W123 280E hard to start

[Melbourne280E]

Hi people,
I have a W123 280E that has trouble starting. It usually takes about 6 good pumps of the pedal to get it started. Once it's running, it's fine and idles like it should. The only other things that has been happening lately is that when the tank is nearly empty it stalls often. I cant help but think they are related.

Cheers

 

[mbenz1]

Your problem may be related to a fuel issue assuming you have enough fuel in tank or could be battery related etc.... Im sure some experienced technical members will be here soon.

 

[219]

I'm wondering about the fuel pump/filter/accumulator assembly .

You should hear the fuel pump run for a second or so when you turn on the ignition prior to starting .

If the fuel filter hasn't been changed during your ownership , or evidence of a recent change , it could well be blocked . The filters are cheap enough , but the associated pipework , which can be rusty and VERY expensive from MB , can be quite fragile , so go carefully with it .

If the pump is faulty or the filter is blocked this could give fuel delivery problems - but this would tend more to manifest as fuel starvation when asking for full power . If the accumulator is faulty , it would fail to maintain pressure in the system when the car is parked up , hence possibly needing multiple attempts to start before fuel comes through .

The other M110 issue ( been a while since I ran one , but I've had more than a few ) is that they are very sensitive to placement and routing of the ignition leads - it is omportant to ensure that the plastic guides are present and not broken ; that the cables are correctly routed - not touching each other , crossing or shorting to ground - particularly in the narrow gap where they come up from the distributor and cross over the left hand cam cover .

Apart from the above , just cover all the basics - filters clean , distributor cap in good condition , good plugs .

Re the reply above , if the battery turns the engine over quickly enough , and lasts for several attempts , it will be fine .

 

[Melbourne280E]

Thanks some good ideas there. I will follow each idea up and see how we go with them. Cheers

 

[mbenz1]

Thanks some good ideas there. I will follow each idea up and see how we go with them. Cheers

You're welcome. Hope you sort out the problem soon and can get back to enjoying those lovely W123's

 

[grober]

Other possibility is the build up of a vacuum in the tank causing fuel starvation. Don't know how well the tanks are vented on these??? Easily tested by running with the filler cap slack to allow air in.

 

[219]

From memory , there was a pinhole vent in the filler cap , which sometimes got blocked . In some cases the suction was so strong that the tank might implode as it emptied . This sometimes resulted in the fuel guage becoming erratic as the sender tube was damaged .

Oh , and on the subject of vacuum , the 123 didn't have a vacuum pump like later models to operate the central locking , relying instead on vacuum from the engine . It used a reservoir , located in the NSF wing , and non return valves to retain enough vacuum in the system for about half a dozen lock/unlock actuations without restarting the engine . Pipes , joins and valves on these systems are all prone to be leaky now that these cars are getting on a bit , and vacuum leaks can easily cause starting/running issues .