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Old 02-28-2014, 02:23 PM   #1
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Default Help isolate fuel problem

So #3's plug is wet, car runs like its on three cylinders, and it's getting spark. How should I go about isolating this problem to the injector or the computer?

Back in November I was at the track and the fuel pump decided not to prime. I jacked with it for hours, then it magically worked and has worked since. However, it's basically run on three cylinders ever since. I have no idea what's going on but now my arm is finally strong enough to turn a wrench so I can work on it.

If a driver were hung open on the injectors would fuel flow when the car is not running but pump primed?

Last edited by hustler; 02-28-2014 at 02:40 PM.
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Old 02-28-2014, 03:00 PM   #2
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If you're not running sequential, it seems like you could swap injectors between the cylinders and injector harness plug between cylinders. I remember reading a JP write-up on how the MS injector firing worked somewhere. If you can do this, see if it follows the injector or the harness plug??

Just thinking out loud, BTW. There's probably a better way.
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Old 02-28-2014, 03:11 PM   #3
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If a driver were hung open on the injectors would fuel flow when the car is not running but pump primed?
If you had a stuck injector, it could do anything from full on spray to just weeping. If the pump is primed, the system should have some pressure.
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Old 02-28-2014, 04:02 PM   #4
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Which car? Green or white?
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Old 02-28-2014, 08:29 PM   #5
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Which car? Green or white?
Green.
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Old 03-03-2014, 11:33 AM   #6
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If you had a stuck injector, it could do anything from full on spray to just weeping. If the pump is primed, the system should have some pressure.
Could it be screwed up and not working properly, or is this a dead give-away that I have other problems?
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Old 03-03-2014, 12:02 PM   #7
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Remove injectors, replace them with automotive 5-15W light bulbs.

The bulbs should be glowing about the same when you crank. All should be off when not cranking.
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Old 03-03-2014, 01:20 PM   #8
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Could it be screwed up and not working properly, or is this a dead give-away that I have other problems?
I don't know. But that's the first thing I would check. I like Reverant's idea of using bulbs to test the connections.

Not sure how to check an injector other than removing it and seeing if it's leaking/spraying with the car off.
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Old 03-24-2014, 02:04 PM   #9
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Is there any reason why the plug would fire outside of the engine, but not when screwed in? I'm a little confused right now, something is not right but I can't tell what or why when using a multi-meter. I guess it's time for the lights.
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Old 03-24-2014, 03:14 PM   #10
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Not unless the wire is borked. If there's a break, putting the plug in may open up the break, but it's in contact when the plug is pulled out.

I'd test the wire for continuity.
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Old 03-24-2014, 03:43 PM   #11
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Not unless the wire is borked. If there's a break, putting the plug in may open up the break, but it's in contact when the plug is pulled out.

I'd test the wire for continuity.
Plug wires have continuity, plugs 2&3 do not reek of fuel. 1&4 are clearly burning fuel. I swapped coils (I have a new pair) and no change. Now I guess it's time to see if the injectors are seeing any voltage.

To output test mode I go!
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Old 03-24-2014, 03:45 PM   #12
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BTW, it's cool how you can turn-off the fuel pump for test-modes in MS3, balleur as ****.

Does each injector have it's own driver, or are the drivers shared?
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Old 03-24-2014, 03:58 PM   #13
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using injector test mode, all 4 injectors cycle audibly with the same pattern. Is this a reliable method to confirm they are working properly?
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Old 03-24-2014, 04:03 PM   #14
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When I test the coils I see .5v on coil A (#1/4), .2v on coil B (2/3) measuring both at the OEM connector, coils obviously unplugged since I'm not talking about electrical shock. Thoughts?
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Old 03-24-2014, 04:14 PM   #15
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any coolant in cylinder 3?
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Old 03-24-2014, 04:18 PM   #16
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any coolant in cylinder 3?
It doesn't appear, but the piston crowns are wet. I'm leaning toward a coil issue. I can swap coils around between old and new, #2&3 never seem to fire. I guess it's the wiring?
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Old 03-24-2014, 04:43 PM   #17
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Any recommendations on a spark plug test light that I can shove up my VVT coil for easy confirmation?
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Old 03-24-2014, 04:55 PM   #18
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Injectors 1 and 3 share the same driver on a 1.6L. The same goes for 2 and 4.

So if this was an injector driver inside the ECU, two cylinders would be affected at the same time.
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Old 03-24-2014, 05:24 PM   #19
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Quote:
Originally Posted by hustler View Post
Any recommendations on a spark plug test light that I can shove up my VVT coil for easy confirmation?
A grounded out spark plug will tell you if you have fire.

Pull out all the plugs, disconnect your coils and turn on your fuel pump.
When you crank, do you a see any extra fuel or a mist of fuel coming out of the affected cylinder ?
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Old 03-24-2014, 05:26 PM   #20
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Quote:
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Any recommendations on a spark plug test light that I can shove up my VVT coil for easy confirmation?
Finger on coil and output test mode
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