Rusty_S85 Posted January 6, 2021 Share Posted January 6, 2021 Ok on PC now What do they do on the FI trucks with dual tanks from the factory? I think the tank valve is switched by the fuel PSI IIRC and this also changes the gauge. I just don't know what that PSI is but why not do that set up on the truck? So you want to get everything for the rear tank like I think you said you got. Tank, straps, the cross member just in front of the tank the straps go to. As for the wiring. On my truck (81 F100) the dual tank wiring is all part of the main & frame harness. My parts truck was also a 81 F100 so it was just swap harnesses and I was good to go. Now I think you are using a newer dual tank harness in your truck so I don't know what you will run in to or have to make work. I think to go through all the work to have a level reading on the rear tank and have that pump transfer gas to the from is a lot of work. If me and I could not get both tanks to work like the factory did I would set up the rear 19 gal. as the main and the 16 gal. as the back up and transfer it to the rear. On the fill tube you are going to fill through the wheel opening? How much road dirt is going to be kicked up on it? Did you get all that from the parts truck? I like the clean factory look and why I molded the rear filler door into the fender. If you have a 2nd door assy. you could have a shop or you mount it in your bed side. I know not a lot of help here sorry. If there is something I might be able to shed more light on ask and hope I have the answer. Dave ---- That was a one of the many reasons why I decided to not attempt a rear tank on my truck. I didnt like the idea of mounting another door on the fiberglass fender it would be too hard to revert back to OE if for some reason I decided to restore back to factory new condition some day. I also didnt like the idea of having a filler through the wood in the bed. I figured my choices were to stick with the OE 16 gallon saddle tank and mount a jerry can carrier on a roll bar if I install one or while the tank is at the local truck shop to have the top cut open so a baffle could be welded in take and inquire with them about chopping the forward nose of the tank off and adding about 3" worth of metal to length the tank forward. This can be done on mine as Im not 4x4 and 3" of length added based off the heigth should be good for a easy 5 gallons of fuel. In theory I should see a 21 gallon saddle tank that would retain the short wheelbase mounting pattern. I just dont know if this would stress the mounting straps doing this like wise I dont know if the extra 5 gallons would be enough to offset the truck and induce a lean in the truck with a full tank. So for me personally I am still unsure what I will do till I am at that point of fuel injection install. As far as the OE setup goes, you have a lift pump in each tank with your high pressure pump on the frame rail. The way I understand it is the switching valve switches feed and return from each low pressure lift pump for saddle tank or rear tank which feeds a reservior canister that acts as a fuel bowl on a carb allowing the high pressure fuel pump on the frame to always have fuel even when cornering. This is why installing a high pressure pump in the tank of a 85-86 truck like I will be doing will not be perfect as there is no baffle to prevent fuel slosh from resulting in your pump picking up air when you get around 1/4 tank. This is why I personally will be having my new tank cut open to have a baffle welded in to prevent this from happening. I could run the same reservior as the OE systems used but I dont like the thought of mounting a fuel pump on the frame rail. They are noisy, they get hot, and they dont last long. Only benefit of them is they are easy to replace when they fail vs the in tank pump that requires the tank to be dropped. Link to comment Share on other sites More sharing options...
Tyler Posted January 6, 2021 Author Share Posted January 6, 2021 Ok on PC now What do they do on the FI trucks with dual tanks from the factory? I think the tank valve is switched by the fuel PSI IIRC and this also changes the gauge. I just don't know what that PSI is but why not do that set up on the truck? So you want to get everything for the rear tank like I think you said you got. Tank, straps, the cross member just in front of the tank the straps go to. As for the wiring. On my truck (81 F100) the dual tank wiring is all part of the main & frame harness. My parts truck was also a 81 F100 so it was just swap harnesses and I was good to go. Now I think you are using a newer dual tank harness in your truck so I don't know what you will run in to or have to make work. I think to go through all the work to have a level reading on the rear tank and have that pump transfer gas to the from is a lot of work. If me and I could not get both tanks to work like the factory did I would set up the rear 19 gal. as the main and the 16 gal. as the back up and transfer it to the rear. On the fill tube you are going to fill through the wheel opening? How much road dirt is going to be kicked up on it? Did you get all that from the parts truck? I like the clean factory look and why I molded the rear filler door into the fender. If you have a 2nd door assy. you could have a shop or you mount it in your bed side. I know not a lot of help here sorry. If there is something I might be able to shed more light on ask and hope I have the answer. Dave ---- That was a one of the many reasons why I decided to not attempt a rear tank on my truck. I didnt like the idea of mounting another door on the fiberglass fender it would be too hard to revert back to OE if for some reason I decided to restore back to factory new condition some day. I also didnt like the idea of having a filler through the wood in the bed. I figured my choices were to stick with the OE 16 gallon saddle tank and mount a jerry can carrier on a roll bar if I install one or while the tank is at the local truck shop to have the top cut open so a baffle could be welded in take and inquire with them about chopping the forward nose of the tank off and adding about 3" worth of metal to length the tank forward. This can be done on mine as Im not 4x4 and 3" of length added based off the heigth should be good for a easy 5 gallons of fuel. In theory I should see a 21 gallon saddle tank that would retain the short wheelbase mounting pattern. I just dont know if this would stress the mounting straps doing this like wise I dont know if the extra 5 gallons would be enough to offset the truck and induce a lean in the truck with a full tank. So for me personally I am still unsure what I will do till I am at that point of fuel injection install. As far as the OE setup goes, you have a lift pump in each tank with your high pressure pump on the frame rail. The way I understand it is the switching valve switches feed and return from each low pressure lift pump for saddle tank or rear tank which feeds a reservior canister that acts as a fuel bowl on a carb allowing the high pressure fuel pump on the frame to always have fuel even when cornering. This is why installing a high pressure pump in the tank of a 85-86 truck like I will be doing will not be perfect as there is no baffle to prevent fuel slosh from resulting in your pump picking up air when you get around 1/4 tank. This is why I personally will be having my new tank cut open to have a baffle welded in to prevent this from happening. I could run the same reservior as the OE systems used but I dont like the thought of mounting a fuel pump on the frame rail. They are noisy, they get hot, and they dont last long. Only benefit of them is they are easy to replace when they fail vs the in tank pump that requires the tank to be dropped. I definitely understand the baffle concern when cornering. I ended up putting a piece of Holley Hydramat in my tank, attached to the retro-fit in-tank pump. The matting I purchased was not nearly as large as I wanted but there was a $450 price difference between the piece I bought and the one that "should" have gone in my tank to prevent fuel starvation down to the last drop. Also, I would have needed to create my own adapter at the pump suction connection to make the larger piece work and I didn't feel like I could do that given the way the suction of the Holley pump is designed. The tech rep also couldn't help me much, and these guys have the best customer service that I've experienced on the phone. It's like they care about what you are trying to do. Seriously. The optimistic side of having the hydramat in there is that the fuel return line dumps right on top of it and as long as that material has some contact with fuel, it won't let your pump lose suction. Apparently...we'll see, I guess. If you end up going with a HP fuel pump on the rail and keep your original tank, or use a non Holley drop in fuel pump with a threaded fitting on the suction, I would seriously look into the Hydramat if you'll be doing any cornering or steep angles at less than 1/4 tank. As for now, I'm going to continue to carry extra fuel with me and save this project for the future. I do like the idea of getting rid of the saddle tank all together and just running a single, slightly larger rear tank for balance of weight purposes but that could just be the 22 years of submarines, LOL. Link to comment Share on other sites More sharing options...
FuzzFace2 Posted January 7, 2021 Share Posted January 7, 2021 I definitely understand the baffle concern when cornering. I ended up putting a piece of Holley Hydramat in my tank, attached to the retro-fit in-tank pump. The matting I purchased was not nearly as large as I wanted but there was a $450 price difference between the piece I bought and the one that "should" have gone in my tank to prevent fuel starvation down to the last drop. Also, I would have needed to create my own adapter at the pump suction connection to make the larger piece work and I didn't feel like I could do that given the way the suction of the Holley pump is designed. The tech rep also couldn't help me much, and these guys have the best customer service that I've experienced on the phone. It's like they care about what you are trying to do. Seriously. The optimistic side of having the hydramat in there is that the fuel return line dumps right on top of it and as long as that material has some contact with fuel, it won't let your pump lose suction. Apparently...we'll see, I guess. If you end up going with a HP fuel pump on the rail and keep your original tank, or use a non Holley drop in fuel pump with a threaded fitting on the suction, I would seriously look into the Hydramat if you'll be doing any cornering or steep angles at less than 1/4 tank. As for now, I'm going to continue to carry extra fuel with me and save this project for the future. I do like the idea of getting rid of the saddle tank all together and just running a single, slightly larger rear tank for balance of weight purposes but that could just be the 22 years of submarines, LOL. Rusty, another factory stock fender in storage would take care of the rear door if you wanted to go back to stock. I also think once you have the larger rear tank with the smaller front one you will never go back to just 1 small tank. Also if I under stand you right on the factory EFI dual tanks the tanks have a low PSI pump and that is what changes the what tanks is used and the gauge as it is done in that assy. So why cant that be used and a high psi pump on the frame, again like factory, to run the after market EFI? Dose the factory high PSI not put out enough to run the after market EFI? Dose the after market EFI have a frame pump to use then you could use the low PSI pumps. You know what they say ... If there's a will there's a way I would go for either the factory 19 gal rear tank or any of the larger and not use the 16 gal side tank. If you have a flare side and need a rear tank door it has to be from a flare side as the style side door is different size and shape and will not fit the fender right. I would just move the front door to the rear and the part you cut from the rear just glass it in to the hole up front. If you have a style side it would be easy to come up with one from the junk yard and weld it in place on your bed. Just my .02 Dave ---- Link to comment Share on other sites More sharing options...
Rusty_S85 Posted January 7, 2021 Share Posted January 7, 2021 I definitely understand the baffle concern when cornering. I ended up putting a piece of Holley Hydramat in my tank, attached to the retro-fit in-tank pump. The matting I purchased was not nearly as large as I wanted but there was a $450 price difference between the piece I bought and the one that "should" have gone in my tank to prevent fuel starvation down to the last drop. Also, I would have needed to create my own adapter at the pump suction connection to make the larger piece work and I didn't feel like I could do that given the way the suction of the Holley pump is designed. The tech rep also couldn't help me much, and these guys have the best customer service that I've experienced on the phone. It's like they care about what you are trying to do. Seriously. The optimistic side of having the hydramat in there is that the fuel return line dumps right on top of it and as long as that material has some contact with fuel, it won't let your pump lose suction. Apparently...we'll see, I guess. If you end up going with a HP fuel pump on the rail and keep your original tank, or use a non Holley drop in fuel pump with a threaded fitting on the suction, I would seriously look into the Hydramat if you'll be doing any cornering or steep angles at less than 1/4 tank. As for now, I'm going to continue to carry extra fuel with me and save this project for the future. I do like the idea of getting rid of the saddle tank all together and just running a single, slightly larger rear tank for balance of weight purposes but that could just be the 22 years of submarines, LOL. On mine I will be using the 16-111 Hydramat which is a 15" x 3" mat with a 11mm fitting with a 6 pin locking position and I am looking at a GSS342BX Walbro Electric pump that is 67 GPH/255LPH which is recommended volume by Holley and it has a 11mm inlet for $90. So my idea is to use the Hydramat in conjunction with a baffle to get the most and help prevent aeriation of fuel. I actually have a parts list of everything I am looking at doing and for the EFI itself the following is what I either already have bought and got put up or is to be bought. x1 : 5/16" to -6AN quick disconnect x3 : 3/8" to -6AN quick disconnect x1 : 3/8" to -6AN male quick disconnect x6 : 3/8" to -6AN Vaporguard Hosebarb x1 : 00-04 Corvette fuel filter with built in 50psi regulator x1 : Holley throttle lever extentsion x1 : '85-'86 16.5 gallon saddle tank x1 : '85-'86 saddle tank sending unit x1 : '85-'86 fuel pump connector x1 : Walbro Electric fuel pump 67GPH/255LPH with 11mm inlet x1 : 3"x15" Hydramat with 11mm outlet One of the things I am seriously contemplating about changing is picking up a stainless steel OE fuel supply line from Inline Tube its for a long wheel base and its in 3/8" but could cut it down to fit my application then can AN flare the hardline at the engine to use an AN hose flex joint between engine and frame. Then I can flare the hardline into a male quick disconnect to fit the fuel filter/regulator then run rubber lines from the filter to the sending unit. This would change my parts list some and it would change the amount of work Id have to do but I feel would be worth it as I feel the hardline would not just look better but it would provide a longer period of time with no issues. Link to comment Share on other sites More sharing options...
Rusty_S85 Posted January 7, 2021 Share Posted January 7, 2021 Rusty, another factory stock fender in storage would take care of the rear door if you wanted to go back to stock. I also think once you have the larger rear tank with the smaller front one you will never go back to just 1 small tank. Also if I under stand you right on the factory EFI dual tanks the tanks have a low PSI pump and that is what changes the what tanks is used and the gauge as it is done in that assy. So why cant that be used and a high psi pump on the frame, again like factory, to run the after market EFI? Dose the factory high PSI not put out enough to run the after market EFI? Dose the after market EFI have a frame pump to use then you could use the low PSI pumps. You know what they say ... If there's a will there's a way I would go for either the factory 19 gal rear tank or any of the larger and not use the 16 gal side tank. If you have a flare side and need a rear tank door it has to be from a flare side as the style side door is different size and shape and will not fit the fender right. I would just move the front door to the rear and the part you cut from the rear just glass it in to the hole up front. If you have a style side it would be easy to come up with one from the junk yard and weld it in place on your bed. Just my .02 Dave ---- If I could source a spare fender I would consider doing it that is for sure. As far as swapping the in tank pumps from low pressure to high pressure pumps it can be done but I dont know about Ford but I know the GMC I did this on the switching valve was marked 50 PSI max which is the regulated pressure of the sniper system. That GMC wired up properly would not switch tanks while the engine was running. You have to cycle the key to get the valve to switch, i theorize it has to do with the fuel pressure on the switching valve that was locking it in place. I feel this would be the same issue one would have using a Ford dual tank setup and simply swapping the in tank lift pumps out for high pressure pumps. Holley does offer a frame mounted electric pump one could use with a OE factory lift pump dual tank setup but those pumps dont seem to last long, Ive seen lots of people complain about how noisy their holley pumps are even their in tank holley retrofit pumps then they complain about the pumps failing not long after. Why I am avoiding using one of holleys pumps and looking at a walbro pump that I can get for less money. If I could find another fender to fabricate a second door for a rear tank what I probably will do is put a large pump in the rear tank and have the outlet of that pump connect to the saddle tank and use my saddle tank as my feed tank for my sniper and use the rear as a bed mounted auxiliary tank, those use gravity to feed fuel into your main tank as you need it but in this case it would be a electric transfer pump you switch on when you need more fuel. Mine is a flareside and I can find the fuel tank doors and pockets and all that, ive came across them before on ebay. Just havent seen the fiberglass fenders before online nor locally. Link to comment Share on other sites More sharing options...
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