Shut down when a/c is running

skipvair · Post by **skipvair** » Sat May 26, 2018 1:26 pm

My 66 -140 hp A/c Corsa is giving me problems shutting off seemingly only when I run A/C. Whenever it does that I can no longer hear the electric fuel pump running. Let it sit a bit and it starts and runs OK. I can continue on without A/c when it restarts. Prior to restarting I can hear the fuel pump again. Is this any symptom of vapor lock? Today when charging the A/C it did it . Fuel lines were not hot to touch and carbs were not either. Broke a fitting loose to see if pressure was built up and it was not. Any ideas? Hate to just start buying parts, but may get another fuel pump. I should
Probably carry a spare anyway.

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Post by **bbodie52** » Sat May 26, 2018 9:42 pm

skipvair wrote: Sat May 26, 2018 4:26 pm

My 66 -140 hp A/c Corsa is giving me problems shutting off seemingly only when I run A/C. Whenever it does that I can no longer hear the electric fuel pump running...

A stalled engine SHOULD cause the electric fuel pump to shut off. Assuming that an electric fuel pump safety switch exists, the safety switch that is tied to engine oil pressure is intended to power-down the electric fuel pump if the engine stalls. Restarting the engine restores oil pressure, which should then reapply power to the fuel pump.

How is your electric fuel pump wired? Is it tapping from a circuit that is also connected to the air conditioning system? Are there any safety sensors associated with the electric fuel pump? These sensors are normally associated with engine oil pressure, so that the switch that senses oil pressure will only provide power to the electric fuel pump when the engine is running. Sometimes a motion sensor is also included that is intended to detect an impact and rapid deceleration of the vehicle, so that power will be cut to the electric fuel pump in the event of a collision or accident.

Where is your electric fuel pump located? Most electric fuel pumps are better at pushing fuel long distances than they are at pulling fuel from the fuel tank. The electric fuel pump should be close to the fuel tank outlet, and should pressurize the entire fuel line from that point to the carburetors. Vapor lock is unlikely, and if it did occur to the point of fuel starvation to the carburetors you should be able to determine if the float bowls are empty by simply looking down the throat of each carburetor and moving the throttle quickly to see if you observe a squirt of gasoline from the accelerator pump in each carburetor.

Fuel starvation may also exist if there is an electrical problem related to the operation of both the fuel pump and the air conditioner. Has anything changed recently in the automobile wiring or air conditioner system? Has your electric fuel pump changed at all, or has it been in operation as it currently exists for a long period of time?

I found this nugget of information in the 1965 shop manual. It refers to the engine idle speed with an A/C system. Could the engine idle be too slow with the A/C running?

skipvair · Post by **skipvair** » Sun May 27, 2018 7:37 am

Thanks. It first started doing it at 70 mph. Yesterday after replacing a clogged drier/filter while recharging it did it again but restarted more quickly. It was the first trip I took using the air when it first did it. Never did it without it. Your response has me thinking. I need to look at wiring. It seems to be a “clean” shutoff and restart. Maybe I have a rely or a breaker that is overloaded with auxiliary condenser fans on same circuit as fuel pump. I guess I will look where they are wired from.

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Post by **66vairguy** » Sun May 27, 2018 2:15 pm

Brad made some good points on "shut off" circuits. I see a possible issue with the oil pressure switch. Of course the warning lamp will be on when the engine stops, BUT the oil pressure switch could be causing the shut down. When running A/C (usually on a warm day) the engine will be operating at a higher temperature and oil pressure will be lower, but still acceptable. It may be a defective oil pressure switch causing the issue when the engine is warmer. Just a thought as the new switches do seem to fail more frequently.

If you system is a R134a it should have a HI/LO pressure refrigerant sensor to shut off the compressor if pressures get out of bounds. Not saying that is your problem, but worth looking at.

skipvair · Post by **skipvair** » Sun May 27, 2018 4:48 pm

The light never came on. And yesterday, it wasn’t hot at the engine at all

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Post by **66vairguy** » Sun May 27, 2018 5:07 pm

When the engine stops with the ignition key on the oil pressure warning lamp SHOULD illuminate within a couple seconds.

To check the warning lamps BEFORE you start the car up, turn the ignition key ON and make sure BOTH warning lamps come on BEFORE turning the key to START.

It's a good habit to get into. When I was a kid I ruined a water cooled engine because the warning lamp was burned out - live and learn.

Post by **bbodie52** » Mon May 28, 2018 6:50 am

If the engine is turning you should still have oil pressure. Even if the engine dies, at high speed with the transmission in-gear the coasting vehicle will still keep the engine tuning and oil pressure up as long as you don't depress the clutch or put it in NEUTRAL. A loss of power could be fuel starvation or an ignition problem. If it is fuel starvation the engine may operate with an intermittent jerk as it begins to run out of fuel, and the carburetor(s) should have dry float bowls and nothing from the accelerator pumps if you inspect them after coasting to a stop. A voltage drop could or an ignition system fault would cause the engine to die, as if the key were turned off, if something disrupts the ignition system. Do you have a stock ignition system, or an electronic aftermarket ignition system?

skipvair · Post by **skipvair** » Mon May 28, 2018 8:42 am

Pertronix 2

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dave t · Post by **dave t** » Mon May 28, 2018 11:21 am

skipvair wrote:My 66 -140 hp A/c Corsa is giving me problems shutting off seemingly only when I run A/C. Whenever it does that I can no longer hear the electric fuel pump running. Let it sit a bit and it starts and runs OK. I can continue on without A/c when it restarts. Prior to restarting I can hear the fuel pump again. Is this any symptom of vapor lock? Today when charging the A/C it did it . Fuel lines were not hot to touch and carbs were not either. Broke a fitting loose to see if pressure was built up and it was not. Any ideas? Hate to just start buying parts, but may get another fuel pump. I should
Probably carry a spare anyway.
IMG_0580.JPG

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It sounds like you have an electric fuel pump. Is there a circuit breaker in the fuel pump feed wire? Does the AC feed off the breaker too? You might have too much current going through the breaker and tripping it when the AC is turned on. It could be old and worm out or simply too small. After it trips, you let it cool down and the breaker resets.
Look at the fuse block. Is there a metal can plugged into one of the fuse locations? That would be a breaker. Is the fuel pump and the AC on the same circuit?
If so, replace the breaker with a 10A fuse and test. If the fuse blows, that is the problem. Get a new breaker and/or move the fuel pump feed to another circuit.
Let is know what you found.

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Post by **bbodie52** » Mon May 28, 2018 2:17 pm

skipvair wrote: Mon May 28, 2018 11:42 am

Pertronix 2

It is common to tap off of the ignition coil positive terminal to power the electronics in the breakerless ignition module. That electronic circuit in the Pertronix Ignitor II module needs a full 12 VDC all the time (when the key is ON). If the factory ballast resistor wire were to be left in the wiring harness, the voltage feeding the coil and the Pertronix module in the distributor would be correct for a 1.5 ohm coil (nominal 3.0 ohms total) but too low for proper operation of the electronics module inside the distributor, and a malfunction in operation could result.

The operation of your air conditioning system could also be causing a voltage drop in the wiring harness, which can further lower the operating voltage that is available to the positive side of the ignition coil. Instead of 12 V DC, a ballast resistor in the circuit that is feeding the ignition coil positive terminal would reduce the voltage to a nominal 7 V DC. This may be barely enough to operate the Pertronix Ignitor II module inside the distributor. Operating all of the electrical components in the air conditioning system may reduce the available voltage even further, which might take it below the threshold that the Pertronix Ignitor II can tolerate. This could be what is killing your engine when the air conditioning system is in operation.

A simple test would be to run a temporary bypass jumper wire between the positive battery terminal and the positive ignition coil terminal. This would ensure a maximum voltage that would be powering both the ignition coil and the Pertronix Ignitor 2 module inside the distributor. Such a temporary bypass would prevent your ignition key from turning the engine off, since voltage would be supplied directly from the battery positive terminal to the ignition coil, which bypasses both the resistor ballast wire in the wiring harness and the ignition switch that powers the ignition system. But the goal here would be to see if the engine runs properly when you have assured 12 V DC is available full time by installing a jumper wire from the battery. If this corrects your problem, you should rewire your Pertronix ignition system as shown in the diagram below. This will provide a full 12 V DC from the ignition switch to the distributor electronics.

Finally, what type of ignition coil are you using? If it is a stock factory Corvair ignition coil, it is designed to operate with a normal Corvair ballast resistor wire in the circuit. This configuration provides a total of approximately 3 ohms of primary resistance (half from the resistor wire and half from the ignition coil primary). The Corvair wiring harness factory design temporarily bypasses the resistor wire when the starter solenoid is engaged, which boosts the ignition coil output voltage to the spark plugs while the engine is being cranked to start. When the key is released and the starter solenoid disengages the ballast resistor output voltage returns to the ignition coil positive terminal to provide a nominal 7 V DC for normal operation. This allows the ignition coil to run at a cooler temperature, which can prolong the life of the coil.

If your car is fitted with an aftermarket high-performance ignition coil please let me know so that I can recommend the correct wiring harness configuration for the type the coil you have installed in your car. Basically, a coil with a 1.5 ohm primary requires the ballast resistor wire to remain in the circuit. If the coil is a 3.0 ohm high-performance coil, the ballast resistor wire should be permanently bypassed. If your coil is an ultra high-performance Pertronix Flame-Thrower II 45,000 volt coil (0.6 ohm primary resistance) it also should be wired to bypass the ballast resistor wire to provide it with a full 12 V DC whenever the ignition key is on. In any case, the Pertronix Ignitor II electronic module inside the distributor should always be powered by a nominal 12 V DC.

This diagram shows a suggested bypass of the Corvair factory ballast resistor wire to power a 3.0 ohm coil and a Pertronix distributor module. This lets the 3.0 ohm coil take care of restricting primary current for cooler operation with the six cylinder engine, while the Pertronix Ignitor II module in the distributor is happy with a full 12 VDC all the time when the key is ON.

http://www.pertronix.com/prod/ig/ignitor2/default.aspx

skipvair · Post by **skipvair** » Mon May 28, 2018 3:48 pm

Thanks. That’s what I was thinking but didn’t know where to start looking for breaker.

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skipvair · Post by **skipvair** » Mon May 28, 2018 4:09 pm

Brad, I am sorry. This car has a standard pertronix igniter in it. The coil simply says 12v external resistance required.

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skipvair · Post by **skipvair** » Mon May 28, 2018 4:12 pm

I apologize. My other car had the ignitor 2

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skipvair · Post by **skipvair** » Mon May 28, 2018 4:41 pm

What sustained voltage should this have coming into coil?

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Post by **bbodie52** » Mon May 28, 2018 5:16 pm

Everything I wrote could still apply to the Pertronix Ignitor I and a standard 1.5 ohm coil. If the red wire that provides power to the Ignitor is simply connected to the ignition coil positive terminal as its power source, that voltage may be dropping too low by the time all of those A/C systems are added to the mix. I would recommend leaving the coil powered as is, but powering the Pertronix Ignitor from a tap on the firewall side of the engine compartment multi-connector (as shown in the wiring diagram example). This wiii provide a full 12V DC from the ignition switch BEFORE the ballast resistor wire.

Another possibility: The coil could be failing when it gets hot, but this is unlikely with the symptoms as you have described them.

skipvair · Post by **skipvair** » Mon May 28, 2018 5:45 pm

bbodie52 wrote:Everything I wrote could still apply to the Pertronix Ignitor I and a standard 1.5 ohm coil. If the red wire that provides power to the Ignitor is simply connected to the ignition coil positive terminal as its power source, that voltage may be dropping too low by the time all of those A/C systems are added to the mix. I would recommend leaving the coil powered as is, but powering the Pertronix Ignitor from a tap on the firewall side of the engine compartment multi-connector (as shown in the wiring diagram example). This wiii provide a full 12V DC from the ignition switch BEFORE the ballast resistor wire.

Another possibility: The coil could be failing when it gets hot, but this is unlikely with the symptoms as you have described them.

Thanks, will check voltage

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