 How to find which cylinder is not firing and why? |
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| velum |
 Sep 9 2010, 04:01 PM
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#1
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Member  Group: Members Posts: 50 Joined: 4-June 08 From: Montréal, Qc, Canada Member No.: 9,135 Region Association: None  |
Hi!
I had to change my FI Wire-Harness ('73 914-4 2.0L), because the old one wasn't good anymore. Barely moving wires broke them. So I installed a brand new harness. However, my engine is not running smoothly at all. It sounds as if it would be running on three cylinders only. You can hear it on this video I posted on YouTube: http://www.youtube.com/watch?v=Uu6K7P4bpQk How can I test weather all injectors are receiving impulses from the ECU? Can it be done with a multimeter? I also have an extra set of injectors taken out from a more recent car ('74 I believe. They are green). Should I just connect each injector wire to one of these extra injectors in loose air one by one and see what happens? Even if there is no gas line connected to the injector? Also, is there an easy procedure (without special tools) to ensure that all injectors are working properly? And if I find an injector that is not working properly can I swap it with one of the extra ones I have. All injectors in my car, and the extra ones are green (sometimes they look black, maybe because of the age). Cheers! JF P.S. I also changed the injector o-rings recently... |
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| underthetire |
Sep 9 2010, 04:33 PM
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#2
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
You can check the pulse with a old analog (dial type) multimeter at idle. The digital ones are just not fast enough. There is also a "noid" light you can buy to test them. Easiest way to find a dead hole is with a thermal gun. Find the cold exhaust.
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| dlee6204 |
Sep 9 2010, 04:36 PM
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#3
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Howdy Group: Members Posts: 2,162 Joined: 30-April 06 From: Burnsville, NC Member No.: 5,956 |
One way to test the injectors is to unbolt all four from the manifolds and place each one in a small jar. Disconnect the coil, then crank the car for a few seconds. Each injector should spray a small amount of gas into each jar and you can tell if they are all firing and flowing evenly.
Another way is, while the engine is running, disconnect each spark plug wire one at a time. If you pull one and your engine doesn't change, you know that cylinder is not operating correctly. |
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| VaccaRabite |
Sep 9 2010, 04:40 PM
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#4
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En Garde! Group: Admin Posts: 13,444 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
To find wich cylinder is not working, just start the car and let it idle. lay down and feel near the exhaust pipes (don't touch them, they will be HOT). The bad cylinder will be way cooler then the others - maybe flat out cold if it is not firing at all. No special tools needed.
Zach |
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| Andyrew |
Sep 9 2010, 05:05 PM
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#5
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Spooling.... Please wait Group: Members Posts: 13,376 Joined: 20-January 03 From: Riverbank, Ca Member No.: 172 Region Association: Northern California 
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I have always liked the wire pull method.. Pop the hood, Pull the wires one at a time. done.
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| IronHillRestorations |
Sep 9 2010, 07:42 PM
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#6
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I. I. R. C. Group: Members Posts: 6,719 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None
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QUOTE(Andyrew @ Sep 9 2010, 03:05 PM)  I have always liked the wire pull method.. Pop the hood, Pull the wires one at a time. done. (IMG:style_emoticons/default/agree.gif) Make sure you use insulated pliers, or plug wire pliers. |
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| yeahmag |
Sep 9 2010, 08:20 PM
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#7
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Advanced Member Group: Members Posts: 2,421 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California
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Eh... If your plug wires are OK and you are wearing tennis shoes you'll be fine. If your super paranoid don't ground yourself. Then again, I'm an idiot...
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| PlaysWithCars |
Sep 9 2010, 09:55 PM
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#8
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Senior Member Group: Members Posts: 524 Joined: 9-November 03 From: Southeast of Seattle Member No.: 1,323 Region Association: Pacific Northwest
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QUOTE(yeahmag @ Sep 9 2010, 07:20 PM) Eh... If your plug wires are OK and you are wearing tennis shoes you'll be fine. If your super paranoid don't ground yourself. Then again, I'm an idiot... You'll know it if you do accidentally ground yourself. Its an eye opening experiencing. (IMG:style_emoticons/default/blink.gif) |
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| velum |
Sep 10 2010, 09:39 PM
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#9
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Member Group: Members Posts: 50 Joined: 4-June 08 From: Montréal, Qc, Canada Member No.: 9,135 Region Association: None |
Many thanks for all that input!
I think I'll use insulated pliers + rubber gloves + tennis shoes! Cheers! JF |
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