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RSFreak The other "John"
Joined: 23 Jan 2004 Posts: 2946 Location: Renton
1989 Chevrolet Camaro RS
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Posted: Sun Apr 21, 2013 9:48 pm Post subject: Found the problem... |
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Injector #1 is not firing. Now gotta find out why. Can I use a multimeter on the plug to see if it is getting juice? I don't want to frag my harness or ecm by randomly jamming probes into things. _________________ '86 Trans Am - 5.0L TPI - LT1 cam - 700R4 - WS6
'85 Camaro Berlinetta - IROC clone
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fiveoformula Member
Joined: 08 Aug 2007 Posts: 1799 Location: OR
1988 Pontiac Formula
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Posted: Sun Apr 21, 2013 9:56 pm Post subject: |
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Shouldn't be any problem if your just checking for power and ground, just make sure it's doing the intermittent miss thing when you check. Then maybe check it again when it's not doing it. _________________
'88 FORMULA |
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iansane Member
Joined: 16 Jan 2004 Posts: 5740 Location: Bothell
1991 Pontiac Trans Am
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Posted: Mon Apr 22, 2013 9:05 am Post subject: |
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Been awhile since I messed with tpi but isn't it powered all the time and the ECM provides ground?
O'Reilly has a 'noid light rental set, btw. _________________
Quote: | Sometimes I actually think I'm slightly retarded in the mouth. |
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Alphius Peanut
Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Mon Apr 22, 2013 11:48 am Post subject: |
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iansane wrote: | Been awhile since I messed with tpi but isn't it powered all the time and the ECM provides ground? |
Yes. It is also batch fire so if the ECU or wiring was messed up in the harness you would lose a whole bank.
Just a single injector not firing means a bad wire after the harness splice or a bad injector. What is the resistance across that injector from terminal to terminal? Is the harness plug in poor shape and possibly not making contact well enough?
What makes you think it is an injector? What proof do you have? _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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RSFreak The other "John"
Joined: 23 Jan 2004 Posts: 2946 Location: Renton
1989 Chevrolet Camaro RS
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Posted: Mon Apr 22, 2013 12:32 pm Post subject: |
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Did the spray test on the header tubes. #1 stayed wet. Pulled the plug wire and attached spare plug. Started car. Plug fired. Pulled injector wire. No difference in idle. Injector plug is in good shape. |
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MrMike98 Member
Joined: 18 May 2010 Posts: 231 Location: Bremerton
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Posted: Mon Apr 22, 2013 1:28 pm Post subject: |
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try a couple cans(2 tank full) of good injector cleaner.........
u might get lucky. |
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Alphius Peanut
Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Mon Apr 22, 2013 3:17 pm Post subject: |
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Stick a multimeter on the injector and see what it's resistance is compared to a couple other working injectors on your car.
Just unplug the injector and measure the resistance from one terminal to the other. _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Apr 22, 2013 4:32 pm Post subject: |
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If that's all the testing you've done, all you know is that you have a miss. Definatly do an ohm check on that injector though. Also if you can use a screwdriver or something to listen to the injector vs a working one. Working one will have a sharp click to it. Non working you'll hear clicking but it'll just be engine noise.. won't be sharp.
Pull that spark plug and look at it. Could be fouled. If it looks ok swap it with a known good one. Check compression if you have a tester.
Firing a spark plug when its under pressure in the cylinder takes more voltage then firing one just connected to the wire. It's still possible to have a bad plug wire or plug even though it fires fine. I like to swap the wire with another cylinders, same with the plug.. if the miss moves you know what's wrong. |
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RSFreak The other "John"
Joined: 23 Jan 2004 Posts: 2946 Location: Renton
1989 Chevrolet Camaro RS
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Posted: Mon Apr 22, 2013 8:22 pm Post subject: |
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Pulled the plug, didn't look fouled, replaced it anyway. Still have a miss. I'll check the resistance tomorrow. |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Tue Apr 23, 2013 5:36 am Post subject: |
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My money is on a bad wire, or maybe a bad pickup coil.
Steve's mechanic put his stethoscope on each injector and didn't hear a dead one, and jostling the wires around "fixed" the problem. |
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BluFbdy Member
Joined: 16 Jul 2010 Posts: 915 Location: Port Orchard WA
1989 Chevrolet Camaro RS
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Posted: Wed Apr 24, 2013 6:22 pm Post subject: |
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You gotta ohm out that injector, if they're multec style its possible the varnish is gone, the only way to tell is to check it, if its on point with the others then I would try to clean it, no sense in cleaning a shotty one
As far as jostling wires around when my coil wire from the dizzy was shot it stopped the entire thing from firing, just for s's and g's check that injector _________________ If you expect a kick to the balls and get a slap to the face its still a victory
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RSFreak The other "John"
Joined: 23 Jan 2004 Posts: 2946 Location: Renton
1989 Chevrolet Camaro RS
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Posted: Wed Apr 24, 2013 8:44 pm Post subject: |
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aaron_sK wrote: | Steve's mechanic put his stethoscope on each injector and didn't hear a dead one, and jostling the wires around "fixed" the problem. |
His mechanic told me that the stethoscope isn't a very accurate way of diagnosing injectors as the sound from the one next to the one you are listening to bleeds through. Also, the only wires jostled were the plug wires and I confirmed that the miss was occurring while the plug was firing. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Apr 25, 2013 10:02 am Post subject: |
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And you still haven't taken ten seconds to ohm the injector? _________________ A redline a day keeps the carbon away! |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Apr 25, 2013 11:24 am Post subject: |
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Remember, this is a John repair.
Once you've taken two years to do a weekend engine swap, taking a week to ohm out a set of injectors is nothing. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Apr 25, 2013 5:42 pm Post subject: |
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Or swapping two plug wires. LOL
How do you know the spark plug is firing? Is your head in the combustion chamber? :OP _________________ A redline a day keeps the carbon away! |
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RSFreak The other "John"
Joined: 23 Jan 2004 Posts: 2946 Location: Renton
1989 Chevrolet Camaro RS
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Posted: Thu Apr 25, 2013 9:31 pm Post subject: |
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Twilightoptics wrote: | How do you know the spark plug is firing? Is your head in the combustion chamber? |
If it isn't, where is the spark going? It would be taking the path of least resistance and arcing somewhere.
BTW, this is the time of year I start working 12+ hour days. Sadly, working on the car takes a back seat to falling asleep on the couch! |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Thu Apr 25, 2013 10:02 pm Post subject: |
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Or it could just plain not have enough voltage to arc anywhere.
Paul's right. Just as I was explaining too, there's a different voltage requirement when the plug is in the cylinder then when its out. The voltage may be high enough to arc through a weak spot in the wire. The wire may have such high resistance that the very little spark actually reaches the plug. Also possible that the resistance of the wire + the resistance of the plug gap under compression is high enough that the spark never leaves the coil.
All easy to rule out just by swapping the wire around with another cylinder. Misfire moves.. you've found the bad part.
Ohming the injector will at least tell you if the electrical coil in the injector is good. Injector can still be plugged or stuck though. One of those tests that if it passes.. you still don't know if the part is good. But if it fails you know its bad. |
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RSFreak The other "John"
Joined: 23 Jan 2004 Posts: 2946 Location: Renton
1989 Chevrolet Camaro RS
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Posted: Fri Apr 26, 2013 8:20 pm Post subject: |
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chevymad wrote: | Also possible that the resistance of the wire + the resistance of the plug gap under compression is high enough that the spark never leaves the coil.
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There is enough spark to activate the timing light. |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Fri Apr 26, 2013 9:32 pm Post subject: |
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Makes no difference John. Unless you have a scope that can read the voltage in that wire in comparison to the others.. then you have no clue whats happening. Swap the wire. Only way to test at home. |
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