Pinto faltering/hesitation when hot

[Spengo]

Having some trouble with my pinto powerplant this weekend. About halfway through a session when everything gets good and hot the engine starts faltering/hesitating like it's misfiring. I am pretty sure it's not a fuel/carb issue, filters are clear and the bowl is full. I also tried lifting on the throttle then stomping again to see if it was an empty bowl that would fill to rule it out. I've replaced the ignition module and the coil with new ones but the issue persists. Going to replace the distributor cap, wires, and plugs next but that all looks pretty ok to my untrained eye. Anyone got any other ideas?

[Steve Davis]

Having some trouble with my pinto powerplant this weekend. About halfway through a session when everything gets good and hot the engine starts faltering/hesitating like it's misfiring. I am pretty sure it's not a fuel/carb issue, filters are clear and the bowl is full. I also tried lifting on the throttle then stomping again to see if it was an empty bowl that would fill to rule it out. I've replaced the ignition module and the coil with new ones but the issue persists. Going to replace the distributor cap, wires, and plugs next but that all looks pretty ok to my untrained eye. Anyone got any other ideas?

I don't know the history, but next best bet for me would be SPARK PLUG WIRES.. or, maybe Dist cap. When these things get HOT, but work perfectly otherwise, THAT'S where I would go. Get the car in a DARK shop. Crank it and watch the spark plug wires for 'shadow arcing'. If you see ANYTHING in the dark, then you likely have spark plug/wire 'cross talk'.. NOT a good thing.
YMMV,
Steve, FV80

[JHerscher]

In addition to Steve's suggestion, there are plenty of other potential culprits.

Happens only at WOT?

1- Fuel delivery - you checked that but it may be
- low fuel volume - possibly replace pump. I know you checked, but I have experienced this problem as well. And I also "verified" that there was sufficient volume. Replaced the pump and the problem went away. So worth a look and not very $$
- possible dragging of carb float on the inside of the bowl - happens in a looong hard right hand flat out high speed curve - look for drag marks on the inside of the bowl. If you have a brass float, you can "pinch" the float together a bit to keep it from dragging. plastic float will need some sanding, I guess. I use brass floats.
- float level. You did verify it was ok, I'm sure.
- intermittent fuel cell blockage. Low probability, but worth verifying you don't have a blockage.


2- Ignition - happens when things heat up.
- Is the coil getting hot? That will cause problems for sure. maybe move it to the cockpit if you can.
- Electronic ignitions sometimes cause problems. Have you borrowed someone's good old fashioned points/condenser/Bosch Blue Coil setup to verify? I've used this setup for 20+ years and never had an ignition problem that couldn't be fixed quickly usually by replacing points and, on occasion, condenser.
-Ignition switch? - is it broken? I had a broken switch that gave me intermittent problems - also seemed to be only after things got hot. Check for a cracked housing or corrosion, etc..
-Master switch? - same thing.
- Short in the wiring? Bad ground from battery?
- Battery shorting?

3- another thing to consider - vibration is a funny thing. It may be heat and it may not. Check those connections..

I'm sure there are other, far wiser people than I who can provide better input. I have no doubt that there will be disagreement with some of this. Good luck.

John

[DaveW]

Having some trouble with my pinto powerplant this weekend. About halfway through a session when everything gets good and hot the engine starts faltering/hesitating like it's misfiring. I am pretty sure it's not a fuel/carb issue, filters are clear and the bowl is full. I also tried lifting on the throttle then stomping again to see if it was an empty bowl that would fill to rule it out. I've replaced the ignition module and the coil with new ones but the issue persists. Going to replace the distributor cap, wires, and plugs next but that all looks pretty ok to my untrained eye. Anyone got any other ideas?

Vapor-lock? Make sure all of the fuel supply routing from the fuel cell to the pump is well insulated, shielded, and away from obvious heat sources.

[Spengo]

It's definitely an ignition issue. Went out this morning and it's gotten worse, only made it around the track 2.5 times and had to tow in. Water temps were only 180F so I can't imagine it's vapor lock. Right after I came in while it was still hot we verified fuel was squirting into the carb when cranking and verified that it wasn't sparking. The only part of the ignition system left that hasn't been swapped is the distributor itself. If that's not the problem then I guess there is a chance that the "new" coil that I used to replace a bad coil was actually a worse older coil. It was in the goodie box that came with the car but it's entirely possible the previous owner replaced it and stuck his old bad coil in the box of the new one. That is exactly what I do too after all haha.

[R. Pare]

Double check your battery, especially if it went thru a shunt recently. We've seen it many times when a car had a shunt ( or a battery got dropped) where afterwards it would crank fine, but would cause misfires at high rpms afterwards.

[E1pix]

Though it seems you’ve confirmed it’s a no-spark deal, you can certainly have vapor lock regardless of what the coolant temps are.

[EYERACE]

You don't want to fix your problem in the same way I fixed a high speed miss in 4th years ago in my Crossle 32F. It got worse so that the miss started at mid RPM in 4th...and then later in 3rd at high RPM.....in spite of tearing apart the carb and cleaning things....and later cleaning more things/tubes inside the carb....

I changed out the fuel cell...and the line coming out of it...and the fuel filter....and the line coming out of it.....and the fuel pump.....and the line coming out of it...and the carb....

Essentially, I changed everything delivering combustible stuff all the way to the intake manifold.

Car ran great...........what was wrong? ...........didn't matter.....still don't care

[Thomas Wirtz]

Check that the ignition coil wires are not crossed. I once bought a car and it had similar issues as you describe.
it turned out to be the coil wires were mistakenly crossed by the previous owner after a engine exchange.
Found it after a lost weekend at the track.

[Messenger Racing]

I am assuming you have no data to verify Fuel PSI and or voltage - so:

Are you running an electic fuel pump or the original design? -

if electric you can still have fuel in the carb at the end of a session and it operate incorrectly - we had one on a kent that was incorrectly mounted and it was overheating due to transfer heat. The guy had virtually rebuilt the whole fuel and ignition system and all he needed to do was put the fuel pump somewhere besides mounting it directly to a bolt hole on the block.

Do you have any electric guages - do they read irratically when the car starts missing?

Would indicate loose connection - most likely is the obvious - battery connections, ignition switch and master switch connections, coil, distributor

Have you killed the motor when it starts running rough and then checked the fuel bowl instead of driving it to the pit?

Thanks for let us think on it with you - good luck and share what you find.

JM

[Steve Demeter]

sounds like a coil to me. Vapor lock might be a possibility. But you did not say you changed out the coil.

[kea]

I'm in the checking battery group.
Had it happened to a customer last year. Changed points, coil, kill switch, fuel pump, float, needle & seat and probably something else. It was the battery.

[Spengo]

Thanks all, unfortunately I wasn't able to solve it at the track. I haven’t looked at the battery voltage in the data yet but it happily cranked the starter when the spark wasn't working so I didn't think to suspect it. I haven’t had any offs this season that may have damaged it. There were 3 other pinto cars running this weekend too and they had all switched to a Pertronix system. Since this was the last event of the season I'll redo the wiring and make the switch to Pertronix myself. That way there will be no mysteries.

[DanW]

Thanks all, unfortunately I wasn't able to solve it at the track. I haven’t looked at the battery voltage in the data yet but it happily cranked the starter when the spark wasn't working so I didn't think to suspect it. I haven’t had any offs this season that may have damaged it. There were 3 other pinto cars running this weekend too and they had all switched to a Pertronix system. Since this was the last event of the season I'll redo the wiring and make the switch to Pertronix myself. That way there will be no mysteries.

If you have points and condenser, be wary of the newer bosch made condensers, especially if the package says "Made in Turkey". I went through three of them in two weekends. They would last less than an hour of run time each. Jay Ivey helped me troubleshoot the issue. I found an old used "Made in Germany" condenser in the bottom of the spares box and it saved my weekend. I've been buying NOS Bosch condensers off Ebay under the repackaged brand of "Standard Motor Parts".

[J Leonard]

New Pertronix is junk. Buy one of the systems Ivey is using now.

[hdsporty1988]

Thanks all, unfortunately I wasn't able to solve it at the track. I haven’t looked at the battery voltage in the data yet but it happily cranked the starter when the spark wasn't working so I didn't think to suspect it. I haven’t had any offs this season that may have damaged it. There were 3 other pinto cars running this weekend too and they had all switched to a Pertronix system. Since this was the last event of the season I'll redo the wiring and make the switch to Pertronix myself. That way there will be no mysteries.

With the Pertronix, be sure and run the matching coil. They need the correct ohm coil or will quickly burn out.

[Rick Silver]

Try running a hot wire directly from the battery to the ignition and coil. I ad a very similar problem a few years ago on my pinto - turned out to be a faulty ignition switch.

[DaveW]

I had a somewhat similar issue that turned out to be a failing cut-off switch. They sometimes vibrate enough that the contact points get burned and dirty. Started out as a high-speed breakup and progressed to the point it wouldn't run. We jumpered it in the pits and I went out and finished the race. There was a long thread on this subject back 10+ years ago.