I have a recurrent problem with hot starting which is a mystery to my local Volvo dealers but I cannot believe that I am the only one. I use the car to tow a caravan, very good it is too, but, mainly in hot weather, when we stop after say a 40 mile tow, and turn the engine off, it will take a good hour before the engine will start again. The engine turns over,but does not fire. This happened for 2 years when we first had the car about 7 years ago, it seemed to stop when we had a new battery fitted but started again last year and despite another new battery, it continues. New belts were fitted last year, could it be a timing problem? It has been suggested on another web site that the fuel injection pump temparature sensor is faulty but the Volvo garage say that to replace this would be an expensive way of chasing faults. There is no fault logged on the ECU and a problem with the crank angle sensor would give a warning light, they can only address the problem if it happens in the garage. It is not much fun sitting in a hot car waiting an hour for it to start so any help would be appreciated. :crying:

Assuming that everything else is OK, reading it again, makes me agree that it would have something to do with the fuel delivery system.

Try this:-

1) When you first plug in the key, switch it to Position II and wait a while. (This is just a position down before cranking the engine.) Could you hear the fuel pump? Its a mild 'rrrr' sound. Some people can listen it better with the doors open, some with the doors and windows all closed. Try see yours. If you do, then your fuel pump is working fine. If you don't, then prolly worth checking into it.
(BE CAREFUL THOUGH, WHEN HANDLING THE FUEL-PUMP. DO NOT SMOKE OR BRING NEAR ANY SOURCE OF FIRE OR IGNITION. WEAR BREATHING MASKS IF YOU CAN'T STAND THE VAPORISED FUEL ODOUR.) This unit is located at the bottom of the boot area or the cargo-bay if you have a wagon.

2) You need to try this a few times - when you first crank the engine at hot, and it doesn't 'catch'. Leave the key at Position II and wait a little longer, say 3 minutes at that position. THen crank again. If still no joy, then wait 5 minutes. If the engine does 'catch' after a prolonged wait at Position II and after a few cranks, then I would think that your Fuel Pressure Regulator is bad. This unit is located under the fuel railing line attached to the engine cylinders. Open the hood, pull the shining protective latch and you will find it there.

Thank you Super Mod, I will give it a try although there has never been any problem starting from cold or when the car is running solo in normal UK temperatures. The odd thing is that it was originally 'cured' when it failed to start while in the Volvo Dealers workshop and they had to use a supplementary battery to start it. The original battery was actually faulty, although it seemed to work OK most of the time, and a new battery was fitted. It was suggested then that a battery needs to give over 12 volts to crank and power the ECU etc but there are always plenty of theories. I have wondered whether the alternator, because it is powering the caravan 12v fridge and the running lights all round, does not fully charge the battery, I have a suspicion that the crank speed is slightly slower when it does not fire because a second or two before it does fire, it noticeably speeds up, as if released from a restraint. Perhaps this is just the time between firing and the exhaust noise.When the problem happened down in Italy, the local Volvo dealer workshop manager merely said that mid european Diesel engines couldn't cope with high running temparatures, not very helpful! :huh:

Does the check engine light (or lambda sond signal lights up)? Whats the code read?

So what did the other Volvo dealers diagnose? (aside from the one who said that mid-euro diesel engines couldn't cope with high running temps)

There was no difference in the warning lights etc. Nothing was reported as faulty by the Volvo garage and I do not know what you mean by the code or where to find it. Where would this appear? I am keeping my fingers crossed when we next take our caravan out as it will meet some very hot weather in France. If there is a problem I will report again. I contacted Volvo but they were worse than useless as they claimed not to be able to answer technical queries.

When the check engine light comes up, you'll have to use a code scanner or reader to read the error codes. Since you're version is the 1996 model, chances are, they use the OBDII system. If its earlier, then it uses the OBDI system, which can be read without using the scanner.

Unfortunately, the cost of the scanner is high and only dedicated Volvo technicians (even independent ones) would have them.

When you are around any, stop by and ask them to scan the codes. It should help to narrow down your search of the problems a lot further.

Interesting point to note is that although the check engine light may disappear after a few days, the message will still be there, and requires manual deletion for it to go off permanently.

To the rescue:

On the Dutch volvo850forum.com there has been some info on this issue.

Problem occurs after or during a long drive, mostly when it's hot +30C.

Given reasons whe have tested on a 850 Tdi Estate of 1996:
- Start relays / not the solution, stops while driving as well.
- Fuel pump / did work properly
- Fuel pump relays / pump works, so relays work
- Startblock / disabled by connecting 50E/51F on relays 210/211, not the solution.
- Airco ECC on - problem occurs / not the solution
- Arco ECC off - problem occurs / not the solution
- Battery check / battery OK.
- Dynamo / works OK, charges OK, also works when problem occurs.
- Electrical system and wiring - After a long search during a moment the problem occurs it seems the contact-lock doesn't switch the startblock off. After 45 minutes we retry and the car works as if there has never been a problem!

Replaced electrical part of the contact-lock, problem seems to have been solved on this car!

At another car it didn't solve the problem. After some searching we found out the relay of the cooling fan in front of the car didn't switch on, car became to warm and stopped, preventing a terminal engine problem!

For what it's worth!

Hope he got it fixed already...

:)

Just back from holiday but still had the hot starting problem on several occasions but it was when the air temparature was in excess of 28 degrees. The worst was a one hour wait despite trying what you suggested ampangbear. Must admit that because position 11 turns on the driving lights I am not very keen to leave them on for 5 minutes or more as it might run the battery down. Perhaps I am misguided! There is no doubt in my mind that the problem is mainly temparature related and happens when the engine has been under heavy load either towing the caravan or after a lot of hill climbing in lower gear.
Denkweb, thank you, I will raise this with our garage, hopefully they will not be so cynical of website suggestions this time. The only other person with an 850tdi who I have met was from Nederland and he had had the same problem but for him it was the first time as he had borrowed the car.

The daylight running lights may be switched off, if you want to save your battery. There's a tiny adjuster just below the ligth swtich that can be turned - refer to the manual for details.

As for the hot starting problems, well, i guess, you may want to give denkweb's advices a try. See if it goes.

Keep us posted, ya?

Thanks!
:)