1977 W116 280SE fuel problem

[Hal116]

Hi! I´m new here, and in deep..

Bought this car weeks ago, no head or intake manif. in the car. Installed a head, manifold+dist from a 1979 230E. the manif i installed have later version of sensor & distributor made from light alloy but as i can see the car originally came with the cast-iron one. Does that matter?

All parts in place now, found out fuel pump was shot. Found a used pump from w201 2.3 and installed. Now it fires up and dies. Possible that the later pumps do diffirent pressure?
Also I noticed that the crank sensor is broken off, how critical is that?

Spark plugs, wires, cap are new
tank was drained and filled with fresh
Cold start valve is new
Pressure regulator is new

All help appreciated

 

[jonnyboy]

Are you completely sure the head etc is off a 230 e?

A 230e is a 4 cylinder m102 engine IIRC, a 280se is a six cylinder M110 twincam again IIRC.

I suspect the head etc came off a 280e ?

 

[219]

I suspect the head etc came off a 280e ?

My thoughts too , John .

 

[Hal116]

sorry 280e is is, sorry for that.

 

[jonnyboy]

One wonders if th cast and alloy setups are the same - extra vacuum pipes, control gear etc?
Have you compared the two setups side by side?

 

[Hal116]

All ports the same, looks same except the material they are made from. The pressure regulator was still on the block, all lines fitted and everything is hooked up as it should be.

 

[Hal116]

i would have used the original dist but I didin´t find any locally, and that crap costs an arm and a leg at the dealers

 

[Ian B Walker]

i would have used the original dist but I didin´t find any locally, and that crap costs an arm and a leg at the dealers

An arm and a leg maybe but you would be sure it was right and under warranty and work first time. Why faf about with dodgy second hand parts for an icon of a car.

 

[Hal116]

True, but thing is I just wanted to get the motor in it up and running so I could move it arround and hopefully drive it to the paintshop. It´s gonna get a detailed respray in black, 3 month job they say. Plan is to buy another engine to rebuild with all new parts in and on it.

 

[Hal116]

Anyone know the purpose of that crank sensor?

 

[Hal116]

Hi

Now the car runs. Great when cold but when hot it idles rough and stalls when shifted to gear. It fires right up and idles smooth for few seconds, if I leave it for a minute or two it will stay smooth for a minute, if I leave it for 5 minutes, it idles smooth for 3 minutes. Noticed that the resistors are really hot, I touched it abd i got a minor burn. Is that normal? Possible that the resistors/coil are bad? Any Ideas?

 

[219]

i would have used the original dist but I didin´t find any locally, and that crap costs an arm and a leg at the dealers

A far better option is the 123 electronic distributor available from the Netherlands - this looks original fitment , but gives you a modern contactless ignition system .

123ignition electronic ignition systems for classic cars

 

[74merc]

Is the crank sensor a black cylindrical plug hanging on a lead near to where the distributor is? If so, it's only used when setting the ignition timing.

 

[Hal116]

Ok so I wont worry about that sensor for now. Is it normal that the resistors become this warm, I measured the temp on them, 85 and 120°c. Is it possible that the coil is shot? or the sparkplugs I installed have built-in resistor? (should not) Or do thore resistors wear out by time?

 

[219]

The usual practice was for Merc to use a 6V coil with series resistors . To ensure a big , fat spark when starting , the resistors were bypassed to put 12V across the 6V coil . Once the engine was running , the resistors come into circuit to drop the extra 6V .

I don't think I ever felt any of them , but next time I have my 280SE running , I'll check ( if my W126 has these resistors - can't remember offhand ) . Certainly all my older cars had this arrangement .

 

[Hal116]

thanks alot, cheers!

 

[Hal116]

Hi again. I just got a fuel pressure gauge, and what I found out is when the car is at normal idle the fuel pressure is about 5 bar but when I rev it the pressure drops down to 3, or bit less. Is that normal?