I am very interested on how that oscilloscope works. Please keep us informed. I am in the process of adjusting my duty cycle now and like okyourabeast, I only have a multimeter with duty cycle.
I have an el cheapo one from harbor freight that works great. I just use it in a dark garage though.Finally Received my oscilloscope yesterday so it will be interesting to see how it looks when i hook it up.
Another thing, my 35 year old timing light isn't so bright any more and my old analogue revcounter doesn't work on any of my cars including the 380SL so i wan't to buy new ones. Any tip on a good timing light and revcounter?
Reading the post, I would rather get an oscilloscope than risk cracking open the ECU and shorting something. I'm going to assume you have done this?No no, I meant the timing light. I used my wife as the rev counter. Got it good enough to pass smog!
Your duty cycle meter will work just fine on the fuel ecu.
Ok, any tip on a revcounter which is what i need the most? I found this on ebay:I have an el cheapo one from harbor freight that works great. I just use it in a dark garage though.
I've done it many many times without issue. I just didn't want to spend $100 but an oscilloscope is just easier to do the work with since you won't be hunched over your chair.Reading the post, I would rather get an oscilloscope than risk cracking open the ECU and shorting something. I'm going to assume you have done this?
Just checked the diagnostic port to attach my oscilloscope and as you can see in the picture, port 3 where i should connect the (-) is the only port without a connector. Are you sure about port 3 or is it a difference between a US and a Swedish model?Since you have the oscilloscope, stick the probes into the X11 diagnostic port that is in the engine bay. Pins 2 (+) and 3 (-). I think that's the correct polarity.
Open your hood and look to where the brake booster is on the driver's side (US). There will be a small black circular object. Unscrew him, stick in the probes, and you're in the money!
It's much easier to use this method than the one I have to do since I only have a duty cycle meter.
My car is a 380SL from 1984 and it is refered to as "S" (Swedish) in the manual that i've seen on this forum. I've already found out that the AAV is the manual one (not electric) as in the US for the year 1984 which can be seen on the left side of the first picture. I can't find anything that looks like the frequency valve so I'm adding 3 pics from different angles in case i've missed it.Hi @ed9msi , sorry I don't know how I missed this.
First, what type of car do you have (model, year, and spec)? If it's a rest of the world r107, then unfortunately your car won't have a fuel ECU and the associate frequency valve which the duty cycle is taken from.
I'm not sure about Swedish spec vehicles, but at least on the US models that had Kjet, there was an add-on emissions control system that basically pulsed the system lean to provide better fuel economy.
Does your car have a frequency valve? It should look like this:
And it should be directly across from your diagnostic connector towards the middle of the engine bay.
If your car does not have one, then this guide will not work for you. Instead, you will have to get a tailpipe emissions sniffer to properly tune or your engine or guestimate where the 50/50 mix cycle is.
My advice, if you haven't played with this screw and don't have proof someone played with it then don't mess with it! You'll have better luck smoke testing the engine and checking fuel pressures first to make sure everything is operating correctly.
Thanks okyourabeast!Hi @ed9msi,
You don't have the frequency valve. You have simple kjet! Your first picture revealed it. He would normally be living right in the middle of that picture with a cable coming out of it.
Don't bother with the tailpipe sniffer. What you should do instead is smoke the intake system and check your fuel pressure. If you see any leaks during the smoke test, replace them. If the fuel test is out of whack, start with the system pressure regulator and look at the warm up regulator next.
Give your vehicle's age, your WUR might be bad but only testing can confirm that. The good news is, your metering screw still has the protective cap on it. A virgin car indeed!
Does your tail pipe smell rich to you?
Just checked my account but can't find anything. What does FSM mean that you posted for me?I would check the FSM I posted for you. It will outline the fuel pressure testing steps and pressure criteria.
You can get a fuel pressure test kit at harbor freight for cheap. Get the master one. Remove the Schrader valves on the fittings you use as they screw with pressure readings.
The warm up regulator is towards the front left of the engine it has a 12volr connector going into the top with two Hardline fittings.
Here's a thread on the topic. https://www.benzworld.org/threads/first-time-attempt-to-check-cis-pressures.1511113