355 What's wrong with this injector waveform ?

No I can move it anywhere.
It’s drag and drop both up and down and left to right after you stop the run
The horizontal trace is the main voltage it is measuring if that makes sense.
Usually around 13.5 to 14 volts. Maybe it’s called the mean but not sure

on the good trace you can see it because when grounded it drops to all most zero
But the main horizontal line is 13.5 or so
Kind of what ever the steady voltage is that it’s measuring

 

So it's the same for the bad waveform, too?

I'm not sure how you'd be able to jumper the broken wire without cutting into the heavy insulation and damaging other wires. On my old broken harness, I found some really dodgy splicing hidden inside the main ECU connector backshell. For a semi-permanent fix, you could splice the wiring there and perhaps feed the wire past the boot on the connector. Then try to string the wire through the firewall, zip tying the wire to the main harness.

Here's the mess I found in my old harness:

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It's a pity that there are no spare wires on these harnesses.

 

I noticed that on mine as well when I did a gold kit
I could push the old wire out and install a new one but it’s getting cold up here in the great white north again so I think I might just run a new wire and see if it fixes it or just drop the engine it’s a toss up right now for me

 

Ah.. I thought yours looked slightly better than mine.

What would you do with the engine dropped? Put in a new harne$$ or try to fix the old one?

Unfortunately, I gave away my old harness. I should have cut it open to find out exactly where all the splices were.

 

Post 108 second and third pic
Second piC shows it zoomed out and third zoomed in
It looks like if you read the notes below the wave that it’s -4.8 and high of about 24.5
The scale is still 10v per division

 

I will fix the old one but inspect the whole thing up to the engine
Want to make sure no others look bad
I suspect the outside of the wire is still intact
This would be why pushing it in makes a good connection but I do not know for sure

 

What the trace indicates is as I diagrammed. There is a large parasitic resistance somewhere between the point where you connected the probe and ground. It's either associated with the wire or internal to the ECU. That's as much as can be determined from the wave form.

If you have a volt/ohm meter you could measure the resistance of the grounding wire between the injector (where you have the probe connected) to the ECU plug with the plug disconnected from the ECU. Then you can wiggle the wire around and see if the resistance changes. I'm guessing that the resistance should be under 1/2 ohm if the wire is good. Since Moro said the injector resistance is about 5 ohm, it would have to be much larger that 5 ohms if bad.

 

Inside a wire harness what would you define as a probable parasitic resistance?
I know it’s not the ecm because it has the same problem with the other ecm.
Would a completely broken wire fit the definition as I think not unless it shorted to something else.

 

"Parasitic" was a bad choice of words. I just meant a large additional series resistance between the probe and ground. A completely broken ground wire would not do it as in that case the you scope trace would just be a flat line at nominally 12v.

As for the idea of an internal short in the harness, the only thing I can think of that might have a similar effect would be if the ground wire was shorted to another wire which supplied power to another component. But I have trouble visualizing how that would result in the signal you see on the scope and not cause other problems. But weirder things have happened.

Again, you need to unplug the injector and probe the length of the ground wire with a volt/ohm meter. What's the resistance of that wire between the injector connection and the ECU? Is there any spurious voltage on that wire when disconnected from the injector? (You might have to look at that with your scope, engine running and injector unplugged.)

If the injector is good and the ECU is good then the problem is in the wires. That shouldn't be hard to find.

 

no on any wave form if you read the min or max that shows in writing then you can extrapolate from there using the known scale of 10 volts per division

 

True, but I'm not familiar with the scope displays.... and some of your min/max values were a little blurry.

What does CH2-10V "Full" and "mV/1x/V mean?


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I see Min = minus 200mV and Max 69.0V. So the baseline seems to be around 13.65 volts.

In this shot... (blue channel 2)

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Ch2 is only 2 volts per increment (I assume). Min is minus 1.86V. Max is 6.80V. I estimate the baseline to be around 1.64 volts above the minimum voltage (i.e. minus 220mV).That's quite different from the other pic.

And I don't really understand why the voltage goes negative.

 

Yes you are reading correctly
That is the correct range scale per division either 2 or 10 as shown
The Mv. V is how you adjust it up or down as it has steps
You push mv to reduce and v to increase
It goes from 2 to 5 to 10 and 10 is max
The other is the setting on the probe or the scope it should match the leed setting
I may have had the probe set 10x and the scope at 1X I can’t remember
I did make that mistake once
Also as I was getting to understand the scope better this may have been before I calibrated the
Leeds
I can not explain that either as I don’t think I have had negative numbers since

 

If it’s a power to the injector problem can a person just run power from the back of the car to the injector to test that theory?

 

I would go with the experts on this on... John is pretty sure it's not a power problem (see post 115):

https://www.ferrarichat.com/forum/posts/149320559/

You need to run a wire from ECU pin 5 to the #4 injector



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(solid yellow)

As seen from the pin side of the harness plug:

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Oh ya I forgot about that diagram
Likely because I checked the wire and it seems to have continuity
But I may be using that tester wrong
I will try a multi meter first and report back

 

Test it when you're pulling on the harness to see if you see a change in resistance.

 

Yes, you can run power directly from the battery.

But you say sometimes it works when you pull on the harness. You need to do the same when you test it for continuity.

Bottom line is that if as you claim, the injectors and ECU are good, then it's a problem with the wiring.

 

Yes I am sure it’s the wiring just do not know how to read the scope like you do
But I could also be using the scope wrong giving you bad info
Thanks will try the Power after I check for continuity

 

Forget the scope. It's irrelevant at this point. Looking at your traces you have it connected OK. The only argument is over the scale. But that doesn't matter. It's the shape of the pulse that matters.

This is what I would do. I would get an EV1 connector (that's the fuel injection connector).

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I would connect two long wires to it. One which could be connected to 12V for power (make sure it's the correct one). The other would be long enough to drape out of the engine compartment and into the cabin trough the door. On that wire I would crimp a pin for the ECU plug (like picture or which ever is the correct pin). You should know since you did the gold connector thing.
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Then I would remove the ground wire from the ECU plug, (I assume Ian is pointing to the right wire), and insert the pin from the wire connected to the new EV1 connector. Then connect the new EV1 to the injector. Now the injectors has power and is connected to the ECU drive bypassing the harness. It should function correctly.

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Now you can connect the scope to the new wiring if you would like to look at the signal. The voltage and time scales aren't really important except so that the signal fits on the screen. What is important is the shape of the signal. The level of the supply voltage can be check with a volt meter.

 

Any suggestions on how to get those plugs out without damaging the 88 pin connector.
I tried getting 2 pins out of my old one this afternoon and both times i damaged the connector because it seems very difficult to push both sides of the pin since there is only 1 recess..

 

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You will need one of this tools
I like the yellow on right works better then the star one

Klein makes the yellow one



Sent from my iPhone using FerrariChat

 

I will check it out
The pins have to be very thin in order to get under the one side with no notch out

 

That would make sense thanks

 

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Here is a pic with the backing plate which goes towards the wires popped part way off and the locking plate below also popped part way off
Inside the car I will have to do the same thing and slide the backing plate up along the main harness then the locking plate can actually stay in place
While I push out the connectors.

What I found is I left the backing plate on for the small wires the crimps are so tight to the backing plate it’s hard to push them out the locking plate and backing plate all together but 1 at a time is easier

So if you slide the backing plate up then you only have to push them out of the locking plate