Carb to Fuel injection conversion?

[jimmer2880]

Originally Posted by rcnjson

.....From a junk yard I would say you could pull this all off an F-150 for $500. IF you go the buy it new route, aftermarket manifold, Ford EFI conversion kit, new fuel system... you are looking at an easy $2500 and that can go up from there depending what you want. FYI the fuel system in my mustang was $2500 (tank, pump, lines, rails). The moral of the story is sky is the limit, how fast do you want to go?

funny - I thought it was... how fast can you afford to go?

[jake]

OK...here is a new twist on the debate. While doing some research on do it yourself carb to efi conversions I came across "Mega Squirt".

http://www.megasquirt.info/

It's an open source, build it yourself, PC programmable ECM that I'm considering using to convert a simple GM TBI system to my boat. So far everything seems to be relatively simple and understandable.

What I'm struggling with is how one would set up the fuel delivery from tank to high pressure pump. From what I can tell, most factory systems use a two pump system, one low pressure to move volume from the tank to the engine, then a high pressure pump to supply the right pressure to the injectors. Would it be reasonable to use the existing mechanical pump as the low pressure pump and just install a high pressure between the low pressure and the injectors?

Another alternative seems to be a fuel control cell like PCM uses. But again with this setup, is it reasonable to use the mechanical pump as the low pressure feed pump or would you have to replace it with an electrical low pressure pump?

[east tx skier]

Originally Posted by Matt L.

Larry told him to expect an annual Holly rebuild due to the poor fuel quality in the Southwest and the newer additives being very carb unfriendly. FI systems are not damaged like carbs by these newer additives.

Any idea which additives? My new 4160 has managed to survive two seasons without a rebuild. Fuel is always stabilized and it is run at least monthly.

[rcnjson]

Jake,
I have seen the megasquirt system and it seemed like a pretty good setup for the price of admission. Other options for stand alone EFI get pretty spendy like FAST or SDS.

The simple solution for fuel delivery is an intank pump. As long as you aren't going nuts with the motor, you can get an intake pump for a fuel injected ford application. For instance a 255 LPH in tank pump will eaisly support 400 HP's and can be had for around $100. It might take a little fabrication to mount it in your tank, but shouldn't be too bad. Another option is just use an inline pump and get the pickup down to the bottom of the tank or in a sump.

Using the current carb pump to get fuel to an inline pump won't work. There is no way the carb pump will keep up and the inline pump will either run dry, cavitate, or collapse the line.
k

[jake]

Originally Posted by rcnjson

Using the current carb pump to get fuel to an inline pump won't work. There is no way the carb pump will keep up and the inline pump will either run dry, cavitate, or collapse the line.
k

Good info, thanks. I was reading on the mega squirt site that many people have been using an in line pump from a late 80's to early 90's ford pickup or econoline van. Any idea if proximity to the tank matters when deciding where to mount it?

Was thinking it would be easier to plumb a return if it was mounted very close to the tank. Running electrical connections back to the tank area sounds easier then running new fuel return line up to the engine area.

[rcnjson]

Jake,
You do have to run a return from the engine to the tank. The fuel pressure regulator controls pressure by regulating flow returning to the tank. Meaning that the line runs from the tank to the pump, pump to the rails, through the rails, through the regulator (just a restriction to build pressure), and then back to the tank.

As far as where to mount an inline pump, you would have to be below the tank. You can use a pickup style feed line like your carb pump uses, the line goes in the top of the tank and extends to the bottom of the tank. Problem here is if the fuel is low and sloshing arround, you may lose the siphon and that could cause problems. I think the best bet is gravity feed. Again, mount the pump below the tank, then put the pickup for the pump at the bottom of the tank or even better is build a sump for the bottom of the tank and put the pick up there. The best location is at the back of the tank because fuel will slosh back when you accelerate and that would put the fuel right over the pickup. For the gravity feed system, the feed line from the tank to the pump should be bigger than the line from the pump to the rail. This gives the pump an extra supply of fuel to draw from and reduce starvation problems at the pump.

I've got a good fuel system basics article (from a car magizine) that I could scan and email to you if you are interested.

k

[jimmer2880]

On my stock '95 PS190, TBI my fuel pump (electric), is in-line at the rear of my motor, between the stringers. The pump is $250.00 new. My system runs a return line from the pump back to the tank, but only 1 line from the pump to the TBI.

It's the same pump that was put on a similiar vintage LT1 for my boat.

[rcnjson]

Originally Posted by jimmer2880

On my stock '95 PS190, TBI my fuel pump (electric), is in-line at the rear of my motor, between the stringers. The pump is $250.00 new. My system runs a return line from the pump back to the tank, but only 1 line from the pump to the TBI.

It's the same pump that was put on a similiar vintage LT1 for my boat.

This pump must have an internal regulator then. If that is the case, the pump from the ford truck or van that Jake mentioned will not work for the TBI system. I guess I am not all that familiar with that system. Is that just one big injector at the throttle body? I guess if that is what the general used, that might be what you are stuck with.
k

[pilot02]

Originally Posted by jake

Good info, thanks. I was reading on the mega squirt site that many people have been using an in line pump from a late 80's to early 90's ford pickup or econoline van. Any idea if proximity to the tank matters when deciding where to mount it?

Was thinking it would be easier to plumb a return if it was mounted very close to the tank. Running electrical connections back to the tank area sounds easier then running new fuel return line up to the engine area.

Early 90's ford trucks are in-tank pumps. Had to replace both of mine in the last year.

[east tx skier]

Originally Posted by rcnjson

This pump must have an internal regulator then. If that is the case, the pump from the ford truck or van that Jake mentioned will not work for the TBI system. I guess I am not all that familiar with that system. Is that just one big injector at the throttle body? I guess if that is what the general used, that might be what you are stuck with.
k

I think there are two injectors on the Indmar TBI setup.