CrazyDiamond

Just wondering if anyone has ever wired their cold start injector manually, so that you can flip a switch when you want it to operate (during cranking only, anyways) and shut the switch off when you don't?

I ask because a ways back I removed the coolant temperature sensor that controls the cold start injector so that I could use the manifold port for a mechanical temperature gauge. The switch evidently is only closed when coolant temp is cold, and as current flows through it during cranking, it heats up and breaks the circuit after a second or two. What I did at the time was instead of the cold start switch in the manifold, I put a toggle switch and a heavy-duty resistor (I think 1k ohm) inline. The CS switch had a resistance of around 1k ohm. I'm just wondering if the resistor needs to be there...I honestly have been lazy and haven't checked if the injector is getting voltage when my switch it turned on.

Just wondering if anyone else had done that and your opinions. Thanks guys.

yotafreakshow

My only thought here is that without knowing the coolant temp., the ecu can't properly adjust the mixture either. I guess it would just run lean while it's cold.

CrazyDiamond

Thanks man, but the cold start injector time switch doesn't give the ECU any temperature info. That's a separate coolant temperature sensor. The time switch is the sensor in the manifold right next to the coolant temperature sensor. The time switch is a mechanical switch that has 2 contacts that are closed when the coolant is really cold...it's like a choke switch. It allows current to flow to the injector only while cranking, and only when it is really cold.

CrazyDiamond

I'm just trying to figure out how to make it like a old style manual electric choke. Thoughts are appreciated...I know it's not that difficult to do. Just have to get the resistances right so the injector doesn't stay open too long and burn up.

Arnold

Wouldn't it be easier to replace the stock gauge sender w/ your mechanical gauge fitting and leave the coolant temp sensor in place? If you want to keep the stock gauge functional, you could run a "T" fitting too. Some '85 lower intake runners/manifolds had an extra port blocked off for adding aftermarket gauges too. Just another option.

CrazyDiamond

I guess I didn't clarify that. There are 3 sensors on my truck:
1. Engine Coolant Temp Sender (to ECU)
2. Temp Gauge Sender (to factory gauge)
3. Cold Start Injector Time Switch

I DO have my coolant temp sensor in place, AND my stock gauge sender (#1 and 2). The only thing I removed was the Cold Start Injector Time Switch --> it determines when the cold start injector is needed. In its place I put a toggle switch (in the cab) and a heavy-duty resistor with the same resistance as the old #3...so I can flip a switch and turn on the CSI. I'm just trying to verify that the resistor is needed, or if there is a simpler way to turn on the CSI when I want to, just like an old manual electric choke.

Arnold

I know what you're saying, meant to say the cold start injector time switch instead of coolant temp sensor. I just thought it'd be easier running a "T" at the temp gauge sensor for your aftermarket gauge and leaving the CSITS alone.

CrazyDiamond

Ahh...
I actually thought of that...it's what I did for the mechanical oil pressure gauge (T fitting at the oil pressure idiot light sender).

Only 1 problem with it: finding a metric T fitting with what I think was a M19x1.5mm thread size I searched far and wide and all over the internet, but even most industrial, straight-from-the-warehouse suppliers just laughed when I told them that size.

Bigblock

run 12 volts to the injector thru a toggle switch and only use it when its hard to crank.also you may want to fluke the old wires to make sure it isnt 5 volt;if it is you'll have to reduce from 12 to 5 volts,otherwise you'll burn up the injector.

CrazyDiamond

Any idea of how long it's safe to have the injector open for? Most injectors are only made to handle open for a fraction of a second, and that's what the purpose of the old CSITS was for...to break the circuit after a second or so.

Thanks again!