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In Tank EFI Fuel Pump Conversion

Written by Gregs78cam

Some background first. One issue I found when I swapped the old carbed 350 out for a TBI 350, was while driving my truck, I noticed that after using about 13 gallons out of a 20 gallon tank, if I stopped too hard the fuel would slosh forward away from the pump pick-up and the truck would stall. This got annoying but served as a low fuel warning, which was helpful because my fuel level gauge wasn't working at the time.

After that swap, I was in the process of planning the Dual TBI swap on the Camaro, and decided to integrate this mod. One thing that I had read many times was that when doing an EFI upgrade to a second generation Camaro, most guys that just stuck the EFI pump in the stock tank would constantly have to keep the tank more than a ¼ full or it would stall while cornering. Some have added elaborate baffles, some add sumps to the tank, but I wanted to do some thing better. Something like the factory would have done today, using today's technology.

The results? After doing the swap on the Camaro, which included this mod, I was able to drive the car to the gas station (which is up a pretty good hill and has both right and left hand turns going up this hill), with the gauge reading empty the entire way, (about 2 gallons in a 19 gallon tank). So I know this pump works very well.

I can say without a doubt that this pump will support up to 400hp at TBI pressures (~13psi), but may only support up to around 200hp at MPFI pressure (~43+psi). However if you are running an MPFI setup, and expect to make substantial power, there is the option of going to and getting their FPA-016, this is a pump that would support 400hp at up to 58psi. Or for more power get the FPA-001 capable of 600hp at 58psi. Now I have not tried either of these options, so I can't say definitively if they will drop right in the housing, but they look like they should and will keep the siphon jet functional. If I do go MultiPort this winter one of these Racetronix pumps will be what I try to use.

Now for the pump.
In the mid 90's GM started putting these fuel modules in vehicles instead of putting the square baffles on the bottom of the tanks. These work by using the pressure from the pump to operate a small siphon jet that keeps the bucket full regardless of the level in the tank. The return from the engine drops right back into the bucket via one of the 1/4” stainless tubes that support the bucket. These pumps do normally run at MPFI pressures, but so far the one in the Camaro feeds two 350TBIs just fine at 13psi. I currently have this pump installed and running in my '74 Chevy truck with a single 350 TBI and have had no problems with too much or lack of fuel flow.

Start with two fuel pump modules, they don't have to be identical, as there are a couple of different styles that incorporate the bucket and siphon jet. I chose identical ones so I would have spare parts. These came from '95-'98 Pontiac Sunfire. There are other styles but they all work about the same and most of the steps here would work for them as well. Basically I will be extending the 1/4” stainless tubes that hold the bucket in place. If your tank is similar in height to the tank you get this module out of, you probably won't need to do any modifications to the module.

[B]Just remember this pump is capable of much higher pressure than the factory TBI pump. Always use EFI rated Fuel hose, and clamps[/B]. I am not responsible for any damages caused by following these instructions.


This is what they look like. Also be sure to get the flange from the tank. I use a screwdriver to punch into the tank and tin snips to cut the piece oversize so I can trim to a nice edge as shown here.

This is the stock shape of the float arm. This sender happened to be a 0-90 ohm one so it should work with the older gauges.

I bent this float arm to be slightly more accurate, which won't be a whole lot since I am adding quite a bit of height to the unit. It is not hard to put a different wire into this sender and make it read accurately for any tank. The wire is 0.128” so 1/8” stainless TIG rod would work great. Near the end you will see how I made the arm longer for better accuracy. In this pic you can also see I have removed the black cushion/spacer from the bottom of the module. Once you do this the sender slides right off.

I thought I would throw this tip in at this point because soon you may be needing to remove the wires from the connector on the bottom of the lid. What I have found is that 0.025” MIG wire works great for removing pins from the metri-pack 150 connectors. Simply insert the wire into the small notch in each socket, while pushing in on the insulated wire from the other side. Then just pull the insulated wire out of the plug.

Now push in the two tabs at the top of the bucket and remove the pump from the bucket. You kind of have to manhandle the thing to get the inner screen out, but don't worry, the small line to the siphon jet is very durable. You will need to do this for both units eventually.

On the DONOR unit you will be cutting the three stainless tubes at the top where they meet the lid. I used this clip I had laying around to hold the spring back.

So what you end up is this.

And after careful measuring to figure out how much added height you need, you will cut the other unit to look like this. The module was right at 10” in the extended position. My tank is 11” deep, So to get 11” compressed I need 12” extended. That is 2” longer that stock. So 2” minus the 5/16” that the couplers add between the tubes that left me with 1-11/16” of tube that I need to leave on the module that is going into the tank.

On to assembly. Put a long tube through the pump holder and slide a spring over it. Then using a clamp/vicegrip to hold the spring back install a 1/4” tube coupler. Do the other two tubes and this part is done.

One issue I ran into with this module that I didn't have with the Camaro was due to the amount of height I was adding, the fuel pump wanted to pull up out of the plastic holder. So to fix this I drilled a small hole through one the locating blocks just above where the rubber lug on the pump sleeve sits, and I installed a stainless pin to hold the pump down. There is no need to bend the other end because as this slides down into the bucket, the wall of the bucket will hold the pin in place.

On the Camaro I only added about 1” in overall height so the wires to the pump and sending unit were long enough. However on this one I had to extend them. Another good reason to get two complete assemblies. Easier to make one splice per wire than to make two.

And the finished product, with 2” of compression available.

Part 2, Tank modification.

This is the new flange that will hold the module and the o-ring that seals the unit. Trimmed to size and hammered flat. To mount the flange to the tank, I like to use a gasket sandwiched between the tank and the flange. On the Camaro I had a friend plasma cut a stainless ring that went inside the tank to add some rigidity and used riv-nut inserts to hold the ring to the tank and to provide a thread for the 12 bolts that squeeze the gasket.

I made a drawing with AutoCad to help with placement of the 18 bolts holding this flange to the tank. This was later changed 24 bolts.

Here is the top of the fuel tank that I am adding this pump to. I used a chisel to remove the old lock ring retainer from around the hole.

Here I cut along the marked line in the previous pic and hammered the entire area flat to remove the drain groove from the area where the gasket will sit.

This is the stainless ring that I had plasma cut for this tank. It was a bit of work getting this ring to sit flat because the heat from the plasma cutter had turned it into sort of a belleville washer. So with some heat to help it relax, and some hammering around the outer edge to stretch it a bit, it sat flat enough to split one side in order to spiral it into the tank. At this point I have also drilled all of the holes out to the required size for the riv-nuts. This ring could be replaced with appropriately sized washers to reinforce the edge and take up the difference between the tank thickness and the minimum thickness the riv-nuts can be mounted in.

Here are the riv-nuts installed with a small amount of loc-tite under the head to help with sealing. Also the new flange with 9/64” holes drilled to the same layout of the tank.

Here you see the tank, flange, and gasket cut from 3/16” rubber. To make nice neat bolt holes in the gasket, I used one of the stainless tubes that were left over and filed the end, stuck in the cordless drill and cut the hole easily.


Here is the new longer float arm made form 1/8” brass brazing rod to make the sender more accurate.

And here is the entire unit installed with stainless screws and loc-tite to ensure no leaks.

With these modules the hard plastic hoses are metric, however, 3/8” on the feed line, and 5/16” on the return and vent lines works just fine after removing the plastic lines. I hope this helps for your next EFI conversion.


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