Help please! injectors

[palmystar]

My injectors arn't giving me any fuel. I have checked that they work. the fuel pump is working and i am getting fuel to the injector housing..
I am getting a voltage reading from the computer. and have also tried my spare computer with no change. I have also tried changing the control relay. I have also checked all the plugs, including the resistor and have made sure all the plug contacts are making contact. I don't know what else is left to check? and are there any other sensors that can be causing this? :x

[Junkers]

Have you checked that the negative trigger on the injector loom is working? I believe they work by a constant 12V feed and a negative pulse.

[palmystar]

What controls this and where? Doesn't the injector curcuit start at the computer and finish up at the control relay?

[Junkers]

The wires that feed directly into your throttle body top hat, have you checked the connector there? From what I understand there should be two 12V feeds and two negative triggers (Two wires that keep earthing out in a pulsing pattern). You may need to crank the engine to get them to do this.

[palmystar]

When i put the voltmeter onto the positive wires and earth the negative on the engine i get a current but when i put negative onto the negative wires i don't get a current so guessing its a conection somewhere. but can't find anything???

The two earthing wires go to a resistor where they join into one wire after the resistor. wouldn't this indicate the pulse comes from the ecu with the positive feed? or is the current coming from the resistor side of the injectors?

[JPC]

In your post above, I'm presuming you mean 'voltage' instead of 'current'.

When you say resistor, are you talking about the small metal box mounted on the radiator support (front driver's side) ?

If so, the single common wire is +12V - that's what supplies the injectors with power.

The ECU grounds the other side of injector connection (via open collector transistor) to fire it. This is done in pulses. You can test the injectors by grounding this side of the injector and see if it operates. Keep it short so you don't burn out the injector solenoid - you should hear a click if it's working.

If you disconnect the starter motor, then you can fool the ECU into thinking the engine is cranking and therefore start the fuel pump and fire the injectors without the audio interference from a cranking engine.

If you still can't tell whether the injectors are firing, you really need to see if pins B9 and B10 of the ECU are being grounded - if they are, you have a wiring problem; if they're not, the ECU is probably not getting some other signal it needs (or there's something wrong with it or the connection to it).

You could do this by setting your voltmeter (if it can measure current as well) to measure current. You will need to plug one of the probes into a different connector on the meter - it will be marked - and it will need to be set to the 10A range. You'll also need to put the two probes of the meter in series with the ECU side of one of the injectors. If you crank the engine (fake method or otherwise), you should get a reading of some sort. If you don't, the ECU or connection to it is a problem.

[palmystar]

Ok have found out the ecu is the problem. the injectors are working and the circut is fine. Have tried the existing and a spare ecu and both have the same result.

What else can cause the ecu to not supply an injector pulse. I have checked that it is getting power and that all the earth wires are grounded.

[JPC]

If two ECUs give the same result, you'd be very unlucky for both of them to be faulty.

You'll need to open up the ECU, plug it into the loom and check the continuity of the injector ground wires to the ECU circuit board. If you don't have continuity, chances are it's a connector problem. With age, the spring contacts in the connector open a little too much to make proper contact. It's a simple matter to close them a little so they make proper contact, with a jeweller's screwdriver or something similar.