1975 280 6-cylinder W114 Solex 4A1 Carb problem - PeachParts Mercedes-Benz Forum

Speedtek · #1 09-03-2002, 10:36 PM

I am trying to fix a car for my Aunt. She has a 1975 280 6 cylinder W114 with a 4bbl Solex 4A1 Carb. The car has a bad vacuum leak and I suspect that the last person that changed the Phenolic gasket/plate overtightend it and warped the carb.

What is the best solution to fixing this? I am ready to put on a Rochester or Holley 4 bbl carb. Seems cheaper than fixing the Solex?

Anyone got a fix?

psfred · #2 09-03-2002, 10:55 PM

Try flipping the carb over and draw filing the base -- if it isn't flat, you will find out quickly, and should be able to get it flat fairly easily. Quadrajets are notorious for warping, every single one I've handled had to have the base flattened (especially if someone used a chisel to remove the idle cap).

If it is really warped, junk it and get another one, or do a replacement. You will have trouble finding a Q-jet or Holley small enough to do a direct replacement, I'm afraid -- you won't need more than 350 cfm, if that.

Check to make sure the throttle body is secure on the venturi block, too -- a leak here will drive you nuts.

Don't forget to check for the other "obvious" vac leaks before condeming the carb -- there are two vac lines to the carb, and the vac pulloff on the carb can leak, too. A bad manifold gasket can cause serious vac leaks.

Most of the usual vac accessories (brake booster, AC, locks) run off a pump on the head, I think, on this car.

Peter

#3 09-04-2002, 01:00 AM

Peter is correct on what to hunt for in vacuum leaks on the 4A1. I might add that these are the major places to look for leaks there also may be minor places as well. The door locks are also vacuum acutated. There is a check valve in line which should prevent back flow leak from the system, but at times the check valve is broken and does not prevent the "back flow". The cruise control also has a vacuum line to it whcih may leak. The transmission modulator has a metal pipe off of the intake to the modulator. At times the bolt to the modulator gets loose and creates a good amount of leakage. Long list, but also check the climate control servo. Numerous vacuum lines are connected to the head of the servo. Insure the rubber lines are set into the head. Lastly, check all the rubber connections in the engine compartment which go to hard plastic lines. They get old and need replacing.

To sum it up, this is not an easy task. Once your elminate the major components which Peter described, I would go for the minor ones I suggest. What kind of vacuum are you getting now from the intake?

leathermang · #4 09-04-2002, 12:33 PM

I have a 1974 280 so I got a MB shop manual for it... It has pages and pages of modifications it suggests for this carb... I have a 1983 import tech bulletin book which also lists suggested modifications... so unless you can fix this carb with simple stuff it might be better to change to a more reliable or more refined carb... or simpler...
When I got the car the original owner had put a HOlley on it.... now I know why....

#5 09-04-2002, 01:13 PM

Hey Greg! Not to get off subject of a vacuum leak v. Solex 4A1, it is problematic for sure. But in defense of the pain-in-the-butt carb, when one is set-up correctly and in great shape it can really howl. Mine is finally back to A-1 performance with the help of a local Solex guru. Just love to hear the roar of the engine when hitting the kick down. Also, nothing like the feel experienced on the highway when the secondaries kick in. I admit it is a poor duplication of a Rochester, but when set right it moves. My only complaint is the lack of gas mileage. Presently only getting 28 mpg.

leathermang · #6 09-04-2002, 04:14 PM

Why don't you post the name and number of that guru... I think a lot of people would like to know it....
I don't know how tall these carbs are ... but I am wondering if any Weber carbs are available to put in their place... My Subaru stock carb was about like this solex... 13 diaphrams, no one who even wanted to fix it.... all suggested I get the Weber... what a difference.... it now howls.... and parts/instructions are available for them....and they are famous for being tunable .....mine is the 32/36 dgav....
Gympie, what kind of gas mileage are you EXPECTING to get? That seems pretty good to me....

psfred · #7 09-04-2002, 07:03 PM

28 mpg out of a 114 280 is excellent, the 300D only gets about 30.....!

Peter

#8 09-05-2002, 01:11 AM

Guess I shouldn't complain about the gas mileage with the 280S. My daily driver is a Nissan Maxima with a V6/5 speed. It gets great milage. Filling the Nissan compared to filling the MB is quite a difference.

If anyone would like the Solex guru's name and address, email me via the forum. I'd be happy to pass it along. He does excellent work. But cannot work miracles on those Solex whcih are better off being made into buckshot.

Understand the Weber is one great carb in itself. Very worthy of consideration to all for a Solex replacement.

ctaylor738 · #9 09-05-2002, 08:27 AM

What was the final resolution on your carb problems?

Last we heard, you were tracking down the puddling in the intake manifold and then you got sidetracked by the EGR valve.

#10 09-05-2002, 12:47 PM

The Solex lives! Sometimes in life when looking for a problem you forget to look at the most obvious. While concentrating on getting the correct tension on the secondary, I neglected to check the secondary pull-down diaphragm. It was opening too soon without the pull down causing a bypass failure. Since replacing the pull-down, no pooling of fuel in the phelum. Runs great now and gas mileage has certainly improved.

Got the old EGR to work once again. Some penetrating oil on the shaft a few knocks freed it. Anyone what to buy a new EGR?

Since, have replaced all the door lock actuators, unscrambled a mess of misguided vacuum lines in the HVAC, and replaced the flex disks/bearing. Now working on brakes/rotor/bearing replacement. Next, seat cushion replacement. Tired of setting on springs.

ctaylor738 · #11 09-05-2002, 07:46 PM

I replaced the seat pad a few months ago and did a post on it. Hardest part is lifting the seat out of the car.

#12 09-06-2002, 01:14 PM

Read your post on the cushion R and R and found it very informative. Thanks. Guess the seats do weigh a bit, which may be the biggest part of the job. Going to replace them with rubberized horse hair cushions. Nothing like the earthly, MB smell in any other car due their cushions.

Wonder where SpeedTeck went? Hope we didn't put him off during our off topic conversation.

Hey SpeedTeck, how's it going with the Solex?

Speedtek · #13 09-09-2002, 12:15 AM

I am still here......Been busy working.

We are going to get the car to the shop and look at things further. Thank you for all your suggestions. We have not checked the Door locks and brake booster yet.

Hopefully we can keep the solex going. I hate doing carb conversions with all the extra things to think about like Air cleaner mount. Would like to keep it all original.

I found a neat Fuel Injection setup at the swap meet. it was an Accel 2 bbl unit. almost thought about it. The guy had all the parts and wanted $250 for it. That would be neat an updated W114? maybe it will get better milage?

THANK YOU EVERYONE!

#14 09-09-2002, 12:55 AM

Good to hear your still hanging in there. Would first check the major items which Peter mentioned before the minor. The 4A1 is very prone to warppage and could be causing the vacuum leak. If it is the Solex which is warpped and you find that a replacement is needed either a Weber or Rochester would be the way to go. A Weber kit is available which fits like a glove. Better gas mileage to boot.

How many lbs. of vacuum are you getting now off the intake?

leathermang · #15 09-09-2002, 09:05 AM

Gympie, Do you have any specifics on the Weber conversion ? Who,where,how much, which Weber it involves... ? Thanks, Greg