missfire at higher speed/rpm

How strong does a coil need to be to trigger a timing light? I honestly don't know but could imagine that a coil could generate sufficient voltage to trigger the light but not enough to make a nice blue spark.

 

my chips are in on this one, I have done a ton of work to the jeep and after about 200 miles i have the same problem. new points and condenser, rebuilt the carb, new cap and wires, plugs. part of the prior work was a new feul pump, all new lines and hoses, filters, cleaned the tank (which is in great shape anyway) and a bunch of crap that doesnt have to do with ignition or fuel.

I am 99% sure my problems don't involve fuel delivery of any sort. the only thing i did not replace were the distributor and the coil (although i did do points condenser cap rotor wires and plugs...). I am ready to go HEI but after spending a couple of grand on it i'm growing ill of spending money. I am not sure if its worth buying a coil and maybe it being a bad distributor then getting stuck with the installed electrical part no returns... right now the beast is sitting so if you get this figured out let me know.

 

Just for grins, do a compression test. It maybe a burned exhaust valve. It sounds like mine sounded when it burned. But, lets do the tests to eliminate what it is not.

Using the timing light is a good diagnostic tool. If you have a maintenance manual, follow its procedure to find your problem. Otherwise we are just guessing in the dark, since we can not see and hear the engine run. This manual is a good tool to have in your box, or on the shelf. The reason the manual goes through a list of tests, is because it will save you and/or the dealer time and $$. Throwing parts at the problem, while it does get you new parts, does cost you $$ and frustrates the H*ll out of you, and may not find the problem. Ask me how I know!

I suggest that you find this problem and fix it before you put in the new electronic ignition. No sense in fighting two problems at one time. Of course if it turns out to be that the ignition system is the problem, then you just install the new one in its place. One problem, one fix. Let us know what you find from the compression test and we will work on the next item. IHTH, Matt W.

 

Thanks guys with the new info, the exhaust is in very good condtion and almost new so i doubt that is it. I will report tomorrow with my new finding, I have two diff service manuals also. I will let you guys know what is up tomorrow afternoon

 

Have you replaced all of the flexible fuel lines? I had this very same problem a few years back and finally found a crack in the fuel line that air was being sucked in. Ran terrible, then great after line replacement. Just my 2 cents. KCJ

 

For you guys having problems - When I was having problems, I used this to troubleshoot - it was extremely helpful ... it says it's for L134, but will work for any points based ignition:

http://mightymo.org/Proj_No_Spark.html

It completely walks you through the entire ignition system.

Also, At FLAPS I bought a pressure/vacuum gauge for cheap that can be used on both vacuum and fuel pressure testing - it has been extremely valuable as a diagnostic tool.

 

1) ok, fuel lines are fairly new, but I will check them. FYI the PO installed an aftermarket elec fuel pump
2) My vac guage does have fuel pressure, where do you connect the line to test that?
3) compression results:
#1 - 105
#2 - 100
#3 - 105
#4 a very weak 90 had to try several times to get it that high, first two tries it was around 80-85 (is this what could be causing the problem)
#5 - is there a way to test the coil?

 

Yes - see my post above with link to mightymo.

 

Yeah I saw that after I posted, thanks!!!
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Coil tested good, so that takes care of number "5"