I recently bought an 89 E-150 Custom with the 300 L6 EFI and automatic. Your basic no options work van. About 8 years ago it had a remanufactured Jasper engine installed. It turns out, whoever did the install removed most of the emissions equipment. The purge valve is gone and the evap canister hose is just dangling. The TAB, TAD and EGR solenoids are gone. There is no vacuum line on the EGR, which probably doesn't matter at this point. A chevy ball style vacuum reservoir was put in, and the original coffee can disconnected.

It starts right up and idles fine but is sluggish and gets horrific gas mileage. I'm getting 20 lbs of vacuum at idle. I'm assuming it is throwing all sorts of codes but there is no check engine light on (probably bulb removed) and the computer is not responding to the odbI scanner I bought.

The question is do I just complete the computer removal by switching over to a carb and vacuum advance distributor or do I start buying and reinstalling all of the missing pieces for the EFI.

 

The EFI/computer doesn't really need the emissions to actually work, but it probably needs to have the electrical connections fitted with resistors so it "thinks" they are connected. But there are quite a number of other things the computer needs to function correctly in order to fuel correctly. Among the list of things are:
MAP sensor
AIC Valve
TPS
Coolant Sensor
O2 Sensor
Then there's the fuel pressure regulator, injectors, fuel pump, must all be in good working order. Also the ignition system needs to be in good condition. I'd first check all of these and get them in order. Check the emissions electrical connectors too. Yeah you could just ditch it all and go carburetor/vacuum advance/etc. I do feel like it would be more work versus just getting the existing parts already on the van and helping it run, in good working order.

 

The van had been barely being used so I swapped out the cap, rotor, plugs, wires, air filters, and fuel filter without a second thought. I also had to change the battery and terminals. The oil pressure sending unit wasn't working so I swapped that too. Threw in some Heet red in case the fuel wasn't great. Have some Techron to throw in once I get this tank close to empty. The vacuum hose that went to the original coffee can reservoir was just hanging loose so I used that port to connect a permanent vacuum gauge. Like I said above, someone had put a chevy style ball unit instead.

Doing all that made it go from surging badly and stalling to instead fire up immediately every time and idle well. It's just sluggish and getting terrible mileage.

The coolant temp is showing very low so I bought a thermostat I'll be putting in tonight but if that fails to fix it, I'll buy a new rear sending unit. I know there is a separate sending unit for the computer up front. But I want to know the engine is actually getting up to temp before I worry about that one.

Next on my list is to pick up a pressure gauge for the fuel system. If that's bad I'll swap out the 2nd fuel pump on the frame rail and the regulator. Supposedly the tank and sending unit were replaced when they did the engine swap so hopefully that one is good.

If I'm still bad at that point I'll make the choice to keep going or switch to carb/vacuum distributor.

 

With the evap left to hang, how is the tank vented? I think you'd notice if it was leaking but it could be allowing gas out under certain circumstances.

Nothing like a leak to fubar the gas mileage.

And if it's running cold that or a disconnected temperature sensor will cause a rich condition as the computer thinks you're in February or the arctic......

 

Right now the vent line runs from the tank along the frame to the evap canister and then the other tube from the evap canister, which is about a foot long, is not connected to anything. It's just hanging there. Even if it was connected to the next hardline on the frame rail, that hardline is not connected to anything on the other end either. The purge solenoid on the engine side does not exist.

So yes, technically it could be leaking fumes out of this. I've been debating just blocking it off or adding some sort of purposeful vent on the end, since the tank is in theory supposed to vent.

EDIT: Looking at the four different vacuum diagrams elsewhere in these forums, I should be able to run from the evap canister directly to one or both of the ports on the top of the throttle body. Not every version has a purge valve, so I'll try it without one for now.