No 1 not firing
October 25th, 2010, 04:26 PM
#1
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No 1 not firing
I been messing around with my motor today and realized No 1 cylinder is not firing....Pulling the plug wire while the engine is running has no affect on the motor...Pulling any of the other causes the engine to stumble a bit...I pulled the plug and checked to be sure it is firing and it is getting spark...Me and my uncle checked again to be sure the No 1 was at TDC...I checked for compression and it reads identical to the others..I took off the valve cover and I could see the the valves working properly. What could be causing this problem....
October 25th, 2010, 04:54 PM
#3
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I tried a different plug,,,plug wire,,,,same result,,,I pulled the dist. out several times to check timing and put it where no 1 would be using a different terminal,,,,same result,,,,I dont no what else to do..The plug is getting spark,,,Good compression,,,
October 25th, 2010, 06:03 PM
#4
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Vacuum leak? What color was the plug?
October 25th, 2010, 06:15 PM
#5
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the plug looked pretty clean,,and appeared wet...
If tdc is correct
plug good
wire good
what else could it be
Iam am only getting around 120 psi on each cylinder,,,,is this low
If tdc is correct
plug good
wire good
what else could it be
Iam am only getting around 120 psi on each cylinder,,,,is this low
Last edited by 1973olds98; October 26th, 2010 at 10:41 AM.
October 26th, 2010, 06:03 AM
#7
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So you had not noticed any problem with the running or performance of the engine, but you pulled the #1 plug and it didn't affect the idle speed, so you want to know if something's wrong?
You have a confirmed good spark to the cylinder, normal valve movement (does not exclude bad seats), and compression you can feel (did you measure it with a gauge, if so what were the pressures for all eight cylinders?).
Number 1: On a big V8, sometimes dropping a cylinder will have surprisingly little effect, but dropping 2 will be noticeable. It may just be that the change in idle isn't significant when that plug is pulled.
I would try warming it up and carefully watching a good tachometer and vacuum gauge, and writing down the readings before and after pulling the plug wire for each cylinder. See if there's a pattern. See what changes if you pull them in groups of 2. Last week I was working on mine and forgot I had pulled 3 wires. It started right up, but sounded a little wrong. Took me a minute to remember and reconnect them, but it wasn't running all that badly.
Number B: If you connected the spark plug wires to the distributor in the just the right wrong way, you could have most of them firing about right, but #1 firing on exhaust instead of compression. Double check that on compression the rotor is pointing to the #1 terminal (and not opposite), then double check that the other wires are connected in the right firing order (cast into the intake manifold) from there.
- Eric
You have a confirmed good spark to the cylinder, normal valve movement (does not exclude bad seats), and compression you can feel (did you measure it with a gauge, if so what were the pressures for all eight cylinders?).
Number 1: On a big V8, sometimes dropping a cylinder will have surprisingly little effect, but dropping 2 will be noticeable. It may just be that the change in idle isn't significant when that plug is pulled.
I would try warming it up and carefully watching a good tachometer and vacuum gauge, and writing down the readings before and after pulling the plug wire for each cylinder. See if there's a pattern. See what changes if you pull them in groups of 2. Last week I was working on mine and forgot I had pulled 3 wires. It started right up, but sounded a little wrong. Took me a minute to remember and reconnect them, but it wasn't running all that badly.
Number B: If you connected the spark plug wires to the distributor in the just the right wrong way, you could have most of them firing about right, but #1 firing on exhaust instead of compression. Double check that on compression the rotor is pointing to the #1 terminal (and not opposite), then double check that the other wires are connected in the right firing order (cast into the intake manifold) from there.
- Eric
October 26th, 2010, 08:33 AM
#9
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I tried putting it in #3 with the same results....My compression test are as follows,,Are these numbers to low for a newly rebuilt 455,,,,I know i have the low compression pistons..
1-120
3-120
5-130
7-120
2-90
4-120
6-100
8-100
1-120
3-120
5-130
7-120
2-90
4-120
6-100
8-100
October 26th, 2010, 12:51 PM
#13
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That's way too low.
It doesn't matter if you have an 8:1 motor, or a 10:1 motor. Compression should be up around 180psi.
Is that the Cold cranking compression with the carburetor held at wide open throttle?
It doesn't matter if you have an 8:1 motor, or a 10:1 motor. Compression should be up around 180psi.
Is that the Cold cranking compression with the carburetor held at wide open throttle?
October 27th, 2010, 05:19 AM
#16
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October 27th, 2010, 05:45 AM
#17
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I just went out and did a compression test again with the motor cold because i have the dist. pulled out from last night....Cylinder 2 was 90 psi with all spark plugs removed and throttle held wide open..
October 27th, 2010, 07:21 AM
#20
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In Hi-Po cams, there is a longer duration that each valves open for air flow.
The degrees both are open at the same time, is considered overlap, which will reduce your cranking pressure.
If you've an aftermarket cam, all this will be listed on the cam card.
On the front of the cam, there should be a manufacturers name, and the numbers represent the 'grind' of the cam. Call them and you can get the lift, duration, etc. for that particular cam.
With #2 being low on the opposite bank, I can't imagine that affecting #1!
If you're talking about the cylinder next to it, #3, I'd suspect a head gasket problem.
Did the shop assemble the engine, or just the short block??
Who did the heads?
The degrees both are open at the same time, is considered overlap, which will reduce your cranking pressure.
If you've an aftermarket cam, all this will be listed on the cam card.
On the front of the cam, there should be a manufacturers name, and the numbers represent the 'grind' of the cam. Call them and you can get the lift, duration, etc. for that particular cam.
With #2 being low on the opposite bank, I can't imagine that affecting #1!
If you're talking about the cylinder next to it, #3, I'd suspect a head gasket problem.
Did the shop assemble the engine, or just the short block??
Who did the heads?
November 27th, 2010, 01:28 PM
#27
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Posts: 99
Glad you got it figured out by all the comments the guys on this site are pretty darn helpful. I would like to bump this also and was wondering what the answer on using the valley pan or the the gasket set
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CALIFORNIA MEDICAL MARIJUANA
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CALIFORNIA MEDICAL MARIJUANA
Last edited by Axeni; August 12th, 2011 at 04:17 PM.
November 27th, 2010, 03:01 PM
#28
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Location: Dahlonega, GA
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I have had issues with the metal valley pan intake gasket sealing properly on engines that have had the deck milled or the heads milled. the metal gasket needs to have all the surfaces parallel and true for them to seal right. I usually use a composit gasket and they seem to seal better. at least for me they do.
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