Cyl 3 on SR redtop not firing

SON240sx Automotive
1

Just started the car and the engine was shaky, so, I went pulling the injector feeds, and found that the cylinder 3 was not working.

I went to replace the injector - no result
Swapped the coilpacks - no change, still same cyl not working
Pulled out the spark plug - no smell of gas from the cyl

this makes me think that there is no signal coming to injector…

What would you suggest? ECU? Ignitor? Anything else?

Thanks!

2

following this. its a tough one to figure out. let us know what happened.

Could be a bad wire/connection to the injector. I think that there’s a way to test signal to the injector with a ohmmeter. There is prob something on youtube about this.

This sounds like a similar problem:

http://www.son240sx.org/showthread.php?243800-No-Start…-no-injector-pulse

3

Update:

  • Determined for sure that the injector is not clicking. This is in spite of replacing it
    yesterday.
    Possible chance that it’s also bad, but not that likely.

  • Checked the voltage with meter, approx 14 volts on both red and green feeds. Same for all 4 injectors.

Thinking if that can be CAS not sending the proper signal to one cylinder. Is that possible for only one cyl? Or ECU?

4

Really good writeup on how the injectors/ECU work
http://www.tiepie-automotive.com/en/Measurement_examples/Actuators/Indirect_Injection_Voltage

5

have you looked inside you ECU box for corrosion/contamination? if you have power you are missing switched ground maybe?

I had an issue where one cylinder would not shut off, there was literally gas spitting out the tailpipe, but looking at the board the damage was water, obvious and easy repair

any water leaks around your windsheild?

6

Huh, that’s a good question I should take a closer look. For now I have measured the voltage coming to the injectors, and it shows about 0.15 v more on that cyl. That may be because ecu gives no interruption? And why it might do that, is it bad, or something else is causing it to function that way?

7

Step 1)
Don’t waste time, get a handy dandy compression tester and test cylinder 3.

Step 2)
If compression is good, unplug the fuel pump fuse, take coilpack and sparkplug from cylinder 3, ground the sparkplug and start motor and see if it sparks.

Step 3)
If sparks are flying, check if injector on cylinder 3 is squirting. wear fire suit if ur a newb.

8

I like the part with the fire suit, BUT: no need to do that because for sure it is the injector. Why? Because it is not clicking. How do I know? There are lots of sophisticated ways, but there is a simple and sure one: just stick the scruedriver to the injector and hold the handle about 1 cm from your ear, and you will hear precisely what this particular injector is doing. So this one does not work.

Then the other part comes in: unfortunately I do not know how to measure voltage interruption sent to the injector from ecu, and i do not have any tools for that. However, the simple voltmeter shows about .15v more on that injector, which may very well account for absence of interruption of 2ms. So, that must be ecu. I can not imagine that cas is causing this for just one cyl.

9

move the injector over to be certain, that would eliminate electrical as a cause if it does the same on another cylinder.

EDIT,

Oops forgot that you replaced the injector. If it has 12v on the red wire? try a direct ground wire from ecu to injector.

10

So, it was ECU, replaced it and it’s all working now. Inside, couple of little parts were corroded, I wonder why it did not go out earlier. Thanks for your idea S13GG!