Injectors not opening

[datsun280zx81]

I have a 1981 280zxt with a bunch of mods that I just got done installing. Everthing works exept the injectors aren't opening to let fuel in. They are RX-7 86-87 Turbo 550cc Low impedence injectors. I tested the injectors with a meter. There are two pins each when tested came out to 12.13V. Are they suppost to both have voltage running thought them? If so how do they ground? Is there a CAS or something similar that I can check to make sure that it works? Any suggestions why they won't open?

[datsun280zx81]

I'm still not sure what it could be so I took some advice from other people. Even though they are new injectors they might be stuck so I am going to let the tips soak in gasoline over night to see if that frees them up a bit. Also I ordered a new higher performance fuel pump that should assist in opening them if they are stuck as well. While ordering the fuel pump I ran accross this article that may help anybody with this situation in the future since so many people were willing to help me with my problem . It explains how injectors work, it's from the site http://osdir.com/ml/recreation.cars.toyota.mods/2005-06/msg00004.html

 

Re: Can't get my 4age injectors to fire

 

 

 

Subject: Re: Can't get my 4age injectors to fire

In a message dated 6/2/05 12:56:58 AM Central Daylight Time, vazfx16-/E1597aS9LQAvxtiuMwx3w@public.gmane.org writes:

 

 

My

turbo

project is back together, but now it seems my

 

injectors are not firing. I intentionally reduced the

 

number of things that I had to undo during the build

 

up to prevent something like this. But here I am.

 

 

What voltage should the injector see with the ig is in

 

position 1?

 

What voltage should they see when cranking?

 

What would stop them for firing off?

 

Nothing in my shop manual really gets into the

 

injector not firing, where should I begin?

 

This is from 3 year old memories.

 

There is either 2 or 3 sensors depending on the model of 4AGE. All three would be NE, G1 and G2. They are either all in the distributor or one may be on the front of the crank. They give a number of pulses per revolution of the engine. If you are getting spark, they are most likely all working. One is a fast pulse used to track enigne speed for accurate timing even while accelerating. The next one is a single pulse every time any piston comes to TDC to sync the sytem. The last one if it has a G2 is a single pule when cylinder 1 is at TDC of the power stroke. It is used to sync sequential injection.

 

The ECU uses these pulses to calculate when to fire the spark. A pulse on the IGT line fires the igniter/coil to make the spark. When a spark occurs the igniter then makes a pulse on the IGF line back to the ECU. The ECU will not fire the injectors if it does not get IGF pulses. This is a safety to make sure it is not spraying fuel into a dead motor.

 

One side of all four injectors gets battery voltage when they are not firing. The other side will also measure battery voltage when no current is flowing. The ECU uses a transsistor to pull the secnd side of the injector to ground to pull current and open the injector. The injectors can be either high impedance which will measure 10 to 20 ohms across the leads, or low impeadance which will measure under 5 ohms across them. High ohm injector will be straight frmo battery to ECU and will have a full 12 volts acros them while spraying. Low ohm ones will have a resistor pack between the battery voltage and the injector. This is to limit the curent to about 1 amp per injector when open. Low ohm injectors operate much faster allowing shorter pulses so they are typically used on higher performance engines which need bigger injectors. Most 4SGE's used low ohm with the resistor pack.

 

If you have a 12 volt test light, you sould be able to connect it to ground and touch each injector wire. It should light at all 8 wires when the engine is not running but the key is on. Now connect the clip to battery voltage and probe the leads while it is cranked. One side will probably never light (the 12 volt side) but may make a faint flicker on resistor pack setups. The other side of the injectors (The ECU driver side) should give a solid flash every revolution of the engine on non sequential, or every two revolutions on sequential engines. The pulses are very short. If you have no IGF signal, they should still fire a couple times and then quit.

 

During cranking, the pulses are basically fixed as the AFM will barely move until the rpm comes up.

 

Some cars (not sure about Toyotas) will turn off the injectors if the throttle is wide open during cranking. So a TPS problem may also cause no injection. This is the "clear flood" mode on GM's.

 

I hope this helps.

 

Gary M.

[mark]

Test them with a 9 volt battery. You should hear them open and close with the battery. If that works you have other issues.

[Thumper]

Didn't feel like reading your second post so I'll answer your first. The injectors will have two 12v's going in and when they want to be fired the ecu will ground it. So connect a test light to 12v source and one of the connectors. If you can a ground(aka light on) then you have a good signal and its a bad injector. If so try to tap it or apply battery voltage for a split second to it. Battery voltage is way too high but it can sometimes undo a stuck injector. Also sometimes when you mount an injector crooked or the holder is off then it will bind internally try testing the injector loose. Good luck.

[sweetleaf]

Put a noid light on the injector connector to see if you get a pulse..