1978 350SE Pulled the relay while running,motor died now runs super rich!Help

[ohsofast]

I have a 1978 350SE with the Gasoline 3.5 liter engine.I was messing around trying to find the turn signal relay(while the engine was running) and there is only one relay in the fuse box.I pulled it out and the engine stopped abruptly.
Im guessing this may have been the fuel pump relay?
When i plugged it back in the car smokes pretty bad and you can smell the raw fuel comming out of the exhaust pipe,prior to the pulling of the relay it ran great.Now im stumped 

Im wondering if anyone has pulled this stunt....looking back it was rather stupid to pull a relay while the engine is running i suppose.

I still need to locate the turn signal relay and now i have to fix the super rich running condition that now exists after pulling the only relay in the fuse box.
This car is a plain jane if you can call a Mercedes a plain jane.
I need some advice,can anyone help with this problem!I would appreciate it greatly!

[Tony66_au]

Hi and Welcome to The Org Ohsofast.

A little more information is needed, 78 350SE which I assume is a K jet system and what country are you in? and is the car a locally delivered car for the country you are in?

The reason why I ask is because the cars differ slightly between markets, for instance Australia didn't have 350's after 1975 and they were all D jetronic cars etc etc

Also where was the relay mounted and can you provide numbers from the relay so we can ID what it was you pulled.

Cheers,
Tony

[ohsofast]

Hello Tom,
Thanks for the reply!
The car came from Germany many many years ago.I actually live in Las Vegas Nevada.The car has Mechanical Fuel Injection.The car is void of any frills...no Power other than brakes and steering.It is a 1978 Grey Market 350SE with the chrome bumpers.At sometime along the way(years ago) A/C was added due to the hot summers here in the Vegas Valley.

There is actually only one relay in the fusebox and it belongs to the fuel pump relay im guessing?
I have actually seen this same relay on several American Spec Model cars in the pick a part yards here in Vegas.
There are 2 main numbers as follows: 001 542 02 19 and SR 9850    Mfg date: 8/78 Made is West Germany.Has 5 prongs.The fuse box sits on the drivers side fender apron.I know of no other relays in this car.

Im just not sure what i did when i pulled the relay while it was running.I wouldnt think it would have done anything other than shut the pump off?All of the spark plugs are now sooty black from way to rich of a mixture.Before this they were all nice light tan....Is there a sensor that detects ratio that i might have fried?collapsed the regulator??
I would love to have a repair manual for this specific car.I bought one from a fella in England but he sent me info related to American versions,im not sure how much i can extract from the manual that will pertain to specific 350SE wiring diagrams.I know the basic chassis is the same,brakes,suspension,etc.
Im not Mr goodwrench but ive tinkered with cars the better part of my life.Im sure there is a systematic approach to diagnosing this problem.....i dont know what it is..

I like driving the car,its fun to drive and has a comfortable ride.Seems like it just a minor problem that im not seeing.
Any help would be appreciated!
Thanks so much!

[Tony66_au]

First up this site has an online manual which you can find here.  http://handbook.w116.org/matrix6.htm

Mechanical is known as CIS or K jetronic injection and K jet is pretty much the same on all the V8's so id select the 450se/sel for info the same year of manufacture to your 350. (Whoops there isnt an SE that matches so pick the 1978 450SEL)

[Tony66_au]

http://handbook.w116.org/ETM%5C77SEetm.pdf

Page 4 of the PDF and you will have to blow the pic up a bit.

it looks like you are spot on and its the fuel pump relay.

Im wondering if the car is running rich due to the cold start being stuck on which has to do with the WUR (Warm up regulator) but my K jet experience is limited.

BTW the WUR looks like this

[djenka018]

I cannot see anything electrical throwing a "mechanical" injection system into rich mixture.

If WUR lacks 12V (parallel connection to the pump) it could extend the worm-up enrichment well into 60*C but all the effects would go away once engine goes close to or over 80*C temp.
WUR should have 12V with engine running (or whenever the fuel pump is running). Its element (heater) should have resistance higher than, I think, 10-20 Ohm but not more than 100-200 Ohms either... When I get home in a few days I can check.

The second option, as silly as it may sound, is that relay had bad contact making pump run at lower speed/pressure and then someone compensated for that pressure drop. Once the connection was properly established, full pressure makes richer mixture. But that's just an idea...   

[jbrasile]

ohsofast,

Do you know when the car was imported into the US? I only ask because it was common practice to modify the straight K-Jet system in these gray market cars to a K-Jet with Lambda,which adds an ECU, O2 sensor and frequency valve to the FI system. This would allow the car to be EPA certified without too many mods. By pulling the relay out with the engine running you may have   damaged the ECU, please do not go crazy over my suggestion, it is just a guess. See if you  can locate the frequency valve, it looks like an injector and sits near the injection mixture controlled with a tube that connects it the fuel distributor. Also if there is an ECU, it should be mounted on the passenger side, behind the vertical panel at the base of the A-pillar.

Let us know so we can try and help you solve the problem.

Tks

Joe

[scraf]

The second option, as silly as it may sound, is that relay had bad contact making pump run at lower speed/pressure and then someone compensated for that pressure drop. Once the connection was properly established, full pressure makes richer mixture. But that's just an idea...

... that would be filed under in of those "can't for the life of me figure out what happened" drawers, like when two things decide to go wrong at the same time, exponentially complicating the troubleshooting.

[ohsofast]

Thanks for the replys and input on the Topic of :1978 Merecedes Benz(European Version) 350SE 3.5 Liter V8 Gasoline Engine pulled the fuel pump relay while running and now runs in overly rich mixture.

The car is not equipped with 02 sensors or controlled by an ECU.The only thing "electronic" is the ignition system.

Im wondering if it did something to the Ignition Module?Very weak spark?Im just grasping at straws at the moment. It is getting spark and it appears to be a strong spark by observing it....i mean it starts the car and keeps it running....actually i dont think its ignition related im just a little befuddled at the moment

The car was running fine prior and something just didnt go bad at the same time.It was definately related to pulling the fuel pump relay while running.
Its just dumping way to much fuel in proportion to the air ratio now.
It doesnt even appear that there are many components in this mechanical fuel injection setup,the injectors are  even mechanical......i dont get it.

[djenka018]

As much as it may sound odd and unusual, you may have repaired an old fault that previous tech just ignored and compensated for.

* Have you confirmed 12V at the WUR?
* Perhaps check WUR function by sticking a CO meter and see the needle drop as engine warms up?

[ohsofast]

I am going to let the car warm up to operating temperature and see if the rich mixture diminishes.(Its getting cold out, even in Vegas believe it or not...)

I will check the WUR as soon as i can to verify if its getting voltage to the plug or not.Have you had a WRU apart?
It allmost appears like it could be rebuildable?

Im more than likely the last owner of this Benz.....it started out life as a well healed about town look at me pampered ride,allways to the Mercedes dealer when something was not quite right....Several owners later its just another car on the road,it was givin to me for free...It was in sad shape,waiting for someone special to come along and give it new life.She gets her parts from the pick a part yard now but shes happy to be on the road again.That front grill still says im still special,and i could care less if a Doctor or Lawyer is behind the wheel,just keep me rollin.

[Tony66_au]

Might be worth checking the AAV while you are at it, Should be wide open when cold and if its stuck shut then it will be quite rich when cold

[ohsofast]

I ran out today and ran the motor up to operating temperature and it still is running very rich even at normal operating temperature,not as bad but you see raw fuel being dumped out the exhaust pipe.

I checked and the WRU and its getting the reqired 12 volts.Whats inside the WRU,is it a rebuildable unit?

Im guessing the WRU is the problem?

[djenka018]

I ran out today and ran the motor up to operating temperature and it still is running very rich even at normal operating temperature,not as bad but you see raw fuel being dumped out the exhaust pipe.

I checked and the WRU and its getting the reqired 12 volts.Whats inside the WRU,is it a rebuildable unit?

Im guessing the WRU is the problem?

IMO it is unlikely it died suddenly. You confirmed it works (mixture goes leaner), albeit it is not a sign of 100% of accurate functionality.

Just another reason for mixture to go "rich" is if a vacuum leak stops. This would mean that previous vac leak was "compensated" at idle by enriching the mixture, effectively pushing the whole engine management in excessive rich run (while at idle it goes normal).

A good foundation for all the engine management problems is to re-plumb all the vacuum hoses, disconnect all the vac accessories (and plug that port temporary) and only then readjust CO at idle as per service manual.

Have you tried to lean the mixture on FD?

[Tony66_au]

WUR is the warm up reg used for cold starts, I believe they are refurbish-able yes but I think more testing is in order to eliminate the WUR as the problem.

To have raw fuel dripping from the exhaust is pretty major and it means that a cylinder or cylinders are not firing, also worth bearing in mind is that if its running out the exhaust then its also going to be contaminating the engine oil which a sniff of the dipstick will reveal and this makes the engine oil worthless as a lubricant and dangerously flammable when warm to hot because of the evaporating petrol fumes.

Im not sure on the test procedure for the WUR and im sure someone will tell you but id be very careful re the engine oil contamination, it needs to be changed out soonish with fresh stuff and a new filter.