Won't idle/start when hot
07-18-2001, 08:13 PM
#1
Racer
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Location: arlington, TX formerly Holland, MI
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Won't idle/start when hot
When the temperature outside is over 80 and my 75 914 2.0 is hot, the car won't idle. The tach will drop below the last line and the car will stall. Also, the only way the car will restart (or start under the same conditions) is to hold the gas pedal to the floor while cranking the motor for longer than is normal. If the weather is cooler, the car runs perfectly. Any ideas of what I should look at to fix the problem? 
07-19-2001, 04:24 AM
#2
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Location: Scottsdale Arizona
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kevin,
In my 1971 914 1.7, I found two causes to hot weather starting/running problems:
a) HOT AIR
The ‘71 had an oil bath air cleaner. When the oil got VERY hot after parking it was very difficult to start. The short term solution was to pull the air duct away from the air filter so cool air could be ingested. The long term solution was replacing the oil bath with a dry type air cleaner. (I think your 75 does not have this problem.)
b) BOILING FUEL
Parking a hot 914 on a hot day sure puts a lot of heat on the fuel injectors & fuel lines. The fuel would vaporize in Arizona and it would take a very long time to start. The solution I used was rigging a toggle switch under the fuse/regulator box in the engine compartment. Normally the fuel pump shuts off automatically after X seconds of detecting a stopped engine. This is a safety feature in case of a crash. I rigged the 3 way toggle switch to have the fuel pump run normal OR continuously with ignition on OR fuel pump off.
- With the fuel pump “off” the car could not be driven away by a thief.
- With the fuel pump “always on with ignition on” I would switch the ignition on and wait about 20 seconds for the pump to flush the hot/vaporized fuel from the engine
compartment with cooler fuel. Then I would click the ignition further to engage the
starter and start the engine.
Other hot running problems could be a symptom of a bad temperature sensor or bad
pressure sensor. My recollection is there is an air temp sensor and a cylinder head temp sensor. You can test these sensors with an ohm-meter.
I had a pressure sensor suddenly fail by sensing lower pressure (leaner control output). I did not know of any way to test the pressure sensor and at the time I could not get a spare. Adding a resistor in series to the cylinder head temp sensor will increase the mixture and this is how I figured out I was running too lean which lead to finding another pressure sensor.
Another issue to constantly check on 914s is poor electrical connections. I cannot
remember how many times I had engine problems traced to a poor connection on a fuel injector or on some sensor. Check all those connections and tighten loose connectors or replace them.
Good luck!
Regards,
George
In sunny Arizona
In my 1971 914 1.7, I found two causes to hot weather starting/running problems:
a) HOT AIR
The ‘71 had an oil bath air cleaner. When the oil got VERY hot after parking it was very difficult to start. The short term solution was to pull the air duct away from the air filter so cool air could be ingested. The long term solution was replacing the oil bath with a dry type air cleaner. (I think your 75 does not have this problem.)
b) BOILING FUEL
Parking a hot 914 on a hot day sure puts a lot of heat on the fuel injectors & fuel lines. The fuel would vaporize in Arizona and it would take a very long time to start. The solution I used was rigging a toggle switch under the fuse/regulator box in the engine compartment. Normally the fuel pump shuts off automatically after X seconds of detecting a stopped engine. This is a safety feature in case of a crash. I rigged the 3 way toggle switch to have the fuel pump run normal OR continuously with ignition on OR fuel pump off.
- With the fuel pump “off” the car could not be driven away by a thief.
- With the fuel pump “always on with ignition on” I would switch the ignition on and wait about 20 seconds for the pump to flush the hot/vaporized fuel from the engine
compartment with cooler fuel. Then I would click the ignition further to engage the
starter and start the engine.
Other hot running problems could be a symptom of a bad temperature sensor or bad
pressure sensor. My recollection is there is an air temp sensor and a cylinder head temp sensor. You can test these sensors with an ohm-meter.
I had a pressure sensor suddenly fail by sensing lower pressure (leaner control output). I did not know of any way to test the pressure sensor and at the time I could not get a spare. Adding a resistor in series to the cylinder head temp sensor will increase the mixture and this is how I figured out I was running too lean which lead to finding another pressure sensor.
Another issue to constantly check on 914s is poor electrical connections. I cannot
remember how many times I had engine problems traced to a poor connection on a fuel injector or on some sensor. Check all those connections and tighten loose connectors or replace them.
Good luck!
Regards,
George
In sunny Arizona
