Care to speculate on tbi fuel system plumbing?

[Overland]

I'm attempting a minimally invasive installation and would like to leave my fuel tank alone entirely. The idea I have is to install a filter housing on the inlet of a frame mounted pump, and to route the return line to the inlet side of said housing. Most mechanical diesel engines I've been around were plumbed this way for injector pump cooling.

I've been away from here for some time, but I recall discussion of fuel heating through pumping it across the regulator and speculation regarding an inline cooler to remedy the condition. My tank is going to stay behind the seat, and is only plumbed for suction, of course from the top. I think routing to a filter would be quieter in the cab and wouldn't heat the fuel in the tank, if the pump can pull fuel across a filter after lifting it up the pickup tube.

I feel like once primed it should work, but you could fill a warehouse with things I don't know. Please alert me should it seem my logic is not firmly based in reality.

[dave w]

Thoughts, ideas, options, and experiences about remote mounted fuel pump and return fuel locations vary between members.

Frame mounted fuel pumps are OK. In-The-Tank mounted fuel pumps are optimal. Routing the return fuel to the bottom of the fuel tank is optimal. . . just like factory.:thumbsup:

[ralmo94]

Some fords use frame mounted pumps. Just make sure it's lower than the tank and not mounted were it would snag anything. I personally don't see fuel heat being an issue with a return line you are not very likely to vapor lock. That's my $0.02

[Overland]

Ford to my knowledge utilized a fame mounted booster pump to supplement the in tank pump in the 80s, where a truck with two tanks had three pumps. In my admittedly minimal experience there, the booster won't work on its own, or at least not sufficiently. That is, pulling fuel through a dead pump in the tank.

I'm considering something like the Carter P5001 suggested on the swap info page here. I'm not a fan of remote pumps, but with the tank in the cab, I'd rather not listen to it. I know someone likely sells a bolt in solution ready for an in tank configuration, but I'm also operating on a minimal budget and would prefer to maintain any original parts I can.

I have a picture in my mind that looks very clean, but that doesn't matter much if it doesn't work. I figure this is the best place to hear of other's trials and errors.

[Overland]

This is in a 62 C10 if it assists with your visualization

[ralmo94]

Ford to my knowledge utilized a fame mounted booster pump to supplement the in tank pump in the 80s, where a truck with two tanks had three pumps. In my admittedly minimal experience there, the booster won't work on its own, or at least not sufficiently. That is, pulling fuel through a dead pump in the tank.

I'm considering something like the Carter P5001 suggested on the swap info page here. I'm not a fan of remote pumps, but with the tank in the cab, I'd rather not listen to it.

I was thinking of the van pumps that you can buy one at the parts store for about $60 usually in stock, pretty sure it's for single tank configuration and has barbed fittings on it. I used on on my motorhome to get it parked when the in tank pump died. These are made for 90 psi 40 gal per min and economical. I don't think you would have a problem with one using the cab fuel tank, as gravity would keep the pump primed plenty easy enough.

[Overland]

Cheaper than the Carter for sure, similar in appearance, like an in tank pump with barbs. The Carter has threaded ends making barbs optional. I'm imagining a soft line between the hard line where it exits the floor and the filter housing, then hard line to the pump, and preferably utilizing the original tbi fuel hoses from there.

Would the fact that the fuel tank utilizes a pickup tube from the top cause difficulty priming at low fuel levels?

[dave w]

Perhaps the attached FITech instructions will be helpful.

[Six_Shooter]

I see fuel pressure regulation issues if you are T-ing the return line back into the fuel pump feed. This IS a restriction and restrictions, even ones that could potentially flow both into and out of the tank will cause issues. Even if your pressure seems to be what it's supposed to be, I could potentially see a problem with reliable fuel supply due to the feed from the tank needing to flow both into and out of the tank continuously.

It's not difficult to add a return line to a sender unit. A drill, some hard line and someway to seal it up, which can be something like JBweld, or epoxy will create a trouble free system that you won't have to second guess.

[Fast355]

I had one of those Ford frame mounted pumps when I first converted my 83 G20 to TBI. It was garbage and loud. It lived a short life without the boost pump supplying fuel to its inlet. I switched it out for a TBI van tank and fuel lines. Used a Vortec fuel pump on the TBI sending unit.

[Overland]

I think it comes down to the suction side. Every high pressure pump I've ever seen had the return ported back into the pump inlet. The difference is pressurized or gravity supply. There's always fluid at the inlet. If the tank had a bung in the bottom, I think it would be okay.

Cavitation will kill it in short order for sure. Also, I think I'd rather pay more for a low pressure pump than try to make do with the excess volume, and probable noise, of a higher output model.

My primary goals here are reliability and economy. It's getting single exhaust. Totally stock Suburban engine, zero illusions of high performance.

Also not changing the location of the tank. I know it's popular, but I wouldn't have a filler in the bed even if there was room underneath for a fuel tank.

[Overland]

I'm surprised to find that a drop in sending unit for the original tank is not common, nor does it even appear to be available in the aftermarket. I didn't see one tank or sender set up for fuel injection to go behind the seat. I guess this is why the average guy puts a fuel cell under the bed in place of the spare. The market caters heavily to that.

[dave w]

1960 - 1966 Chevy Pickup - Fuel Sending Unit: https://www.tanksinc.com/index.cfm/page/ptype=product/product_id=712/category_id=64/mode=prod/prd712.htm

[Overland]

Lots of those, nothing equipped with a pump or accommodation for extra wires and return. I'd modify the original before buying new, especially if I need to modify the new one anyway.

I didn't look long, but I'm honestly surprised it didn't show up on the usual sites alongside original equipment style.

Looks like I can get a replacement Suburban pump for ten dollars on rockauto to use for.mock up and testing, then tank flushing.

[dave w]

A return line similar to the picture below is both low cost and the optimal return line solution.
Picture is snippet from the .pdf previously posted. . . (possibly the picture is worth 1000 words?)

18547

[Six_Shooter]

I think it comes down to the suction side. Every high pressure pump I've ever seen had the return ported back into the pump inlet. The difference is pressurized or gravity supply. There's always fluid at the inlet. If the tank had a bung in the bottom, I think it would be okay.

Cavitation will kill it in short order for sure. Also, I think I'd rather pay more for a low pressure pump than try to make do with the excess volume, and probable noise, of a higher output model.

My primary goals here are reliability and economy. It's getting single exhaust. Totally stock Suburban engine, zero illusions of high performance.

Also not changing the location of the tank. I know it's popular, but I wouldn't have a filler in the bed even if there was room underneath for a fuel tank.

I've never seen a return line plumbed back into a fuel pump inlet. Every vehicle I've worked on, or looked at, and it's many, many vehicles, has the return line back into the tank itself, so there is little to no restriction on the return line, allowing the bypass regulator to perform it's job easily.

[NomakeWan]

Perhaps he meant near the pump inlet? I know on my Corvette, the return line is plumbed to a metal line that exits right next to the filter sock on the pump inlet. Yes, it's technically exiting into the tank, but it's also exiting right next to the pump inlet.

[tayto]

if you're tank doesnt have a sump/anti-slosh it's a waste of time IMO regardless if in tank or out of tank. most that run an external pump seem to run without an intake sump. having to keep the tank always above 1/2 way or you'll potentially have issues turning corners, hard acceleration or steep inclines is not for me but maybe you can live with it. i also do not like to listen to pump whine, but again maybe you can live with this too. definitely run a return line, your pump will be happier internal or external. do you have fab skills or know someone that does? i have bought a new tank added a sump and internal pump on efi conversions before.

[1project2many]

I have worked on diesels with the return line connected to the pump inlet. This method was common in the 50's and '60s for sure, but not so common today. I believe my '80s Mercedes diesel OM617 plumbed the return line to the high pressure pump inlet as well.

Mercruiser EFI engines in the late '90s used a "fuel module" which contained a reservoir, a needle valve connected to a float, and a high pressure pump. The reservoir was filled by a traditional mechanical pump on the block. I used one of these systems when I installed a mercruiser manifold and ecm in my '67 Chevelle. It worked well for me. Mercruiser decided the system needed improvement though and developed "fuel coolers" to be used in later systems. Internet folks predicted that I might have trouble if I ever cruised through the southwestern states. I never had the opportunity to try.
http://home.metrocast.net/~shannen/pics/Chvlngn2.jpg


I have been posting for years about my experience adding a return line and electric pump to a tank never designed for such things. I was young when I did this, and the internet was literally a phone call to another town away so there was little to guide me. Long story short, without baffles and vapor handling the system was not as successful as I'd hoped. Without a reservoir to hold fuel, the engine stumbled whenever fuel level fell below pump pickup level. Without vapor handling, the tank built pressure and fuel vapor escaped as fuel warmed up. I added a fuel cooler on the return line and a baffle in the tank for some improvement but today I would do it differently. I would build / buy / scrounge a remote fuel reservoir similar in principal to the Mercruiser unit. For reference, this is in a '57 Chevy truck, also with an in-cab tank, which I still own.

Edelbrock makes a system similar to the Mercruiser module. https://www.edelbrock.com/adjustable-universal-efi-sump-fuel-tank-assembly-67gph-35-90-psi-36032.html It's spendy. There are companies that make small, frame mounted remote tanks which contain the high pressure pump and act as a reservoir. I'm not having good luck searching now but they are out there. Recently I have found that you can buy a weld-in retaining ring to use the Dodge / GM remote "fuel bucket" system. The fuel bucket system really solved a bunch of issues for GM by providing a single point for pump, sender, return, and baffling within the tank. There is a stainless version found here: https://rickstanks.com/product/weld-in/?v=47e5dceea252 Searching can locate other versions, possibly less expensive. Will it fit in the '62 tank?? Possibly?

I would not place a filter on the inlet side of the pump. I have had issues with this in the past. Most electric fuel pumps are not good at creating suction. Spinny pumps generally work because the pressure of the fuel around the pump forces fuel into the pump body even as the vanes are forcing fuel out to the engine. An electric diaphragm pump would likely have better luck pulling fuel through a filter and could be connected to a remote reservoir with a float and high pressure pump.

In talking this through, your original idea might be very doable if you use a diaphragm pump to supply low pressure fuel to the Ford inline pump previously mentioned and use a 99+ Corvette fuel filter with return and pressure regulator built in connected between the low and high pressure pumps. The only concern I would have would be how the system would perform at low fuel levels. Without a way to eliminate fuel slosh, or to supply a temporary supply of fuel while the pickup tube is exposed in the tank, you're risking engine stumble.

[Overland]

Y'all are golden. I'm fabricating everything which is not original or factory equipment. I'm not bad at making my own parts and tools as need be and have access to a machine shop.

Yes, my return line idea went not to the pump inlet but to the filter housing on said inlet. I have my own reservations regarding using a spinny pump to pull fuel through a filter but this was, I supposed, a reservoir so to speak. I'm thinking spin on filter base with two inlets.and two outlets, one outlet plugged, within six or eight inches of the pump.

This becomes too convoluted for me when adding another pump style to support the other. Yes, I can do it, but that doesn't mean I should.

To clarify, I've never seen a gas engine plumbed this way, of which I've been into countless, but most every diesel ever made nearly up to the common rail era where I look away. Pressure washers are plumbed this way though with an unloading control in place of a regulator. They circulate directly back into the inlet until loaded. They also have pressurized or gravity feed.

Rather than drilling the sending unit, why not drill the tank instead for gravity feed.to the pump? Then I could use the pickup tube for a return line.

[Overland]

Sorry, by high pressure I mean like 2k+ psi.

[Overland]

if you're tank doesnt have a sump/anti-slosh it's a waste of time IMO regardless if in tank or out of tank. most that run an external pump seem to run without an intake sump. having to keep the tank always above 1/2 way or you'll potentially have issues turning corners, hard acceleration or steep inclines is not for me but maybe you can live with it. i also do not like to listen to pump whine, but again maybe you can live with this too. definitely run a return line, your pump will be happier internal or external. do you have fab skills or know someone that does? i have bought a new tank added a sump and internal pump on efi conversions before.

I can see making a pump mount on the sender, but I'm working with maybe a three inch hole at the top of a flat tank turned sideways. I like to think I'm not as dumb as I look, but baffling in there has me baffled.

[357L98]

On pickup trucks with the tank in cab, I connect the return from the regulator to the filler vent with a T connector.

[dave w]

On pickup trucks with the tank in cab, I connect the return from the regulator to the filler vent with a T connector.

Would this type of return promote vapors in the fuel tank. I ask because it seems fuel draining into the air space of a fuel tank would create unwanted vapors.

[357L98]

It might contribute some, but with all that gas sloshing around the tank when you're driving, I don't think it would make much difference. The return line doesn't generate a spray of fuel, just a flow.

[AzDon]

I think the scheme you describe will fail to maintain the siphon effect on the tank supply line because you will be blowing pressurized fuel into your intake line and even if the loop was tight enough to maintain the siphon, you would be continually re-introducing pre-heated fuel instead of fresh cool fuel from the tank.....Have you considered drilling and tapping a hole in the top side of the filler neck (inside the cab) or sending unit plate and screwing in a return line fitting?

[357L98]

I think the scheme you describe will fail to maintain the siphon effect on the tank supply line because you will be blowing pressurized fuel into your intake line and even if the loop was tight enough to maintain the siphon, you would be continually re-introducing pre-heated fuel instead of fresh cool fuel from the tank.....Have you considered drilling and tapping a hole in the top side of the filler neck (inside the cab) or sending unit plate and screwing in a return line fitting?

Don, I checked out your page on the van project, very cool. I also tried connecting the return line back to the fuel pump inlet one time, and it did not work very well. As you thought, the fuel pump got hot and noisy after a short run time. I routed the return back to the filler vent and had no more problem.

[1project2many]

To clarify, I've never seen a gas engine plumbed this way, of which I've been into countless,

Rochester EFI. Low pressure pump supplies fuel to reservoir containing high pressure pump plus float and needle valve. Unused high pressure fuel is returned to reservoir.
http://www.oldcarmanualproject.com/manuals/Chevy/53-75Corvette/Rochester%20Fuel%20Injection.pdf
I believe the '59 - '64 Benz petrol mechanical injection systems were similar.

Here's a picture of the fuel system design in the early Bendix electrojection system. Pump in tank, regulator mid-system, return line directed to the tank.
https://www.allpar.com/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=192 0,fit=scale-down/https://www.allpar.com/attachments/air-intake-jpg.42849/


I can see making a pump mount on the sender, but I'm working with maybe a three inch hole at the top of a flat tank turned sideways. I like to think I'm not as dumb as I look, but baffling in there has me baffled.

My solution was to leave the fuel level sender intact and to build a pump hanger beside it. After removing the fuel supply line from the original sender I brazed the hole shot. The '57 tank has a seam through the center, so I used a hole saw to cut two overlapping holes next to the fuel level sensor. The baffle I created is a simple open top box that's attached to the pump sender, sitting under the pump filter sock. I drilled holes in the lower corners of the box so fuel could flow in when the tank level is low. I still try to maintain fuel above 1/4 tank because this isn't perfect. But this reduced stalling while cornering when fuel was lower than 1/2 tank.

Fun reading:
https://67-72chevytrucks.com/vboard/showthread.php?t=767225

http://67-72chevytrucks.com/vboard/showthread.php?t=593796&highlight=67-72+efi+in+cab+tan