Author Topic: Cylinder Not Firing - Car in the Shop - What to Expect?  (Read 3621 times)

67L48

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Cylinder Not Firing - Car in the Shop - What to Expect?
« on: June 17, 2008, 09:40:59 PM »
1967 350. Powerglide.  Stock.

Late last summer, the car started running like crap.  Let it sit over the winter.  Checked the spark plugs.  Looked fine and that was about the exent of my engine diagnostic abilities.  Checked the carb air/fuel mixtures and it didn't seem to do anything to improve or worsent the engine behavior.  Hadn't driven it yet this year, other than to confirm how poorly it still ran.  Can't even drive it, as it felt like only half the engine was running.  Finally took it to the shop this week.  They found bad spark plug wires that were causing 4 cylinders not to fire.  These were original wires, so I guess they wear out after 40 years. 

Waiting for a GM part to arrive from Denver, but in doing some more diagnostics, the mechanic found that even with good wires, a cylinder isn't firing.  I don't know whether there is a spark at the "dead" cylinder.  Part of the original diagnostics was to check the vacuum, so I'm assuming that that's not the culprit (assuming that vacuum could have an effect -- clearly, I'm not an engine guy).

Anyway, with this very incomplete diagnostic, any ideas on what I might expect as the reason why I have a dormant cylinder?

Thanks.

K. A. Young
1967 Camaro SS 350
Fort Collins, CO

tom

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #1 on: June 18, 2008, 01:23:20 AM »
Could you have dropped an intake valve? Tough to fire when there's no fuel in the cylinder. Start with a compression test, if needed pull the valve covers to inspect the top end.

Good luck,

Tom
69 X11 Z21 L14 glide
looking for a 69 export model (KPH) speed
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1968RSZ28

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #2 on: June 18, 2008, 02:32:43 AM »
K.A.Y. -

A leak down test will tell you alot more than a compression test.  Read this CRG thread...  http://www.camaros.org/forum/index.php?topic=1735.0

 :)

Paul

crobjones2

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #3 on: June 18, 2008, 03:00:55 AM »
I assume it has hydraulic lifters - i have heard of instances where one fails, gets clogged, etc
would have to pull the valve cover off to watch the rockers

also - did your mechanic replace the cap and rotor? - lets start with the most obvious!
did they replace the plugs?
Chris
69 SS 350

67L48

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #4 on: June 18, 2008, 03:38:39 AM »
Thanks for the responses.  First of all, let's get one thing clear:  I'm not doing a thing, the shop is!  :)  I'm not sure what the mechanic has or has not done at this point.  I only know that the spark plug wires were the culprit for 4 cylinders not firing.  When new wires were put on, one of the cylinders was not firing.  That's it.  I'll talk to them tomorrow and use some of this info provided here.  Thanks a bunch.  I'll update as I find more.

K. A. Young
1967 Camaro SS 350
Fort Collins, CO

1968RSZ28

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #5 on: June 18, 2008, 06:07:31 AM »
Thanks for the responses.  First of all, let's get one thing clear:  I'm not doing a thing, the shop is!  :)  I'm not sure what the mechanic has or has not done at this point.  I only know that the spark plug wires were the culprit for 4 cylinders not firing.  When new wires were put on, one of the cylinders was not firing.  That's it.  I'll talk to them tomorrow and use some of this info provided here.  Thanks a bunch.  I'll update as I find more.

Is the cylinder that is not firing now, one of the original four that wasn't firing?

Paul

67L48

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #6 on: June 18, 2008, 01:37:24 PM »
Is the cylinder that is not firing now, one of the original four that wasn't firing?
Paul
Yes, that's the way I understand it, anyway.

K. A. Young
1967 Camaro SS 350
Fort Collins, CO

67L48

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #7 on: June 18, 2008, 03:25:13 PM »
Spark plugs.  He checked distributor cap and rotor and then went back to plugs.  I pulled the plugs and took them to a shop and they thought they looked OK.  Apparently, you get better service when you pay for it -- nothing's free.  Anyway, the mechanic today pulled the plugs and thought they looked a bit fouled.  Replaced them and the car runs like a top.  The shop wants to preserve GM parts for me and is ordering plugs and wires from a GM distribution center in Denver.  They actually did this without asking me, which was great -- nice to have people who recognize that it's an original car and that the owner probably doesn't want neon green spark plug wires from Autozone.  Anyway, everything seems to be fine at this point and I'll hopefully have my car back in running form later today.

Thanks for the help you all provided.  Really taught me some things about how engines work.  I know so little.  I think if I won the lottery, I'd quit my job and go to mechanics school -- I understand so little about engines and they fascinate me.  I watch Horsepower TV on Spike every weekend and am always amazed how they take complicated systems and make it look simple.  Anyway, thanks again.  I'll post back when I have car in hand, so to speak.

K. A. Young
1967 Camaro SS 350
Fort Collins, CO

67L48

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #8 on: June 18, 2008, 07:42:43 PM »
Bad news.  Installed all the new parts and the car ran great.  Took a 5 mile drive and went back to the garage.  After sitting, the car had a hard time starting.  So, the mechanic pulled the plugs and found that they were already starting to foul.  The thought is that carb is leaking fuel through the internals and that it needs a complete overhaul.  I'm into it $700 (which included a new fuel line to replace the one I damaged).  They want $425 for the carb overhaul, P&L.  Thoughts?

K. A. Young
1967 Camaro SS 350
Fort Collins, CO

jdv69z

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Re: Cylinder Not Firing - Car in the Shop - What to Expect?
« Reply #9 on: June 20, 2008, 12:34:53 PM »
Bad news.  Installed all the new parts and the car ran great.  Took a 5 mile drive and went back to the garage.  After sitting, the car had a hard time starting.  So, the mechanic pulled the plugs and found that they were already starting to foul.  The thought is that carb is leaking fuel through the internals and that it needs a complete overhaul.  I'm into it $700 (which included a new fuel line to replace the one I damaged).  They want $425 for the carb overhaul, P&L.  Thoughts?

if the plugs are already fouling, way too much fuel sounds correct, ie fuel leak. When you had hard time startiing, did it also idle very rough? Plugs will look black, ie lots of carbon on them if this is the case. Good luck.

Jimmy V.
Jimmy V.