[Josh]

I've got some pressure testing and voltage testing I need to do for the 500SE. Suggestions for the best tools to get for doing that? I've got a multimeter, so that's taken care of for measuring voltage, but what about fuel pressure?

 

[gring]

Still 3 volts

Thank you for your quick response. That thread is really nice and useful.
Last time I checked I had only 3 volts. You wrote that the other injectors use 3 volts.
I will check again with another voltmeter and I will unbolt the injector to see if it spays.

Still 3 volts with other voltmeter. Injector unmounted and no spay. Next step ? Clean injector with caburetor cleaner ?

 

[Granpa Tony]

Excellent Post! Clear & Concise, without the Usual Pontificating, Self-Serving (Aggrandizing) Babble! I shall return to ask future questions in a similar manner as you have addressed THIS 'Malady Of Maintenance'! THANK YOU SIR!

 

[miko1aj]

Hi Nutz 4 Benz, everyone,

I found the summary of potential faults with K-Jetronic extremely useful, i.e. it saved my butt I just wanted to add my experience regarding

5) Shorted or defective thermo time switch; The cold start injector will not work if the thermo time switch is defective. Check this in the event that your cold start injector does not function before replacing"

In my case, the cold start valve & thermo time switch were working and spraying fuel - but after long and painful troubleshooting it turned out that the thermoswitch wasn't working correctly in cold state, i.e. it was keeping the cold start valve energized for longer that actually required and thus flooding the engine. The valve should spray fuel for 0.3 sec for every 1deg Celsius below 15deg C (approximately of course). For me replacing the thermo switch resolved the issue where the car, '79 450SL, would crank away but wouldn't start.

Nutz 4 Benz - thank you for taking the time to compile all the info, hats off to you good man! :bowdown:

 

[Xavier11]

Hi Benz 4 Nutz and everybody!. I got a Mercedes 260E, W124, year 1992 with KE3 Jetronic. But I dont know this car has no O2 sensor, so how can I adjust the mixture if there is no sensor 02??

Thank you!

 

[1976 450 sl]

Self diagnose your fuel injection woes here.

K Jetronic Basics

Any Ideas??? - 1976 450SL. it runs but will not start. Once started and warmed up it's fine. The entire cold start, warm start system are getting 9.6 of 12 volts. upon testing each with 12 volts they all work as they should. I am seeking any ideas where a voltage drop could be. Relay - OK Fuses - OK Ground from bell housing to frame -OK Batt 12.74 volts- OK it turns over just fine and with a shot of gas in the air intake starts. and runs fine. I'm open to ideas.

 

[gring]

wires to the cold start injector are very thin and probably very dry. Can be bent near the injector creating a resistance and drop of voltage.

 

[1976 450 sl]

wires to the cold start injector are very thin and probably very dry. Can be bent near the injector creating a resistance and drop of voltage.

Thanks - the voltage for the entire system is somehow being reduced to 9.6 volts. It feeds from the warm start system that too is at 9.6 volts.

 

[gring]

What do you mean by "warm start system" ? Where is it located ?

 

[1976 450 sl]

On top of the manifold it has an additional gas pressure line running to it.

 

[gring]

Good luck. Tell us if you find the source of the problem. Personnaly, I drove a new wire to the injector and I control it with a manual switch. Usually, the engine starts within 2 seconds. Just my two cents.

 

[1976 450 sl]

Good luck. Tell us if you find the source of the problem. Personnaly, I drove a new wire to the injector and I control it with a manual switch. Usually, the engine starts within 2 seconds. Just my two cents.

After checking and double checking everything I and a 30+ year auto/electric guy could...... I ran 12 volts with a switch to the cold start. Problem solved.

 

[gring]

If you have other problems, just post.

 

[1976 450 sl]

If you have other problems, just post.

? - is it possible now that I have manual control of the cold start injector that I am flooding the engine ? I wants to start but stumbles with a low idle then dies..... 😳

 

[gring]

You flood the engine only if you energize the injector too long if temperature is too high (100 F) or not long enough if it is very cold outside (-40 F). Best is a push button switch.Mine always start within 2 seconds but I never use it in winter.

 

[1976 450 sl]

You flood the engine only if you energize the injector too long if temperature is too high (100 F) or not long enough if it is very cold outside (-40 F). Best is a push button switch.Mine always start within 2 seconds but I never use it in winter.

- FIXED-
As the car was/is literally a Barn find and sat for 20 years..... The fuel pressure can in the rear above the fuel pump was replaced. I tested the old one... the diaphragm was completely gone, the fuel system could not build any pressure. Once the new "Fuel pressure Reservoir" was replaced. Started right up. The cold start valve is still run off a hot wire but it runs quite well.

 

[ianrandom]

Fabulous