No Spark

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
Verified spark at the coil wire and fuel in the carb!!
What could have changed overnight?
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
Thought of another possibility.
When I 1st diagnosed the "No spark" condition I did so by putting a screwdriver in the coil wire and placed the screwdriver over the center of the distributor.....no spark observed...spacing was ~1/4" or more.
Now using a spark plug in col wire to check for spark......spark is present but now suspect "weak spark" condition.
Spark was yellow/orange......S/B Blue???

Going to pick up this adjustable spark tester tonight.......how far should the spark jump?
If it is in fact a weak spark......what would cause this?

Thanks......hope I am on to something!

http://www.autozone.com/test-scan-an...ster/10257_0_0
 
Last edited:

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Thought of another possibility.
When I 1st diagnosed the "No spark" condition I did so by putting a screwdriver in the coil wire and placed the screwdriver over the center of the distributor.....no spark observed...spacing was ~1/4" or more.

Not really the right way to check for spark. All you're doing is adding another gap for the spark to jump. If you must use a screwdriver, hold the end about 1/4" from the BLOCK, not the cap...

FreeBeeTony said:
Now using a spark plug in col wire to check for spark......spark is present but now suspect "weak spark" condition.
Spark was yellow/orange......S/B Blue???

Should be blue, yes. But I have seen many that look yellowish and are actually ok. The real test is, does the engine start?

FreeBeeTony said:
Going to pick up this adjustable spark tester tonight.......how far should the spark jump?

The best I've seen is about 1/2", but anything over 3/8" is good.

FreeBeeTony said:
If it is in fact a weak spark......what would cause this?

Weak spark...
Bad coil (about a 0.1% likelihood)
Bad module
Low voltage to the module
too much gap in the HT path (like between the rotor and cap)

FreeBeeTony said:

As I said, does the engine start? If it starts and runs, nothing to diagnose...

Chris..........
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
Engine does not start.....
What is the peak voltage of the TBIV system?ā€‹
 
Last edited:

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Engine does not start.....
What is the peak voltage of the TBIV system?ā€‹

It will fire a coil upto about 30,000V, but the usualy firing voltage of a spark plug is around 1200...
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
If that's the case, then using the spark tester I should set it for 30KV..........
 
Last edited:

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
If that's the case, then using the spark tester I should set it for 30KV..........

I think you're over-thinking things.

Just set it to 3/8". If it fires that, spark is good. Or do as I often do, pull the plugs out, lay then on the block and spin the engine. If there's spark and the engine's not running, you have a fuel problem.

Chris..........
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
Isn't it true that if you have a weak spark it won't fire the spark plug when under compression?
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
After further testing w/ my new spark tester, it looks like I have good spark out of the coil (jumped ~ 0.75") but not at a plug wire.
Removed the cap again a found the tang of the rotor had a burn mark where it contacts the cap.....I say to myself "I found the problem".
I removed the rotor cleaned/sanded the tang, pulled it up a bit and re-installed. Couldn't get a good visual on the cap.
Tried to start to no avail. Purchased a new cap/rotor to install tonight.

Hope this is the fix! The current cap/rotor were replaced over the winter.....only have ~ 5hrs on them.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
That's sounding like good news. At least you have a certain troubleshooting path now. šŸ˜Š
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
I did have a troubleshooting path, following the flow chart and such....maybe missed a few things
I did overlook the cap and rotor because I just replaced them in the winter.
Wonder why it burned the way it did?

Thanks for following @achris........:joyous:
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
OK......replaced cap and rotor (Sierra, no choice short term).
Now no spark @ coil !!! Had to walk away.
Going to start replacing parts w/ original and start from square one tonight!!

Again, thanks for monitoring me!
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Is that the coil primary winding, secondary winding, or the HT lead to the distributor cap?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
With HT leads it varies with the conductive material. Some are copper wire and anything from 1 to 6.5k per Metre is acceptable. Others are resistive carbon and permissible resistance is from about 2k to 8k per Metre. Yet others are resistive silicon and I have no idea about those. You have 'continuity', call it good.

Chris. ...
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
Again, starting over.
Measured 12v at the coil (both terminals).
Grounded the wht/grn wire from the dist......no spark at coil.
Happened to look at gnd connection at block...........very questionable.
Measured ~3ohms between the neg terminal of the battery to the block.
Had to walk away again........batteries are charging.
Planning to go back to the boat in a couple of hours to clean the gnd connection and try again!!
 

FreeBeeTony

Captain
Joined
May 15, 2002
Messages
3,991
Cleaned the gnd connection.......no change.
Is there a way to test the module independently?
 
Top