Hi guys, question, how do i measure if there is voltage on the injectors. I know the big connector has 6 wires, 2 wires for one injectorset of 3, 2 for the other row of injectors and 2 for the cold start. How must i measure that there is voltage on both injector rows? My engines wants to start but it wont. It wants to fire up but doesn't. Full throttle and it doesn't fire up at all so last resort must be the injectors. Any help on how to measure the volt is needed.
Holding the throttle open won't do anything for starting the car. It'll just cause the engine to rev up very fast when it does start.
Are you sure the cylinders are getting spark? Are you certain they are not getting fuel? Are the injector fuses good? Does the tach move when you crank the engine, or does it stay at the bottom of the gauge?
Hi guys, the ground is good. Has been cleaned thoroughly. The fuses are both good also. First i thought it was getting to much gas so i put a pressure gauge on the fuel rail. Turned out it lost pressure so i pulled off the injector rails and cold start. The cold start was broken so i put a new one in. Now psi is 45 psi. The tach moves when starting the engine. I bought this fiero as a non runner. It hasen't started in the last 3 years. ICM, coil, plugs, wires, cap and rotor a new from FS. Pick up coil is not new but i tested it with ohm meter. And no, i am not out of gas
This fiero was from someone who liked to tear it apart.....so when i got it, it was just a frame and many parts. Everything is back together with pisa dash, mr Mike seats, really nice but that PITA engine......i just can't get it to fire up. Set the time a few times already, swapped ECM...... Still no go
So help from you is definately needed cause i am out of ideas. So maybe i thought, one injector rail may not be working? Tommorow i will test the injectors by getting the fuel rail out of the engine and put it in a bucket just to see, when i crank the engine, if the injectors will work.
The injectors might need to be cleaned. If it's been sitting for a long time, any fuel that was sitting on top of the injectors could have gummed up, and it would prevent fuel from going through them.
This may seem crazy, but the engine will actually start and run (although not very well) with one injector bank not firing. Don't ask me how I know this...
That said, measuring the voltage output to the injectors may be difficult, because the power to the injectors comes in very short bursts. Your multimeter probably doesn't react fast enough to get a good reading. However, you can use a "noid light", basically a 12V light bulb that fits into the injector plug. If the circuit is getting power, the light will flash.
Have you tried starting the car with starting fluid? If it starts then it's a fuel problem, if not then likely an electrical problem.
Best way to measure injector voltage is with an oscilloscope. You may still get a reading with a voltmeter, but if you do it won't be accurate, it'll be significantly lower than the rated voltage since you're reading a pulsed signal.
Strangely, the engine did run when the cold start injector was broken. The cold start injector could not close anymore so when i started the engine it ran but bad. It looked like it was not running on all cylinders. After i replaced the broken cold start injector the fuel pressure is steady now at 45psi but know it doesn't even idle. It just wants to start but it seems its just not getting enough fuel. I have no light but maybe the bulb idea is a way to start eliminating some problems. I like fiero's but this fiero is my nemesis i think. And i have searched fiero.nl with archives, haynes, chilton, and all the other books
The two posts ahead of me are wrong. The injectors have power all of the time with the ignition on. So to test them, although I highly doubt this is your problem, with the ignition on just test the plug with a voltmeter. If you see +12v, not your problem. Be warned, the ground wire won't go to ground, you'll need another ground when testing.
Originally posted by RobertGT: The two posts ahead of me are wrong. The injectors have power all of the time with the ignition on.
You're kidding, right? The injectors absolutely do NOT get constant power. If they did, they would be fully open all the time. Think about it.
The circuit is wired so the ECM switches the ground leg of the circuit. Power to the injectors comes straight from the fusebox. But the ground is controlled by the ECM. And when the ground is interrupted, no power flows through the circuit.
You're kidding, right? The injectors absolutely do NOT get constant power. If they did, they would be fully open all the time. Think about it.
The circuit is wired so the ECM switches the ground leg of the circuit. Power to the injectors comes straight from the fusebox. But the ground is controlled by the ECM. And when the ground is interrupted, no power flows through the circuit.
They get constant power, but they don't get constant ground. They are opened by grounding the connection, IIRC.
The injectors are mounted on a fuel rail and are activated by a signal from the ECM. The injector is a solenoid-operated valve which remains open depending on the width of the electronic pulses (length of the signal) from the ECM; the longer the open time, the more fuel is injected. In this manner, the air/fuel mixture can be precisely controlled for maximum performance with minimum emissions.
Blacktree and dobey are correct, the ECM uses ground to create the PWM to the injectors. (pulse width modulation)
Blacktree and Neils88 are also correct that a noid light or an oscilloscope are the proper tools to check injector circuits. The noid light will quickly tell you the ECM and injector harness are working. Multimeters are cheap, but too slow to see injectors opening and closing. An oscilloscope is far more versatile: it displays the changing voltage on the switched side of a fuel injector and, with a current clamp, can even show the current through the injector coil.
[This message has been edited by Robertzep2 (edited 03-04-2014).]
Originally posted by Robertzep2: Blacktree and Neils88 are also correct that a noid light or an oscilloscope are the proper tools to check injector circuits. The noid light will quickly tell you the ECM and injector harness are working. Multimeters are cheap, but too slow to see injectors opening and closing. An oscilloscope is far more versatile: it displays the changing voltage on the switched side of a fuel injector and, with a current clamp, can even show the current through the injector coil.
An injector harness pigtail connected to a battery with a button on one side, is also a good and simple test tool. You should be able to hear the injector open and close as you push and release the button.
Trying to get anything in while the engine is running, on the 2.8, is also terribly difficult, due to the design of the intake manifold. It's much easier to test the injectors with the engine off and at least the top plenum removed.
My first youtube movie. To bad its nasty. This is what the fiero sound like when the cold starter injector was still broken so it stayed open continuesly. I keep the gaspedal half way in to keep some sort of idle. That engine sound bad
[This message has been edited by Gambit (edited 03-05-2014).]
Half of the injectors don't sound like they are firing. Engine running try this. On the multipin Injector harness to engine harness - Read the voltages on the pins. Do this with the engine running, and the connector connected. Slip a pin up the backside past the rubber seal until you can read a voltage. Read the voltage referenced to ground. On both the pink and pink/white you should be reading battery voltage. On the Lt. Green and Blue you should be reading about 4-6 v less than what you read on the pink and pink/white. If you are reading the 4v less that indicates the ECM is trying to fire the injectors on those two wires.
If the above test reads ok, then pull the upper plenum and pull the injectors. Test each one by attaching a 9v battery to it and see if you can blow slightly through the injector. A crude test but it works. Don't leave the 9v attached too long as you could burn out the injector coil. If you can't blow through the injectors soak the tips in injector cleaning fluid. Test again. You should also hear a click when you attach the 9v battery. Sometimes stuck injectors can be free-ed by giving them a sharp rap with a screwdriver handle however since you can't reach them in a Fiero with the upper intake installed this doesn't do much for you.
They don't get any power until the circuit is completed. The ECM completes that circuit on the ground side, a few milliseconds at a time.
If you want to be pedantic, perhaps.
Power gets to them, it doesn't get through them. If the ignition switch is in the "run" position, and you check for voltage at the injector, you'll see voltage (unless the fuse is blown or wire cut somewhere along the line, or some other similar issue), and depending on which side of the injector you check, you'll either just get voltage, or you'll get the injector opening, which should be audible, and tactile (vibration of the solenoid is likely to be felt through the probe).
[This message has been edited by dobey (edited 03-05-2014).]
@phonedawg. I already put in new injectors but that doesnt help at all. I cant get it to run. It want to start but as soon as i put in the gaspedal it doesnt want to come on anymore. So with not pressing the gaspedal at all it WANTS to idle but it doesnt. And when i turn the ignition on, the IAC starts humming? Is it suppossed to do that?
whats your voltage on your map sensor? does the voltage drop when you gas it? should be close to 5V and when throttle applied that voltage should drop.
@phonedawg. I already put in new injectors but that doesnt help at all. I cant get it to run. It want to start but as soon as i put in the gaspedal it doesnt want to come on anymore. So with not pressing the gaspedal at all it WANTS to idle but it doesnt. And when i turn the ignition on, the IAC starts humming? Is it suppossed to do that?
It might hum if you have a battery charger attached and the charger is putting an AC signal on top of the battery voltage.
It might also be making more like clicking noises if you have a jumper from A-B on the ALDL connector. That will also cause the ECM to close the IAC passage and make it hard to get it to idle since when starting the engine the IAC passage is closed. The ECM is programmed to continuously extend the IAC pintle whenever A-B is jumpered and the key is on but engine off. No that will not burn out the IAC motor.
whats your voltage on your map sensor? does the voltage drop when you gas it? should be close to 5V and when throttle applied that voltage should drop.
The MAP sensor should read about 1v at idle and go up as intake vacuum drops (like you floor the throttle).
When jumped it hums. Pretty anoying. I find it strange that it does not fire up at all. Maybe bad pick up coil? With ignition on i get power on the injector connector. Not on all wires, just 2 out of the 6
[This message has been edited by Gambit (edited 03-05-2014).]
Key on, connector unplugged, reading voltage referenced to ground, engine not running (it can't since the injectors are not connected) you should read +12 on the Pink and Pink/White only.
Oké, i will measure this tuesday cause i am on a short vacation. Furthermore, when i replaced the cold start injector i also saw 2 broken vacuüm pipes??? It did run with the broken vacuumhoses and cold start injector? Thats where the YouTube is from
So, i will check the pink wires tuesday for 12v. If there is 12v on it, where else can i look?
Have someone start the engine and hold your hand near the exhaust headers. See which ones are (getting hot fast) firing and which are not. Check the wires and plugs of the ones that are not firing. I assume you are not able to drive it so checking plugs at this time isn't of use. Check the compression of the cylinders and see where you are with them.
You only need the A-B jumper in place when setting the timing or to read codes. It will make starting harder expecially if you give the ECM time to close down the IAC passage.
For what its worth, i swapped the plug wires already, put in new plugs. The engine has been rebuild and all seals are new!!! Compression is somewhat because of the shaved heads. Could a broken map sensor cause this? Or am i need to look at the ignition stuff?? It gets gas and injectors are new ones. Also new pressure regulator
Unbelievable. The compagny that rebuild the engine forgot to do 3 valves so they were loose in the engine . i will post a movie i made of this on youtube
