Thick white smoke and gas coming from tailpipe

Tiny
USERNAMEMN
  • MEMBER
  • 2009 FORD EXPEDITION
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Engine run fine. Then I added a drop of dielectric to coil boots and tighten spark plugs. While doing it I accidentally shorted to ground the PCM wire (not the second 12 volt wire) on one of the fuel injectors.
Now, after I fixed the short on the wire:
1)With engine running, still, there is a very thick white smoke and gasoline coming from tailpipe. Seems like, there is also a little bit of a gas smell under hood.

2) Resistance of all fuel injectors is around 12ohms.

3) When Key is in ON position, I measure DC around 3.4V on the PCM wire and 12Volts on the common wire of all fuel injectors.
Is PCM wire reading of 3.4V normal?


What do you think got damaged?
I am thinking it might PCM, PCM driver, might be the new coil boot dielectric, might be over tightened damaged spark plugs, or I might have pulled something else while doing the work.
Thank you
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Saturday, September 28th, 2019 AT 4:33 AM

13 Replies

Tiny
ASEMASTER6371
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Good morning,

With the key on, engine off, you should have 12 volts from the common feed and 12 volts on the wire to the PCM. That means the PCM driver is open and there is no ground.

With 3.4 volts, that means either you have a bad injector, wiring to the PCM is damaged or the PCM.

I attached a wiring diagram for you to view. I would disconnect the PCM and check the voltage of the wire from the effected injector at the PCM connector.

If it is 12 volts, then you have a bad PCM. If you have any other reading, it is either the wiring or the injector.

Roy
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Saturday, September 28th, 2019 AT 5:01 AM
Tiny
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Hi Roy,

Sorry for miscommunication above: I measured PCM wire voltage of 3.4V with the fuel
injector connector totally disconnected from the injector.

Due to the short I had, I am able to connect and disconnect easily the PCM wire near the fuel injector connector (not at the PCM, I do not know where to tap it). In this case, per your suggestion, with key on, engine off, I get 12 volts reading on PCM wire when it is connected and 3.4 volts when it is disconnected.

1)So looks like PCM is good (allows the injector to pull PCM voltage to 12 volts), injector resistance is good. Can you tell me where to tap the PCM connector, so I can check the PCM wiring on cylinder 1?

2)Do you think any of the PCM issues could cause a little bit of fuel smell near the engine block? Perhaps, it might be that over tighten spark plugs broke.

3)For how long can I run the engine with fuel and white smoke in exhaust system before it goes bad? I am thinking I might simply have a lot of residual fuel in the exhaust system I need to clear, but I am afraid to run the engine for too long and ruin catalytic converter, engine or something else.

Thank you,
Gene
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Saturday, September 28th, 2019 AT 1:58 PM
Tiny
ASEMASTER6371
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Okay. First, the 12 volts does not come from the PCM. It comes from the fuse box. The only thing the PCM controls is the ground.

The diagram I sent you has the wire marked for the number 1 injector. It is pin 1 on the PCM connector as marked.

Disconnect the PCM connector and measure the voltage at pin 1. If it is 12 volts, the wiring is good. If it is not then either the injector or the wiring is the issue.

Do not drive it like this. You will damage the cylinder as all the fuel will wash the rings out.

Roy
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Saturday, September 28th, 2019 AT 2:06 PM
Tiny
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There are 3 PCM connectors there, which one is it? And in which corner is the pin #1? Thank you.
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Saturday, September 28th, 2019 AT 4:35 PM
Tiny
ASEMASTER6371
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The connectors should have pin numbers on it.

It is a black connector. I attached a picture of the connector and the wire color for pin 1.

Roy
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Saturday, September 28th, 2019 AT 4:43 PM
Tiny
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Great. I got the 12V. I measured practically no wire resistance from PCM to fuel injector as well. Wiring is good. Not sure what to do now.
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Saturday, September 28th, 2019 AT 5:14 PM
Tiny
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I pull the error codes. File is attached Looks like cylinder 3 is the cause of the problems.
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Saturday, September 28th, 2019 AT 8:26 PM
Tiny
ASEMASTER6371
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Okay, so now it is number 3?

As far as number 1, if that is what is causing the excessive fuel, the PCM is bad.

As far as number 3, you need to check the plugs, coil, wiring as you are doing for number 1 and lastly the compression.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

https://www.2carpros.com/articles/how-to-test-engine-compression

Roy
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Sunday, September 29th, 2019 AT 4:28 AM
Tiny
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I pull the codes for the first time and it showed the above number 3 problem. I replaced the spark plug and coil assembly on number 3 with new ones. Started an engine, it sounds normal, for a 30 seconds or so it looked like the smoke was clearing up and then it started to smoke up heavy again. Anyway, I cleared the above codes, idle an engine for couple of minutes and tried to get codes again. And none are reported while thick white smoke is pouring.

1)For how long typically do I need to run an engine for the codes to get reported?
2)For how long typically do I need to run an engine to clear the gas inside of the exhaust system? (Initially gas was dripping from tailpipe, now after the above spark plug/coil assembly change on 3 it does not drip). On cylinder 1 PCM wire was shorted to ground 3-4 minutes before I shut down the engine and found the short, not sure how much gas it would flood into the system.
3)Do you know if PCM fuel injector pins are designed to handle to be shorted to ground and not ruin the PCM? Would fuel injector get damaged if it has continues 12V across it for 3-4 minutes?

"As far as number 1, if that is what is causing the excessive fuel, the PCM is bad."
4)Why do you think that? PCM is measuring open with key on and voltage on the disconnected PCM connector is pulled to 12V. For whatever it is worth, all PCM wires seem to behave identical: reporting 3.4V with fuel injector connectors disconnected; engine sounds smooth as well.
Thank you.
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Sunday, September 29th, 2019 AT 6:22 PM
Tiny
ASEMASTER6371
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Based on your information and testing, the PCM is the issue with number 1. I stated why in a previous answer.

Where was the short for number 3 cylinder? A short is a short. It does not be fine one minute and short the next.

It takes about 5 minutes to burn up the extra fuel.

Roy
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Monday, September 30th, 2019 AT 2:22 AM
Tiny
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Good morning,
I measured PCM wire voltage of 3.4V with the fuel injector connector disconnected from the fuel injector. Since PCM driver acts like an open, it was an irrelevant measurement, easily effected by the impedance of my multi-meter. What matters is that PCM driver acts properly like an open with key on, engine off.

"With the key on, engine off, you should have 12 volts from the common feed and 12 volts on the wire to the PCM. That means the PCM driver is open and there is no ground."

"I would disconnect the PCM and check the voltage of the wire from the effected injector at the PCM connector. If it is 12 volts, then you have a bad PCM. If you have any other reading, it is either the wiring or the injector."

Therefore, I do not see how your conclusion can be correct: one on hand 12V reading indicates proper PCM function (PCM driver is open, for all practical purposes it is the same as disconnecting PCM connector), on the other hand 12V reading with PCM disconnected indicates bad PCM.
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Monday, September 30th, 2019 AT 10:35 AM
Tiny
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"Where was the short for number 3 cylinder?"
There was no short on number 3 cylinder. I am not able to get any error codes, after I replaced coil and spark plug on 3.
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Monday, September 30th, 2019 AT 10:40 AM
Tiny
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If the code has not returned, then most likely number 3 is now good.

Roy
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Monday, September 30th, 2019 AT 11:47 AM

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