hi all
ye might be able to help me, i have been having a cold start idle problem.
on a cold start the car starts fine but idle quickly rises to 1800 2000 rpm, i had assumed it was the aav but i have replaced it twice, hit it, squeezed the bulb soaked it and ended up with 3 aav's which do not open enough but closes at 60/70 degrees.
i put in a second hand aav ( thanks arcijack) the other day and the car behaves as it did when i bought it, perfect start but after 5/10 seconds idle rises if your driving it feels as if the choke is out.
i think the aav is good i gave it a soak cleaned it a bit and it openned and closed fine maybe 80+ degrees
i think i have a vacuum leak but only when cold? when i went looking for a leak i pulled the large vac hose from the top of the wur as it was quite loose in the aav hose and put my finger on the openning in the aav hose and the cold idle dropped to 1300 /1400. i put a screw in temporarily and it idled great i returned the hoses and the high idle returned.
the other vac hose from the side of the wur connects to the intake on the other side of the aav.
would this suggest that the wur is faulty, it is certainly enriching on cold start or could the leak be elsewhere.
the car drives great although sometimes i feel it could be more responsive if i push it hard between 60 and 80 kph after that it flies
one other wur question my wur lies on its side on a bracket as opposed to on the flat is this a feature of early 116s? mine is a 450 1976.
thanks in advance
Hi. I had wur hassles on my 79 k jet 280sel. The problem was that the main chamber of the wur had filled with oil over three decades which led to slow warm up and running rich. I don't know if the same gravity/plumbing problem exists with the v8's. I carefully dismantled it (watch the fragile diaphragm and pin) and cleaned it with brake cleaner. All good thereafter.
Maybe none of this applies to D jet.
hi
its a kjet , im just not sure if its a vacuum leak , cold start valve or the wur, my local mechanic doesn't have much time for old cars
i will bring it to a good guy i know in january.
i would be nervous to take the wur apart without a spare the car is a daily driver.
john
Hi John
I lived in Galway until I was 24, But have been in the US for 30 years. I just got a 77 450 SEL It was off the road for about 10 years I am having problems with WUR, AAV, etc, etc Looking forward to hearing more about your problems. PS I also have a 71 Rover 3.5 RHD I got in London.
hi Gerry
good to hear from you, i hope the car works out well for you they are great fun when working.
in the u.s you will be able to get parts much cheaper than here which will help, i am not very mechanically minded although i will do easy jobs and i over think problems and these cars are quite simple.
my prob is high idle till warm and sometines it wants to die for a few seconds at start up apart from that it drives very well, some rust which i hope to sort this year.
i used to love those rovers its a 3500s? a rarity in new jersey I'd say great looking car .
i think you might have a fuel mix issue did you set idle speed when warm ? getting the aav and warm idle screw correct can be a bit of a balancing act.
best of luck
john
Hi John
I bought a used WUR on ebay last night for $35 I will take it apart to familiarize myself with how it works. I am a mechanic (air compressors), But I did serve my time at Galway Motors in 1976 Datsun and Hillman , So I enjoy the challenge. by the way the Rover is a P5B, off the road at the moment. There are people (wife)who reckon I would do better getting the Rover going before buying the Merc. But I always wanted a 116. I think you said you had taken your WUR apart is there anything I should look out for? Also John if it is not too much trouble could you measure the distance from centre of the back wheel to wheel arch. I am not sure if my car is a bit low in the back, I posted this question a few days ago but have not got a responce yet. Thanks for your help.
hi gerry
My car is in getting the alternator fixed, should have it back today, I will measure height then. The cars have a slight wedge shape ie higher at the back and my previous 116 was, my current one appears lower but not by much. the rear springs do get tired after 30 years and I think are a pain to change.
i never took my wur apart although i have doubts about mine, getting one for a 450 for 35$ is pretty good
like the aav they are basic the strainer can get clogged, there is an element that heats up and the unit can fill with oil / gunge, to test you need a pressure guage to measure fuel pressure.
when you changed the aav did you open the idle screw it may have been closed to compensate for a bad aav
which happens a lot, is it when the car warms up it dies?
ps my brother had a 120y were they from your time at datsun
Good morning John
Yes $35 + $15 for shipping, The guy had 3 of them, said they had been sitting around for a while for that price it is worth it even just for parts, By the way if you see something over here, and you need help with shipping or anything let me know. I live in NJ but I work in New York, so I get around. Yes I worked on the 120Y. Thanks again John.
hi gerry
just got my car back after getting alternator sorted, i measured the height from the centre of the hub to the arch and it is 31cm, thats not scientific mind. i imagine they vary a bit, they are a lower looking car than modern cars.
all the best
john
If you have CIS test gauge I is pretty easy to test control pressures and to compare cold control pressures during warm up with the chart given the ambient air temp. I think it is a bad idea to take one apart yourself or to by a used unit not meant for your car with the hope you will fix your problem. Larry Fletcher at CIS Flow Tech in Texas can check your WUR and rebuild it if needed. I have sent him a WUR to check on Monday and had it back on Friday of the same week! He has all the equipment and knowledge to test and rebuild WUR and fuel distributors at reasonable prices. I have no financial interests in his business. He has rebuilt several WUR's for me and checked one of my fuel distributors with perfect results. He is a good guy and will treat you right. I am trying to fix a maddening cold high idle problem on my 1985 Euro 280E and have replaced a huge number of parts and still have the issue. Only a couple possibilities left. Thought it would be easy to put right but I was wrong. I also had a new AAV installed from MBCC and sent it back when my mechanic thought it was not closing all the way. Didn't make a bit of difference. We also smoked the intake hoping to find a vacuum leak and could not find anything except other than EGR valve leak and I removed all of the EGR stuff a couple days ago.
Quote from: w116john on 07 January 2014, 03:58 AM
My car is in getting the alternator fixed, should have it back today, I will measure height then. The cars have a slight wedge shape ie higher at the back and my previous 116 was, my current one appears lower but not by much. the rear springs do get tired after 30 years and I think are a pain to change.
With the right compressor (http://www.ebay.ie/itm/261333337609) the rear springs are an easy job. I had mine in and out in under two hours, including fitting new shocks. Removing the fronts in my parts car was like a roller-coaster ride. One actually went airborne (but luckily I did take precautions, knowing it's a risky job).
The rears in my 69k miles, 1979 450SE were shorter by just over 11mm, if memory serves right, compared to the new Bilstein B3 (http://www.rexbo.eu/bilstein/coil-spring-36129799) springs.
hi ptashek
so there was only 11 mm difference new v old my rears look as if they could do with change but its not a priority
etmerritt if my idle issues conyinue thats what i will do, thanks
john
Thanks for all the info guys.
I just went out and started the car and it started and ran as it should, and it is very cold (10 degrees f) but when it got warm (170), it started to run bad again I mean- not drivable - will not take acceleration at all. A few day's ago it ran OK when hot for a short while, then the same problem. Does the WUR affect the running when hot? How about the cold start valve?
Thanks
In those temps, without a properly operating cold start valve, you'll have a devil of a time getting the car started. Once the car is running, if the cold start valve is leaking (not closing fully), you'll have a rough/rich idle. If I recall, the CSV is only supposed to cycle for about 10 seconds at startup, and only when the engine temps are below a certain value.
If you understand carburetors, think of the CSV as the equivalent to pumping the accelerator pedal a couple of times before cranking the engine. All (I think) carburetors have an "accelerator pump" which is a mechanically actuated plunger that squirts additional fuel down the carb when you press on the accelerator. "Pumping the pedal" squirts extra gas down the carb to help with starting.
The WUR (Warm Up Regulator) actually has two purposes. As the name indicates, it helps with fuel delivery when the engine is cold by increasing the control pressure in the system, which causes more fuel to be injected into the engine. Think if the WUR as the equivalent to the choke plate on a carburetor. As the car warms up, the WUR slowly reduces its effects on control pressure. An additional feature of the WUR is to provide full throttle enrichment. That's the purpose of the attached vacuum line. Under full throttle, virtually all vacuum in the intake is eliminated due to the fully-open throttle plate. The WUR senses this and increases the control pressure to cause more fuel to be injected.
WUR's on cars of your vintage are installed on the side. Later models have the valve standing up. There has been a lot of discussion as to whether the "laying down" versions are swappable with the "standing up" versions. There is a difference between the two as to where the vacuum line attaches (one on the side, one on the top).
If you can get some assistance, I'd try to see if squirting a little petrol down the throat will help compensate for your "will not take acceleration at all" problem. Take a small spray bottle with gasoline - make sure it's configured to spray a stream, not fine spray. Have your helper step on the gas and when the engine stumbles, squirt a couple of pumps at the big air intake plate and see what happens. If the motor responds favorably, then you're too lean.
Frankly, I think that's what's happening anyway, based on your issues. You said in one of your early posts the car seems under powered until you get past 80kph (are your really talking kph or mph?) - either way, the faster you go, the more the WUR is going to enrich the fuel delivery.
I have an entire manual that deals with diagnosing fuel problems on our generation MB's. I can send you a PDF version of the document if you'll send me your eMail via the message boards "send email" feature.
Regards
Good explanation of the WUR, Brian. I'd like a copy of that manual, if if you don't mind
Ken
I will add to what Brian has said. WUR is really a misnomer and does not adequately describe what this important component does. It is responsible for mixture control the entire time your car is running. When cold it is responsible for enriching the mixture by lowering the control pressure. When the engine reaches operating temp it is responsible for maintaining steady state control pressure which directly affects your fuel air ratio the majority of the time. During acceleration it is responsible for lowering the control pressure to enrich the mixture. Each WUR has specs for what those control pressures should be under each of those conditions. If any are out of spec and everything else is perfect your engine will not run right. While the WUR is on the engine the only was to determine that is to connect a CIS test gauge and carefully test and record those control pressures and compare them against factory specs for that specific WUR. While doing this you also need to check the fuel pressure that the WUR sees against spec. If you can not do this find a shop to do it for you and make sure you have the mechanic record what the test gauge says and give the numbers to you.
Any other monkeying around, taking the WUR apart, trying to clean it, or trying to swap in a used WUR is just a waste of time IMO. You might get around your immediate problem but your engine is not going to run right. The CIS tester is not that expensive and not that difficult to use. The specs are available in the small blue Mercedes tech books which are not expensive and will contain specific specs for the exact model of WUR the factory engineered for your engine.
Another tip that I was unaware of for a very long time until Larry Fletcher made me focus on it. That is the very precise requirement for the rest position of the air metering disc. Even 2-3 mm can make a big difference if it is not perfectly positioned. I never believed it until I got it perfect on my 6.9. Why does it matter? Because that position establishes the relativity for the fuel air ratio for the entire range of different air flows and operating conditions based on the precisely engineered shape of the walls of the air metering device. If is not exactly right you will be too rich or too lean under different operating conditions and there is no way to adjust or modify the WUR to account for that. It's a difference that makes a difference. Check yours against the diagram in the Mercedes service manual for your car and make sure it is right if you want your engine to run as the factory intended.
Hope this helps!
Great explanation! Thanks for the info :D
Hi guys
I have a 1977 450 SEL 4.5. It was not a running car when I got it but someone had played with it, the WUR has vacuum lines going to the top and bottom, the line going to the bottom is connected to the manifold side of the Auxiliary air valve, and the one connected to the top is going into the big hose on the other side of the AAV I just got a book Mercedes-Benz CIS theory and operation. This shows the vacuum port on the bottom open to atmosphere. Mine is the one that stands up (not on its side). Can anybody tell me witch is correct? Thanks for in advance for any responses.
Do you have any factory workshop manuals and the small tech book for your car? If not, they are well worth the cost. Mercedes made changes in the WUR specs from time to time and you need to check the number on yours first to see if it is the right one for your car and then check the manual for the connections. As I recall the larger port is usually the vacuum line and the smaller one is for atmosphere. But, check to make sure. If you don't have this documentation write down the Bosch number for the WUR and pot it on this thread and I will try to find it for you. You could also pull the intake side vacuum connection to the WUR with the engine running at idle which will put the WUR in acceleration enrichment mode and you should hear that difference. The WUR sees vacuum most of the time which keeps it in steady state but when the throttle opens the vacuum goes away and that causes the control pressure to drop which makes the mixture richer for acceleration. If nothing happens you have the lines backwards on the WUR so swap them and test again. I like to be meticulous and use the factory manuals so I know exactly what I am doing. You can also get a year's subscription to StarTek EPC for $ 12 and get a lot of the same info. Those small blue soft cover tech manuals have a ton of good info and they also cross ref the Mercedes and Bosch numbers for the WUR and Fuel Distributor. Hope this helps!!
On reading the original thread I wonder if the WUR is really the problem at all.
In some cars the AAV lets in too much air when cold and you get an exaggerated fast idle when cold which is useful under very cold conditions but not so useful in milder climates.
The solution was to fit a restrictor into the inlet side of the AAV to restrict the airflow and reduce the idle.
As concerns the WUR cvacuum leads there are several dfifferent options depending on markets, smog gear and year.
I think the lines were reversed sometimes during the 1978 year which makes it even more confusing but all will be revealed in the correct manuals.
Most of the available manuals are produced for the US market only which is not so handy if your car was produced for elsewhere but there are supplements but there are yearly supplements that give market differences.
Some years ago I digitised my manuals and I am sure they were sent to this site as well as the other Sydney Site and they will give this level of detail.
Bill
hi bill
totally agree with you, i had changed the aav twice and both times i had this very high cold idle 1700-2000 rpm so i thought it must be something else. when looking for vac leaks i did notice that blocking the large vac line from the wur dropped the idle, so i was wondering if the wur was causing the problem.
i took out the aav again, tested and subsequently squeezed the bulb assuming that an aav that closed too early was less of a problem than one which didn't close fully.
my idle is pretty good it can still rise to 1500 rpm but drops back to 900-1000 quickly.
i do think i have a vac leak which is more evident when cold, i will get the mechanic check it out next time its in
thanks
john
Hi Guys, I am near the end of my rope. Bought the car in Oct. as a non runner, the guy I bought it from was a mechanic who had tried to get it running with no luck (it had been sitting for about 10 years) he had drained and replaced the fuel, changed fuel pump and filter. When I got it, it would run only by spraying starting fluid in the fuel distributor. I suspected the fuel distributor, I bought a rebuilt kit took it apart did not find anything obliviously wrong put it back together and the car ran very well for about an hour, then started to splutter and died, if I remover the distributor from the car and replaced it, it did the same thing ran well for a short time then died. I decided to have it professionally rebuilt, this guy also did not find anything wrong with it, but when I reinstalled same thing again, then I turned my attention to the WUR checked incoming voltage disassembled and checked ohm rating cleaned and reassembled again ran great for about a half hour then spluttered to a stop, while I was working on the WUR I noticed one of the ballast resistors was cracked so I took a brake from the fuel and went to work on the ignition new cap, wires, plugs, and two ballast resistors (waiting for a new rotor) again started up and ran so well for about an hour I decided to take it to the gas station broke down after about 2 miles. I was able to get back home by letting it sit for 1-2 minutes then it would run 3-4 hundred yards. I did buy a CIS test kit, control pressure between WUR and top of Distributor is 3.6 bar, fuel pressure to Distributor from pump is about 6.5 bar. my VIN # is116 033 12 070243 the WUR #is 0438140010 The StarTek site does not support Mac. so I will have to join at work. What are the small blue soft cover tech manuals? do you mean the Mercedes workshop manuals?. PS I am a mechanic with about 30 years experience but not familiar with this system, So any and all help is greatly appreciated, and yes I know I repeated some stuff from early posts, But I had to vent a little. I still love the car and know it is just a matter of time.
As far as technical documentation, here's close to the complete set.
M110 Engine 2 volumes Complete info on all aspects of Service, and adjustment. The best technical manuals I have ever seen in my 50 years of working on cars. The M110 manual came out as an 1 volume manual which doesn't apply.
Chassis 116 2 Volumes
Technical Data for Passenger Cars (year) This is the small softcover book which contains setting data, torque values, adjustment info. Extremely valuable - the go-to reference.
Mercedes Benz Model Year (year) Introduction Manual for Passenger Cars These don't come out every year, and detail changes from earlier manuals + info on newly introduced models.
Mercedes Benz Maintenance Manual USA Model Year (year)
Parts Book Mine is Catalog H. Good for seeing parts and assemblies. Very clear drawing that match up to EPC.
It's taken me a long while to accumulate all of these, but eBay is an excellent resource - just don't overpay. Also if there are any I have missed, someone let me know.
Note: I have a Mac and use Parallels. Pain but it works.
It is Sisyphus's work to adjust K-jet without pluging all the vac leaks first, make sure ignition timing is default and there is no significant stretch in the timing chain.
In case like OT, after vac leaks plugged and timing is set at default, I'd adjust CO value at 80*C engine temp (no more, no less) using 98 fuel and with idle rpm forced to be 750 at idle screw
All the other problems should be addressed from such starting point and then CO and rpm revisited after any adjustment. IMO, AAV adjustment should be the last.
Most of the problems are purely due to vac leaks but most of the know-it-all mechanics start to fiddle elsewhere, messing up the whole system so even if you end up plugging the leaks, they introduced bucketloads of other off-tunnings making your task a nightmare.