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skydiver 11-10-2017 04:58 PM

Fuel injector
'92 SC 285000mi. comp 175 178 174 175 rings and valve job at 189000 because of burnt exhaust valve.

I have an issue with #1 injector control.

Much work has been done to come to this analysis.
New plugs indicated no fire on this cylinder ie: still shiny new no indication of combustion.

With engine running (missing on #1) I can cycle the injector with a pigtail and the engine will smooth out.
Engine off, spark plug removed, fuel rail pressured I can cycle the injector and hear pressure release and also gauge goes to zero.

Is there a way to test the wires to that injector?
Or, does anyone have an idea how to proceed?

toggenburg 11-10-2017 07:11 PM

Re: Fuel injector
If all you are missing is an injector pulse then you are only left with the injector wiring and the computer. I would try to find a good used one.

These guys have a good wiring diagram for a 1994


fdryer 11-11-2017 02:03 AM

Re: Fuel injector
If I'm not mistaken, all injectors are powered in parallel. That means every injector has 12v on each side of its connector with ignition on. What may confuse many is one injector wire returns to the pcm as the electronically switch ed ground connection where a switching circuit switches ground on and off to activate each injector. With this ground held open in the pcm for each injector, both sides of every injector connector should measure as battery voltage when the meter negative probe is grounded to the engine block. If you see 12v on every injector connector (ignition ON) the injector wiring is fine. What you don't know is whether or not the individual switching circuit to each injector is faulty (faulty pcm). The easiest way to determine injector failure is simply swapping it with another one. If the faulty injector fails to operate in the other cylinder, the injector is dead. If the new injector doesn't work in the cylinder that has the problem, wiring or pcm is faulty.

skydiver 11-11-2017 10:05 AM

Re: Fuel injector
I checked the 12v ignition circuit to #1 injector and it was good. My plan today is to do the injector swap. My hope is that it is partially plugged.

I was hoping someone had a easy way to check the pulsed ground wire before I went to the trouble removing the fuel rail. I am certain that the injector cycles with manual activation.

fetchitfido 11-11-2017 01:12 PM

Re: Fuel injector
Pink w/Blk stripe is sourced directly from the INJ 7.5a fuse in the UHJB.

The other colors are ground control wires from the PCM ("hack" it to ground to test-fire with key-on). INJ1 use's pin J1-D-16, INJ2 use's 15, 3 = 14, 4= 13 (for the TBI SOHC's this is also their injector wire location).

Blue connector at the PCM, with the plug latch on the left, row C is on the latch side and D is the other; pin 1 is on the bottom and pin 16 the top (should be marked on the connector as well but its usually hard to read).

Sounds like there's a faulty connector either on the injector or on the harness rather than a wire problem if resetting the connector activates the injector. The washer fluid motor connector should be a nearly direct swap, only wire color difference, if you don't want to buy a brand new one or go through the hassle of pulling a injector connector from a junkyard.

billr 11-11-2017 01:19 PM

Re: Fuel injector
There are [I]two[/I] easy ways to check for pulsing at the injector: use a "noid light" or the voltmeter. The drive (grounding) wire should read 12VDC, same as the other one, at KOEO, then start pulsing when the engine is cranked or running. This pulsing may be easier to see using an AC voltage range, and will be fairly low. You can read AC volts either from the 12V wire to the drive wire, or from the drive wire to ground; whichever is easier. Try it on an injector that seems to be OK to see what a "normal" reading looks like...

skydiver 11-11-2017 08:53 PM

Re: Fuel injector
The injector was mostly partially plugged or not cycling fully. It would only let some dribbles through when cycling manually with 9v battery I have a new one ordered from Rock Auto.
Thanks for the hints

toggenburg 11-11-2017 09:13 PM

Re: Fuel injector
That's a good find, however, in your first post, you stated:

"With engine running (missing on #1) I can cycle the injector with a pigtail and the engine will smooth out."

So, I took it to mean that you could somehow 'fire' the injector and thereby smoothed out that misfire. My bad to think you were mimicking an ECM pulse.

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