1990 Ramcharger 360 TBI with A518, we are converting this to a carb, making a hot rod street truck, can we just replace the in-tank pump with an older Ramcharger sending unit and use a mechanical fuel pump? We didn't know if the tank changed when they went to throttle body, if we can do that, how do we get the factory fuel gauge to work? The bigger issue will be what can we eliminate wire wise from the computer? We will be going to a standard Chrysler electronic ignition setup, we are just not sure what the factory computer all controls in these vehicles, don't want to eliminate any circuits/wires that we have to retain, and would like all the factory gauges to work as well, this is just for a street toy that will be getting a cam, intake, Holley 600, and good exhaust, I can find tons of info on GM TBI to carb swaps, but nothing on the Mopar swap, I know someone has had to do this before, I just want to do it correctly. Thanks!

It has been years since I fooled with the old LA TBI setup and it was on a stick truck.

That said, what I remember, and it's been decades so take a grain of salt, the computer used it's own sensors and the gauges used the normal old school setup. IOW the gauges don't need the computer to function.

I do want to say the computer has some control over the auto trans though. Lockup and OD I suspect there are workarounds for that. Such as this setup.

As for the fuel pickup, I would pull the pump out and replace it with a bit of tube and a sock. But to be honest I think the mechanical pump will pull thru it anyway. Fuel gauge will still work as the sender is separate. Fuel tanks for this vehicle are virtually nonexistent anymore so be careful.

You will need to wire in the older voltage regulator as that is one thing the computer does control, you can keep the existing alternator.

Will need a new intake.

That's all I remember for now

My 89 has a line that goes into the tank which looked like it would work perfect and was the one that I was going to use, Its located on the outside of the frame on passenger side behind the rear wheel. You wont have to drop the tank or disturb wires by using it.

Mitch

Thanks for the quick reply! We have a 4 bbl intake, I knew the trans would need some mods/switches/wiring, didn't know what the computer controlled other than injectors & spark timing, do we need to leave the computer in the truck for anything? Can we put a standard fuel pump pickup with float/sending unit in and hook it up to the existing sending unit feed wire? , (I have a new one for a '81-'87 carb application) didn't know if the Ramcharger fuel tank itself was different between the earlier carb models and the later TBI modelsI just don't want to remove anything that is going to bite us in the butt further into the conversion!

Is that the return line? I thought about using the stock in-tank fuel pump and using a regulator to knock down the pressure to work with a carb, and using the factory return line to take some of the stress off the pump going down to 5 psi

Yes, the tanks are different, but that shouldn;t be an issue going from TBI to carb, would be the other way.

You don't need to fool with the fuel gauge sending unit at all, it is separate from the pump module. In the picture, number 8 is the fuel pump module, number 9 is the gauge sending unit. they go into separate holes in the top of the tank.

All I would go is pull the fuel pump relay, plumb in a mechanical pump and see if it will draw through the in tank pump and feed the carb. One thing that did pop into my mind, your engine may, or may not, have the fuel pump eccentric bolted to the front of the cam, it probably does. If it does not you will need to add it. If you want to try to regulate down the in tank pump instead, the computer is what turns that pump on and off via the fuel pump relay. You would need to address that.

Ramcharger tank drawing

Thank you! That helps clarify things! I assumed the electric pump and sending unit were one unit, I should be able to just use my brand new old style fuel pickup/sending unit in the hole where the current electric pump goes then and just not worry about the carb-style sending unit wire on it, we will be using an LA roller cam with the long snout for the fuel pump eccentric

Not the return line and is on the other side of the truck where the fuel lines run, you could just use the tank pump too but should be regulated but I was messing with mine a few years ago and made an aluminum adaptor for one of those old 318 2bbls which worked and it ran as good as the TBI, I just rigged the fuel line so it was using the returned and it never did over pressurize the float.

That is assuming the old style pickup/sending unit assembly goes into the same hole as the electric pump? If we were to regulate the pressure down, it would be with a mechanical fuel pressure regulator and use the factory return line, then we would need to keep the fuel pump relay hooked up and keep the computer, not remove it entirely?

You would need to find some other way to trigger the fuel pump relay.

Maybe tie into the switched 12V line that feeds the ignition setup.

That would be easy enough to do, I would rather use an old-style pickup tube since we already have one from a mid- 80's IF it would go into the same hole the current electric pump does, but I have a sneaking feeling it isn't going to be that easy!

what adapter are you talking about?, you used the in-tank pump with just a return line with a carb?

I had a brain fart, you used an adapter to put a Carter BBD 2bbl from a 318 on your TBI intake and then used a regulator to get the pressure down, correct?

All 360 TBI motors kept the eccentric on the cam for the mechanical fuel pump. What cam are you swapping to? Keep in mind that the stock valve springs will not accommodate a lot of lift. Your real problem is compression, stock should be around 8:1. Don't forget to plug the air ports if you change the exhaust. There's an old Mopar Action article about installing a switch to trigger the lockup feature on the trans, or you could you just swap to a non-lock up converter? You'd be looking at something like a CR20 probably. I don't know about the computer but I do have a TBI wiring diagram saved somewhere if you need it. AFAIK the computer controls the engine and trans only. There may be a cab computer, too.

I made an adaptor so I didn't have to switch intakes,but that left me without a choke but it was warm out when I was doing it anyway

were those low pressure fuel pumps, something like 15-18lbs. ?
something rattling around in my feeble mind came up with this memory.

TBI wiring diagram would be great! We will run a mild hydraulic LA type roller cam with the long snout, lift under .500" with short duration to work with the lower compression, stock converter with the wiring mod, 3.55 gears and 28" diameter tires, just looking to make a fun warm weather driver that has strong midrange power and will burn the tires a little if it has to. :), and will swap valve springs, air injection holes already plugged, have a 4bbl intake and carb ready to go.

SB mechanical and old style electronics I can do in my sleep, it's the computer stuff that makes me hesitate!

the fuel tank pic is wrong. that pic is of d150 pickup. r/c has rear mounted tank. also fuel pump sending unit and fuel gauge sender is screwed together. tank reading part all does thru top of electrical connection. new fpm does not exist unless you find and nos and u will pay dearly for it. oem pat number is 52004636 from mopar parts giant web site. stock pump can be regulated down with holley blue reg to 4-7 psi. oem efi pump is 14 psi for tbi. i think fabo has a schematic of the 90 alt showing hooking up an old style reg. patc kit is easy but u can find those switches cheaper on internet. good luck.

Thank you everyone!!!

Try this

http://repairguide.autozone.com/zne...2/80/07/78/4d/large/0900c1528007784d.gif