How do you test injectors? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

IchigoMae · 01-25-2003, 07:47 PM

how do you test fuel injectors if they work, out of the car? like can you rig a battery to them? if so wat voltage? and can i dip them in water and see if they spray?

*AceInHole* · 01-25-2003, 08:05 PM

Well... the injectors need pressure on the feed side in order to actually spray anything. They're basically valves with a solenoid actuator. Dipping them in water and "powering" them won't really do much.

Here's what I'm told you can do:
Unbolt the fuel rail with all 4 injectors in it.
Lay the fuel rail over a white cloth.
Crank the engine a couple times with the starter (probably a good idea to unplug the spark plugs in case some leftover fuel in the intake... you've probably been swapping injectors and dripping fuel in)
That way, you can see which injectors are leaving wet spots on the cloth, thus finding out which injectors work.

240racer · 01-26-2003, 12:45 PM

to test if the injectors are spraying the correct amount of fuel, you need the rail, a 12v power source, and four graduated cylinders. Take the rail off the car and disconect the electrical connectors. THen get a longer piece of fuel line so you can pressurize the rail out of the car and place each injector in one graduated cyl while they are still atached to the rail. Then when you open each injector with a supplied voltage, fill up a graduated cyl and time how long it takes. then you can figure out how many cc/min the injector is actually spraying. I'm not sure how well this method works with our side feed injectors, because I haven't tried it, however it works just fine with top feed injectors.

*sykikchimp* · 01-26-2003, 01:56 PM

Quote:

Originally posted by 240racer
to test if the injectors are spraying the correct amount of fuel, you need the rail, a 12v power source, and four graduated cylinders. Take the rail off the car and disconect the electrical connectors. THen get a longer piece of fuel line so you can pressurize the rail out of the car and place each injector in one graduated cyl while they are still atached to the rail. Then when you open each injector with a supplied voltage, fill up a graduated cyl and time how long it takes. then you can figure out how many cc/min the injector is actually spraying. I'm not sure how well this method works with our side feed injectors, because I haven't tried it, however it works just fine with top feed injectors.

why would the way an injector feeds matter?

mrdirty · 01-26-2003, 03:45 PM

how do you keep the injectors from firing out of the rail?

Also, I'm assuming you're just using the starter to turn it over; what about throttle input?

*AceInHole* · 01-26-2003, 04:48 PM

Quote:

Originally posted by mrdirty
how do you keep the injectors from firing out of the rail?

the stock fuel rail has caps over the injectors that should hold them in place. (at least with our side feed injectors).

Quote:

Also, I'm assuming you're just using the starter to turn it over; what about throttle input?

for the method i described.... the injectors shouldn't need throttle input for them to inject fuel. at idle and on starting, they have to inject fuel, otherwise your engine wouldn't fire up or stay running.

mrdirty · 01-26-2003, 08:37 PM

the sohc injectors are just held into the rail by the runners; there must be an easy way to get them to stay in there...

sxtasy · 01-26-2003, 09:11 PM

Yes the SOHC injectors are held in place when bolting down the rail, so there is no way to test the actual spray pattern without some magical special equipment. About the only test you can perform is an impedance test. Just put your multimeter on the 0-200 ohm scale (or the lowest scale) and measure the resistance between the 2 "prongs" on the injector. It should be 2-3 ohms. If it is higher or lower replace the injector. If the impedance checks out ok, but you still suspect an injector (leaking into the intake or bad spray pattern) replace all the injectors. I would do it anyway just to be on the safe side. I got a set of high flow python injectors for about $250.

01-25-2003, 07:47 PM	#1
IchigoMae Zilvia Junkie Join Date: Dec 2002 Location: socal Age: 41 Posts: 353 Trader Rating: (4) Feedback Score: 4 reviews	How do you test injectors? how do you test fuel injectors if they work, out of the car? like can you rig a battery to them? if so wat voltage? and can i dip them in water and see if they spray?

01-25-2003, 08:05 PM	#2
AceInHole Autox Technician Join Date: Dec 2001 Location: New Haven, CT Age: 44 Posts: 3,961 Trader Rating: (0) Rides Gallery: AceInHole Feedback Score: 0 reviews	Well... the injectors need pressure on the feed side in order to actually spray anything. They're basically valves with a solenoid actuator. Dipping them in water and "powering" them won't really do much. Here's what I'm told you can do: Unbolt the fuel rail with all 4 injectors in it. Lay the fuel rail over a white cloth. Crank the engine a couple times with the starter (probably a good idea to unplug the spark plugs in case some leftover fuel in the intake... you've probably been swapping injectors and dripping fuel in) That way, you can see which injectors are leaving wet spots on the cloth, thus finding out which injectors work. __________________

01-26-2003, 12:45 PM	#3
240racer Zilvia Junkie Join Date: Nov 2001 Location: Minneapolis, MN Age: 46 Posts: 574 Trader Rating: (0) Feedback Score: 0 reviews	to test if the injectors are spraying the correct amount of fuel, you need the rail, a 12v power source, and four graduated cylinders. Take the rail off the car and disconect the electrical connectors. THen get a longer piece of fuel line so you can pressurize the rail out of the car and place each injector in one graduated cyl while they are still atached to the rail. Then when you open each injector with a supplied voltage, fill up a graduated cyl and time how long it takes. then you can figure out how many cc/min the injector is actually spraying. I'm not sure how well this method works with our side feed injectors, because I haven't tried it, however it works just fine with top feed injectors. __________________ Adam '89 coupe KA24DE+T 14.1 @ 104 MPH '88 Celica All-Trac turbo stock, but no more ecu codes!!

01-26-2003, 03:45 PM	#5
mrdirty Zilvia Addict Join Date: Mar 2002 Location: Thunder Bay Ontario Age: 47 Posts: 650 Trader Rating: (0) Feedback Score: 0 reviews	how do you keep the injectors from firing out of the rail? Also, I'm assuming you're just using the starter to turn it over; what about throttle input?

01-26-2003, 08:37 PM	#7
mrdirty Zilvia Addict Join Date: Mar 2002 Location: Thunder Bay Ontario Age: 47 Posts: 650 Trader Rating: (0) Feedback Score: 0 reviews	the sohc injectors are just held into the rail by the runners; there must be an easy way to get them to stay in there...

01-26-2003, 09:11 PM	#8
sxtasy Join Date: Aug 2002 Location: MT Posts: 17 Trader Rating: (0) Feedback Score: 0 reviews	Yes the SOHC injectors are held in place when bolting down the rail, so there is no way to test the actual spray pattern without some magical special equipment. About the only test you can perform is an impedance test. Just put your multimeter on the 0-200 ohm scale (or the lowest scale) and measure the resistance between the 2 "prongs" on the injector. It should be 2-3 ohms. If it is higher or lower replace the injector. If the impedance checks out ok, but you still suspect an injector (leaking into the intake or bad spray pattern) replace all the injectors. I would do it anyway just to be on the safe side. I got a set of high flow python injectors for about $250.