Hello everyone and good day. I recently registered on this forum because of the mercedes-savvy people on here. I hope you can help me with my current problem....
Well it started when i swapped the engine in my 1985 380sel and swapped in a 1987 420 engine. The engine was known to be good. I swapped the injection from the 380 and put it on the 420 including the fuel distributor and all the sensors. The car has spark and all. But it will not start. It is flooding itself in 3 or 4 cranks of the engine. I can crank it with the fuel relay in, then take the fuel relay off and it will start after the fourth crank but it will only run for about 4 seconds. I am very new to the cis injection on these cars. I know it is something simple. I know the engine was good. When you crank the engine, the pump is on THE WHOLE TIME you are cranking over. I checked the fuel return line and its fine. Also, to verify it is flooding out i toook all the spark plugs out and cranked it over. A whole bunch of fuel is coming out of the cylinders. It is like its WOT or something. I dunno but it is WAY more than it should be. What would cause this???? Please help me i would greatly appreciate it.
Patrick

you should have converted the 380 fuel system over to the 420 style. but it sounds like the fuel didtributor may have a binding plunger that is stuck open

so a binding plunger stuck OPEN will cause a massive amount of fuel delivery at cranking??? Also the plenum is hard to push down, but maybe it is supposed to be like that????? I WAS thinking of converting the 380 injection to the 420 but what would you need to convert it???
THANKS AGAIN

A couple of things come to mind...

Constantly powered cold start valve.
Fuel distributor plunger incorrectly set or stuck in the 'down' position.

Remove an injector or line and turn on ignition.....if squirting fuel, the distributor head needs fixed.


Air flap will resist being pushed down if fuel pump running. It will feel like there's a spring pulling it back.


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hmmmm. a fuel plunger set incorrectly will cause flooding to the point of not starting???

If I am reading this correctly, you put the 380s FI setup on the 420?

How long did the 380 sit?

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Patrick, I'm wondering why did ou not just use the 420's FI system? I'm just asking for my own information. That seems like the logical thing to do to me, but I have a lot to learn about such things. Was there a problem with that component?

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well i dont think it is a simple swap of electrical, so i am told. I would have if it was that easy. Unless i was fed a bunch of BS by that person. If anyone would know about this it would help immensly. But if i thought it was a straight swap, i would have done it. I think the 420 uses more modern electronis therefore it wouldnt be a straight over "swap". On a 420 you have to worry about the EZL and there are more sensors on the 420 than the 380.