Temperamental 850.

[moorlander]

Hi everyone,

I'm new to the site and new to Volvo's. I have a 1994 volvo 850 2.0 SE that has an aftermarket Tartarini LPG kit on it, put on a few years ago. I have so fallen in love with this car I had it resprayed when I couldn't really justify the cost. But its been such a great car through a dreadful winter it had always started first time. It's safe forthe kids, comfortable, looks good, and so reliable....or so I thought.

Over the last couple of weeks I've had start up problems whent the engine is hot. It starts fine cold, but once up to temperature if I stop and then try and start it minutes later it won't fire. I've replaced the rota arm that helped for a short time. Similarly with the spark plugs. It's as if its flooding, in fact the oil does smell of fuel after these episodes. However I can't understand why. I just don't know where to go next.

A couple of other points.

It starts up on petrol autiomatically, but It automatically moves onto LPG.

The air hose from the air filter to the engine block has a large tear in it, probably caused by a gas "blow back" I am told, and it shouldn't cause the restart problem, again so I am told.

I f you have read this far thanks for bearing with me, If you can help well, I really would appreciate it.

[jblackburn]

I would say that it sounds like you need to replace the coolant temperature sensor. It's located just under the thermostat housing, and the thermostat should be replaced while you're in there.

I had problems with mine and hard starting when hot as well - it took me 5 minutes of cranking one time, and a HUGE cloud of black smoke before I finally got it running. Basically, if the coolant sensor is bad, it still thinks the engine is cold when it's not, it will flood the cylinders with gas at startup and make for a very hard start. Try holding the pedal to the floor and then cranking it a few times, and let up on the gas.

The hose from the air box to the engine should be replaced as well - that's unmetered air going past the MAF sensor that is entering the engine.

[moorlander]

Hi thanks forthe reply. How odd, I taped up the air hose,and I hardly dare say it, but sincethen it has run fine. Goodness knows why?!!

[jblackburn]

The O2 sensor won't give a reading until it's hot.

When it does, it realizes, hey, there's too much air here I don't know about (from the cracks in your hose), and adjusts the fuel mixture accordingly. What it doesn't realize is that that air missed the MAF sensor and is being sucked directly into the engine.

That should (hopefully) keep it running for now - you might want to scout around for a new hose.

[FCPEURO]

A vacuum leak of that size would defnitely give you the issues you were having. I would get a new hose when you can because the tape will not hold forever. Also, if you start having the issues again, then temp sensor would be the next thing to take care of.

[moorlander]

Many thanks for the help given so selflessly. I really do appreciate it.