355 What's wrong with this injector waveform ?

Yes I connected to all the different color wires not the green black and then to ground with the aligator clips

 

Before I was connected to each injectors both wires green black and the others
The green black was to the probes and the other side was to the clips

 

Here is at 1 ms starting at the left first 2 peaks

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I think I am only reading the ground side of the injector now as my probe is only hooked to one side of the injector 1 and 3 and then ground
Black and grey
And red yellow
And then ground on chassis
Mitchell said we want to see the wiggles and there are lots of them ha ha

 

Perhaps too many. I don't know if there is something wrong with your test leads. They should be shielded from interference.

So something like this...

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The transistor in the ECU acts as a variable resistance (across the collector/emitter). It should be close to infinity when the transistor is not activated. If you have a small resistance in series with a large resitance, most of the voltage will be across the large resistance. This gives the oscilloscope the steady or "baseline" voltage. When the transistor is activated, firing the injectors, the resistance across the transistor drops dramatically. Less voltage will be measured by the oscilloscope.

To put it mildly, your baseline is all over the place.

Correct. Unmetered air can be fed into engine via air leaks in the manifold (after the MAF) and also into the exhaust (via exhaust leaks and leaks in the secondary air system). I've been told that even exhaust leaks after the rear O2 sensors can allow unmetered air to get to the O2 sensors. If the O2 sensors see too much air/oxygen, the ECU adds more fuel (unnecessarily so if the leak is not part of the normal combustion process).

 

Remember my test Leeds are set to x10
Would that matter?

 

So because the injector resistance is larger than the small transistor resistance and very small when the transistor ground I should See a straighter line higher voltage about 14 v most of the time when the transistor is grounded and then a very low voltage spike when the transistor switches the injector on

Ok it’s late here so will do tomorrow after work
I do have it hooked to the chassis ground bolt by the positive bolts at the back

 

Just so you know I left the trace on and scope plugged in so I could manipulate scales etc for these traces if someone needed me too

 

I am quite sure of that as I checked 2 injectors by pulling back the boots and tracing the wires to the probes

 

The resistance of the transistor is not necessarily zero at the time of firing. If the resistance of the transistor was, say, the same as the injector, in theory, the voltage actross the transistor (at the time of firing) should be half of your supply voltage (13.5 volts divided by two).

The transitor resistance can be varied by putting a different voltage on the base of the transistor (i.e. on the third leg). You could probably compute the resistance of the transistor by seeing how much your voltage drops when the injector is fired (if you knew the resistance of the injector coil). Note that coils are not true resistances, though. That's why you get the spike when the transistor is turned off. Anyway, we are probably getting off track here.

 

So all I need to do is hook 2 of them back up the way I had it and instead of saving the trace to R1 just keep it on the scope as a trace and this would show that they are open most of the time and only closing for a micro second?
They are working backwards?

 

It's the signal to noise ratio I'm worried about. If your signal is bouncing up and down erratically, we don't know what the injector is doing. There may even be a foreign signal on the line activating the injector.

 

The transistor that switches the injector on & off is a so called switching transistor (MOSFET nowadays) and it is basically an electronic switch. For any analysis of the injector circuit, it can be taken that, when "off", the resistance between collector and emitter is infinite (open) and, when "on", it is zero. Just like in the case of a mechanical switch. The control of the transistor is such that it is brought to either "on" state or "off" state with the switching between the two states happening very fast, typically in 20 to 200 picoseconds (1 picosecond = 0.000,000,001 milliseconds), that's fast!



With regard to the scope, x 10 setting on the probe might be too sensitive. I would try with lower sensitivity.

 

Since there is still a voltage of around 1.7V on the scope when the injector is firing, I guess there must be some kind of additional resistance in the ECU in series with the MOSFET.

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Too many voices.

Both side or just 1-4?

Sounds like a bad exhaust leak in the exhaust before the first O2 sensor or a cylinder not firing, or air injection is not shutting off.

 

Given that the pulses look as expected with the exception of the voltage scale, common sense would say that since this is a 12 volt system the voltage drop when the switch is closed must be on the order of 12 V or a little less. No way you et 17v out of a 12v system. Conclusion, the scope or probes are miscalculated.

If, as Grant said, the O2 sensors are telling the ECU to richen the mixture, then either there is excessive O2 in the exhaust or the O2 sensors are shot.

What are LT ans ST fuel trim doing. Grant's comment would indicate that they are increasing with time. Has that been verified?

 

Yes it’s all been smoke tested and there is nothing for leaks

 

Yes before all leaks were fixed now they just stay around 18 hrs and 11 with a STFT on that side of -4 but I don’t let it idle too long due to cat overheating on rhs

 

Have you looked at the O2 sensor signal on the right? Is it switching? Is it pinned to low voltage?

 

If the car is over fueling (aka rich) and the O2 sensor is the fuel mixture not being burned the pulse with will be less (aka on time of the injector) to lean the mixture

By leaning the mixture (aka give it more air the what the throttle plate can give you should see a change in the O2 sensor


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What the O2 sensor sees because that controls the pulse with


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