Warm running device cleanup - Mercedes-Benz Forum

 
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post #1 of 8 (permalink) Old 09-22-2013, 02:26 PM Thread Starter
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Warm running device cleanup

Hey.

So I've been calling around a bit on this rather annoying issue I have. Engine (W108 M130.980) won't idle properly when cold, has trouble keeping up its pace when cold, etc. Then when it hits 80 degrees Celsius, its operating temp, it will dive to way too low RPM's for like 10-30 seconds (you gotta keep it alive with the pedal). Then it idles totally fine afterwards. If you fire it up 4 hours later, it'll take a good 5-8 seconds of cranking until it fires. It idles a lot cleaner but it misfires on random cylinders.

Now I've been told some different stuff, but you gotta start somewhere. First thing is, the battery in my car is currently a 420 CCA (55 AH) battery. Apparently, the recommended is 680 CCA. The starter does crank over slow(er) than when it's hot by a good shot, but would it lead me to have idle issues when cold?

Option two would be the check valve (pressure holders) on top of the MFI leaking, causing it to not have any pressure when left over night. However I'm not really sure if this is the case, as it just fires randomly on cylinders when cold, no pattern as far as I can see. It also fires up quicker cold than partly hot (say sitting for 4 hours after being driven). So I'm pretty sure it's not a problem there.

What's most likely the case is the WRD sticking / blocked filter. I've been talking with a person who owns a 280 SL, and he says he can clearly hear the MFI / WRD sucking in air under cold starts. I don't hear this at all, no air seems to be going in anywhere near the MFI pump. I tried calling up a Mercedes classic specialist who told me "it's most likely the WRD and not pump related".

I'm thinking of just driving the 180 km there to get it fixed, considering I am terrified of messing with anything that has to do with the MFI. Pal gave me a great site (The SL113 site) which has some info on the WRD - I'd just like to hear if there's a way to test if it's the WRD and not the pressure holders.

Thanks!


I'm not touching the pedal in the first clip, however the hopping up and down in the revs seems to have seized after the CSV got a new seal, so it'd stop leaking petrol.
You can clearly hear the engine misfiring between 0:17 and 0:20. That's the first startup after 2-3 hours of sitting.

Last edited by Jackpody; 09-22-2013 at 02:31 PM.
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post #2 of 8 (permalink) Old 09-22-2013, 08:05 PM
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That website has a detailed procedure for setting the lengths of the various accelerator related linkages. I think it's called a "linkage tour". Find it there and make sure your linkages are correct before you do anything else.

The throttle plate also has a "specification" (slight binding) that needs to be set. Many people try to adjust idle speed with this adjustment, but that is incorrect.

There is also an air intake valve for idle mixture on a hose between the throttle body and the intake manifold that needs to be adjusted, either with a CO2 gauge or a tachometer. Check the warm-up device air filter before you do anything, also.

The last thing you do is mess with the IP adjustment. Be sure timing and ignition are correct before dealing at all with the fuel system.

That website has everything you need to know regarding the m130. If you take the time, you will be able to learn about starting and idling principles on this motor. Did you know that there is a time and temperature function that regulates if/when/and how much fuel the CSV injects?

My WUD has a slight whistle until it warms and closes.

1981 300TD--310k miles
1970 280sel--172k miles
1966 230--162k miles

Last edited by carpenterman; 09-22-2013 at 08:14 PM.
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post #3 of 8 (permalink) Old 09-23-2013, 05:13 AM Thread Starter
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I do believe it's related to the WUD (Warm up device / WRD / Warm running device?). It does not appear to suck in air when cold, which it apparently should. There's definitely no "shoosh" coming from the area around the MFI. I'll try and check the SL113 site again, maybe I overlooked something.
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post #4 of 8 (permalink) Old 09-27-2013, 06:05 AM Thread Starter
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I shot some video of it cold starting, to try and see if any of you know what this sounds like. My microphone amplifies all high sounds a lot, so any real obnoxious chugging is due to that.
If you cold start it and just rest your foot on the pedal, the idle cleans out to a near perfect idle. The moment you lift off, it chugs and stutters until its properly hot. No issues whatsoever when its hot.
Also what does the chugging sound like? I mean I've heard a lot of other W108's and SL's from the period, and they all have that diesel injection sound when up front. I'm not sure if mine is making it abnormally though.

EDIT: Mneeh, watching some other videos of M130's and it seems like mine makes the exact same sound. So I just need to figure out why it has such great difficulty starting cold. We have tried driving it only a couple minutes after it was started, just to figure out if it evened out. And don't try that, we had to just stop 20 meters down the road because it was shaking terribly (so we noped and let it heat up).
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post #5 of 8 (permalink) Old 09-27-2013, 10:19 AM
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I would do the split-linkage test during the post-startup period to determine if more/less air or fuel is needed at that time. If you suspect your WRD, splitting the linkage allows the other side to be manipulated to gauge the effect on idle. You can pop off the top ball closes to the drivers side, then hold them "together", then move the rod and lever in relation to each other, ie hold rod to IP steady and move the lever down to add air, move the lever up to reduce air. Or hold lever steady and move rod slightly up and down to add/lessen fuel as may be the case, but you get what I mean. Simple test that at least informs you if the engine is calling for more air during warm up in order to idle smoothly. The 113 site's linkage tour is great reading, too.
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post #6 of 8 (permalink) Old 09-27-2013, 10:46 AM Thread Starter
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I could try that. It's hard to tell but the engine ran a lot nicer if you revved it up just a bit, making me think it's an air to fuel mixture problem. It's hard to tell though because it's obviously not getting enough air at higher RPM's too, but it's a clue.
Also the WUD / WRD makes no noise at all when cold starting. No shoosh or anything. How is the WRD kept in place? Looked like you could just take it off easily in the pump assembly website you showed me.
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post #7 of 8 (permalink) Old 10-05-2013, 10:37 PM
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Check your spark plugs, wires, cap and rotor. What type of spark plug are you running?
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post #8 of 8 (permalink) Old 10-07-2013, 01:04 PM Thread Starter
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OEM Bosch sparkplugs. They need a replacement next season, they seem to be pretty nicely worn by now.
It has electronic ignition and the timing is perfect when the engine heats up (after about 2-3 minutes, even) which makes me think it's not a timing related issue, more of an issue with the fuel to air mixture being wrong. This is why I suspect the WUD / WRD is failing on me, as it does not appear to suck in any air at all under cold circumstances.

EDIT: My cold cranking amps are only 420 CCA or 45 AH. Does this make a difference? I've been told not, but the car nearly stalls when idling when cold if you turn on accessories, such as the headlights.

Last edited by Jackpody; 10-07-2013 at 01:16 PM.
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