Alright, I have a 1990 chevy one ton cab chassis crew cab 4x4, v in the vin code. This means it is the boxy body with the two suicide gas tanks. This is off road farm truck so mods I did do not have to be road legal. I bought it last fall, let it sit all winter and fixed it this spring. cheap fleet truck, automatic and 4x4 are most likely the only options.

The stock throttle body got funky, and since I had chevy parts around, I mean who does not have manifolds and carbs running around, I dropped a carb on it. I went to vacumn advance distributor and had it running pretty sweet. I used the stock fuel pumps by letting the incoming line feed the two lines to the carb and then letting it go back to the return line. Worked fine for around 500 miles or so. No regulators, using the factory inline filter and the carb has a small filter for each fuel bowl.

Now the computer is still hooked up, I used the 12 volt ignition controlled wire for the fuel injectors to run power to my hei. Gauges worked, had power, have high idle as the manifold is an air gap and lost some torque. Also can not get it to time right, have another engine but am not doing that till current problem gets fixed.

Right now I can go sit in it and turn the key to run and hear the pump run. I can then pump the gas peddle and it fires right up. Have to mess with the gas pedal as choke ain't working right now. What happens is that as it runs it drains the fuel bowl and dies.

I can shut the key to off and wait a bit and repeat, the pumps work for initial fuel pressurization, but after that they seem to not work. I do this with both tanks and if I have a pump in both tanks I am guessing it is not the fuel pump.

I bought a new fuel filter, but as it does not run enough to get it in the barn I have yet to install it.

I was wondering if anyone knows if there are seperate paths for making the fuel pumps run. One for initial pressurization and then another when running. If so, most likely I am after a blown fuse, still muddy around the truck so I have not checked them all out.

Both tanks do it, the gauges all work, the switch for the tanks work. This started suddenly, I drove it around and worked it for the day moving and hauling stuff and shut it off. Next morning this starts. I am hoping it is my cheap fuel filter not flowing enough. But if there are seperate paths for running the fuel pumps, has anyone installed a switch to just turn it on manually?

I unhooked the battery and let it sit a bit as I have newer obdII stuff and clearing the computer often helps. I have a scanner but it shows so much stuff out of whack because I neutered this fuel infected engine.

No way to check fuel pressure, not much to mess with as this thing is jury rigged pretty bad. Works great for off road and around the place though.

Oh, is someone sure there are two fuel pumps, one in each tank and what all is there with this flip switch to the tanks? I have been under it for some work like a new fuel filter before I ran it around this spring but this thing has been sunk in mud so much I am sure I could spend a day washing the underside off.

I need to get a book for it, I have a basic one for the chevies but it lacks a lot of info on this one ton for some reason.

All help appreciated, I am a bit frustrated as I have had flood watches for the last 36 hours and no time to fix this thing unless I want to get seriously wet and muddy.

I am suprised it ran at all with that setup....If thats a computer controlled TBI setup. The fuel pumps are high pressure, carburated engines are low pressure 5-7PSI. All you fuel is probably bypassing back to the tank.
It would probably be cheaper and much easier to put a throttle body back on it.....:skull:

I talked to a lot of people and they said the throttle bodies ran lower pressures than something like a camaro z28 tuned port with 8 injectors.

I also feel it should not just go from running great to not running as I have several hundred miles on it from when I did this to now.

the camaro can run around 40psi, I have a friend with one we modified and it runs around 30-40 stock I think.

I was told throttle bodies run at 15 or so psi, and by removing the factory restrictions pressure got lowered as it has no restriction to limit flow which raises pressure.

Is there a place on the motor for a fuel pump my 1990 new body style has a place for one If it has one just put one on it will work with the fuel pumps in the tanks. Just my .02

Nice weather hit and I got a chance to get some seriously overgrown spots mowed down a bit. Been busy.

Played with the truck a little, the high idle is too much pressure sending more gas than needed by the floats or something. Like brake torquing the engine. Idle in neutral around 1500 and in gear 800-900 I think. Did not figure out why it dies, but this is a problem and I might as well fix things.

I talked to a lot of people and some friends have some used but fine parts around.

Got a fuel pump and regulator to install. A towing cam as well. Some headers and some exhaust parts.

Going to get it running good again and set it up for towing.

Looking at some factory heads like the tuned port z28s used to make good use of the cam and headers.

Someone has a wrecked truck I can make my farm truck, so this one is headed for the road.

Thanks for the advice, sorry I have been busy and could not even check for replies till now.

Hey, look I want the old efi parts! Trade you a quadrabog and intake for them:-)

You have a real big problem there pulling the throttle body. The factory pump puts out around 15 psi which is enough to overide the needle and seat. You need a pressure regulator on this thing NOW.

I am not sure what to do about the factory regulator and return line. I think the regulator is part of the throttle body... the forst thing I would do is remove the factory pump, put in a sock filter and install a external fuel pump on the engine if possible. This eliminates the fuel pump relays and the low oil pressure switch that could be shutting off the pump.

Now you should have "reliable" fuel to the carb at a PSI that it can handle - troubleshooting is now "old school" :-)


I guess you pulled the TBI cause the carb is more familiar but IMHO you should get a book and learn the basics of the TBI and you'll find that it is superior to the carb 'specially OEM EFI...

But if you are really set on running that carb please contact me about the old EFI parts :-)

LiZArd