So I will say up front the whole fuel system is pretty messed up, and the rear tank is completely disconnected. I am running a stock electric pump at the moment. As far as running a return, is that simply a line that goes from the pressure regulator back to a dedicated port on the top of the tank?


I'm running new 3/8 tubing from the front tank to the carb. Once I get the truck running, I'll tackle the rear tank and all the check valve/electronics/etc that goes with it.

Sounds like I need to take the bed off and spend some quality time with the undercarriage...

 

What ignition system are you running, Duraspark or TFI? Ignition modules have been known to react badly when hot but work OK when cold.

 

I'll do that. When it won't start, it cranks normally.

 

Desperate times call for desperate measures....just how exactly do you bottle feed a carb?!

 

just make sure when you do any testing that the truck will no start when you do it. to bottle feed the carb take an old squeeze bottle something like stop leak would come in and full it with fuel then plump an appropriate size line to the feed of the carburetor and completely disconnect the rest of the fuel system just squeeze the bottle so that a small amount of fuel makes it into the float chamber then crank it up and see if it now starts. I know its not very professional but all i can say is it does work just don't blow the needle off its seat or seats i should say.

 

Ok --- that stock elec fuel pump (originally spec'd for a smaller engine) isn't cutting it......combine that with the lack of a return, uninsulated fuel lines and you'll get fuel delivery issues..........

the other prob is residual ECU related components which may or may be misguiding.......or have flat out heat related component issues.........

 

I disagree. It doesn't sound like a fuel delivery problem. He says he's getting fuel at the carb, and he's getting fuel from the accelerator pump. Plus even a way undersize pump will get enough fuel to a carb to get a 460 to fire. Maybe not enough to run it at WOT at redline, but certainly enough to fire. Also against the idea of vapor lock is that vapor lock happens when the pump is trying to pump vapor instead of liquid. With an in-tank pump it has cold, liquid fuel, so it'll pump fine. If the fuel is boiling between the pump and carb the fuel pump will replace the boiled fuel and you'll be fine (an electric pump upstream from the heat was a very effective band-aid solution for vapor lock back in the day).

To verify that it's not fuel dump a little gas down its throat and then try to start it. If it's not getting fuel you'll get a brief fire out of it that way. If it's flooded obviously you'll make it worse and it won't start. And if it doesn't have spark obviously you won't get any fire. But squirting fuel out of the accelerator pump does the same thing, so you've already proved that lack of fuel isn't your problem.

 

Thanks guys, this is all extremely helpful. It sounds like I may have wasted a few hundred bucks on the fuel system when it is possibly something else. I am going to try the things suggested tonight and post an update in the morning. I will say that when I start it cold, it will run fine, plenty of power at full throttle, and it will run indefinitely. It's only after I turn it off and let it sit that it doesn't start. Though I get fuel out of the accelerator pump, it vaporizes instantly as soon as it hits the carb.

 

sure sounds like its flooding one last suggestion try checking to see if the plugs are wet if so dry them and clear out the cylinders. Best of luck to you looking forward to what you find.

 

Check for fire. This can be the pickup in the distributor it can be the ICM. A can of freeze it can trouble shoot this issue. When it won't start spray the ICM with this stuff and try it still won't start pop distributor cap and spray pickup coil. You can spray the carb or any suspected sensor.

 

Awesome, this is the sort of electrical advice I was looking for. I'll take some pictures, but my ICM is ugly looking....it's got a wire harness coming out with most of the wires clipped. Since I went from modern EFI to low tech carb, I think the only two wires in use are the + and - going to the coil. Would I be better off at this point just running a straight hot wire from the ignition relay and one to a ground?

As a future project, I want to get rid of the rat's nest of wiring harnesses that are no longer in use.

 

Oh, and by a can of freeze, are you talking about hitting it with some A/C coolant, or is there something specific you are referring to?

 

Just so you're not chasing your tail looking for leftover EFI parts, the 351 and 460 should both have been carbureted from the factory in 1987 model year. If the emissions label is still under hood, it should confirm. The truck may not have had a fuel return line originally and if it did not, it should operate correctly without one.

 

Your truck is not using the Thick Film Ignition (TFI) system, it's been converted back to a Duraspark version based on this photo from your build thread:


The silver box on the right is the Duraspark control module.

So any reference to the Ignition Control Module (ICM) is incorrect.

 

Which is why I posted a link to the correct wiring (I guess) for the Duraspark retrofit.