. Ford Diesel Sending Units
 

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Discussion Starter · #6 ·
Thanks for the link to the pickups, that's good stuff. I'll have to see what is different in the pre 94 units. Sometimes I see 7.3 idi trucks in the junkyard. I'm also considering ditching the front tank and running a 38 gallon bronco tank in the rear.
 

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There seem to several variations in those sending units. In various years there were slightly different fuel capacity and there were both steel and plastic tanks. Those guys at GTD seem to have covered all the bases including the 40 gallon rear tank.
 

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Having done it both ways, the simplest solution is to leave the pumps in the tank and plumb them right into the lift pump. However, the super secret trick is to install a "T" before the pump with one leg pointed up. make an orifice with about a 1/16" hole to fit in the T and hook that into the return line. Jump the FP relay so it turns on with the key in start and run. The orifice ensures there's no pressure and air goes back to the tank.

After screwing around with selector valves and re-plumbing the entire system a few times I did it that way with great results. Several have been on the road that way for more than a decade without problems. I would guess the famously unreliable Ford in tank pumps have an easier life pumping diesel instead of gasoline and at no pressure.

If you don't like it you can always change it down the road, but it takes a pretty big undertaking and turns it into a 20 minute job.

There's also the bonus of bleeding the fuel system is a breeze. One feature I would add (but never did) would be to retain the fuel pressure relay and control it with a 5 PSI oil pressure switch. That way fuel pumps only run when needed.
 

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Sounds vaguely like the fuel system that I built for an old boss's wife's Suburban ski boat TR. High pressure electric pump at the tank, 'T' at the input to the typical Holley regulator with a 6 psi check valve (something like this: Aeromotive 15106 Aeromotive High Flow One Way Check Valves | Summit Racing but it's cracking pressure needs to be checked) on the branch, fuel thru the check valve returned to the tank. The regulator/check valve assembly was placed so that it had less than 12" of line to the carb. I used a Chevy Vega fuel pump driving oil pressure switch (now marketed by Carter as a "universal fuel pump safety switch": Carter A68301 Carter Oil Pressure Safety Switches | Summit Racing) to run the pump. Didn't bother with key-on, key-off, if the engine had oil pressure or was cranking the fuel pump ran. The amusing thing was that you could bomb that truck down the freeway, pull in somewhere and turn it off. the fuel pump would run, with the engine fully to temp, long enough for you to get out and lock the door. It was almost like locking the door and closing it was what turned off the pump.
 

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I have a 1993 F150 and use both tanks. I took the pump out if the front tank and put pick up and return hoses down to the bottom of the tank and the 4bt lift pump supplies the engine with fuel. Both tanks use the same return line so I cut it into between the tanks and put a 3/8 rod in the hose hooking the 2 ends together and clapped the hose that way fuel only returned to the front tank. I put a toggle switch on the dash and it turns on the rear in tank fuel pump and fills the front tank. You just have to watch the front tank gauge to make sure you turn the pump off before over filling it. All the dash switch does is shows how much fuel is in the tanks.
One last thing you have to do is take the rear pump out and cut a hole in the bottom of the little tank where the filter thing is so fuel can enter that tank. I'm not sure now but I think there are 2 chambers in that plastic tank. The return fuel goes into that little plastic tank and now that the return is blocked the pump will suck it dry real quick. I had to take the bed off my truck a second time to figure out why fuel wasn't transferring to the front tank. I tested to make sure there wasn't excess pressure to the engine. Light finger pressure stopped the flow as the fuel was then pumped into the front tank while the lift pump might have a very slight assist pulling the fuel to the engine.It works good for me.....
 

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I have come to the point where I am tired of replacing the fuel bowls in my OBS and dealing with the fuel leaks in the valley. Can anyone comment on what is the best to get and what results they have had with theirs?
 

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Having done it both ways, the simplest solution is to leave the pumps in the tank and plumb them right into the lift pump. However, the super secret trick is to install a "T" before the pump with one leg pointed up. make an orifice with about a 1/16" hole to fit in the T and hook that into the return line. Jump the FP relay so it turns on with the key in start and run. The orifice ensures there's no pressure and air goes back to the tank.

After screwing around with selector valves and re-plumbing the entire system a few times I did it that way with great results. Several have been on the road that way for more than a decade without problems. I would guess the famously unreliable Ford in tank pumps have an easier life pumping diesel instead of gasoline and at no pressure.

If you don't like it you can always change it down the road, but it takes a pretty big undertaking and turns it into a 20 minute job.

There's also the bonus of bleeding the fuel system is a breeze. One feature I would add (but never did) would be to retain the fuel pressure relay and control it with a 5 PSI oil pressure switch. That way fuel pumps only run when needed.

I am having a hard time visualizing what you are saying you did here. Can you take a picture of what you did?

Thanks a ton.

Paul
 

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130830


So my Paint skills are amazing here. But this is what you are talking about right? Where Red is the return and Blue is the feed line?
 

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At the mechanical lift pump, where you have to install an NPT fitting to connect your supply hose you'd install a Tee here. One leg of the tee hooks into the return line. Put an orifice in the plumbing connecting the supply to the return side. Point the leg of the Tee you install in the lift pump vertical-up so any air will hopefully go to into the return.

I have no pictures of this. Was many years ago, not my vehicles.
 

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I know you were proposing putting a restriction headed to the return line, but am thinking about putting the restriction to the feed line.
 
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