Can I test injectors with a 9 volt battery in the car/on the fuel rail?

[BrakeL8]

Engine's back in the car after 2 years and my newly rebuilt injectors sat for ~13 months after rebuild.

I've seen the notes about potentially stuck injectors - I have spark and noids are correctly blinking when trying to start so I presume my new speed/reference sensors (all new sensors, cylinder head. temp/oxygen all senders, etc) are functioning fine.

I know the 9 volt battery to confirm injector pulsing with injectors on the bench, but can this be done with the injectors in the fuel rails so I don't have to disassemble and pull?

If there's a concern re: emmiting fuel into the cylinders would a remdy here be to open the fuel pressure test port on the driver's side rail and drain/relieve pressure here?

Forgive the dumb question this is my first time 'testing' injectors. Thank you all and Happy New Year!

[911obgyn]

You can use a stethoscope or a long screwdriver to hear if they click while installed. Or pull the fuel rails off and watch them while cranking.

[BrakeL8]

Originally Posted by 911obgyn

You can use a stethoscope or a long screwdriver to hear if they click while installed. Or pull the fuel rails off and watch them while cranking.

Only while cranking or is iit safe to jump them off a battery while using a long screwdriver to test this?

[wazzz]

Whatever you do just make sure you first separate the injectors from the ECM by disconnecting the 4-terminal plug near the shock tower at the back. Then you can play with a 9V battery. Only send short pulses as these injectors are low impedance and require a high current to open. Leaving them open for long periods may not be a good idea. Besides you will empty your 9V battery pretty fast if you do so. Short pulses only and you should hear them click. Do it with one injector at a time and with the fuel pump not running so you will not send fuel to cylinders. You only want to check that they click open and are not stuck.

[BrakeL8]

Originally Posted by wazzz

Whatever you do just make sure you first separate the injectors from the ECM by disconnecting the 4-terminal plug near the shock tower at the back. Then you can play with a 9V battery. Only send short pulses as these injectors are low impedance and require a high current to open. Leaving them open for long periods may not be a good idea. Besides you will empty your 9V battery pretty fast if you do so. Short pulses only and you should hear them click. Do it with one injector at a time and with the fuel pump not running so you will not send fuel to cylinders. You only want to check that they click open and are not stuck.

Thank you very much. If there is pressure in the rail is it worth relieving to prevent fuel from entering the cylinder OR with the pump not running is there not sufficient pressure to worry about?

Don’t know how much volume the check valve actually holds but don’t want to flood the cylinder obviously.

[wazzz]

A small quantity of fuel will be released in the cylinders until the pressure drops. It will evaporate, no worry.

[BrakeL8]

Originally Posted by wazzz

A small quantity of fuel will be released in the cylinders until the pressure drops. It will evaporate, no worry.

Thanks! Got it working and firing- after only running on 4 cylinders pulled and used electrical contact cleaner on all injector harness connections including 4 pin plug and female socket.

Voila!

Thrilled I managed to go from engine with everything but cases split re-assembled perfectly correctly and running like a champ! Good learning lesson to always clean and gently blow out with compressed air every electrical connection!

After two years the car is back.


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[wazzz]

Congrats! I know the feeling. Had almost the same experience when after stripping down every bit of what is sticking out in the engine compartment except the long block itself I managed to clean, replace, rebuild and put back everything in order and the car started and ran just fine at the very first try.