MB 280SE Coupe idles ok, no pull - PeachParts Mercedes-Benz Forum

Hugin · #1 05-08-2006, 10:48 AM

Hi

Just recently my -69 280SE Coupe has developed a nasty lack off power.
It will start easily, idles ok, but totaly lacks power.
I have cleaned the distributor, the airfilter/gasfilter are new and the sparkplugs looks ok.

I do not have a lot of tech skills....so ant hints would be great.

It misfires and lacks power in all revs exept idle.

Tom

Arthur Dalton · #2 05-08-2006, 11:03 AM

Check fuel pressure.
There is a filter/screen in the bottom of the tank, accessible from 22mm hex under tank..also , a pre-filter screen on the electric pump suction side,
A fuel flow/pressure test will verify the condition
You are looking for 1 litre/15 secs. flow rate.

Hugin · #3 05-08-2006, 11:37 AM

Hi

And opening this filter/screen in the bottom of the tank, accessible from 22mm hex under tank, will flush the content of the tank in my face I guess ??

ctaylor738 · #4 05-08-2006, 11:49 AM

Definitely. Not a bad job to farm out to someone with a lift and a gas caddy.

Arthur Dalton · #5 05-08-2006, 11:50 AM

< >>

... only if you are not smart enough to drain the tank first.
If you are challendge with this sort of thing, you may be better off going to a tech than asking techs here......................we just assume one would know common sense

Hugin · #6 05-08-2006, 11:55 AM

Hey, just kidding....

Thanks for the advices, will check these things for sure.

I'm a novice in car repair, have not done these things since I was a poor young man and had no choise

Learning new things every day!

ctaylor738 · #7 05-08-2006, 12:28 PM

... only if you are not smart enough to drain the tank first.
If you are challendge with this sort of thing, you may be better off going to a tech than asking techs here......................we just assume one would know common sense

Gee, that was a bit mean-spirited.

Even if you siphon most of the gas out, you are still left with unhooking the fuel pump hose and draining the remainder into a container of some sort, difficult on the floor. Then you need to get the screen out, and there will be some residual fuel down in the well where the screen goes.

I just did this on a 108. If it was running, I would have taken it to our local gas station. Believe me, it is better to pay an hour's labor if you can afford it.

Arthur Dalton · #8 05-08-2006, 12:30 PM

Very good..

If you want to try it , here are some further suggestions.

If you look at the filter container in the engine bay , you will notice the line coming from the tank to the filter container .. if you take that fitting off and slip a rubber hose over the line you just removed , you can put that into a container on the ground and turn ON the key.. this will start the electric fuel pump and you time how long it takes to put a litre into that container. If it is around 15 seconds, you do not have a blocked fuel filter in the tank.
If that test shows low flow rate, then you can drain the tank by simply putting this same line into a larger gas can and use the electric pump to empty the tank...then take the hex plug off the bottom of the tank and the screeen will come out with it.
A Tech trick for this hex plug is to use a 1/2' drive spark plug socket with an extension inverted into the socket.. this other end of the plug socket will fit that hex and a 1/2 drive ratchet will fit the extension...........

Tomguy · #9 05-08-2006, 12:59 PM

Misfiring indicates lack of gas. Misfiring AND backfiring (combustion either in the intake manifold or somewhere later in the exhaust system) indicates a bad spark.

Check the little carbon brush in the distributor - This is quite brittle and if it breaks, your car WILL run like crap. Trust me - I've been there. I was lucky to get home with a broken one. If it did break you'll need a new cap AND rotor - the rotor will be scarred and tear up the new brush quite fast. Symptoms are an ok idle (although it can be rough if the brush is really bad), but as soon as you hit the gas, backfiring and misfiring - even without load.

Hugin · #10 05-08-2006, 01:03 PM

Quote:

Originally Posted by ctaylor738

...

If it was running, I would have taken it to our local gas station. Believe me, it is better to pay an hour's labor if you can afford it.

I would too, only here in Norway the local gas station WILL provide you with burgers and hotdogs + softdrinks, however, they WILL NOT have the equipment or skills to do this job.
Sad, but true.

And, if you are so lucky to have an oldfashion gas-station nearby, the WILL charge you big bucks....around 100$/hour.

So, besides learning, I would like to save the bucks too ;-)

Will report back after the job is done.
Thanks again for the tips.

BTW, can you guys recommend a GOOD repair handbook for the w108 and w111 ?

Mark DiSilvestro · #11 05-09-2006, 08:20 AM

Some simple things to check before pulling fuel lines and draining tanks - make sure all vacuum/air tubes, hoses, lines, etc.., to the intake manifold, are un-broken and secure. Also check that one of the linkages between the intake throttle and the fuel injection unit hasn't gotten disconnected.

Happy Motoring, Mark

Hugin · #12 05-09-2006, 11:02 AM

Hi

Ok, first observation is that the fuelpump will only deliver a pityfull 200ml in 15 sec.

So, either the filter in the tank is VERY dirty, or the pump has had it's best days.

So, while waiting for the tank to empty....what is the cost of a fuel pump?

I seem to recall seeing something about using a fulepump for VW...at a much lower cost, but same specs.
Anyone?

Edit: Ops...it's 580 USD.....I can't wait to hear the price here! Praying for the filter to be the cause.
Any way to repair the pump?

Arthur Dalton · #13 05-09-2006, 11:15 AM

There is a pump rebuild kit for short $$$, but you can not condemn the pump until yu verify a healthy flow from the tank.

It is also recommended that you have a 1/2 tank when testing flow..

Another way is to pinch off the hose that goes from tank to pump in order to remove the hose from the pump inlet port... you then put that end in a container and open your pinch clamp and see if you have plenty of gravity flow...if not, you have a restricted hex screen......
..Next step, if you have good flow with that test, is to check the screen at that same inlet port on the pump itself..these BoscH MFI systems use 3 filters..one screen in the tank, followed by a screen at the pump suction side port , and a final pressure fine filter at the engine, pre Injection Pump.

Hugin · #14 05-09-2006, 12:37 PM

Hi

Ok, so it's not the filter

Will conduct the gravity-test later.

The screen on the pump-intake, how do I access it?
Is it by removing the 5-6 screws in the bottom end of the pump?

Excuse my technical english if faulty....it's not my native language

Arthur Dalton · #15 05-09-2006, 01:01 PM

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How did you determine that??