W123 overfuelling- gallons per mile!

[Wakeywillfixit]

Hi,has anyone any ideas on this problem with my 1981 280E? I recently swapped the engine for a good s/h one that I'd driven for 100 miles and knew it was good- the old engine had head gasket and piston ring problems at 170K,but also had got VERY thirsty. After fitting the fresh engine, I found it would blacken the plugs as soon as it warmed up. The old one had been the same. The fuel filter is not blocked, the return line is clear, the tank is not vaccuuming, so that leaves me with the pump, and the collector, as suspects, but I'm thinking I'll replace these, and may still have the problem. Anyone else experienced this, or similar? ...and fixed it? Wakey

 

[grober]

More Info Required

It would help if you tell us if you shifted your entire fueling system to the replacement engine ( e.g. the replacement engine being a naked block) or did you use the new engines fueling system too? In other words what parts of the fuel system were common to both engines? What exactly is your fueling sytem Bosch jetronic- carbs or what? And whats a collector? Sorry to reveal my ignorance

 

[Dieselman]

I assume this is going to be the K-jetronic mechanical system. The mixture strength is controlled by the flap in the air intake venturi. The greater the pressure on the flap the wider it opens the fuel distributor port so lets in more fuel.

Check the setting of the flap against the linkage arm and check that the cold start injector isn't activated all the time.

The flap adjustment is by using an allen key through the top of the housing via a small hole.

Just for info, the running rich is what finished your old engine, due to bore washing and probably oil dilution.

 

[grober]

Warm up regulator.

There might also be a problem with your warm up regulator or your primary pressure regulator leading again to too rich a mixture. You need to get the system pressures tested by an injection specialist. Dieselmans right this fault will damage your new engine too unless you get it sorted. If you have an accurate pressure gauge with suitable adapters you could test the pressures yourself see http://www.fordfans.cz/download/manual/0686-04b.pdf but you GOT to know what your doing so best left to a pro with experience.

 

[Wakeywillfixit]

re overfuelling fault

Thanks guys for the quick response- I took the entire engine and auto box from a 280E w126, which ran perfectly. It is mechanical injection, I used the injection system which came with it, and now I've had some feedback, I think it could be to do with the throttle settings, as I did have to use the throttle linkages from the old engine, I'll check this tomorrow. I did suspect the cold start system on the old engine, but everything worked fine on the replacement one when it was in the donor car. The wiring connections to the switches are the same as used by the old engine. The fuel pump is {now} from the donor car, which hasnt made any difference of course, The collector on the fuel pump, as I understand it, is just a small reservoir feeding the pump, so I can't see that being a source of the problem. Will do what checks I can with the info provided and letyou know how I get on! Cheers, Wakey