Vintage Cars: 1983 Mercedes 380sl, cranks, but wont start, oil gauge, kjet


Question
QUESTION: Ron, problem started when car would start right up, then when engine got to operating temp. it would start sputtering or cutting off when you came to a stop or made a hard right turn, especially if on an incline, oil pressure would drop from 3 to 1 on the gauge and then start to fluctuate. when you stepped on the gas it went back to 3 and ran like a top.....last week-end I was on the interstate going 65 mph when it just cut off....waited a few minutes, it started up, puffed some black smoke , then ran like a top again. Monday, on my way home, cut off again while turning right, started up but ran sluggish, put the petal to the metal and it was going 15 mph and tach at 1200. got it home and it died....It cranks now, but won't start..The fuel pump is running, checked distributor, clean & dry. I haven't been able to keep 1/2 tank of gas in it (unemployed)...does it sound like fuel filter, and where is it...There is a cylinder next to fuel pump by gas tank, is this it ?
Thanks in advance for your time and reply...Alan
Two days later

ANSWER: yes that is it, but  try running it with your gas cap off and let me know what happens, sounds like a vapor lock

---------- FOLLOW-UP ----------

QUESTION: Ron,
I haven't gotten back earlier because I was charging up the battery....I thought about the vapor lock thing awhile back....The cap is super hard to remove, and gives a sigh of relief when opened, but it still won't start, also there is a strong smell of gasoline (around the back end) Fuel pump area after I try three times...Also the oil gauge starts at zero, takes about 5 seconds to move, then only goes to about 1 1/4 on the gauge....Thanks in advance for your timely answer....Alan

Answer
 At idle your oil pressutre guage will not peg.

I'd get a new (oem) gas cap , just to make sure that is not an issue
The following although not all the resons are the main reasons a KJet ( CIS) system will not start.

Engine does not start/starts hard cold:
1. Sensor plate or plunger not moving freely:
Remove air filter and gently apply pressure to the sensor plate. If the plate does not
move, there may be an internal problem. Look for any possible cause for the binding
externally. If this fails, remove the fuel distributor and have it repaired or replaced by
a qualified repair shop.
2. Auxiliary air valve does not open:
Remove the hoses from the valve and verify that the valve is open. If not check that the
electrical connection is good and that there is voltage present with the ignition on.
3. Electric fuel pump not operating:
Check the fuel pump fuse and the pump relay, if both are good check voltage at the fuel
pump, if good replace fuel pump.
4. Thermo time switch defective:
Disconnect the connection to the cold start valve. Put a test light across the terminals.
Run the starter, the light should stay on for a few seconds, depending on the temperature
of the engine. If the light does not work, check for voltage on the yellow wire between the
starter and the Thermo switch. If there is voltage to the switch and the light does not
work, replace the Thermo time switch.
5. Cold control pressure out of tolerance:
Check the control pressure Regulator. Check the voltage at the connector to the
regulator - at least 11.5 volts. With power off and the connector off, check for continuity,
if none replace the regulator.
6. Injector leaking, opening pressure low:
With the engine not running pull the suspected injector and look for any leaks. If leaking
replace with it new injector.
7. Injected fuel quantities not equal:
Suspect that there is an injector problem. Pull each injector and test for quantity of fuel
injected into a measuring container. Run the engine for a short time for each injector.
Compare the amounts of fuel. Replace the injector that is not operating correctly.
8. Basic idle setting incorrect:
Check the speed and adjust as necessary.
9. Fuel Accumulator and/ or Fuel Pump Check Valve:
These keep pressure on the system.