Got my 94 Chevy TBI to TPI conversion up and running...the truck cab has a 10A injector (TBI) fuse...since the circuit is now powering 8 (TPI) injectors think a 15A fuse is more appropriate?

 

I just checked my 1985 service manual and each bank had a 20 amp fuse. I will look at my 86 in the morning to verify this also.

 

8 injector system uses 2 fuses, one for each bank. TPI injectors have a nominal resistance of around 14 ohms. If you take 4 injectors in parallel, you have an effective load of around 3.5 ohms. If you run 8 injectors in parallel, you have an effective load of around 1.75 ohms. Using these values at a system voltage of around 14 volts, you would have a current draw of 4 amps for 4 injectors (14 volts/3.5 ohms=4 amps) or a current draw of 8 amps for 8 injectors (14 volts/1.75 ohms=8 amps). Roughly 1 amp per injector. The use of 2 fuses and 2 wires is to keep the current to a safe level for the wiring as well as the ECM output driver circuit. GM didn't waste money by putting in extra wire or fuses for no reason. Pulsing 8 amps through a circuit designed around 10 amps is not a healthy situation. Will it work? For a while but it is very taxing to the circuit and will fail eventually. When choosing a fuse for a circuit, all things in that circuit need to be considered but most important is the wires current rating. You don't want to burn up your wiring or possibly your car! It would be prudent to at least follow how GM wired these circuits. JMO. GL!