Author Topic: Rich fuel mixture  (Read 5633 times)

mda

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Rich fuel mixture
« on: July 04, 2016, 12:09:37 »
Hi, guys. I have collected a car. The car has stood without any movement for 15 years. So I rebuilt engine  and washed fuel system. I started engine and engine started fast and easy and after the starting, the mixture is so rich, that after several seconds of working, I have to throw away spark plugs because of black soot. I turned cold start valve off but it didn't help. So, I have read this website for 2 days with dictionary but I didn't find where on the fuel injection pump there was adjusting screw which adjusted rich of mixture. And also I didn't find how to define whether WRD worked correctky or not.  And I also don't hear air rushing and I don't know what to do.

Pinder

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Re: Rich fuel mixture
« Reply #1 on: July 04, 2016, 23:09:24 »
fuel mixture nob is on the back of the fuel injection pump. you have to push it in to engage a slotted not then counter clock wise to reduce fuel. your WRD may be stock. its on top of the pump.
1970 280 SL Light Ivory DB 670. 4 Speed manual shift no AC Limited Slip Diff.
1997 Corvette C5 Silver. automatic
2015 BMW 320i xdrive
2021 Mercedes GLS450 Silver

Cees Klumper

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Re: Rich fuel mixture
« Reply #2 on: July 05, 2016, 05:02:42 »
Do not try to turn the idle mixture screw at the back of the pump while the engine is running, it must be off. If you don't hear air going into the small air filter on the injection pump when the engine is running cold, then it seems the WRD is stuck in the closed position. The cold start valve can leak also when it doesn't get power. Good luck with sorting this out.
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

Pinder

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Re: Rich fuel mixture
« Reply #3 on: July 05, 2016, 16:45:13 »
yes good point about having th engine of when adjusting.
1970 280 SL Light Ivory DB 670. 4 Speed manual shift no AC Limited Slip Diff.
1997 Corvette C5 Silver. automatic
2015 BMW 320i xdrive
2021 Mercedes GLS450 Silver

mda

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Re: Rich fuel mixture
« Reply #4 on: October 26, 2016, 06:45:17 »
I feel like I'm on the right way in finding the solution. The adjustment screw of the mixture in the back of the pump twisted to end in the right. How it to adjust? thank you

rgafitanu@gmail.com

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Re: Rich fuel mixture
« Reply #5 on: October 26, 2016, 12:36:04 »
In the last post, do you mean that the idle mixture screw is turned all the way to the right and cannot be turned further (clockwise or counterclockwise). This screw has a screwdriver end inside the pump that when pushed-in engages a slotted screw. If the slotted screw is too far in (very rich mixture) the push-in screw will not engage the slot anymore turning freely. At least that's what I have on my 230 engine.
If the push-in screw engages but cannot be turned clockwise you should try to turn it counter clockwise anyway for leaner mixture. You should do the throttle linkage test to see how rich is your mixture. Unfortunately there are at least a dozen potential causes for rich mixture and you may have to check them all.

Radu

ja17

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Re: Rich fuel mixture
« Reply #6 on: October 26, 2016, 14:28:59 »
Many problems originate when the engine linkages are not set-up correctly. Make sure they are correct. The rack on the injection pump should be free. If the car has sat idle for a long period, it could be stuck. Research the information on the WRD and make sure yours is operating correctly. Along with basic tune-up procedures, these items are critical. The knob on back of the injection pump, only adjusts mixture up to 1700 rpms.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
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Shvegel

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Re: Rich fuel mixture
« Reply #7 on: October 27, 2016, 23:31:11 »
I second Joe's advice to check the rack.  Search here for "Stuck Rack"  Assuming the car was put away in good order a rack stuck at anywhere near full flow with a throttle that is at idle will cause what you describe.

Pinder

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Re: Rich fuel mixture
« Reply #8 on: October 29, 2016, 14:10:33 »
If it sat for 15 years the rack and pistons in the pump will highly likely be stuck. I was in the same situation when I rebuilt my engine. Before putting the injection pump back in i took the side plate off and observed the motion of the pistons. while rotating the pump and pushing on the rack in and out. 4 pistons were totally stuck. I used sea foam, transmission oil, Marvel Mystery oil and it freed up after about a week of soaking and rotating. when you open it dont mess with any settings in there. just keep soaking and rotating etc. The sea foam worked the best. WD40 also helped a bit as did Mystery Oil.
1970 280 SL Light Ivory DB 670. 4 Speed manual shift no AC Limited Slip Diff.
1997 Corvette C5 Silver. automatic
2015 BMW 320i xdrive
2021 Mercedes GLS450 Silver

mda

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Re: Rich fuel mixture
« Reply #9 on: November 03, 2016, 19:00:51 »
 :) ;)

mda

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Re: Rich fuel mixture
« Reply #10 on: November 03, 2016, 19:01:24 »
by the way, before and after

Cees Klumper

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Re: Rich fuel mixture
« Reply #11 on: November 03, 2016, 19:43:35 »
which one is the before?  ;)
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

turbinmech

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Re: Rich fuel mixture
« Reply #12 on: November 26, 2016, 08:25:53 »
 Adjusting the pump can be  tricky ,make sure the engine is warmed up to temp on temp gauge. Only do a few turns at a time to see how engine responds. After you adjust the pump screw you need to go to top the engine and adjust the air bleed in the right front of engine. That should get a good idle that is not to rich . Idle rpm is 750-800 after warm up. The other item that can cause problem is the water thermostat on the fuel injection  pump it may be dirty or not working. Fuel cleaner in the gas tank will also help if pump is sticky from bad fuel.
Cheers Benzmech43 Livermore  Ca