MTFCA Forum

Helping a buddy switch out a failed Pertronix in a Bosch distributor and change back to points. Seemed easy enough, we thought. Car was running normally, but the owner left the key on and apparently burned something up in the electrical system. Car is 12 volt. We installed the points and condenser and checked all connections - seemed to be good. Point gap is .020. We have power to the points but very weak spark at the plugs. Car will not start. We have good fuel flow, so that's not an issue. Checked timing...with #1 piston at TDC and both valves closed rotor is pointing to #1 on the cap. We've checked and double-checked and can't get it to start. What are we overlooking??

Run a separate wire to the distributor ,unrelated to the cars wiring, if good spark, follow the wiring, could be a wire got hot and melted over into something,reducing voltage.

Sure won't hurt to try your suggestion. I'll report back with an update. Thank you.

Replace the ignition coil.

Run a ground wire from the block to the distributor body if it does not have one currently.

All good suggestions, if you have got to here without any success try replacing the rotor. Bosch rotor's have a noise suppression resistor in the
rotor ( the little epoxy in the middle of the brass contacts ) they are prone to failure especially if used with high output coils & resister wires
that are recommended for use with Pertronics. I have seen this several times even on my Grandsons sand rail.
Craig.

mgarrett wrote: ↑

Sat Oct 28, 2023 10:00 am

Helping a buddy switch out a failed Pertronix in a Bosch distributor and change back to points. Seemed easy enough, we thought. Car was running normally, but the owner left the key on and apparently burned something up in the electrical system. Car is 12 volt. We installed the points and condenser and checked all connections - seemed to be good. Point gap is .020. We have power to the points but very weak spark at the plugs. Car will not start. We have good fuel flow, so that's not an issue. Checked timing...with #1 piston at TDC and both valves closed rotor is pointing to #1 on the cap. We've checked and double-checked and can't get it to start. What are we overlooking??

It would help to understand what led you to replace the Petronix
"the car was running normally, but the owner left the key on and apparently burned something up in the electrical system.
If you think he burned "something" in the electrical system that may have been the coil, have you replaced it when you switched to the points & condenser.?

Good explanation of the electrical flow when he key is on https://www.championautoparts.com/Techn ... -Work.html
"The primary circuit carries low voltage. This circuit operates only on battery current and is controlled by the breaker points and the ignition switch. When the ignition key is turned on, a low voltage current from the battery flows through the primary windings of the ignition coil, through the breaker points and back to the battery. This current flow causes a magnetic field to form around the coil......"

Pertronix states in their instructions that leaving the ignition on for even a short time with out the engine running will burn out the pickup. That
is the reason behind most failures of Pertronix. Second is running solid metal plug wires. I believe that info came from Pertronix tech support.
Craig.

FOLLOW-UP to above replies.............The owner did replace the coil being used with the Pertronix with another known good 12 volt coil. We checked both terminals of the coil with a test light...with key on, test light burns nice and bright. When turning the engine over with the starter, the opposite terminal on the coil (going to the distributor) the light flickers with the opening and closing of the points, so that seems good. With the key ON, we see sparks when we open and close the points, so that is good. We've switched back and forth with the two rotors he has but makes no difference, still NO START. He is going to add a ground wire from the distributor body to the engine block as suggested.

was thinking of switching to the electronic ignition for the texas T distributor. The warning for the petronix ones is that for all E I's? sorry not trying to hijack thread.

Tim

Also what "BOSCH" distributor is it. The term "BOSCH" has been used for a variety of models - American Bosch 600 & other variations, Front Plate, VW, Texas T's Bosch knock off....


Petronix Trouble shooting http://www.pertronix.com.au/assets/pdf/ ... lation.pdf

WHAT TYPE OF COIL CAN I USE WITH THE IGNITOR? HOW DO I CHECK MY COILS RESISTANCE?
(12V NEGATIVE GROUND ONLY)
To determine if your systems coil is compatible with the Ignitor, some measurements should be taken prior
to installation of the Ignitor. Caution… While performing this test, never leave the ignition switch on for more
than 30 seconds at a time.
Set your voltmeter to a 15 or 20-volt scale. Attach an 18 or 20 AWG jumper wire from the negative coil
terminal to an engine ground. Attach positive (red) lead of your voltmeter to the positive side of the coil,
and the negative (black) lead to an engine ground. Turn the ignition switch to the run position. Now read
the voltage at the positive coil terminal. Turn the ignition switch off. If the voltage measured is
approximately 12 volts, no resistance wire is present. A typical resistance wire will provide 9 - 6 volts.
The next step is to determine the resistance in the primary ignition. Label the wires attached to the coil
terminals and note their appropriate location. Make sure that the ignition switch is off and disconnect all
wires from the coil. Adjust your meter to the lowest ohm scale. If you are using an analog style meter make
sure to zero the needle.
Measure from the negative terminal to the positive terminal. Write your measurement down.
Now the maximum system amperage can be determined. Divide your voltage measurement by your coil
resistance measurement. This will give you the system current or amperage.
Four and six cylinder engines should not exceed 4 amps. Eight cylinder engines should not exceed 8 amps.
If the total amperage in your system is higher than the amount recommended for your application, you
should install a ballast resistor.
EXAMPLE
Voltage 12
Resistance 1.5
12 / 1.5 = 8
Total amperage is 8

UPDATE:
I think we have found the problem!! My buddy called and said he pulled the spark advance lever to full advance and hit the starter - the engine started! After hearing this, we need to make some mechanical adjustments to the spark advance linkage. I did notice a lot of looseness an slop in the advance mechanism, but since the car had been running fairly well I didn't suspect that as a possible culprit. We'll know for sure tomorrow.

Thanks to all for the helpful feedback!

mgarrett wrote: ↑

Sat Oct 28, 2023 6:21 pm

UPDATE:
I think we have found the problem!! My buddy called and said he pulled the spark advance lever to full advance and hit the starter - the engine started! After hearing this, we need to make some mechanical adjustments to the spark advance linkage. I did notice a lot of looseness an slop in the advance mechanism, but since the car had been running fairly well I didn't suspect that as a possible culprit. We'll know for sure tomorrow.

Thanks to all for the helpful feedback!

Your ignition is way out of time. You need to set your timing correctly.

Is there an external ignition resistor or does the coil have an internal resistor in it? If it’s external you’ll usually have a white porcelain like block in the circuit. That could be causing a voltage drop which it’s supposed to do when it warms up. An internal resistor will be marked on the coil. I’m suspecting the coil is bad with the power left on and the points closed it probably cooked. If your coil has an internal resistor make sure you replace it with one that has a resistor in it and is 12 volts. I would also consider replacing the capacitor in the distributor. That’s cheapest so maybe it should be first.

With your timing being off you may want to check your dist gears, one might be worn to the point of near failure.

In my experience with old JD farm tractors with distributors, I would try another condenser. I once put a complete tune up kit in a ford engine in a Versatile swather, first day in the field it ran like new then, all of a sudden, it started missing. So I thought cracked distributor cap, tried new cap but did not help, new spark plug wires, did not help. Then I bought another condenser, and it ran like new! For some reason new condensers today are not like the ones from fifty years ago. Hope this helps you solve the problem. Good luck!

SUCCESS! The fix was fairly simple. The engine has the Texas T Parts Bosch 009 distributor setup. We discovered that there was a lot of excess play/looseness in the advance/retard linkage attached to the distributor bracket so we corrected that. Also, the bracket clamp on the distributor body that the linkage is bolted to was clocked slightly off so we adjusted it to align more correctly with #1 on the distributor cap with the advance lever all the way up. Once those adjustments were made, the engine fired up right away and ran great. We also have full travel of the advance/retard lever in both directions without all the excess, unwanted play. Appreciate all the helpful replies and tips.

Excellent report Mike! Glad it's running again!
Your thread also produced good info about dizzys and Pert-fired dizzys!
Harvey beat me to it about modern condensers and I have a Pert II in a machine so interesting tidbits. Thank you.