1975 450 SL fuel injection problems

[DE Watson]

My 1975 450 SL has been experiencing fuel injection or electrical command problems. At first the four middle cylinders of the V8 cylinders were starved of fuel. The plugs were sparking but the cylinders weren't 'firing'. With the cylinders that were 'firing' an electrical bridge to those that weren't seems to solve the problem but I have no desire to leave things like that for fear of damage. We have replaced the ECU but the problem (under normal wiring) still exists. There appears to be 2 injector sequences the outside 4 (1,5,8,4) receive their fuel but the inside 4 (2,7,3,6) do not. Does anyone know if there is a relay or other component which could be faulty to cause this effect?

Help anyone? : Doug W


Update 30th Oct:

An auto electrician has traced the fault to the trigger contacts. Cleaned up they are now working properly. If anyone has need of a replacement ECU for a 1/3 european price (£700) please make contact before it get returned.

Thank you all for your assistance.

Doug W

 

[guydewdney]

complete guess - but bad earth for those injectors?

 

[mlc]

Not quite sure what an "electrical bridge" is, but I agree with the bad earth theory. I cant remember what earths where, but I do recall that their is at least two earth points for the injectors along the top of the engine, however I would have expected the split to be front / back or sides rather than inner and outer.

How sure are you that its running on 4 cylinders? are the other cylinders fouling up at all? The final thing that comes to mind, and im' only guessing that it is on your car, do you have the mechanical injector triggers in the distributor? I think that they work as pairs?

good luck

Mark

 

[dawood]

I really want that ECU! Have you returned it? Contact me +353 86 2714614