HELP, HAVE A 2000 S500 THAT STARTS FINE WHEN COLD, OR USED ON SHORT IN TOWN TRIPS. BUT WHEN DRIVEN MORE THEN 20-30 MILES, AND SHUT OFF, CAR WILL NOT START AFTER SITTING FOR 4-8 MINUTES. CAR WILL CRANK FINE, BUT WILL NOT RUN. LET CAR SIT ANOTHER 5-10 MINUTES, WILL START UP FINE, LIKE NOTHING HAPPENED. NO CHECK ENGINE OR MALFUNCTIONS LIGHT. ANY SUGGESTIONS? THANKS!!!

 

I'll think about this for a while.
Its obviously heat soak related so suspect fuel rather than electrics. However I'm not excluding electrics but in the mean time.....

Does fuel tank level make any difference?
Mileage? When was the fuel filter changed?

Any other potentially associated anomalies?

 

Been thinking.

Could it be the starter relay?
Since the relay is in a box which to some degree is heat insulating, I'm surprised the relay gets warm enough after 20-30 miles sufficient to cause it to malfunction. Relays are cheap so its possibly worth a try.

Could it be the oil pressure switch. Doesn't quite fit since car doesn't start then stop but in the same fault area as the starter relay.
Fuel pump is set running by automated "Startup" procedure then maintained due to a signal dependent upon oil pressure.
Cold oil = adequate oil pressure therefore car runs. Thin (hot) oil inadequate pressure so engine stops should the threshold pressure on the switch have become out of limit

Next variation is that the automated process is NOT sending the pump initiation signal. Not exactly sure whether this process is "computer" controlled or just some straightforward electric circuit.

Other alternative is somesort of fuel vaporisation issue due to low fuel pressure, blocked filter, poor fuel pick up.

Try scanning the EMS (Engine Management system) to determine whether there is a code which has not initiated the CEL (Check Engine Light). If there is one it just might provide the missing link.

I think there are codes for low fuel pressure but these may not be operative during startup.

Is there fuel in the injector rail during startup procedure? There is a valve on the rail (need to remove air intake cleaner etc. Pulls off upwards) to which a pressure gauge can be fitted.

 

Agree that it is probably a heat soak issue. Info posted lends thoughts towards a low/no fuel provision during the high heat soak period. Unless it has recently been changed, I suggest a new fuel filter and question the integrity of the fuel pressure regulator. It could be electrical signal problem of not energizing the fuel pump or fuel pump relay, but that should be a last option. Agree a code scan will assist. A review of troubleshooting info for a “crank but no start� condition in alldata.com may assist also.
Bill Mercer

 

temperature related.

fuel filter is new?

it can be CPS too.

 

THANKS FOR THE QUICK RESPONSE!!!! WILL TRY THE FUEL FILTER FIRST, SINCE I DON'T KNOW WHEN THAT WAS REPLACED LAST, IF EVER. WILL ALSO SCAN COMPUTER, SINCE A FRIEND HAS A SNAP ON SCANNER. WILL KEEP YOU POSTED. THANKS!!!!!

 

your most likely cause is probably going to be your crank sensor. when they get hot there internal resistance goes up and the engine control unit cannot reconize the signal. many times a fault in the crank postion sensor will not store a code in the engine control unit. if your remove the cranks senor ( on the trans bell housing behind the drivers side cylinder head) and connect an ohm meter you will prob find that when heated to operating temp it will go open circuit.

if the crank sensor is bad the engine control unit has no idea what postion the cylinders are in so it shuts off the fuel pump and wont fire the injectors or the spark plugs.

 

Just had the same problem with my 2000 S500. Same as above, but didn't take a long trip to develop the symptoms. 10 or 15 minutes would do it.

racerx seems to have had it right -- a faulty crank position sensor is the culprit.

 

I had a Pontiac that acted the same. It turned out that if I left the fuel cap loose, it was not affected. That is an inexpensive fix, if it works.