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 Post subject: hand held scope
 Post Posted: Tue Jan 23, 2007 11:57 pm 
 
I was told that a scope is the best way to catch a bad cylinder, that wasn't firing, and will even indentify a cylinder with bad combustion pressure. Is this true? That would be a lot easier than compression or leak down tests, pulling plug wires while trying to watch RPM, or checking header temperature, looking for a bad cyclinder. It dosn't seem logical to me that a scope could know anything other that if the cyclinder had spark or not. Thanks for the feedback. Ty


Last edited by fasthappy on Wed Jan 24, 2007 12:27 am, edited 1 time in total.

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 Post Posted: Wed Jan 24, 2007 12:10 am 
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a scope will know, the easiest thing to do is a cylinder drop test by removing the plug wire and watching the rpm. you should be able to hear the engine drop and labor when plug wire is pulled. i do this on a regular basis just about every time i work on an engine. you get so use to it when you do it all the time it becomes second nature. i use a pair of fuse pliers to pull high tension lead. it is one of my most prized possesions in my tool box. it will put you on the right track of what cylinder or cylinders have a problem and then you can trouble shoot the individual cylinders from their.\:D/

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 Post Posted: Wed Jan 24, 2007 12:19 am 
 
Thanks Tony, are you watching the RPM, hand held tach or something, or do you just use your ears? If I walk into a tool store and ask for "fuse plyers" will I end up with the right thing? Being shocked by a MSD never feels very good. =P~ Ty


Last edited by fasthappy on Wed Jan 24, 2007 12:30 am, edited 1 time in total.

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 Post Posted: Wed Jan 24, 2007 12:30 am 
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tonyy358 wrote:
the easiest thing to do is a cylinder drop test by removing the plug wire and watching the rpm. you should be able to hear the engine drop and labor when plug wire is pulled./


I don't think MSD condones this anymore on their systems. It used to be standard faire on points type ignitions.

George


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 Post Posted: Wed Jan 24, 2007 12:36 am 
 
I've heard you shouldn't do that also, but it seems to work for Tony. If nobody is using a scope can I assume they arn't very helpful? Ty


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 Post Posted: Wed Jan 24, 2007 6:30 am 
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by removing a plug wire you cause major restance!! Very hard and oor fatal to eletronic compants!!

Ever get hit with a msd 7al!! O:) Tech at msd said it can make your heart stop!!!!!!!! OUCH

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 Post Posted: Wed Jan 24, 2007 8:47 am 
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when you pull the wire you are going to leave it out for about a second and plug it back in. it is not long enough to cause damage. you want to see the drop and pickup of rpm gauge. and use fuse pliers. if you have a pacemaker do not attempt this. and as a matter of fact if it has msd you should not be under the hood at all with a vehicle that has msd type ignition. rf interference can cause your pacemaker to stop or if you have one that gives you a jump it may go off. O:)

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 Post Posted: Wed Jan 24, 2007 1:15 pm 
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Yup, scopes are good, IF, and that's a BIG IF the guy using it knows WTF he is doing! I use to sell those things for Allen Electronics and believe me, there is a lot to be said for the info you can get from one if you know what you are doing. Now they have the computerised ones that are even better because it doesn't depend so much on the guy using it any more.

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 Post Posted: Wed Jan 24, 2007 2:14 pm 
 
thanks you guys. I think I want one. Any idea what they cost? A scope that shows positive and negative KV- does such a "scope" have a certain name? I'll look online, but it would help to be aimed in the right direction. Ty


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 Post Posted: Wed Jan 24, 2007 2:49 pm 
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Ty I'm not too sure you can get one of those in a "hand held" unit. My bad as I didn't notice you were talking about the hand held units. They (hand held) are pretty much for computer controlled new model stuff, something you won't find on your AMX. =P~

I may be wrong on this though as it's been a while since I was involved in that end of the industry. Mel IS more familiar with that stuff than I as he works for a car dealer and they have to have that stuff to service the new cars.

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 Post Posted: Wed Jan 24, 2007 3:11 pm 
 
What about it Mel, do you use a scope on your race car? My problem is that a spark plug may spark when out and grounded to the block, but won't in the motor under combustion pressure. I could use a temperature gun but I'm told that doesn't work well when the motor is warmed up. As usual-thanks for the advice. Ty


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 Post Posted: Wed Jan 24, 2007 7:06 pm 
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you can use a handheld kv meter, i have one of these but seems to be very inconsistant. and it was not cheap. i purchased it from snapon. the kv meters we use at service training school hook inline with the high tension lead and work excellent. but cost a small fortune.

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ecbrc super stock 315 4bbl 2007 champs. high point boat overall 2007.
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 Post Posted: Wed Jan 24, 2007 9:34 pm 
 
I'm glad I talked to you guys before I bought a scope. Every now and then the car seems to run rough, I replace the plugs and it seems to smooth out and run better. I've tried using a temperature gun, either I'm waiting until everything is too hot, or the plug is only failing at higher RPMs. I thought buying a scope would be a more difinative way of locating a bad cylinder. If you guys have access to a scope and don't use one, that answers my question. I'll won't waist my money. Ty


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