Starts in the morning, at lunch, but not after work
 

Started yesterday. Pack up and left the office around 4:30 outside temp around 92. Car acted like it wanted to start but would not. Left it, came back in this morning and it started right up, went back out at lunch and it started right up. Just went out and it won't start. Temp is around 90 with high humidity. Relieved the pressure on the gas tank with no effect. Checked fuses, no bad ones.

Any ideas what is causing this? Car is an 89 190e 2.6.

Probably, vapor lock?

Does it crank over?

Do you get any spark?

Turns over like normal and sometimes acts like it wants to start.

Now the mystery deepens. Got in this morning and it started right up. I drove it home 20 miles with no signs of any problems. With the engine at operating temp, I shut the car off and then started it right up with no problems. This has got to have something to with air temperature. Anybody able to make heads or tails out of this? Me and my buddies who are all pretty good with cars are all scratching our heads on this one.

someone had mentioned the O2 sensor somewhere on this board - MB calls it a ZONDA something

Do you mean LAMDA?

Car has started everytime I tried this morning until now. Just tried again with the air temp at 79 F and it will not start now. Turns over fine but will not start.

Hope this sounds familiar to somebody, I am stumped.

Your hot start problems occur because the engine is flooded due to leaking fuel injectors.

Try starting with accel pedal down half or more.

OK, now it wants to start. Here is what I did:

1. depressurized the fuel system
2. tried to start, no change
3. pulled the #1 plug wire and had the wife turn it over while I grounded the plug wire to the block
4. damn thing started right up
5. reconnected the #1 plug wire
6. restarted it 10 times with no problems.

Without being there to look and listen to diagnose your problem, it's pretty difficult to find out what is causing the no start problem. We can only assume that the spark plugs, wires, coil, distributor cap, rotor are all ok.

First, you will need to determine if it is fuel related or ignition related.

Are you positive that the fuel pump/pumps are operating when the engine doesn't start? If not, you could have a bad Fuel Pump or Fuel Pump Relay.

http://i179.photobucket.com/albums/w...pumprelayB.jpg

http://i179.photobucket.com/albums/w...pumprelayD.jpg


If it is ignition related, you could have a defective CPS, Crankshaft Position Sensor. You need to verify that you are getting spark when it doesn't start. If it isn't, then I would unplug it at the Ignition Control Module and check the resistance when the engine is not starting, then measure it when the engine cold and does start.

http://i179.photobucket.com/albums/w...Sensor300E.jpg

Pretty sure they are. You can hear the momentary buzz when you turn the key on as usual. Will check the relay and see what I find.

The momentary buzz is a good sign, how about when the engine doesn't start? Do they operate while the engine is turning over during a few attempts.

Intermittent problems are a real pain!

You should try to determine if it is a "hot soak" condition or not, even though "hot soak" includes a variety of different problems. If it is hot soak then it goes like this:

Engine cold - no problem
Engine warm but not fully warmed up - no problem
Engine fully warmed up (30 min driving) but only parked a short while - no problem
Engine fully warmed up (30 min driving) but parked a long while (over 1 hour) so it cools down - no problem
Engine fully warmed up (30 min driving) and parked about 30 to 45 min - big problem

Does that fit your symptoms?