GP no start

[hobigusn]

So I’m helping a friend try to start a GP after sitting for years. My question is would a malfunctioning spark advance cause a no start situation? Also what is the proper way to test the coil and what should I be seeing. I’m getting readings I don’t understand. Thank you

[Wolfman]

A GP is just a Ford tractor engine with a different manifold to use a down draft carb. instead of an updraft carb.
I have a friend that has a GP but I don't remember off the top of my head if it has a front mount distributor, mounted on the front of the timing cover or an angle mount distributor that sticks out the right front of the engine. But still on the timing cover. ??
The angle distributor uses a coil like a GPW or MB.
On the front mount distributor, the coil is fastened to the top of the distributor housing. The high voltage connections are internal. No outside coil wire.
Either way. See if you have power to the coil with a test light, with the key on.
If you do, after all this time, most likely the points have corroded and need cleaned or replaced.
Quick check: if a side mount distributor, pull the coil wire out of the distributor. Hold the wire next to the engine block, key on and crank the engine.
Get a spark, you are still looking for the problem. Fuel would come next.
On the front mount distributor, you will have to remove the spark plugs. Connect the plug wires. Lay the spark plugs on the head and crank the engine. See if you have a spark.
On the front mount distributor, the distributor body is held to the timing cover with two bolts. Take the bolts out and the distributor comes off. The drive is an offset slotted drive that will only go on one way. Just fit the drive back into the slot and bolt the distributor back to the cover. No further timing needed as long as you don't remove the point plate from the distributor body. That is adjustable and will screw up the timing.

[hobigusn]

This has the old firewall mounted coil. Same as the model A. I’m seeing 6 volt battery side and different reading key switch off and on. So I went from battery to coils battery post to eliminate the key switch. Had constant 6 volts on coil distributor side of coil now. Did not check coil side while cranking. Ran out of time. Pulling plug and checking spark is next. Friend recalled a weak spark couple years ago. But don’t know how he came up with that conclusion. Thanks

[Wolfman]

Sounds like you are on track with your test so far.
Next I would check the distributor side of the coil with the jumper from the battery in place.
If the voltage goes from 6 volts to zero and back as you crank, the points are working.
If the voltage on the dist. side comes up to 6 volts and stays there while cranking, the points need cleaned or replaced.
If the dist. side stays at zero, take the dist. side wire off and see if the voltage comes up to 6 volts.
If it does come up, there is a short in the distributor or a bad condenser.
If with the dist. side wire off, the voltage stays at zero, you have a bad coil.

[hobigusn]

Thanks for the guidance, this old school stuff is still new to me. I grew up with fuel injection, lol

[Wolfman]

I understand,
I have a nephew that graduated from a Mechanic trade school not too long ago.
One of the first repairs someone brought him was a carb. to rebuild.
He brought it to me ??
My first remark was " you just got out of mechanic's school, why can't you fix it ?? "
All they taught him in school was how to fix electronic fuel injection.
I will be glad to help you both out if I can.

[slatgrille]

Check the coil for an OHM reading between the primary and secondary circuit. (One lead to the small stud, one to the large opening.) Should be 10K or more. Are you wired to positive ground? My Model A stopped producing a spark when the points 'broke' one day. Ran fine the previous day. Turned out the coil went bad....not enough Ohms. Changed it out and 'vroom', off she went!

Haven't restored my GP yet, so just using general antique auto info to troubleshoot....

Craig

[hobigusn]

Some coil as a model A I understand. Yes it still is positive ground.

[hobigusn]

Check the coil for an OHM reading between the primary and secondary circuit. (One lead to the small stud, one to the large opening.) Should be 10K or more. Are you wired to positive ground? My Model A stopped producing a spark when the points 'broke' one day. Ran fine the previous day. Turned out the coil went bad....not enough Ohms. Changed it out and 'vroom', off she went!

Haven't restored my GP yet, so just using general antique auto info to troubleshoot....

Craig

7.1k ohms on this coil. Low enough to cause a problem?

[Wolfman]

7.1 ohms for the secondary resistance sounds really low.
The windings in the secondary coil winding may be shorted together internally.
If you have access to any 6 volt coil, you could temporarily install it to see if this solves your spark problem.

[hobigusn]

That’s exactly what we did. Wires up a coil from a gpw. No start. Had good spark. Took the elbow off the holly carb. Found when you press accelerator, 2 large streams of fuel spray down carb center at downward angles. Flooding carb basically. I think the air bleed plug has backed off and the holes are spraying fuel. We stopped and did research when we found this. Will have to report back. We ordered a new coil for good measure.

[Wolfman]

What color is the spark plug porcelain ??
Could be a combinaton of things.
If the porcelain is black, the flooding condition in combination with an initial weak spark may have fouled the plugs. Shorted the spark plug.
Now that you have a good coil in place with the old plugs, still joy.
Maybe ??

[YLG80]

That’s exactly what we did. Wires up a coil from a gpw. No start.

Hello,
I do not see any previous post about the engine ignition timing.
Did you double check the ignition timing, static with a lamp/mutlimeter or better with a stroboscope?
Yves

[steve w]

just got done reading posts, alot of good info there, my guess is likely bad coil but thought i would add this, one time had my gp running and suddenly stopped, checked everything i could finally found the post that points pivot on had enough corrosion on that it stopped points from opening and closing properly, just cleaned off then ok. good luck.

[hobigusn]

Coil has been replaced. Good spark verified, correct wire location and new spark plugs. Down to carburetor, original Holley carb. Owner says it was rebuilt by him. He has rebuilt WO with no problems. Any ideas on a crank no start involving the carb. This design seems more complicated then a WO operation.