Fuel pump relay failure symptoms: engine stops, hard cranking and high idle RPM KE Jetronic Benz 

Nice result!

Hopefully you have found your intermittent shut off issue. It is quite annoying right?

@@straybenzes Extremely annoying if it shuts off in traffic.

@@Cpcsof1 ...and dangerous. It did that to me on a three lane highway and I was in the left lane.

​@@Cpcsof1 hi, this happened to me yesterday in my 500SEC. It did it while I was doing about 60mph and a couple more times when slowing down. The speedometer started to drop and the car lost all power. Would you say your issue was the same?

Great job, Mark. Amazingly a lot of electrical gremlins in electrical components is related to cracked old solder joints. All the best.

The best of luck to you!

The best of luck troubleshooting!

Awesome! Hoping that you can keep them on the road. All the best.

Nice result. Great job.

Any updates?

@@victorsaguenay yes, I ordered a rebuilt unit from ProgRama. It was pricey but worth it. Once I got it and replace it it started right up and never shut off during a drive again.

Thanks and good luck!

Good luck

Thanks!

شكرا لك ونتمنى لك حظا سعيدا.

Good luck!

Thank you!

It could be that little green relay, but I actually doubt it as an electrical issue is typically rather erratic and independent of engine temp. If this happens consistently with a warm engine it could still be fuel pump and / or fuel filter. Especially if you used non Benz parts. I have had both fail internally with the fuel filter causing starting and running issues. Good luck.

You lucked out. They are very difficult to come by anymore.

Really nice car!

Glad it helped!

Oof! Wow and I thought losing power on the Turnpike three times while in the left lane was an adventure.

Thanks. Good luck.

Hmm. That is difficult to diagnose from afar. What car model, engine, and transmission do you have?

Got a2005 C class Kompressor and driving today it just lost all power no fuel getting to fuel rail could it be the relay thankyou for your time

@@DarrylBates You can check the relay and fuse. Should be behind a little cover on the driver side in the trunk (left upright wall). It's the top relay and the fuse should be the 4th one 30Amp. Found a video that covers troubleshooting the fuel pump pretty well: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RAYp8l2Q250.html Good luck!

Maybe or maybe not. That is a fairly new car model and there is no comparison between yours and these really old cars.

Jump 30 and 87 of the fuel pump relay and the pumps will continuously run. If your car runs the pumps are ok and it is the relay that is bad.

Glad it worked for you. Good luck.

Wow. That is a nice result.

The relay should be the same. Trouble is that the parts car's relay may not be in much better shape. Good luck.

@@straybenzes Thank you appreciate it

They are unfortunately a lot smaller than for instance the cruise control amplifier. They have only few items that I could see that could possibly be replaced. Good idea to keep one in the car when you need it In a pinch a jumper will work as well, but that is certainly more messing around that can be avoided by having a new one handy.

Pumping gas with the gas pedal or are you literally pumping gas into the intake?

@@straybenzespumping gas pedal. If I hold gas it runs nicely. As soon as I let go of gas it stumbles and dies within seconds

Did you figure this issue out?

Check OVP for proper function, check the idle control valve at around 5 Volts it should be closed, check the throttle position sensor for proper function, and make sure that you do not have any vacuum leaks. Too much to go over in text answers and doing this remotely is really difficult.

Cool. That does indeed work sometimes.

Do you have a code reader? That is where I would start. Mind you that any codes represent just raw data as very often they hide the actual root cause, but they give you a starting point where to look without throwing money at replacing stuff. That usually introduces new variables and further complicate the failure search.

Go to the trunk and gain access to the fuel pump relay )small cube looking thing to the upper right of the spare tire with a 30 Amp fuse). Have someone turn on the ignition and listen if the relay "clicks". You should also hear the fuel pump humming. Second thing to do is using some starter fluid and squirting it into the intake (remove the plastic intake pipe). Turn over the engine. If it starts right away it it most likely the fuel pump that needs replacing.

@@straybenzes thanks 🙏 will do

@@12dougreed Good luck.

Sorry, I am not familiar with that spray., but I am a little pessimistic that this will anything.

Issues with the relay cause for the engine to run one minute and then to shut off completely and no pushing of the pedal will keep the engine running. It will not even start unless the relay comes back to "life". Your issue may be related to a few other issues that you will need to hunt down. Changing out the relay will not hurt and you will have instant confirmation if that was the issue.

It'll hurt you wallet. A FP relay is £160!

Are you referring to the wiper arms? There is a washer under the center mouning nut and yes, they have to be tight.

Try this one: www.partsgeek.com/catalog/1983/mercedes/380sel/body_electrical/fuel_pump_relay.html Sitting is the worst for these cars. You may have some more "fun" with other fuel and fuel injection related parts.

Every little bit helps.

@@straybenzes well I have a question my car is 420 SEL I started and is don't start then I don't have fire in the spark place? What should I have to do???

@@yousifyousif8659 Oh wow. That could have a variety of reasons. Are all spark plugs not getting power? Did you check the distributor cap and rotor for any issues? It could also be the EZL ignition module. How did you establish that you do not have any spark?

Make sure that the fuse(s) in the overload protection relay are ok. With that checked I would take out the fuel pump relay and put a jumper between pin 7 and 8. That turns on the fuel pumps. You should have 12VDC on pin 7 with the ignition on. Hoping this will help

Scary, huh? It is not for the faint of heart when the car engine just totally quits.

You'll need a 10mm socket to remove the plastic footrest under the carpet mat on the passenger side and you will see it to your left in the footwell area. Just unplug and push the rubber grommet through.

That engine has electronic fuel injection and is thus completely different than the older KE Jetronic fuel injected engines. There are quite a few ways why your car won't start. Check the spark plugs after cranking. Are they wet with fuel or are they dry? If they are dry I would check the wiring harness and the connections between ECU and the injectors. If yours is a 1993 model chances are that you have wiring harness issues due to the known biodegradable wiring insulation that had been used around that time period. It could also be an issue with your ECU and / or OVP relay. Hoping this will help. Also, this is a fairly common issue so you may want to Google it.

@@straybenzes yes its 1994 model

@@Mnisimnisi The best of luck!

It could be, but I think that is highly improbable. Hot start issues are usually caused by low fuel pressure and that is usually due to an internally leaking fuel pressure accumulator. Did you change that one? That part sits right next to the fuel distributor on the driver's side. www.pelicanparts.com/More_Info/0004761021.htm?pn=000-476-10-21-M253&gclid=CjwKCAiAsYyRBhACEiwAkJFKotmqdMUDvinAuGKHfafQWnrvK49ra-z4REAv3YH8Wzdw8ngRyWKwWxoCDzwQAvD_BwE

@@straybenzes thank you. Yes, I changed the accumulator and it worked about 6 months ago. The problem is back. I changed the injectors but didn’t seem to fix it. Could it be the fuel pressure regulator?? I think it’s time to get my mechanic to check the fuel pressure.

@@sophiathe380sl Yeah, that would be a good start if you cannot work on this yourself; Good luck!

Can you please give a diagram to jump it.

No, they are two separate components.

That sounds like the lever position switch mounted on the left side of the transmission is either out of alignment or it is defective. That would be my best guess at least.

Natural safety switch

You are correct. I have saved some of the electrical parts by merely desoldering the solder joints on the boards.

Thanks for writing to me. That should have the 2L M111 4 cylinder engine in it. It has a completely different engine fuel and control system than the old KE Jetronic cars. As such it is best to first use a OBD 2 code reader to scan for any trouble codes so that you can narrow down your particular issue. It is very difficult fi not impossible to diagnose this from remote.

Glad it helped

The relay is unlikely the reason ofr the low revs upon acceleration. That is more likely due to the air fuel mixture being too lean. Check the main fuel injection and differential pressure first.

Thanks for the reply! I had this issue since I bought the car, now I fitted an electronic fuel injection system and it behaves exactly the same....

@@shorecarul yeah go back to the basics

Will check the fuel pump and fuel screen in the tank, I'm running out of ideas lol

good luck!@@shorecarul

Here is one from Peach Parts: www.pelicanparts.com/More_Info/0035452505A.htm?pn=003-545-25-05-A-INT

This can be a symptom of the modulator needing replacement, faulty vacuum level, or even debris built up in the tranny valve body. Checking the vacuum level and modulator are the easy check ups. Opening up the tranny is more complex.

@@straybenzes I think it might be the potentiometer now , but I will look at vacume when I get it up on the lift.

Thanks for fast reply, your videos are a great help

@@Rossithailand I hope you will find the root cause.

@@Rossithailand Glad they are helping.

There should be a replacable cap in it, but that is for using a 3mm allen wrench to adjust the idle mixture.

You don't. This is the most misunderstood function of the KE Jetronic. You need to make sure that your idle mixture gets you the highest RPM and no stalls or surges. Then you tend to the overload protection relay, vacuum leaks, the throttle position sensor, the idle control valve, and I am sure I am forgetting a few items. There is no idle adjustment screw like in int golden days of carburetors.

It can be - they are not esy to buy anymore.

That is another couple of great tips. Thank you!

Hi Patrick; What year and model is your car? The 722.3 is a very sturdy transmission. To me this sounds like a bad or stuck kick down switch. Look under your gas pedal and locate the kick down switch. Make sure that there is no carpet or foam material stuck there. Does that switch move freely in and back out? For the heck of it disconnect the wire connector to the switch and take a test drive. If your tranny shifts ok it is definitely the kick down switch. Good luck.

@@straybenzes thanks for quick response, pedal switch in perfect condition and solenoid cable already disconnected and tested with no change.

@@straybenzes car is w124 1990 M103 and 722.358 gearbox... 124.930 chassis.

@@serverdll Got it.

@@serverdll This also can be the auxiliary oil pump not working or not working properly. Potentially, it may be a blocked passage(s) in the valve block assembly.

Any time

Try the MB Classic Center or Ebay. I have not found another source for new ones for the V8 gas cars yet.

Thanks!

Not sure what to make of this comment and were it belongs. Sorry.