hard starting when hot

Question

1995 Toyota Tacoma 4 cylinder 2.4 liter

Since I've owned this first year Tacoma, it is hard to start in the summer after shutting it off 3 times in a day. No problems in the winter, no problems in the mornings, just in the heat of the afternoon in summer. If it sits an hour then no problem.

I've checked for a plugged fuel vent on the fuel pump and also changed the fuel pump, changed the air filter, new plugs, plug wires, distributor cap and rotor, oil/filter, engine ground, fuel treatment for a vapor lock situation, unscrewed the fuel cap to release pressure(?), have tried looking at the distributor, checked fuel pressure regulator, checked for flow at the fuel rail. It must be that fuel is not getting through somehow only when it's hot and I have too many short stops with engine off. I've driven it 500 miles no problem but when I shut it off on a hot summer day, I have to wait an hour for it to restart.

JLT · Answer

You might want to look into your starter-motor.

When it's hot outside the metal from your engine expands. Making it harder for the starter to turn it around. If it turns around with no problem it could be that the resistance of the starter-motor is to high making the power for the ignition curcuit to low.

If the problem isn't there, you should look at the workshop manual of your car and trace if your ignition components are still good. Hope this helps.

-JLT

peteran · Answer

Disclaimer: I am unfamiliar with the car/engine in question, but own a car from around the same age and have experienced a similar problem.

It could be a faulty coolant temperature sensor. If the ECU thinks the engine is cold starting when it is in fact not, then air-fuel ratio will be too rich.

Depending on sensors available, I guess one of the oil temperature or various pressure sensors could have a similar effect.

hard starting when hot

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