Technical Flathead getting weak spark, ideas?

So I took dad out for dinner ;ast night for Father's Day and I had a kid that I used to mentor stop by our table. He had picked up a 1934 Ford BB truck and he is trying to get it running. Of course, I was trying to troubleshoot it fromt the dinner table and I have no idea what engine he has, but it sounds like it is a 41-48 ish flatty. He said it had the crab style distributor.

He said he has a very weak spark. He has changed the coil and all of the ignition pieces. Any idea what might cause it to produce some spark but not enough to start?

I'm supposed to go over this week sometime and see if I can help him. Flatty are not in my wheelhouse, so any ideas are appreciated.

 

Coil could be hooked up backwards. Try reversing the connections.

 

The first thing I would look at is the ground. Make sure the cable is sized properly for 6 volt and is clean.

 

I'll check that.

 

Condensor? Ignition wiring?

 

Ford barn, Ford Barn!!!!!!! They are the flathead experts.

Root,
I imagine that you told the kid this but if it were me the first thing I would check is the grounds after then I would take look at the ignition switch. bad grounds and bad contacts in a switch will both make for weak spark.

 

Yeah, that's kinda what I am thinking. He has changed all the points, condensor etc.

 

There's that resistor up under the dash ...

 

I have heard of several new condensers going bad recently. I had one, a guy at work had one in his 68 F100, Kyle had one on his wagon, etc. I might start there...

 

Do tell......

 

Maybe '34 didn't have one - recently worked on '36 & '37 that used one. Cuts 6 volts down to 4 ..

 

Wonder why they did that? I am not doubting you I just winder why they would have done that? They just have run an oddball coil those years.

 

Where is said resistor?

 

I would recheck ALL of the connections to include that resistor if it still had one. Maybe the resistor is cracked. Maybe he has an improperly placed connection. He would sometimes still get a spark.

 

Sometimes the resistor is on the firewall inside the engine compartment and I have seen them placed up and under the dash.

 

I have yet to see one on a 6 volt car. Doesn't mean that they don't exist and I am taking @302GMC at his word, he's got no reason to make that up. he is normally a good source of solid info besides.

 

As I remember never had a big snap spark,just a small blue spark, that's why only had .025 spark plug gap. It would still wobble your knees.

 

Condensor, especially if Auto Z. Squirrel had a tech post on here somewhere regarding condensors, very informative. Ive had a rash of bad condensors in the past year, just repaired a friends 66 IH Tractor last week that would barely start, run about a minute, then quit, with all new components, it was also the condensor....pink spark.....BTW, you can add jumper wire across terminals on ballest resistor to see if it will start.

 

'46-'48 Fords had the resistor right behind the extreme left side of the dash, lower...just poke your head under, you'll see it.

A bud bought a mostly original '38 Ford humpback at the Reno run some years back...59AB mill had the original coil bracket/coil on left front of engine, resistor on top...
Engine had POOR spark, wouldn't start. After a brief look, I 'discovered' a resistor under left side of dash, (original, presumably)
Removed the resistor from atop coil, left the original 'underdash', engine started right up.

 

Correct...it looks like this. It's on the left.

 

They have these on 34's?

 

So, I got a little more info from him. He has bought the remote coil kit and it has 6V at the coil.

 

Yes, they had the resistor inside under dash.
The one pictured above is for the 46-48 Ford.
'34 truck will look similar to pic below. Resistor on left.
Atwater Mike's post above may be your answer.

 

But he shows 6v at the coil?

 

as a guy that uses a lot of points....maybe about 20 or so cars....sometimes a new set needs a little polishing - like running some sandpaper or file over them - just make sure there's a good spark with the cap off and you/someone - opening the points with a screw driver....jump back...

 

I had a run of bad condensers. Couldn't figure it out but someone here mentioned he uses vdub condensers. Put one on and fired right up perfect. The repro crab condensers are junk.

Same symptoms, chased my tail for weeks. Just because it's new doesn't mean it's good.

Definitely agree with checking grounds. My understanding is the points make the ground circuit complete.

 

Not quite. Ground circuit still has to travel from points to distributor housing, engine block to battery ground post.......

Ray

 

That's what I meant. The points link the ground circuit from the ground cable/ battery ground, through the block etc. to the distributor. The opening and closing of the points is the interruption in that path that causes the spark. A poor ground from the distributor path to battery may limit spark intensity but I could be wrong.

Again!

 

^^^^^^^^we are in agreement on that.

Ray

 

That's good info.