380SL non start

[MIKE196]

hi all
been 3 years since you've helped me with my SL issues but i'm stuck again. My issue is my SL has been in storage for 9 months and when I now try to start, the engine fires for approx. 3 seconds then shuts off. it does this over and over. For background, I changed the fuel pump and filter 3 years ago. The fuel pump relay was changed last weekend. As far as I can tell all fuses seem good including the OVP. Any suggestions would be sincerely appreciated.

Mike

[meltedpanda]

how was she put to bed?
Fuel system drained? Have the injectors been checked for fuel delivery?
What year is the car?

[MIKE196]

Ron

no special treatment when put away. covered in dry garage with about 4 gallons of gas in tank. car is a 1984 model with 72k miles. i'm embarrassed to say I don't know how to check injectors.

mike

[meltedpanda]

Are you handy with tools and testing of fuel systems?


well 9 months with old gas ...before Id mess with injectors , you need to either drain tank or try some dry gas, replace fuel filter make sure you have fuel to the rails and that the airflow sensor on the intake is not jamed or sticking.
check for fuel delivery at the cold start injector.

[rowdie]

Pour some gas down it's throat. A cup should do. If it starts it is most likely fuel supply.

[meltedpanda]

may clean our some gunk too....
but do be careful..this advice comes with the usual disclaimers - right Rowdie

[Frank Reiner]

The OP's starting description in the first post suggests that the engine runs only on the cold start injector. If there is a safety switch on the air meter, it can be unplugged to keep the pump running, and the air sensor plate can be exercised to determine if there is control pressure and then for flow at the nozzles.

[MIKE196]

I'm fairly handy with tools so with some guidance from you folks I can check things out. I do not understand exercising the air sensor plate and it seems to me if the issue was with the filter then the car wouldn't repeatedly start for 3 seconds then shut off. Also, it seems that i'm getting gas to the cold start injector. You guys are giving me good ideas but i'm having a difficult time thinking this through.

mike

[meltedpanda]

it may simply be the old fuel, varnish deposits on the throttle plate. How does it look?
I know you mentioned you replaced fuel pump relay, but "with a known working one"?
This sure sounds like a FPR issue

For me on these Kjets , I always start with pressure test

from the KJet book
Engine cranks but will not start;

1)Lack of fuel pressure
Test the fuel pump and pre-pump.Perform a pressure
and volume test.
2)Airflow sensor that is jammed and/or sticking
Remove the airflow boot and loosen center hose on
the fuel distributor to relieve control pressure.
Apply pressure with finger tip placed on the center
bolt.Also check for proper centering and rest
height.
3)Auxillary air valve sticking
If you need to press down on accelerator pedal to
keep running,this is highly suspect.
4)Cold start injector not opening
Self explainatory.
5)Defective thermo-time switch
This is one of the most common causes for your cold
start injector to not work.
6)Control plunger sticking(below fuel distributor)
If this sticks,chances are the plate and arm will
be stuck also.
7)Restricted injectors
For this to happen though,the injectors have to be
severely restricted.

Porsche site, but good info
K-Jetronic: Troubleshooting Symptoms

[Frank Reiner]

Agreed: The pump and filter are OK, and fuel is reaching the cold start injector.

1) Remove air cleaner.
2) The air cleaner mounts to the inlet of the air flow sensor; the large round plate in the throat of the air flow sensor is the sensor plate.
3) Push down on the plate; it should move smoothly thru its full range, and return to the original position.
4) Aft of the air flow sensor is the fuel distributor(FD); it has eight steel fuel lines exiting the top which go to the injector nozzles at each cylinder, and one from the top center which goes to the control pressure regulator (aka, warm up regulator[WUR]).
5) Between the air flow sensor and the FD are two more devices; a tower immediately in front of the FD which has a mixture adjustment screw inside, and, slightly to the right of center, a safety switch plug. When the safety switch plug is disconnected the fuel pump will run continuously with the key on.
6) With the safety switch unplugged and the key on (pump running), again depress the air flow sensor plate. The resistance should be greater than with the pump off. By exercising the plate through its range, full fuel pressure will be supplied to the nozzles. Do this once or twice, and again attempt a start.

Let us know the results.

[MIKE196]

the FPR is brand new from Autohauz. installed last Sunday. the car does fire and start foe approx. 3 seconds, then shuts off as if fuel flow stopped. seems like something is causing a fuel interruption but I can't tell if it's electrical, mechanical or both. is it possible that my new FPR is bad?

mike

[meltedpanda]

Do as Frank suggests first.

You can really get off course with these Kjets , good to rule out one thing at a time

[Frank Reiner]

With regard to the safety switch:

The 85 SL may not incorporate a safety switch, rather the pump run time control will be in the fuel pump relay. The relay will run the pump for ~ 2 seconds with the key ON and then shut off, then will run the pump continuously while the engine is being cranked, and when an engine run condition is detected (TD signal) the relay remains latched closed.

Mike: When you turn the key to ON can you hear the pump run for ~ 2 seconds and then shut off?

[MIKE196]

hi Frank
haven't been able to test if pump running when key is on as i'm working through this alone right now. i'll enlist the aid of my wife tonight to work the key while I listen at the pump. i'll give the results tomorrow as well as the results from your recommendation posted above. by the way , this is a 1984 model if that makes any difference. on another note, I can't locate the part number or vendor for an OVP Relay if I have to replace. Any suggestions?

thanks to all for the help.

mike

[rowdie]

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