850 not starting from Volvo-challenged newbie

'93 850GLT purchased 4 months ago has been great.

One morning engine would turn over but not start.
Tried to start several times then made arrangements to tow into shop.
Next morning, gave it one more try. Kazaam! starts up fine.

Runs fine for three weeks.

Day before yesterday, again engine turns over but will not light up.
Two days pass, much grieving, towing arrangements made.
This morning Kazaam! Car starts up again.
I am happy yet perplexed.

Any Volvo gurus out there have any ideas?

The gas tank did get low the night before
Fuses are good
I have read one possibility about fuel pump relays (there are 2) (?)

Another was that if the radio and blower cut out occasionally,
(and they do), it could be the "j-switches" located under the fuse box
cover.

If anyone has any input here it would be greatly appreciated.


Thanks all

 

Camshaft position sensor?

Fuel pump/relay....If you turn on the ignition, you should hear the
fuel pump whirr for six seconds before cutting out if you don't start
the car..best heard with drivers door open. If you don't hear the
pump, then check the fuel pump relay ...also check there should be
fuel reaching the injector manifold.

 

I had the same problem a few times with my '93 850. I learned that they
will do this AFTER they are started and abruptly shut down before any
opportunity to warm up. In my case, this would be after I backed a cold car
out of the garage into the driveway to be washed. The only fix for me was
to continue to crank the engine until it stumbled and FINALLY started.
Something to do with a sensor not getting a chance to set or reset.

This happened not every time to be sure, more like twice in the 8 years we
had the car.

 

On the non turbo engines the "fix" was to use the multi electrode plugs
to help overcome the fuel mapping problem on cold start/stop/short
wait/start cycles.

Bob

 

Some people say that's due to valves sticking open, or the fuel
management ecu thinking it needs a rich mixture to start and flooding
the engine.
I believe the three pronged plugs were introduced to help stop this
happening?
I had this once when I started the engine and turned it off
immediately..took about 8 goes to start again. If I run a few yards I
usually rev the engine a little, and the problem's never reoccurred.

 

I had an '93 850GLT that a couple times would not start but would turn
over. I assumed that the computer was confused and shut the key
completely off and waited a couple seconds. Then tried again. In all
cases it would start.

Another common problem in all older cars is a bad ignition switch. It
may provide power to the starter but not to the ignition. Usually a new
ignition switch is required. This is more common if you or the previous
owners had a heavy set of keys.

 

I had to replace the ignition switch on my 94 850- look at Bay 13 for
how to- contacts get worn and will only start with a little tourque on
the key.