68 280se Mechanical fuel injection info repair manual links

[Wrightbenz]

Hi guys. I recently picked up a 1968 280se it has the MFI on it. I have not had much luck finding info on this system.

The car seems to be flooding during startup. Once flooded plugs need to be removed to get things going again.

[Idle]

The first place to check is the cold start valve. It is that round thing with an electrical plug attached to it and a gas line from the injection pump that is bolted to the side of the intake manifold.

If it is stuck in the open position then it is just blasting gasoline into the intake manifold and fouling your plugs. The best way to test it is to disconnect the electrical line going to it, removing the gas line going to it (which is under pressure or should be so careful here!) and then hooking up a length of rubber hose to it and seeing if you can blow through it. If you can then it is stuck open. If you can't then it is closed.

Now hook up the gas line, leave the electrical plug unconnected, shoot some starter fluid into the intake through the air filter hose (to simulate the extra gas the cold start valve would provide if it were hooked up) and see if the engine runs like it should. If so you have discovered a leaking cold start valve and the source of your extra gas.

Now you will need to determine if it is the cold start valve that is sticking in the open position or if the sensor is telling it to stay open longer than it should.

You can pick up a nice online manual, which is really a download, on Ebay for about $25 or perhaps find someone selling a DVD of the manual on Ebay. This manual was meant for the Mercedes techs so it can be somewhat difficult to understand when you are trying to test sensors but if you own one of these cars you MUST have the factory manual to keep it running.

[Carpenterman]

Here's some very good information on the fuel system on your car:

Pagoda SL Group Technical Manual :: Fuel / Injection

The 280SL Pagoda has the same engine and system as does your 280se.

[Idle]

By the way....

This system seems complicated but after you start to read up on it you will come to see that it is really pretty simple. Lots of things to get just right, but they are all simple things that can be run down one at a time.

[Idle]

And...

If it is not your cold start valve that is leaking or staying on too long then it could be your fuel pressure regulator has failed. This would allow more gasoline to reach the cylinders than is necessary and give you the same results as a leaking cold start valve.

There are a lot of things to check on this system and they all must work as they should, but it is easy to check them one at a time.

It is, though, time consuming.

[cth350]

the most readable printed manual I've seen is the Glenn's manual. Look for posts by Ron Bunting on various forums about it including the M-100 forum. Same basic system with several minor variations over the years.

-CTH

[Wrightbenz]

Originally Posted by Idle

The first place to check is the cold start valve. It is that round thing with an electrical plug attached to it and a gas line from the injection pump that is bolted to the side of the intake manifold.

If it is stuck in the open position then it is just blasting gasoline into the intake manifold and fouling your plugs. The best way to test it is to disconnect the electrical line going to it, removing the gas line going to it (which is under pressure or should be so careful here!) and then hooking up a length of rubber hose to it and seeing if you can blow through it. If you can then it is stuck open. If you can't then it is closed.

Now hook up the gas line, leave the electrical plug unconnected, shoot some starter fluid into the intake through the air filter hose (to simulate the extra gas the cold start valve would provide if it were hooked up) and see if the engine runs like it should. If so you have discovered a leaking cold start valve and the source of your extra gas.

Now you will need to determine if it is the cold start valve that is sticking in the open position or if the sensor is telling it to stay open longer than it should.

You can pick up a nice online manual, which is really a download, on Ebay for about $25 or perhaps find someone selling a DVD of the manual on Ebay. This manual was meant for the Mercedes techs so it can be somewhat difficult to understand when you are trying to test sensors but if you own one of these cars you MUST have the factory manual to keep it running.

Thansk for the suggestions idle. I haven't been receiving notifications so I had not read everyone's posts here. I will sort that out.

[Wrightbenz]

I finally had some time to look at the old Benz today. Pulled the plugs and they were terribly fouled. Cleaned them up reinstalled and she fired up. Running a bit rough but I was able to drive the car from its parking space to my garage a half mile away.

The car is missing on at least a cylinder I beleive. It has original plug wires so they need to go. Lots of old stuff under the hood.

Originally Posted by Wrightbenz

Hi guys. I recently picked up a 1968 280se it has the MFI on it. I have not had much luck finding info on this system.

The car seems to be flooding during startup. Once flooded plugs need to be removed to get things going again.

[Wrightbenz]

Originally Posted by Idle

The first place to check is the cold start valve. It is that round thing with an electrical plug attached to it and a gas line from the injection pump that is bolted to the side of the intake manifold.

If it is stuck in the open position then it is just blasting gasoline into the intake manifold and fouling your plugs. The best way to test it is to disconnect the electrical line going to it, removing the gas line going to it (which is under pressure or should be so careful here!) and then hooking up a length of rubber hose to it and seeing if you can blow through it. If you can then it is stuck open. If you can't then it is closed.

Now hook up the gas line, leave the electrical plug unconnected, shoot some starter fluid into the intake through the air filter hose (to simulate the extra gas the cold start valve would provide if it were hooked up) and see if the engine runs like it should. If so you have discovered a leaking cold start valve and the source of your extra gas.

Now you will need to determine if it is the cold start valve that is sticking in the open position or if the sensor is telling it to stay open longer than it should.

You can pick up a nice online manual, which is really a download, on Ebay for about $25 or perhaps find someone selling a DVD of the manual on Ebay. This manual was meant for the Mercedes techs so it can be somewhat difficult to understand when you are trying to test sensors but if you own one of these cars you MUST have the factory manual to keep it running.

I checked the cold start valve and it appears to be fine. A lot of fuel is being pushed through from somewhere though, I pulled the dip stick and the oil is gas soaked. This may be from the previous owner just cranking away trying to start the car. So hard to say at this point, still poking around a bit. I need to change the oil before I continue.
Any ideas what else could be flooding the engine? Where is the fuel pressure regulator on these? Sorry still no manual.

[Haris]

Originally Posted by Wrightbenz

I checked the cold start valve and it appears to be fine. A lot of fuel is being pushed through from somewhere though, I pulled the dip stick and the oil is gas soaked. This may be from the previous owner just cranking away trying to start the car. So hard to say at this point, still poking around a bit. I need to change the oil before I continue.
Any ideas what else could be flooding the engine? Where is the fuel pressure regulator on these? Sorry still no manual.

I had the same problem, the car would get flooded very easily on startup. Go through the linkage tour here Linkage Tour and make sure yours is setup correctly. Next you need adjust the screw at the back of the pump if it's running rich or lean. DO NOT ADJUST IT WHILE THE CAR IS RUNNING! You will destroy your pump. The pagoda forum is a great resource for the 2.8 6cyl M130 engines. Have a search on there for any issues you are having, it has helped greatly getting my car up and running again. You may also be interested in a series of videos **************.com are doing restoring a pagoda and getting the engine to run correctly here (Mercedes W113 280SL Pagoda Rescue Part 6 - Engine…: http://youtu.be/PLedjKWbU5w) it's only up to episode 6 at the moment.

Also check your ignition timing, if it's out it will cause hard starts. Check the condition of your points in the distributer also if your spark isn't good enough you will be left with unburnt fuel in your oil and blowing black smoke from your exhaust.

Regarding the rough running you need to check through your whole ignition system from coil all the way to spark plug. Personally I'd get a new cap, rotor, points (or replace with an electronic ignition kit) and spark plugs as these are service items anyway, I'd check the condition of the leads and check if the vacuum advance is working correctly.

To check that the fuel pump is providing the right amount of fuel, disconnect the return line on the pump, connect some sort of hose and use a suitable container to catch fuel. Turn the ignition on, you should here the fuel pump buzzing away and you should get 1L of fuel every 15 seconds.

Hope this helps get your car running properly! Feel free to PM if you need some more help

[cth350]

if it looks like you have too much oil, change it. Aside from looking for coolant in it, an over abundance of gas in the oil thins it out to make it far less a protective goo than it should be. -CTH

[Haris]

Sorry I've recalled the wrong numbers above it should be 1L of fuel every 15 seconds!

[Wrightbenz]

Originally Posted by Haris

I had the same problem, the car would get flooded very easily on startup. Go through the linkage tour here Linkage Tour and make sure yours is setup correctly. Next you need adjust the screw at the back of the pump if it's running rich or lean. DO NOT ADJUST IT WHILE THE CAR IS RUNNING! You will destroy your pump. The pagoda forum is a great resource for the 2.8 6cyl M130 engines. Have a search on there for any issues you are having, it has helped greatly getting my car up and running again. You may also be interested in a series of videos **************.com are doing restoring a pagoda and getting the engine to run correctly here (Mercedes W113 280SL Pagoda Rescue Part 6 - Engine…: http://youtu.be/PLedjKWbU5w) it's only up to episode 6 at the moment.

Also check your ignition timing, if it's out it will cause hard starts. Check the condition of your points in the distributer also if your spark isn't good enough you will be left with unburnt fuel in your oil and blowing black smoke from your exhaust.

Regarding the rough running you need to check through your whole ignition system from coil all the way to spark plug. Personally I'd get a new cap, rotor, points (or replace with an electronic ignition kit) and spark plugs as these are service items anyway, I'd check the condition of the leads and check if the vacuum advance is working correctly.

To check that the fuel pump is providing the right amount of fuel, disconnect the return line on the pump, connect some sort of hose and use a suitable container to catch fuel. Turn the ignition on, you should here the fuel pump buzzing away and you should get 1L of fuel every 15 seconds.

Hope this helps get your car running properly! Feel free to PM if you need some more help

Thanks this is very helpful. Obviously I have a bunch of things to check. Still hoping there is no serious damage to the engine and that I can get her going without major engine work.

I have ordered plug wires
New plugs
Points and rotor
Car came with some oil filters and such so I am good there.
I figure I need to start with the ignition and go from there.
I will however do some inspection of the linkages and other things that may be way off.

Thanks for the help really appreciated

[Sugar Bear]

When my 70 280SE was fouling plugs and had gasoline in the oil, the problem was a defective injection pump thermostat. It is located on top of the injection pump where two small 10mm? coolant hoses attach. IIRC the retainer for the thermostat was held down by two slotted screws. It was a simple fix.

While doing a tune up a cap and rotor is suggested along with a valve adjustment.

As suggested, don't make adjustments to the fuel injection unless you have a manual and understand the system.

[Wrightbenz]

Originally Posted by Sugar Bear

When my 70 280SE was fouling plugs and had gasoline in the oil, the problem was a defective injection pump thermostat. It is located on top of the injection pump where two small 10mm? coolant hoses attach. IIRC the retainer for the thermostat was held down by two slotted screws. It was a simple fix.

While doing a tune up a cap and rotor is suggested along with a valve adjustment.

As suggested, don't make adjustments to the fuel injection unless you have a manual and understand the system.

Thanks I will check the thermostat at the mfi pump. Probably best to just replace it as I'm sure it is original.

Anyone have the point gap or dwell numbers handy? Also need to check the timing need those specs to and is it checked with or without vacuum to the advance?