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.Originally Posted by Overland
The man who says something is impossible, is usually interrupted by the man doing it.
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.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
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 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.
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...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.
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.
Last edited by Overland; 10-20-2022 at 06:27 PM. Reason: A word
62 C10 Long Bed Step Side, 5.7/4L60E, 16196395 swap in progress
Sorry, by high pressure I mean like 2k+ psi.
62 C10 Long Bed Step Side, 5.7/4L60E, 16196395 swap in progress
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.
62 C10 Long Bed Step Side, 5.7/4L60E, 16196395 swap in progress
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.
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.
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.
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.To clarify, I've never seen a gas engine plumbed this way, of which I've been into countless,
http://www.oldcarmanualproject.com/m...0Injection.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.
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.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.
Fun reading:
https://67-72chevytrucks.com/vboard/...d.php?t=767225
http://67-72chevytrucks.com/vboard/s...efi+in+cab+tan
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