Hello folks,

My dad has a high-miles 1996 Volvo 850 GLT with an automatic transmission, and the problem we're trying to figure out is why it's very difficult to start the car when the engine is still hot, like when you need to start the car again after 15 mins to an hour. It cranks and cranks and cranks, sometimes sputters a little, and eventually it will catch, but it takes a while.

What I've done so far is the obvious -- replaced spark plugs, the wires, distributor cap and rotor, cleaned out the air mass sensor, checked around for any torn vacuum lines, but the problem is still happening.

From poking around on the web, I see that it could be an engine coolant temp (ECT) sensor, possibly a leaky injector flooding a cylinder after shut-off, or possibly a gearstick position sensor (if the car doesn't think the stick is in PARK).

Right now, the gearstick won't get out of PARK unless the manual override button is held down. I read somewhere that this is a possible cause, BUT the car always starts perfectly when the engine is cold or cool, so I thought that would rule out the gearstick position sensor as a possible cause and point to some sensor directly on the engine.

I can't test injectors myself, but I could replace the ECT myself if I don't have to drain the coolant, and I could probably replace the gearstick position if it really comes to it.

Where should I start?

Thank you for any help!

 

I would check fuel pressure, camshaft positioning sensor and coil.
Checking the resistance of the ECT is not a bad idea, but in most cases it causes a starting issue when cold.

 

Oh I forgot to mention, the cam position sensor is brand new -- we had the car in the shop for this problem in the past, and they replaced the cam position sensor. That made the problem go away for a little bit, but then it came back. It was a Volvo indie shop, and they put in an OE Bosch cam pos. sensor that they put in, so I doubt the sensor would have been defective.

I do have my suspicions about the coil... I had some issues on my previous car, Saab 900, where hard starting when warm was fixed when I replaced the ignition coil.

 

Check the crank sensor also. Any one of those three after a heat soak will cause starting issues. Fuel pressure regulator can be a culprit too.

Bosch parts fail just like any other parts. They are good don't get me wrong, it is possible that it is defective. If it is still under warranty it would not hurt to have it checked out.

 

Just to make sure, is crank sensor same as the cam position sensor we were discussing above? Any tips on how the proper test procedure? I have the multimeter, but I'm not sure what sort of readings I need to be looking for.

Also, does the coolant need to be drained to replace the Engine Coolant Temperature sensor, or is there a way to avoid doing that?

 

No you do not need to drain the coolant to change the cts. Just leave the overflow tank cap on and tight. Some coolant will come out but not gushing. You have to be quick when installing the new sensor.

These are the coolant temp sensor resistance specs

2800 ohms at 68 degrees F
1200 at 105 degrees
300 at 180 degrees

If the reading is off, replace the sensor.

You can unplug the maf prior to starting and see if it will start up and run better.
Check MAF sensor signal. Terminal 4 (White wire) should be .2V key on engine off and .9V at idle.
If key on engine off voltage is correct, but has high voltage at idle, check for intake air leaks between the turbo and throttle body.

Hope this helps. Another thing to check is a leaking fuel pressure regulator. Do a fuel pressure test to see if pressure is dropping out. Fuel pressure should be 43-45psi.

 

Many many thanks for that, eeeewidner -- I very much appreciate the help.

I'll get to those as soon as my schedule matches with my dad's (he has the car), and I will report on the findings.

Did you get those Ohm readings from a Volvo service manual? I am considering buying one of those on DVD that I've seen on that auction site.

 

Get Alldatadiy for more info. It cost's $20 a year to have.