Yellow spark vs White spark

STARCRAFT63 · Nov 15, 2012

I have an auto part spark tester and am seeing a yellow spark instead of a white bolt of lightning. I have 90 psi in both cylinders and fuel to the back of the carb but can not get it to start. So my question is do i need to solve the spark problem first to get her started? She is a 1968 evinrude Big Twin 40 hp.

nwcove · Nov 15, 2012

Re: Yellow spark vs White spark

what type of tester is it....open air? how much gap will the spark jump?

STARCRAFT63 · Nov 15, 2012

Re: Yellow spark vs White spark

The tester is from advance auto store and it is enclosed in a plastic bubble it has at least a 1/4 in gap

nwcove · Nov 15, 2012

Re: Yellow spark vs White spark

can you adjust it out to 3/8? ( your motor has reasonable compression and should fire up or at least kick with the spark jumping 1/4 open air gap tho) jmo

durban · Nov 15, 2012

Re: Yellow spark vs White spark

sorry to but in here , this is somthing fo those that did not know white metal sparks normaly indicate the hardness off metal & yellow sparks the metal got more carbon in in it meaning softer material when you use a bench grinder you will notice the differance in grinding the 2 metals as park goes

boobie · Nov 15, 2012

Re: Yellow spark vs White spark

Yellow spark used to indicate a weak ignition system.

laotou · Nov 15, 2012

Re: Yellow spark vs White spark

I bought an open air spark tester from Auto Zone and did some tests last week. 7/16" is a big gap in comparison to the actual gap of a spark plug. I saw white/blue sparks in #2 and #4 cylinders. The sparks were not evenly fired. It was like "pa-pa-pa- - -pa-pa- - pa -".

F_R · Nov 16, 2012

Re: Yellow spark vs White spark

Folks, you gotta consider what motor you are working on, as well as other variables. That '68 40hp should run on a 1/4" open air spark...Unless the coils are cracked, in which case forget it till you replace them. Modern CD ignitions on the other hand will fire a 7/16" open air gap with ease, even an inch if you torture them. And in any case it they will be a thin white spark. That's just the way they are because of being a very high voltage and fast spark. The old high amperage/slow spark stuff where we worried about color were a very different technology.

Faztbullet · Nov 16, 2012

Re: Yellow spark vs White spark

sorry to but in here , this is somthing fo those that did not know white metal sparks normaly indicate the hardness off metal & yellow sparks the metal got more carbon in in it meaning softer material when you use a bench grinder you will notice the differance in grinding the 2 metals as park goes

What does this have to do with ignition spark as poster is not grinding anything??????

STARCRAFT63 · Nov 16, 2012

Re: Yellow spark vs White spark

The ignition system will be reinspected as far as the connections are shinny and grounded properly. the points and coils are new and the interior of the flywhell is clean. The plugs and wires are new, when fuel is sprayed directly in the cylinders the engine runs, i get fuel delivered to the back of thr carb, not sure what happens after that. I will continue to search the threads for info and the manual. i like this discussion i am learning. Thanks everyone. I will updated when I have more info. M

geoffwga1 · Nov 16, 2012

Re: Yellow spark vs White spark

If it runs when you squirt it your problem is not with the spark but with the carburettor.Have you stripped it and cleaned it properly or just given it a wash off and blow through.If the latter it's obviously not enough.You need to soak it in carb cleaner and clean out all the little passages individually.

Good Luck geoffwga1

Yellow spark vs White spark

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