EFI with factory Fuel Tank??

[lolife99]

subscribing to this one,...

[stevencvn72]

Originally Posted by DirtyLarry

Here is my ’72 C20 with a TBI 350 sending unit with a factory return line. With the low fuel pressure TBI runs I haven’t had any issues running the return fuel through the little 5/16 line.

However, I wouldn’t recommend the little 5/16 return line on a higher pressure TPI system that runs in the 40 psi range or the later LS engines run up as high as 62 psi. The 8.1L in my ’78 K10 did not like the small 5/16 return line through the original fuel tank switch valve as it was way too restrictive causing the fuel pressure to run extremely high….like a 100 psi at idle! I ended up having to completely redesign the fuel system on that truck to create a larger return line and still have dual fuel tanks.

Again, this will work for low pressure TBI but not for higher pressure multiport.

Thanks for the pic. I might have ordered the '72 sender had I not seen the size of the return. Pretty sure that won't work with TPI. It'll just be easier to make my own return out of a '67 unit. I don't have much trouble with the pump I have now being too loud. I can't tell who makes it because it's covered in silicone rubber. Maybe that's an option for some of you. The little bit I have driven the truck, it seemed like it was starving for fuel, but that could be a timing problem. It's backfiring in the intake right now, which I'm guessing is a timing issue, or a stuck intake valve. Not really on the same subject of this thread, just kinda where I'm at with the PU right now.

[harlyworkr]

I used a 72 tank with the tank vent behind the seat for my TPI setup, I mounted the pump under the passenger door frame rail and put a vented cop on the tank, so far, no issues although the injectors are noisier than a blown engine bearing.

[Andy4639]

I have a Iroc TPI in my 71 since 87.



I tried using the stock tank and it just didn't seat well with me having that loud 12 volt 25 amp pump sitting behind me in that tank full of gas. I had problems the whole time with gas sloshing around at anything less than 3/4 full. I ran a in tank pump, and electric pump's don't like sucking air. I had replaced them a few times when I decided to go with a baffeled tank. Do yourself a favor and buy a tank for EFI. Baffeled tanks are the only way to go.

[short-t]

Originally Posted by Andy4639

I have a Iroc TPI in my 71 since 87.



I tried using the stock tank and it just didn't seat well with me having that loud 12 volt 25 amp pump sitting behind me in that tank full of gas. I had problems the whole time with gas sloshing around at anything less than 3/4 full. I ran a in tank pump, and electric pump's don't like sucking air. I had replaced them a few times when I decided to go with a baffeled tank. Do yourself a favor and buy a tank for EFI. Baffeled tanks are the only way to go.

I too have been thinking of using the stock tank for my lsx swap. I was going to mount a walbro inline pump on the frame but I don't think they are self priming and would need a lift pump to support the walbro. If I do this would the lift pump become a restriction during high fuel flow conditions?

Anyhow I've been looking at more pumps and come across this walbro unit that can go inside the tank with a filter screen on the inlet side. I thought that this is the one but I didn't think about how loud this thing is going to be humming inside the tank behind the seat? Does anyone no how loud these walbro pumps are?

Here is a picture of what I am talking about.

[IMG][/IMG]

[Andy4639]

The pump isn't that bad with a full tank. When it get's around a half tank you better have a good radio to over come the noise.

[short-t]

Originally Posted by Andy4639

The pump isn't that bad with a full tank. When it get's around a half tank you better have a good radio to over come the noise.

Did you use the same pump as I put up in the picture?

[Andy4639]

I don't know if it's the same but it looks the same. I got mine at O-Riley's auto parts for a TPI camaro.

[Lugnut64052]

A lot of them look exactly the same but they come in different pressures. You can mistakenly install a TBI pump in a TPI vehicle (or visa-versa) and not know it until you start up (I've done this before). The pump picture is what a common GM in-tank pump looks like. Just make sure you get the right pressure.

As for noise, they all do make some noise. Cheap pumps tend to be noisier than quality pumps. And they all tend to get a little noisier as they age and begin to die. You can usually hear the pump when the car is running by getting down and putting your ear close to the tank. You'll hear a muted high pitched buzz. Sometimes old or cheap ones are so loud you can clearly hear them standing 10 feet away from the car.

[short-t]

I saw this lsx build thread over at ls1tech
http://www.ls1tech.com/forums/conver...vy-pickup.html

He uses a low pressure (lift pump feeding the walbro pump) all from the stock fuel tank.

[IMG][/IMG]

[stevencvn72]

Originally Posted by short-t

I too have been thinking of using the stock tank for my lsx swap. I was going to mount a walbro inline pump on the frame but I don't think they are self priming and would need a lift pump to support the walbro. If I do this would the lift pump become a restriction during high fuel flow conditions?

Anyhow I've been looking at more pumps and come across this walbro unit that can go inside the tank with a filter screen on the inlet side. I thought that this is the one but I didn't think about how loud this thing is going to be humming inside the tank behind the seat? Does anyone no how loud these walbro pumps are?

Here is a picture of what I am talking about.

[IMG][/IMG]

I'm still working this issue. I'd rather use an in tank pump. Did you end up doing this yet? If so, did you just use the factory opening for the pick up tube? How about the wires? Do you have any pictures of how you ran the wires through the cap? I pretty much have to rebuild the whole fuel system. Started it up today and all the lines are leaking. Looks kinda like a sprinkler!

[structures]

Steve, how did it turn out? What was your final configuration. External walbro pump? I'm looking to keep the factory tank on my 65 with a 07 4.8l and would like to install a walbro 255 inline pump on the frame rail. Also open up a new 3/8" hole in the sending unit plate for a return line.

[stevencvn72]

It's been working out great. I got a '72 sender with the return line in hopes of making it work, but the return was just too small. I pulled it, and put larger stainless line in and ran it down about half the length of the pick-up line. All new lines to the fuel rail and back...(EFI line wasn't cheap) and an in line fuel pressure gauge shows me running between 38 and 45 psi steady. So far no problems! No cavitation, and no leaks. I'll snap some pics if you need, but I'm running a pre pump filter and a post pump filter all mounted to the frame rail on the drivers side. I put a couple drops of oil in the inlet side of the pump and made sure to prime it before letting it run. Necessary...? I dunno, but I figured it couldn't hurt.

[Rodk65]

Here is my set up for TPI. Radiator shop soldered in the 3 threaded bungs on the bottom of the tank. Gravity feed to frame mounted high pressure fuel pump. When I turn hard in a corner or have a low fuel level I never have a problem with fuel starvation. I use the original fuel line from the sending unit as my return.

[structures]

Thanks steve. I like pictures, if it's not too much hassle...


Rod thanks for sharing! I was contemplating using the original line as a return and putting a hole in the bottom. I might just take your pic up to a local radiator shop and see if they can duplicate something similar. I've been a little concerned with putting a centrifugal pump down on the frame and then asking it to pull the fuel up to the top of the tank and back down to the frame rail.

[6772owner]

From my experience, sucking fuel is very hard on the inline pumps, I had mine mounted too high and it burned up pretty fast running anything below half tank. I would recommend either in-tank or something like what Rodk65 did, I think its the only way to have a reliable system. The intank would also be far quieter, my Walboro is pretty loud and it only gets worse when its hot out or lower fuel levels. Just my .02

[structures]

I like the idea of an in tank pump, I'm just a little concerned about the noise. I'm thinking the buzzzzzzzzzzzzzzzzzzzz.... would get annoying after a while.

[eagleuh1]

I mounted a Wallbro 255 on the frame under driver seat, with a prepump canister filter and the after pump corvette filter/regulator and 5/16th return line. The supply line is the stock 3/8 from tank. I used all new hard fuel line and double flare fittings to prevent leaks. Had to drill and J/B weld the return into sender at the dimple. Just make sure you follow the pickup line close with the return, or its hard to get into the tank. So far no problems. This is with a 2005 5.3 in a 68.

[69sixpackbee]

I am running a FAST EZ-EFI with a frame mounted pump drawing from the cab tank and the saddle tank as well. I am using the '72 original sending unit with the return plumbed into the vapor line that is on the unit and extended to the bottom and away from the pickup to lessen the chance of sucking in air bubbles.. My saddle tank has a modified 90-OHM unit from a '75 stepper with the same return arrangement. It is feeding into a Ford van reservoir and changeover valve. No problems whatsoever. I have even run the tank dry (not that you would want to--kills HP pumps!). No cornering/sloshing problem due to the added reservoir. This is where a swirl pot is handy in some cases. Keep the pump below the lowest fuel level and you should have no probs. If you want a quiet in tank pump, go with a low pressure puller pump and feed it into a swirl pot and then go with the high pressure pump from the pot. The low pressure pumps are generally alot quieter but still make some noise.

I want quiet so I live with my setup. You could even fill the swirl pot with the OEM mechanical pump if you don't have alot of hungry horses to feed.

Good luck,
Bud

[AMD6769]

I also had a EFI 5.3 4l80 trans W/ the fuel tank behind the seat it ran good BUT the smell of gas was bad so I sold the truck. And now Im building a other and was considering doing the blazer tank but I have a 4/6 drop and wonder if the tank would be to close to the ground?

[Andy4639]

Some fuel for thought.

First off the return line needs to go all the way down into the tank. This is so it doesn't cause static build up inside the tank when fumes are present. If the truck isn't grounded properly.
Leave the tank as is and build a small tank just big enough to fit the electric fuel sending unit inside it and mount under the truck. Plum all the fuel lines back to it. It will be feed by gravity. Stock tank has no modes done to it.

[wzuke]

Advantage of in tank pumps are that they are not as loud and the pump runs cooler. Throttle body fi would be ok with external pump as they do not require as much pressure as port injection. In tank pumps can benefit from internal baffles or a "sloush" pan so you don't get a lean condition when the gas level is low and you go around a corner. The newer Corvettes do not use a return line - maybe use that pressure regulator and skip the return line.

[stevencvn72]

Here's the pics I promised. Not as nice as RodK65's but it works like a charm. I must admit I've neverhad it below a quarter of a tank yet. You'll see the orange rubber behind the pump. It kept it off the frame and helped with the noise. Like I've said before, the trucks over 40 years old, there's nothing quiet about it and I'm okay with that. And now that I've taken a pic, I realize I need to do something with that power wire....yikes!

[red71cheyenne]

When I first put the TPI in, I ran the stock tank. I just didn't care for the smell of gas. My pump is loud on initial prime too, but after that I never heard it. The fuel sending unit with the returns on it are the same after 71. I just used the same 5/16th line to dump back into the tank. Never had a problem other than the smell. One note though, you need your pump to be no further than 4 feet from the tank. Otherwise it has a tough time getting suction, like you said, they push better than pull. I'm using the same $100 dollar frame mounted pump from Autozone or where ever. After figuring out the 4 foot thing, I've had the same pump for 4 years now.

[70blackfish]

good info!!!!