starting issue weak spark ?

[miahlloyd]

Hi all im new 1st post
I have a mark twain 1977, its got a gm 305.
Its been worked on for the last 2 years to restore it.
I have replaced the plugs wires coil starter battery and insides of the dist. and the carb is new quadrajet,
I checked and set the points properly,
It is sitting at about 5 oclock or so for the number 1 spark plug
It has correct firing order,
My problem is I am getting a weak spark, if I take the number 1 plug out and ground it, the colors light orange and I know we are suppose to get a strong blue or white.

I cant get the engine to start. I got a small backfire 1 time, frusterated as it is I need help, any and all suggestions will due.

I have tried to turn the dist, 180 deg. and all that good stuff, I have done some troubleshooting Im sure its got to be either dist, or ignition im guessing?

 

[WizeOne]

Re: starting issue weak spark ?

Turning the distributor will not alter the strength of your spark. Have you checked the voltage at the coil while you are cranking? You should have two positive leads to the coil. One is ballasted the other should come straight up from the starter solenoid and provide a full 12+ volts when starting.

FWIIW I am not entirely clear on the nature of the ballast resistor. Some have said that it is in the form of a resistor wire. According to the factory wiring diagram, it looks like the switched positive comes thru the choke coil.

Try disconnecting both of your positive coil leads and run a jumper wire straight to the battery. This will surely let you know if you have a low voltage issue. Of course you better recheck your firing order, your initial timing and make sure the distrib is in right first.

 

[TowRoper]

Re: starting issue weak spark ?

I checked and set the points properly,
It is sitting at about 5 O'Clock or so for the number 1 spark plug
It has correct firing order,

how about dwell? and cam timing and compression? even fuel flow?
and welcome to iboats BTW

 

[proxyx]

Re: starting issue weak spark ?

gap the points correctly, remove high tension coil lead from the dist. center (best if u use spark plug tester with adjustable gap - set at 1/2 inch or more), either turn or crank the engine and watch spark from the coil. Should easily jump 1/2 inch and blue. If not (as suggested) connect extra wire from good "+" source to coil plus and test again if better/normal then your coil is not powered properly. If red and weak you may need to replace the coil. Get the adjustable spark tester from whatever source. Like this:
http://www.princessauto.com/tools/auto-repair/auto-repair/2990221-spark-tester

 

[jtybt]

Re: starting issue weak spark ?

Check if you have a resistor coil AND external resistor or wire. That would also cause weak spark.

Wrong rotor can cause weak spark.

 

[miahlloyd]

Re: starting issue weak spark ?

Thank you all for your replies I will try all of the things you have said.
I love this forum.
Ill let you know what happense next