The weather has gotten hot enough the last few days that I've been having lots of crank but no start in the middle of the day (or anytime after driving for more than 5 minutes), but fine starts in the morning and in the evening. I assumed it was the crank position sensor or the fuel relay and ordered parts accordingly. In the meantime, I cleaned the flame trap and when I tried to start it at high noon today, it was no problem (well, the oil light was on for 5 seconds...). The little nipple was totally clogged on the flame trap, but the rest of it was relatively open.

It doesn't seem to make total sense, but could a clogged flame trap cause a hot start problem, or did I just get lucky and jostle the CPS when I was messing around in there?

so i'm right in the middle of trying to change the CPS. I got the old one out and it had a little split near the connector. the sensor was also extremely fouled.

BUT I can't get the new one in! I just can't get the bolt to fit into the block. I'm about to kill someone! Any tips? Is it doable without a flexiable socket extension?
Also, does anyone know how long that bolt is supposed to be? I feel like a few extra threads would be of great help?

at this point, frustrated beyond belief,
david b

The flame trap clog could cause more oil usage. Driveability gets worse if it blow all the oil out.

I would suspect that the in tank fuel pump has a problem. One of its primary jobs is to keep air bubbles out of the fuel to the main pump. The bubbles could cause a vapor lock situation.

The pump could have a bad hose connection between it and the oulet line inside the tank.

Is the hot start problem any less prone to happen on a full tank of gas?

Something to help prime the thinking tank for you.

Phil

Does the car start after the a few moments or not start at all?

Delayed starting while hot could be a bad fuel line check valve.

It starts after I let it cool off. Sometimes that means just opening the hood for 10-15 minutes. Sometime it means waiting until the sun sets.

In my case, cleaning the flame trap and replacing the clogged tube back to the intake manifold which was completely blocked and perishing solved a hot start/hot stall problem. Also cleaned AMM and throttle body, so these could have contributed too but it seemed to be the flame trap and hose to manifold that did the trick for me.

According to the FAQ a hot start problem is usually the crankshaft position sensor going south.

Do a search on fuel relay and find out how to test it, bypass it. Hot weather does effect the soldering inside the relay. It could be that having the hood up cooled things down enough for the relay to work again. Or the CPS wires?

Having the oil pressure light on for 5 seconds is a real concern and should be investigated some more. Is your oil level good? What weight oil are you using? What kind of filter? Using the starter a lot can cause the unburned fuel to wash past the rings and wind up in the oil, so check the dip stick of gasoline smell and flush the oil if so. Gas in the oil sump will thin out the oil considerably and cause the pressure to remain low.

Klaus
--
The more I learn, the more I forget. So why learn?

The fuel relay is strong when you jump 4/6.
It is possible the CPS is finicky and me messing with the flame trap caused it to be bumped back into good behavior. A replacement one has been ordered.

5 seconds is actually more like 1-2 seconds. I've checked the level and it's full up with 10-30W non-synthetic. Not sure on the oil filter as it was changed elsewhere (sorry, lazy) but I will be sure to put a recommended one in. I didn't notice any gas smell on the dipstick.

It has been starting nicely since the flame trap change in all weather and even after 20 mins of freeway driving. This was not the case before.

That should not cause that but a clogged flame trap will cause pressure to build inside the crank case and cause a good seal to leak. Check the air box thermostat and the fuel pressure regulator. I have never Volvo with a mann or mahale oil filter installed, oil light to stay on more than a 1/4 second. even with a a fram or some other non recommended oil filter oil light is off much quicker than that. Sound like there may some other issues going on. Where is the compression?

I have the hot air feed to the air box disconnected so it should always be getting 'ambient' air.
I haven't messed with the fuel pressure regulator before, but I will take a look. I don't have any blue smoke or rough idle at start up - just the oil light on for a few seconds.

I'm a pretty big novice, so I don't really understand the "Where is the compression" question.

thanks

Have you performed or had a compression test done for you recently?

No. I need to read up on how to do this. I have pressure meters used with bottled gasses here at work but I'm guessing there is a specific way to fit everything on the engine. Still a pretty green mechanic, unfortunately.

http://www.brickboard.com/RWD/index.htm?id=1364111&show_all=1

okay, doesn't seem so bad difficult.