How do you adjust timing using a vaccuum gauge?
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Junior User
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From: Charlotte, NC
How do you adjust timing using a vaccuum gauge?
I'm having problems adjusting the timing on my 90 bronco. Its has a 302 EFI. I think the balancer has turned. I'm going to have to find TDC and remark it. My bronco has 165000 miles on it and I heard, possible here, that you can set the timing by using a vaccuum gauge. I have done this on a old 63 1/2 ford Falcon but never on anything injected. Could some one walk me through the process?
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From: Independence, MO
How do you adjust timing using a vaccuum gauge?
First thing, you need to find the (spout connector) in your wiring harness, it needs to be disconected be for you set your BASE timming, Then you plug it back up and the computer takes over again, its not like the older vacum advance units, to find TDC remove the 1st spark plug on the pasg. side take a long thin blade screw driver slowly insert it in the plug hole and have some turn the crank (BY HAND) only and follow the piston up with the screw driver, you will be able totell when it reaches the top, and you'll have (TDC) if at any point it (binds) just back the crank up a little. I realy think you should buy a $12.00 HAYNES manuel and a cheap timing light Then you wont be guesing. Hope this helps DW
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From: Memphis, TN
How do you adjust timing using a vaccuum gauge?
I agree - don't use the vacuum method on an EFI engine. Use a timing light.
But I'd recommend using a plastic drinking straw to observe piston movement instead of anything metal.
But I'd recommend using a plastic drinking straw to observe piston movement instead of anything metal.
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From: Charlotte, NC
How do you adjust timing using a vaccuum gauge?
Thanks for the info. I was planning on doing that eventually. I heard that doing it by the vaccuum gauge would take up for some of the slack in the engine from the mileage. I'll have to do something. I have it timed by ear right now. Its running fine so I have a few days to play with it.
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From: Loveland, CO.
How do you adjust timing using a vaccuum gauge?
An easy way to find TDC without having to crank the engine by hand, or stick anything into the cylinder is to remove the #1 plug, wad up a napking and stick it tightly into the spark plug hole, and keeping bumping the key (as shortly as possible) until the napkin pops out. You will be at TDC.
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From: Green Bay
How do you adjust timing using a vaccuum gauge?
Originally posted by JBronco
An easy way to find TDC without having to crank the engine by hand, or stick anything into the cylinder is to remove the #1 plug, wad up a napking and stick it tightly into the spark plug hole, and keeping bumping the key (as shortly as possible) until the napkin pops out. You will be at TDC.
An easy way to find TDC without having to crank the engine by hand, or stick anything into the cylinder is to remove the #1 plug, wad up a napking and stick it tightly into the spark plug hole, and keeping bumping the key (as shortly as possible) until the napkin pops out. You will be at TDC.
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From: Independence, MO
How do you adjust timing using a vaccuum gauge?
Well that is very good way to know your on the compresion stroke, but if you suspect the balancer has moved then the only way for gona know your at true TDC is by feeling the piston movement or removing the cylinder head, otherwise when the napkin blows out, you can still be off of TDC +/- 10 degr. easy! DW
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From: Loveland, CO.
How do you adjust timing using a vaccuum gauge?
I always stick something into the cylinder after the napkin pops out to make sure that the piston is up. It's all guesswork anyway, you can't be positive even if you feel it go up and down with a screwdriver. All I'm trying to do with the napkin trick is to get a ball park idea of where TDC is, so I have somewhere to start.
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From: Independence, MO
How do you adjust timing using a vaccuum gauge?
in your your first reply you said you didnt have to turn the crank or stick anything in the cylinder. so you just contradicted yourself, by the way go down to your local drag strip or dyno shop and tell them its all gueswork, just 2 deg. of timing can make the difference of 5- 10 HP on the dyno and as much as 1/2MPG in fuel economy on the street. maybe thats why some peoples stuff runs better than others! 
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From: Loveland, CO.
How do you adjust timing using a vaccuum gauge?
Getting TDC by way of a screwdiver or napkin is all guesswork, to try to get in the ballpark of TCD so you can start your tuning procedures. I never said that timing was all guesswork.
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From: Loveland, CO.
How do you adjust timing using a vaccuum gauge?
PS - I meant not have to turn the crank "by hand" which is a PITA without taking all the plugs out. And you do onot have to stick anything into the hole, but I just touch the piston to be sure after the napkin pops out. It's not required.
I was just trying to tell the guy how to easily find TDC without having to manually spin the crank or put screwdivers in the cylinder while the piston goes up and down. I'm not trying to start a theoretical argument on ignition timing. If you are so concerned that this be exact; why not tell him to get a degree wheel.
I was just trying to tell the guy how to easily find TDC without having to manually spin the crank or put screwdivers in the cylinder while the piston goes up and down. I'm not trying to start a theoretical argument on ignition timing. If you are so concerned that this be exact; why not tell him to get a degree wheel.
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From: Charlotte, NC
How do you adjust timing using a vaccuum gauge?
Couldn't you also pull the distributor cap and wait until the rotor is near the number one position and turn it by hand, using a straw or screwdriver until you feel the piston at TDC?
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From: Independence, MO
How do you adjust timing using a vaccuum gauge?
yes you can do that and its not a bad idea either, be cause its a good way to confirm that it has jumped time if that is a suspected problem, once you know the piston is at TDC if your rotor is not point to #1 position on the rotor cap, it could mean you have a chain problem. DW
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From: Charlotte, NC
How do you adjust timing using a vaccuum gauge?
Thanks for the help. I pulled the number 1 and found TDC. Judging from the factory marks on the balancer, it shifted about 8 degrees. So when I set the timing at 10 degrees BTDC, I was really at about 2 degrees. No wonder it didn't run right. I was amazed it even ran. I've used timing tape to reset the marks, timed it in where it should be and it runs alot better. IMAGINE THAT!!!