Engine Missing on #1 Cylinder, Duraspark 2 System
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Engine Missing on #1 Cylinder, Duraspark 2 System
Hi
We have a 72 F250, 390, C6, 2wd, with Duraspark 2 (blue connector) ignition from a 76. Maybe someone here can help solve a miss-fire issue on the #1 cylinder..
A little engine history.. Rebuilt last summer, 600 cfm Holley carb, new plugs, plug wires, rotor, cap and distributor. The ignition module was tested at NAPA today and was fine. Timing is set at 10 degrees, idle at 800rpm.. Engine was tested for vacuum leaks with a smoke generating machine (pretty cool system). Compression is running 160 to 170.. Vacuum is running around 22 with a drop on the miss-fire.
Any ideas as to why it is miss-firing on the #1 cylinder would be appreciated!
Thanks
Dan
We have a 72 F250, 390, C6, 2wd, with Duraspark 2 (blue connector) ignition from a 76. Maybe someone here can help solve a miss-fire issue on the #1 cylinder..
A little engine history.. Rebuilt last summer, 600 cfm Holley carb, new plugs, plug wires, rotor, cap and distributor. The ignition module was tested at NAPA today and was fine. Timing is set at 10 degrees, idle at 800rpm.. Engine was tested for vacuum leaks with a smoke generating machine (pretty cool system). Compression is running 160 to 170.. Vacuum is running around 22 with a drop on the miss-fire.
Any ideas as to why it is miss-firing on the #1 cylinder would be appreciated!
Thanks
Dan
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Would the best way to check the exhaust valve be to pull the valve covers and check from the top?
The firing order is good and the plugs were just installed with the gap checked. I have a thought that it could be the distributor. Is there a way to check that for this problem??
Dan
The firing order is good and the plugs were just installed with the gap checked. I have a thought that it could be the distributor. Is there a way to check that for this problem??
Dan
Last edited by dgrant09; Mar 17, 2009 at 08:59 AM. Reason: Addition in post
Mountain Pass
Joined: Feb 2009
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From: Aubrey,TX north of Dallas
Yeah, pull the valve cover on that side to check the valve, check both exhaust and intake to be sure, but exhaust valves are more common to sticking. It could be some carbon **** buildup on it. By chance is your distributor cap loosely mounted? I know sometimes even with both clamps holding it, they can still be loose. look inside your distributor and see if the contacts for number 1 cylinder look ok, it might be possibl that its arcing the spark from that cylinder to another, it dosen't usually happen, but its a know problem. How old is the dist. cap, you could try getting another new one.
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Easiest thing to do is to move the sparkplug wire to another cylinder and see if the miss follows it.
New plugs doesn't really mean anything either. I have had brand new Autolites and Champions that were bad from the get-go.
Josh
New plugs doesn't really mean anything either. I have had brand new Autolites and Champions that were bad from the get-go.
Josh
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MSEE
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From: Austin, TX
I too agree - check the plug wire and plug itself. I believe the specification on plug wires is under 7 Kohms per foot. Try it on another cylinder like Josh said. Since your compression is good, about the only other thing I can think of to check is to pull the valve cover and watch the valves move like you were thinking. You might try watching the motor idle with the hood up at night and see if anything is crossfiring across the motor.
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We swapped wires and plugs, one at a time, and the problem remained on the #1 cylinder. We even replaced the plugs and wires after this and again there was no change.
Ranger 76,
The cap and rotor are also new but we'll try your idea of running the truck while it is dark to check for arcing. Then maybe we'll look at pulling the valve cover and see what the valves are doing. I've tried moving the cap while it was running and there was no change..
I'll be able to work on it Thursday afternoon. Any more suggestions are certainly appreciated!!
Thanks again,
Dan
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From: Cullman Alabama
I think your supposed to have Hydraulic lifters on that engine.
If the Vacuam drop follows the miss, I'd sure use a feeler guage to check to see if your lifter is collapsing.
Also, you can use a Timing light to get a look at the Valve action. Cool eh?
Set it up on any cylinder that fires about the time your exhaust valve should be coming up. You'll get a 'stopped' action look at that Ex valve. If it's sticking you'll see something odd.
If the Vacuam drop follows the miss, I'd sure use a feeler guage to check to see if your lifter is collapsing.
Also, you can use a Timing light to get a look at the Valve action. Cool eh?
Set it up on any cylinder that fires about the time your exhaust valve should be coming up. You'll get a 'stopped' action look at that Ex valve. If it's sticking you'll see something odd.
Mountain Pass
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From: Aubrey,TX north of Dallas
Thats a really good idea Thudpucker, I almost bet its a sticking valve or lifter or a bad dist. cap. You said the cap and rotor are new, how new are they, and are they an el cheapo brand? Crummy brand parts are never all that good even straight out of the box. I have bought new caps and rotors, solenoids, and ignition modules that were junk as soon as I put them on the vehicle.
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From: Cullman Alabama
An aside on spinning the distributor.
Back in the 50's some salesman brought a Sun machine to plunk a distributor down into and spin it. It showed bad bearings, missfiring caps etc.
My Dad looked at that and said to the Salesman:
" The day I need a %$#@@*& Computer to help me work on a Car, is the day I pack it in!"
He died long before the computers of today, but wouldnt he be shocked?
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Thats a really good idea Thudpucker, I almost bet its a sticking valve or lifter or a bad dist. cap. You said the cap and rotor are new, how new are they, and are they an el cheapo brand? Crummy brand parts are never all that good even straight out of the box. I have bought new caps and rotors, solenoids, and ignition modules that were junk as soon as I put them on the vehicle.
I'll also see if there is anyone in Anchorage that can check this distributor. I was tempted to try MSD ignition parts but ouch! Those are pricey!
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From: Cullman Alabama
Before you go buy more stuff, look at those Valves or use a Vacuam guage to verify the valves. I think your electricity is OK.
If you really think you have an electical problem on the #1 cylinder, and have time to fool with it this much, pull the Distributor, move the wires all one position in the cap, and put the distributor back in One tooth in whichever direction you can. I think the Vacuam advance cylinder will only let you move the distributor in one direction.
Then, if the problem moves, its electrical, if not its the valves.
Desperate times call for desperate measures!
PS I lived in Anchorage and Peters creek for almost 30 years. I know what its like to work on stuff at 10 Below or in the spring with the Mosquitoes singing in your eyes.
I hope you have an indoor heated garage to do all this work.
If you really think you have an electical problem on the #1 cylinder, and have time to fool with it this much, pull the Distributor, move the wires all one position in the cap, and put the distributor back in One tooth in whichever direction you can. I think the Vacuam advance cylinder will only let you move the distributor in one direction.
Then, if the problem moves, its electrical, if not its the valves.
Desperate times call for desperate measures!
PS I lived in Anchorage and Peters creek for almost 30 years. I know what its like to work on stuff at 10 Below or in the spring with the Mosquitoes singing in your eyes.
I hope you have an indoor heated garage to do all this work.