Ignition problem
Thread Starter
Former Vendor
Joined: Mar 2011
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From: spring branch Texas
Ignition problem
Engine was only firing on 3,5 7, (determined by heat gun readings at exhaust manifolds and at exhaust pipes).
Pulled spark plugs, ran compression and leak down check (all good), and checked valve lash (solids---097 Duntov).
Installed new plugs, points, condenser (checked resistance on coil terminals)
Re started engine and now firing on 4,6,8 only.
What--da???
Pulled spark plugs, ran compression and leak down check (all good), and checked valve lash (solids---097 Duntov).
Installed new plugs, points, condenser (checked resistance on coil terminals)
Re started engine and now firing on 4,6,8 only.
What--da???
Thread Starter
Former Vendor
Joined: Mar 2011
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From: spring branch Texas
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From: Eagle, Idaho
Your screen name is 1960FI. Are you running a 1960 with an original FI? If you are running an old points/condensor set up there's very little chance you aren't getting any spark to one side of the engine then it flip flops. I would bet there is a fuel delivery issue.
Thread Starter
Former Vendor
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From: spring branch Texas
Fuel supply is perfect---it is an ignition problem.
Thread Starter
Former Vendor
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From: spring branch Texas
This one does.
Really weird sensation putting one's hand at the exhaust outlet pipe and feeling the cold air coming out of the non firing side.
And remember, the side (engine bank) that is firing has flip/flopped from one side to the other.
Also, even though I described the firing as either 3, 5, 7 or 4, 6, 8, the #1 or #2 cylinders do get a bit hotter (maybe 10-15 degrees when their respective side is firing.
As to hear readings from the infra red gun:
Firing side ----- 360 to 450 degrees
Non firing side --100 to 115 degrees
Really weird sensation putting one's hand at the exhaust outlet pipe and feeling the cold air coming out of the non firing side.
And remember, the side (engine bank) that is firing has flip/flopped from one side to the other.
Also, even though I described the firing as either 3, 5, 7 or 4, 6, 8, the #1 or #2 cylinders do get a bit hotter (maybe 10-15 degrees when their respective side is firing.
As to hear readings from the infra red gun:
Firing side ----- 360 to 450 degrees
Non firing side --100 to 115 degrees
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Seems like the first thing you'd want to do is to verify that there's spark at every cylinder. I'd use a method other than the IR gun...like pull each wire and make sure there's fire, or use your timing light on each wire to prove there's spark. Obviously, if there is, it's fuel (assuming good compression and third component of the triad of fuel, fire and air is present). steve
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I've seen where debris floating around in fuel injection distribution blocks has done the same thing. It covers the line feed to some cylinders cutting off fuel. Then later it moves around and cuts off others. Low fuel pressure can do the same thing, but not likely in this case.
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I was wondering the same thing - and how do you keep it running long enough to figure out which 3 cylinders it's running on?
I'm not sure I can think of a plausible fault in the ignition system that would behave this way. Sounds more like the FI system metering system to me for my 2 worthless cents.
I'm not sure I can think of a plausible fault in the ignition system that would behave this way. Sounds more like the FI system metering system to me for my 2 worthless cents.
Last edited by DansYellow66; Oct 1, 2015 at 07:11 PM.
Thread Starter
Former Vendor
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From: spring branch Texas
I have never seen anything like this
Team Owner
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From: Greenville, Indiana
Something ain't right here.
Thread Starter
Former Vendor
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From: spring branch Texas
Have tested flow on non firing cylinders while engine is running.
Again, the firing cylinders have flip flopped from left bank to right bank, and always on rear three cylinders
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Change your cap and rotor out with a different brand. If that doesn't fix it I'm with some of the others, its fuel, and only FI can account for this behavior unless the cap or rotor is damaged or the distributor is hideously screwed up. I like the plugged FI theory for this one.
Dan
Last edited by dplotkin; Oct 1, 2015 at 09:10 PM.
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What method did you use to test the flow on individual cylinders? Plugged nozzles can increase the flow to open nozzles and will still show the same GPM.
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I'm not quite sure how you would do this unless you simply unscrewed the line at the nozzle and observed/measured fuel pressure. That wouldn't mean the fuel was getting through the screen.
You could have developed a huge vacuum leak?
I'd start the engine and squirt some gasoline or flammable mist in the air meter and see if the engine speed picked up and rule out air/fuel issues. I use aerosol non-chlorinated brake fluid for this. It's safer than gasoline.
I don't see how the idle speed can be 1200 rpm either on only three cylinders but life is filled with little mysteries.
You could have developed a huge vacuum leak?
I'd start the engine and squirt some gasoline or flammable mist in the air meter and see if the engine speed picked up and rule out air/fuel issues. I use aerosol non-chlorinated brake fluid for this. It's safer than gasoline.
I don't see how the idle speed can be 1200 rpm either on only three cylinders but life is filled with little mysteries.
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Make sure you check the side play in the dist. shaft. If it's got play it may be only making contact on one side of the cap. Easy check. 
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How about connecting a vacuum gauge? And what about doing a cylinder balance test to verify the dead holes? This is really strange, that the dead holes are changing places....Does it drive at all? Super low power? Or does it drive on all 8 cylinders when you go down the road? I guess what I'm trying to figure out is if the problem is in neutral in the driveway, or actually going down the road.......