QuestionQUESTION: Ron, I inherited a 79 450SL with 160,000 miles. This car was purchased in CA by my Dad in '91. The car is immaculate and always been garaged. He took it to several mechanics for this problem, to no avail. The car starts first kick, until it warms up (20+ minutes driving). Then there is a strong fuel smell while driving and after parked. To get it started, I have to hold the gas pedal to the floor and crank for almost 10 seconds, and then it chugs up to rpm. At this point it runs great, however, there is the strong fuel smell. I don't see any injectors leaking, hot or cold. Any ideas?
Thanks!
John
ANSWER: hey John , could be a few issues. First and foremost , I would renew all rubber lines on the injector rails and renew any other rubber fuel lines. Also renew any vacuum lines under the hood. These car are very vacuum dependent and need solid lines and connections. These cars are designed to run hot so a little fuel leak is hard to detect because it vaporizes, or if you have a leaking seal around an injector this gas vaporizes also. You wont see it cold because the rails are not presurized.
The second common reason for gas smell is the vent system of the fuel tank. You have to remove the rear panel in the boot and renew those lines as well, as well as the connections. Make sure your gas cap is sealing properly.
Other suspects for fuel smell is leaking injectors( post shut off) and leaking cold start valve ( after shut off)
Just eliminate one item at a time. If I were to guess - fuel lines on the rails and leaking injectors\
Let me know how else I can help
---------- FOLLOW-UP ----------
QUESTION: Ron, Thanks for the help! I'll check all the vacuum lines, however the ones I've looked at seem to be in good condition, or have been replaced recently.
My concern is the hard starting problem when the car is warmed-up. What should I be looking for?
Thanks! John
AnswerThese are the most common hard warm start issues with a Kjet system, I would focus on CSV or leaking injectors....
1. Air flow sensor plate not adjusted correctly:
Remove the boot and the air filter and check the position of the plate as compared to the
barrel. The plate should be even to the bottom of the barrel, a tolerance of +/- .020 is
allowed. You can adjust the plate: 1976- 1983 by
adjusting the screw with an allen screw driver. The screw driver is put m at the top of the
mixture control unit through a hole.
2. Fuel pressure is not correct:
Check fuel pressure at the fuel pump.
3. Cold Start valve leaking:
Check the cold start valve by removing the part from its location. Leave the fuel line
connected. Remove the connector, place the valve over a container and apply voltage to
on of the connectors and a ground to the other. Look for a coned shaped injection of fuel.
Turn off the power and wait a few seconds. Watch for leaks. If either of the above does
not work, replace the valve.
4. Vacuum Leaks:
Carefully inspect the complete engine for any cracked or worn hoses.
Look for connections that may be loose or have come loose.
5. Control Plunger in Fuel Distributor binding:
Check this by first depressurizing the fuel system. Do this by relieving the fuel pressure at
the warm up regulator. Remove the fuel filter and carefully move the plate up and down.
This movement should be free and with no binding. If you detect binding, replace the fuel
distributor with a rebuilt unit.
6. Fuel Accumulator and/or Fuel Pump Check Valve:
These hold pressure in the fuel system.
7. Fuel injector Clogged:
Pull the injectors and inspect for correct operation. Apply power to the fuel pump,
jump the wire terminal numbers 30 and 87a. Caution fuel will flow from the injectors
when the air flow plate is moved in an upward direction. Check for correct operation.
8. Control Plunger in the fuel distributor binding:
Remove the air cleaner and carefully move the plate up and down, do not force the plate.
If it binds investigate. If it is not simple to repair replace the unit.
9. Idle speed, Ignition Timing, and mixture out of tolerance:
Check and adjust all of the above.
RON
