The Stovebolt Site Forums The Shop Area Engine Shop Just can’t find the issue with starting

Hi guys

I’ve tried everything I could think of and still no spark on my 49 Chevy 235 3500 (12v, floor starter)
To try and fix it I put in
New coil
New points and condenser
New leads

I have 12.4v at the ballast (both sides, engine not running) and 12.4v going into the coil


Still no spark at all

Is there anything else I can try?

I’m at my wits end !

I’m pretty sure you changed the condenser? I wouldn’t rule out a bad ground.

Hi
Thanks
I’ll check the engine ground but starter works so I’m guessing it’s ok

Do you have 12V at the points? A friend had the same issue and the wire connection at the points was frayed and grounding out. Just a thought.

How are you testing for spark?

Do you have the 12 volts while cranking?

Try running a temporary ground wire from the distributor housing to the block. With the points closed, engine not running, and the ignition switch on, you SHOULD NOT have 12V on both sides of the resistor. The coil side of the resistor and the + terminal of the coil should read about 9V if current is flowing through the points.

With a spark plug touching the block

I’ll test that

Lot of great advice thanks

I’ll get into testing these and see if anything works

Hold on there. Let's back up a little and get some history of when it happened and what you've done.

1. When was motor last running? Recent?...never yet?
2. Was running and then you posted this? I hope the scenario is "Motor won't start, so I checked spark, no spark" Is that right???
3. Most times it's that the person thinks the point gap is correct and it's not. So close gap a little. Try. No spark? open gap a little.
4. Next common issue: bad new condenser.
5. Next common issue: you took the dizzy out and didn't get it back correctly.
6. Next, timing off...same as 5.

Sometimes you have to look pretty close to see spark in sunlight, need to be in the dark somewhat.


The starter working has nothing to do with grounds that members are asking about. Grounds involved with ignition spark, not cranking. Grounds like what Jerry is speaking of. Grounds like spark plug not getting grounded sitting on motor.

You should have two wires on coil positive. One from ballast, which is energized by ignition switch. The other from the side terminal of switch on top of starter. So Highly unlikely coil is not getting spark. So the issue is bad coil or beyond. Please answer/check 1-6.

You said you tested with engine not running. It will not run anyway right? So have to ask.....are you testing spark with engine being cranked by starter?

Ok I tested as advised

With points closed

I have 8.35v at the ballast going into coil
I have 7.7v coming out of the coil lead
I have continuity between the coil earth and the points

Thanks for your help here’s some more info


1. When was motor last running? Recent?...never yet?

A few weeks ago. It’s been getting harder to start over last month or so

2. Was running and then you posted this? I hope the scenario is "Motor won't start, so I checked spark, no spark" Is that right???

Yes wouldn’t start and I checked for fuel and spark


3. Most times it's that the person thinks the point gap is correct and it's not. So close gap a little. Try. No spark? open gap a little.

I set points correctly I think but I also varied it a lot so see if I could get a spark and nothing


4. Next common issue: bad new condenser.

I have 12.4v in and 8.35v out when points closed and 12.4v both sides when open

5. Next common issue: you took the dizzy out and didn't get it back correctly.

Checked

6. Next, timing off...same as 5.


I haven’t touched the timing at least not deliberately…and it was running ok before for most part

“ are you testing spark with engine being cranked by starter?”

Yes


My truck has a floor starter if that changes anything

The way it’s wired is i have only two connections to the coil one is live in from ballast and the other earth out to distributor

I don’t know if that’s correct it’s been like that since I’ve had it 15+ years

Does the "floor start" operate a lever to slide pinion gear into place or is it an electrical switch?
How many wires to the positive terminal on the coil?

Hi

Its a lever that engages the pinion and pushes the starter button

One wire to the coil positive terminal (from the ballast)

Voltage on the - side of the coil with the points closed SHOULD BE ZERO VOLTS. That is where your problem is. Either the points are defective, the wire from the coil - to the points is defective, the distributor is not "grounded" (not a separate wire, just the physical contact to the engine block) or maybe (I don't know if these distributors has one, but some do) the wire under the plate in the distributor that connects to the case of the distributor is missing/broken.

Rotate the engine until the points are closed. Turn the ignition on and open the points by pushing the spring loaded arm. If there is no spark between the points, do the following:

Take a piece of business card or index card and work it back and forth through the points while they are closed.
Some new points have something put on them to stop corrosion, which also insulates the points from conducting electricity.
Once you have cleaned the points, open them manually again to see if the spark forms between the points as they open.

Try this:

Remove the distributor cap.

Turn the key back on and get the points closed.

Verify that the voltage on coil - is 7.7 volts (or so) as you mentioned above.

Measure voltage from the outside terminal on the side of the distributor case to ground.
If it is 7.7 volts go to A below
If it is zero volts the wire from from coil - to the outside terminal is bad.
If it is significantly different than 7.7 or zero volts let me know. Something funky going on.

A. Measure voltage from the inside terminal on the side of the distributor case to ground.
If it is 7.7 volts go to B below
If it is zero volts the terminal from outside to inside is bad. New ones are available from Steiner Tractor.
If it is significantly different than 7.7 or zero volts let me know. Something funky going on.

B. Measure voltage from the moving arm of the point set near moving point itself to ground.
If it is 7.7 volts go to C below
If it is zero volts the connection from the inside terminal to the moving point arm is bad.
If it is significantly different than 7.7 or zero volts let me know. Something funky going on.

C. Measure voltage from the fixed (non-moving) the point to ground.
If it is 7.7 volts go to D below
If it is zero volts the points are bad.
If it is significantly different than 7.7 or zero volts let me know. Something funky going on.

D. Measure voltage from the plate the points mount on to ground.
If it is 7.7 volts go to E below
If it is zero volts the connection from the point set to the plate is bad. Remove the points, clean up the area and try again.
If it is significantly different than 7.7 or zero volts let me know. Something funky going on.

E. Somehow the plate is not grounded. Some distributers (I don't know about yours) had a wire under the
plate from the plate to the case of the distributor. Checking it requires disassembling the distributor.

Don't push the points open with your finger. You'll be momentarily connected to the collapsing field in the coil which can reach 200+ volts. Use a wooden or plastic stick.

Thanks bill for those great instructions

I followed your testing and it turned out that the wire from the coil to the distributor was not good.

She starts!!!!

Very happy to get the old girl back to work

She’s a working truck

Thanks all !

Much appreciated!

Been following along. Glad to see your truck is in business again! And along the way, I've learned some new troubleshooting skills.

Hallelujah!

That wire has to flex when the vacuum advance operates. Probably got tired after 70 something years.

You're probably the only person in the whole country with a truck like that. Do you ever drive it into town?

Drmike - Super glad you were able to diagnose and repair the issue. Your truck looks nice and looks like maybe you use it like it was intended be worked. Next time you get a chance, maybe post a picture or two in the Who uses their truck as a truck thread in the General Truck Talk fourm.

I usually replace that wire with a piece of high flex wire made for voltmeter test leads. Lots of it on ebay, with either red or black insulation.
Jerry