Hi I have a Volvo 850 estate, 1997. The engine is the B5252s. 2.5L Petrol, non-turbo.
It won't hot start some of the time. It cranks but won't fire. Cold starts are 100% OK. Occasionally, it hot-starts OK too. But it's let me down in gas stations and outside stores where I've just stopped for a few minutes.
Following online advice here and elsewhere, I have changed the coil, both the crank AND cam sensors, HT leads, rotor, distributor cap, fuel filter, thermostat and fuel-pump relay. This has cost me quite a lot of money and I'm not a rich man.
The problem persists.
The only other thing I can think to change is the coolant-temperature sensor. However, the dashboard needle seems to be working OK.
As I said, the car starts perfectly if I let it cool down. But that takes 2 hours!

Would a new battery be likely to change this problem? I imagine that the good cold starts (even after a week of not driving the car) rule this out.

Thanks for any advice you may have. I really appreciate your comments.

 

A few budget sensitive steps: Start with the engine coolant temp sensor - measure resistance - should be low when cold, ie under 300 ohms, high when warm ~ 3000 or more. Next is inspect/ clean your idle air control valve. it may not be closing fully... Finally its possible you have a leaky fuel injector. Try running some injector cleaner in your next tank of gas. I doubt its the battery if you can get a full cold crank, but again get your VOM out and measure voltages when warm. should be 12.6 or so at the terminals. after cranking feel the cables - if they get warm at the terminals (=resistance) clean and secure. running engine should show 14+V without a load, so turn on your heater blower, headlights, rear defrost and turn up the radio (lol) and measure voltage - should stay over 13 or 13.5...

 

Do you have a check engine light on? If so, can you get the code read? It could very easily be the coolant temperature sensor. The dashoboard temperature gauge is not run off the coolant temperature sensor (at least not on our 95 and 98) so that is not going to help. All the coolant temperature sensor does is send a signal to the computer telling it how warm or cold the engine is and to send the appropriate amount of fuel to the engine based on that temperature signal. I had a similar issue that turned out to be the coolant temperature sensor, except with my issues the cooling fans kept running long after the engine was shut down, so the computer thought the engine was still hot even when it was stone cold. Ran good when warm, but cold starts were nearly impossible. In your case it is just the opposite, but I'm betting a new sensor will fix the issue. Battery sounds like it is fine BTW.

 

Thanks to you both, mt6127 and psaboic, for taking time out of your day to help me. It's good to get advice from more experienced mechanics such as yourselves.
From your 2 posts, it seems that a new ECT sensor once I've tested it. How interesting that it is "independent" of the dash dial.
For information, I have a service light which goes out after less than a minute (always has) and no codes on my very cheap reader.
I have already run some injector cleaner through, sorry I forgot to mention that. I'll try it again after a couple more tanks.
In any case, you have both been prompt and helpful. Thanks so much!

 

Your service light is a 'time to change the oil' light, nothing more.

I agree with the temp sensor, those usually cause havoc when the engine is warm.

I did not read that you have tested the fuel pressure at the rail when this is happening. This is something you should find out to make sure you have fuel to deliver.

 

My bad CT sensor gave the same symptoms you have (at first). However, my temp. gauge needle
would bounce around while driving as the CT sensor got worse. On "hot starts", the needle
would lay flat (it should jump back to 3 or 4 o'clock) when I turned the key. Result was computer sending a rich mix to a "cold" engine and engine flooding.