Stuck open fuel injector

[CaptonZap]

I have a '95 ranger with the small six engine, and two days ago it started missing on one cylinder. My timing light showed spark on all cylinders. When I started the engine, I could smell gas, and when I drove I could see smoke coming out the exhaust pipe. Today I started it, and what seem ed like raw fuel came out the exhaust pipe. The right front plug was wet and washed clean with what smelled like gas. The others looked dry and slightly off white.
The question is, can the injector fail open, and is there a way to get it to close, short of taking it out? Is it better to get a new one?
The truck has 130 K miles on it, and I bought it new.
Thanks for any help.

CZ

 

[RonD]

Fuel pressure should force needle closed, and it has a filter screen so nothing large could get in and block it open.
So injector failing should be closed and cause the misfire

The fuel injectors all get 12 volts when key is on, but no Ground so they stay closed.
With 6 cylinder Sequential injections each injector will have a Ground wire running back to the computer, so 6 Ground wires.
Computer then Grounds the injectors to open them.

So.............chaffed wire could be Grounded and that injector would open when key was on.

Unplug the injector's connector
Disconnect Coil Packs 4 wire connector, so no spark
Crank engine then check that cylinders spark plug, should be dry
If it is wet then yes injector itself is leaking fuel.
If dry then you will need to trace the Non-red wire on that injector to find the short to Ground.
Test wire with OHM meter, 0 ohms is a short to ground, then move wiring harness around and OHM meter might jump up in OHMs if short is moved

 

[scotts90ranger]

Injectors do fail open, that many miles in 20 years isn't a lot and the newer gas has a tendency to do stupid things... I had an injector fail on my way to work one day on my daily driver Geo Tracker, sent them off to an injector shop and sure enough one was bad...

 

[CaptonZap]

Thanks for the response, guys.
I disconnected the injector wire to #1, the one that was all wet with gas,
and drove around to warm up the engine, and other than the miss, which wasn't that bad, it quit smoking.
I could not get any voltage or ground readings, but it may have been that i didn't get the probe all the way into the socket. I will get a small strip of tin and try that after lunch.
This makes me wonder if the computer grounding transistor is shorted, which would call for a new ECU.

Thanks for your inputs.

CZ

 

[RonD]

I use a sewing pin to pierce a wire to test voltage or ground

 

[CaptonZap]

I use a sewing pin to pierce a wire to test voltage or ground

Good idea Ron,
They make a tool that has a spike that is in one jaw of a pliers like tool, and you put it on the wire and clamp down and it does the same thing. I took a small strip of sheet metal and stuck it in the socket, and hook my lead to it.
With key on, I had no readings either wire.
With the engine running on 5 cylinders, I got 12 volts on one injector wire, and .008 ohms on the other. That one was a steady reading, and since I had a digital meter, I would have expected there to a jittery reading, with the refresh rate of the meter not corresponding to the grounding rate.
So it looks like there is a defect in the ECM, according to my thinking.
I used to have a manual for this truck, but I can't find it, not having any trouble with the truck for a long time, and I don't know where the ECM is located. This is a '95 3L V6. Any ideas about where it is located?
I disconnected the wire to the #1 injector, and that cured the blowing smoke enough so that I could go finish a job that required the ladder on the ladder rack, so now I have time to diddle with this problem.


Thanks for your help, and Merry Christmas, CZ

 

[RonD]

Digital meter won't show the millisecond grounding, analog may "jitter".

A NOID light is need to test running engine injector pulse, it plug into injector and injectors wiring, flashes if computer is sending pulse or would stay on if steady ground.

But there should be 12volts on Red wire with key on, that wire just daisy chains from one injector to the next.

 

[CaptonZap]

Thanks, I'll try again tomorrow, if it isn't freezing. Now that I know I can drive it without getting a ticket for visible pollution, I can approach this in less than a panic mode.
I may dig out the Nano pocket oscilloscope. That should tell me if there is any sort of signal on the white ground wire.
If there isn't, does that mean the ECM is faulty?
Thanks again,

CZ

 

[pjtoledo]

engine off, remove big connector on ECM, remove connector on suspect injector. that isolates the wire harness.
test at the injector connector for continuity to ground on the white wire. there shouldn't be any, it should be an open circuit. if there is any continuity follow the wire and look for damage.

if no continuity to ground, plug in the big ECM connector and compare white wires on several injector connectors. they should all be the same. I'm not sure exactly what reading you would get with the ground side essentially "floating" since the ECM has no power, but they should all be the same.

reviewing the volts expected at the injector, remember when the engine is running there will be constant 12v on the red wire, and almost a constant 12v on the ground side too!!!
the ground side will (should) only drop to zero volts during the few milliseconds when the injector is signaled to open.

the meter or scope will be looking for a near constant 12v with short pulses to zero on the white wire while running. if using a testing light/probe, hook it up backwards. put the ground lead on the white wire and the + lead on the battery + terminal. that way the light will illuminate only when the injector is grounded and current is flowing. its easier to see a flash than a dropout.

 

[CaptonZap]

My first problem is that I don't know where the ECM is located. I will BING it and see what I can find.
When the engine was running with the wires to the injector disconnected, and my meter connected to the white and ground, in the ohms mode, I assumed that the meter battery would supply the voltage to make the trip through the white wire through the grounding transistor to chassis ground, and then back to my meter. In the past, when I tried to measure a pulse circuit completion with a digital meter, I found that if the frequency of the measured pulse did not match the refresh rate of the meter acquisition circuitry, that the readings would jump all over the place.
And yesterday, it was a steady .008 ohm, which could be meter error. ( I forgot to check probe to probe reading.)
I am going to plug #1 back in and try the same reading on a know good cylinder, if I can get it to idle on 4 cylinders long enough to get a reading.
What I would like to do is to hook up a resister between the red and white disconnected lead, and the put the scope on it so that I could compare that with a known good cylinder. Would you happen to know the resistance of the coil?
I suppose I could measure one that I know is good.
Come to think about it, an internal short in the injector would have the same effect as an external ground. Haw! One more thing to check.
Anyway, thanks for your help, and any more thought would be appreciated, as well as the location of the ECM.

Merry Christmas, CZ

 

[RonD]

11 to 16 OHMs is spec on Ford Injectors

 

[CaptonZap]

Thanks Ron

I have just the thing. Now I just need some warmer weather.

Merry Christmas. CZ

 

[pjtoledo]

My first problem is that I don't know where the ECM is located. I will BING it and see what I can find.
When the engine was running with the wires to the injector disconnected, and my meter connected to the white and ground, in the ohms mode, I assumed that the meter battery would supply the voltage to make the trip through the white wire through the grounding transistor to chassis ground, and then back to my meter. In the past, when I tried to measure a pulse circuit completion with a digital meter, I found that if the frequency of the measured pulse did not match the refresh rate of the meter acquisition circuitry, that the readings would jump all over the place.
And yesterday, it was a steady .008 ohm, which could be meter error. ( I forgot to check probe to probe reading.)
I am going to plug #1 back in and try the same reading on a know good cylinder, if I can get it to idle on 4 cylinders long enough to get a reading.
What I would like to do is to hook up a resister between the red and white disconnected lead, and the put the scope on it so that I could compare that with a known good cylinder. Would you happen to know the resistance of the coil?
I suppose I could measure one that I know is good.
Come to think about it, an internal short in the injector would have the same effect as an external ground. Haw! One more thing to check.
Anyway, thanks for your help, and any more thought would be appreciated, as well as the location of the ECM.

Merry Christmas, CZ

are you meaning .008 ohms on the 1.999K scale, which would be 8 ohms. or .008 on the 1.999 scale which is basically zero resistance?

there is more than .008 ohms in the test leads.


I would suspect an internal short in the injector would cause the current to bypass the coil, resulting in the injector not opening at all.

 

[CaptonZap]

are you meaning .008 ohms on the 1.999K scale, which would be 8 ohms. or .008 on the 1.999 scale which is basically zero resistance?

there is more than .008 ohms in the test leads.


I would suspect an internal short in the injector would cause the current to bypass the coil, resulting in the injector not opening at all.

Yep PJ,

That was what I thought of after I came in. When I go back out today, I will check the meter error. It was on the 200 ohm scale.
A while back, I had a miss in this truck that was ignition related. On checking the ohms of the coils, they all read good, but I still had a miss. I finally figured out that one coil was grounded internally, on the end of the coil away from the feed side. My thought is that if the same thing happened here, that would cause the effect I am seeing.
The sun is out, the wind is gone, so I'll go see what I can figure out.

JR

 

[CaptonZap]

Well, the resistance in #1 injector is 16 Ohms. Does anyone know where I can get a pin out of the ECM connecter? I could test for shorts between the injector and the ECM.
The guy across the alley says that it sounds like the injector nozzle is cracked. If that were the case, would it not still leak when the wire connection is off? When I disconnected the coil pack connecter, and the injector connecter, and cranked it over, then looked at the plug, it was dry.
Tomorrow I will see if I can find someone that has a tester to see if the signal is good from the ECM.
The plot thickens.