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How to turn injector fuel flow off for testing

Black1990jeep

NAXJA Forum User
Location
california
How can the injector fuel flow be disabled? I want to be able to crank the engine without having fuel flowing into manifold. Do I disable the pump, or pull a wire to turn of the injectors, or....?

This is for a 1990 XJ, six cylinder, Renix system.

Thanks!
 
Disconnect the injector's electrical connection.
 
How can the injector fuel flow be disabled? I want to be able to crank the engine without having fuel flowing into manifold. Do I disable the pump, or pull a wire to turn of the injectors, or....?

This is for a 1990 XJ, six cylinder, Renix system.

Thanks!

Pull the ASD (Automatic Shut Down) relay out. It controls both the fuel pump and the injectors.
 
Pull the ASD (Automatic Shut Down) relay out. It controls both the fuel pump and the injectors.

Ditto. Just be aware that when you are done doing whatever it is you are doing, put the ASD relay back in, start the Jeep to run, I think it will throw a CEL. When doing a compression test on my '00 I removed the ASD relay. When I started it back up I had the CEL. Of course my first response was WTF. But it was a P1389. Once I Googled it and realized what it was more like "oh yeah huh. LOL.
 
How can the injector fuel flow be disabled? I want to be able to crank the engine without having fuel flowing into manifold. Do I disable the pump, or pull a wire to turn of the injectors, or....?

This is for a 1990 XJ, six cylinder, Renix system.

Thanks!
Hold the throttle open 100% while cranking. Under that condition, the ECU shuts off the injectors to clear the engine of potential flooding.
 
Hold the throttle open 100% while cranking. Under that condition, the ECU shuts off the injectors to clear the engine of potential flooding.

X2 on that!
 
If your linkage is working correctly....Ha Mike?

CPS is best.....

It worked on mine for 14 years even with the Uncle Bob linkage Mods, LOL :laugh3:

Best answer would depend on what the OP wants to test.
 
well then, It must clear flood earlier than we thought, eh?

The air flow rate during cranking at 65% open on the butterfly (like I had) is enough are cranking rpm to move plenty of air, and the ECU learns over time what the MAX TPS open value has been historically, and likely uses that instead of a data table of 87% of 5 volts, to decide to not open the injectors (Like I saw when I had that Uncle Bob throttle link issue)?
 
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