Volvo 740 hot start problem

[Tomca]

Hello,

I have a 1990 Volvo, 740 GLE, B200E motor, K-Jetronic CI system. Recently, if I stop the car in hot weather, and want to start it, lets say, in half an hour, sometimes I cannot do that. When I turn the key, I can hear only a soft click and nothing happens, no crank. However, if I open the motorhood and wait 10 minutes to cool the system a bit down, I can start the car immediately.

It is true, that formerly, I had some problems with the thermostat. Even that the cooler system was renewed (hoses, cooler are new now), the car "ate" three thermostats. Two of them stuck out, the third one after a year opened too early. However, those thermostats were cheap copies and 88 Celsius not 92 one as the original. So, now, I got a real, 92 Celsius original Volvo thermostat. It works properly already for a year, no stuck out, nothing. However, now I have this hot start problem. When the thermostats were out, it never happened.

I also have to tell you that the motor temperature seems absolutely normal: when the motor is hot, the pointer of the gauge is in the middle, even in winter and summer, uphill, downhill, waitng at the red lamp, running on the motorway. And, as I know, this is not the temp of the water but really the temp of the motor block. The sensor is mounted directly in the metal part.

At that time, when I try to start the car but I can't, the temp gauge still shows normal temperature (pointer is in the middle). What I can see then is that the intake-system (that big shiny thingy on the top of the motor on which the gas pedal is connected to) is as hot as the motor body. When the weather is not so hot, it is always cooler a bit and that time I can always start the car immediately.

Is there a temperature switch in the car that protects the motor in-take system and don't let me to re-start? Or is this something more serious?

Thank you for the answers in advance,

Tamas

[93Regina]

soft click and nothing happens, no crank

Engine may be too hot, and the pistons are seizing up on cylinder walls.

[lummert]

Starter motor may be weak. Heat makes a worn starter worse.

[gbm97]

My 91 Volvo had the same troubles. Actually I think every vehicle I ever owned had the same troubles.
Usually ended up as a bad starter or bad cables, solenoid connections.

[lifeofgold]

A few things at which you can look. 1) check out the pre-heat system. The aluminum hose (looks like a smaller version of a dryer vent hose) coming from the exhaust manifold , upfront and over to the air filter box via a thermally controlled flap valve. That may be causing your intake manifold to be heating up. 2) If you have a multi-meter, you can check the resistance differential of the battery cables when cold, and when hot. many people do not realize that even if a cable looks good at the ends, they can be severely corroded under the insulation. 3) {most likely) Do the same test on the starter and the starter solenoid, the problem is called "Hot-Soak Open Circuit". When the windings heat-up, the thermal expansion causes a fracture to become an open circuit.

[lifeofgold]

...Addendum to #3) : or a "Hot-Soak Short Circuit", the expansion causes a short circuit, reducing the resistance, thereby causing a failure.

[Tomca]

Hello everybody,

Sorry for the long silence. It seems that my hot start problem was caused by a weak battery. Before last summer I replaced the old battery. Since then I have no start problems.

Tomca

[dorvin]

Hello everybody,

Sorry for the long silence. It seems that my hot start problem was caused by a weak battery. Before last summer I replaced the old battery. Since then I have no start problems.

Tomca

Hey, thanks for taking the time to let us know what solved the problem