Hard starting when warm

[macrisel]

I have an issue on my Jeep with it being almost impossible to start when the motor is warm.  When the motor is cool, it will fire off and run very well.  This is not a new issue, but one I have had since I reassembled the jeep.  I have searched the forums and did some troubleshooting.  Here is what I have done up to this point....

1.  I have confirmed I am getting spark at the plug.  The plugs, wires, points, rotor and condenser are new.
2.  I have confirmed I am getting fuel to the carborator.
3.  I checked the float height in the carb.  I rebuilt the carb three years ago and have used it very little.
4.  I HAVE NOT moved my fuel line yet, but I do not think it is vapor lock.  The fuel line is not warm when you touch it and plenty of fuel is coming through at the carb.
5.  I have timed the motor with a timing light and set it at 5 degrees TDC.

I have a load of questions/observations.....
1.  Could a weak starter be at fault?  When the engine is warm it seems it is harder for the starter to turn over and it turns slower.  My brother-in-law is a tractor mechanic and works on a lot of 6 volt tractors.  He thinks the culprit is the engine turning over too slow.
2.  When it is running, I notice my amp gage does not show a large amount of charging....probably only around 7-8 amps
3.  When I pull the plugs when it doesn't start, the plugs do not look like they are covered in gas like it was flooded.
4.  I haven't checked the valve clearance since I rebuilt the motor, but it has very little time on the motor.

I know I'm forgetting something, but it is late at night and my eyes are getting blurry.  I honestly cannot figure out if it is a fuel or fire problem or where to go to next.  I know it could be anything, but I'm at a dead end.

Help!

[1oldracer]

Hi Mark, Don't despair.  With all of the mechanical knowledge available on the forum I'm sure it won't be long and the problem will be history.  Unfortunately I am a little short on mechanical knowledge so I have to rely on experience.  I had the same exact problem.  Just before I launched into a major money spending search for the cure my Willys embarrassed me in front of my friends by not starting and I got mad and thought, "OK you little bleep take this," and I stomped the foot feed to the floor with my left foot and hit the starter with my right and it fired right up.  It works for me every time.  If you haven't tried it, give it a shot. It would be a cheap fix.  Good Luck  

[scoutpilot]

Do you have a diffuser gasket between the carb and manifold?

[garage gnome]

Do you try pumping the throttle several times to start it when warm? Do you use the choke? When engines are hot, they have a tendency to lean themselves out. My '53 fire right up when warm, but my '49 requires a few pumps of the pedal.

[macrisel]

I have tried all of the above at different times and not had much luck.  ONE TIME it started when I held the throttle all the way open, but I have not been able to repeat it.

On these engines, will the spark plug get very "wet" if the engine is flooded?

Also, something I thought of this morning on the way to work.  I have not tried to take the gas cap off when it is warm to relieve some pressure.  Don't know if my cap is vented or not or if this would even make a difference.

[1955CJ-5]

Ignition coils can sometimes stop working or become intermittent when hot......it might be worth swapping out if you have a spare....

[athawk11]

1955CJ-5 beat me to it.

I believe it was at the 2A page where I read a discussion that talks about an older coil causing hard warm starts.

Tim

[ZekeD]

Ok this is weird........

On a ford 2n (1945) tractor if that happens it is your ignition switch. (!)

No joke....   Dont know if you have a ignition switch with a lump of bakelite
On the backside where the wires connect, but if you do.....  Change it.


Its cheap and works on fords.   Dont ask, but if you want confirmation
Go to the YTMag old iron website and checkout 9n 2n fords......

That is where I found the answer.


Zeke

[PaulS]

Zeke--we have more than Willys in common.  My tractor is an 8N, though!

On the YT forum for old Fords, the common wisdom is that the difference between an overheated coil and an overheated ignition switch is the time it takes to happen. (IIRC, the switch is 15 minutes and the coil is an hour.)  However, both of these failures will kill the engine at the time.  The original poster doesn't say that his Jeep dies, only that it won't start warm.  So I wonder if either of these failures apply in this case.  Of course a CJ3A is not a Ford tractor, so the symptoms could be different here.

To check the switch, simply put a jumper wire across it.=

-Paul

[PaulS]

Mark:  does your Jeep have a ballast resistor in the ignition circuit?  Mine does--but I don't think it's in the wiring diagram, so yours may not.  But if you've converted to 12V, it may have one.  If so, it is possible that the resistance of the resistor changes substantially as it heats up.  (This is a design feature on the old Ford tractors.)  Try putting a jumper across it to see if that helps--it will give you a stronger spark.  Take the jumper off after the engine starts or you could fry your coil eventually.

-Paul

[macrisel]

Thanks guys!  My jeep is still 6 volt and has a brand new ignition switch and wiring harness from Walcks that are less than 2 months old.  I called and talked with Carl at Walcks this morning.  His opinion was to look at the starter.  According to him, if the starter is weak it will turn the motor over when the engine is cold, but when the engine and starter warms up the internals of the starter will swell a little bit and cause the starter to be harder to turn over.  This draws more current to the starter and sends less to the ignition for the jeep to start.

I have pulled the starter and will be taking it to a shop for testing.  At the same time, I'm also taking my generator and voltage regulator to the same shop for testing.  These are some of the only parts that are not new/rebuilt on the engine.  I figured I would get these professionally checked and eliminate them from the equation and have a clean starting point.

I'll keep everyone informed.  Meanwhile, I'm still not ready to write off a fuel issue.  I know I'm getting fuel up to the carb, but I'm not convinced everything is exactly right from the carb into the cylinders.  :-/

[macrisel]

Do you have a diffuser gasket between the carb and manifold?

Sorry I missed your question earlier!  Yes, I do have the thick diffuser gasket with the "V" in it installed under the carb.  I was a brand new one from Walcks when I rebuilt the carb 2-3 years ago.

[Matto]

I had a similar problem last year. If I ran the Jeep for a half hour or so it would refuse to restart untill it cooled down. The problem turned out to be a weak fuel pump. I rebuilt the pump and the problem went away.  My starter was turning the motor over at the same speed hot or cold though.
Matt

[ZekeD]

The way to see if it is the solenoid or starter. Is to wait for failure, and then hose them down with a co2 fire extinguisher......   If it starts immediately after the application of co2 you have found the problem.


Wisdom from an old desert rat at 116 in the Mohave.


ZD

[macrisel]

Another update tonight.  The starter, generator, and voltage regulator are dropped off at the shop and getting checked out.  Hopefully I will have them back for the weekend.

I messed around with the carb some more tonight and found that my accelerator pump was too tight and not working properly.  It looked like the seal on the pump had swelled up.  This is extremely aggrevating because I just rebuilt the carb three years ago and it has set on the shelf since then.  Stupid new parts.  Thankfully, I had kept all my old parts and pieces and swapped in the old pump.  I don't know if this is related to the warm starting issue, but is should help the drivability.

I'm hoping I can get my parts back and put them on this weekend to test it out!