i have a 85 ta with the electric qjunk and a 89 formula with tbi what kind of job is it to change this over

 

I've recently been working on an electronic Q-jet to TBI conversion myself on my '81 TA. Here are some of the things I've seen (so far...)

NOTE : If you have the entire 89 Formula, it would be easiest to take all these parts from that car and put them on your '85.

Fuel Storage/Delivery :
- You'll need to swap out the gas tanks. The carb gas tank won't have any baffles to keep the fuel from sloshing around and starving the new fuel pump I'm going to mention next... . If you never run with less than 1/4 tank of gas, this might not be a problem??

- You'll need a new fuel pump to supply the required pressure to the TBI. (On the order of 12-15 psi, I think?) Your carb. fuel pump likely doesn't supply enough pressure.

- Wiring and relay for the above fuel pump.

- You'll need to run a fuel return line from the TBI to the gas tank.

- Depending on how you do the above and what's on the engine now, you'll want to remove the existing mechanical fuel pump (if that's what's there).

TBI vs. Carb Wiring :
- Connectors/actuators on carb that aren't used on TBI : MC Solenoid, Idle Boost Solenoid. (There may be more? I'm not completely familiar with the '85s equipment.)

- Connectors/actuators on TBI that aren't on carb : IAC, Injectors. If there are enough wires from the "unused" list above, you *might* be able to get away without having to run new wires from the computer to the TBI unit by reusing them. Generally speaking, you'll probably end up having to run a few wires from the computer to the TBI. At a minimum, you'll have to splice in the IAC and Injector connectors to the '85.

- Connectors/actuators that are on both but are "different" : TPS. This should just be a matter of rewiring the existing wires to the TBI-style connector.

Computer :
- Swap out the carb computer for the TBI computer. This will require a pretty substantial effort since the connectors are physically different between the two computers.

- Wire in the fuel pump, fuel injector and IAC wires, as needed, mentioned above into the computer.

- Again, I'm not certain this applies to you, but I also had to change my knock sensor to something compatible with the new computer. (Remember, I'm going from an '81 to ~'90.) GM used different types of knock sensors at different times. If the style changed between '85 and '89, you'll want to swap this out.

- Don't know if the engines in the two vehicles are *identical* or not. (I.e completely stock 305's) Just using the '89 computer will probably be enough to get things up-and-running. If things have changed like camshaft/heads, you may want to consider programming the chip in this computer.

Keep an eye out for other things the '89 computer might control or need as input that aren't present in the '85 computer. If you have access to copies of the shop manuals for both vehicles, it would be good to compare the I/O lists of each to see if something pops up. Things like Manifold Air Temperature (MAT) or Intake Air Temperature (IAT) sensors will be used on fuel injected applications to help determine air density that carbed applications don't use.

There are probably other things I'm missing. But, this should be the bulk of the issues that need to be addressed. Good Luck!!