swapped 420 into 380.....floods now plz help
 

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.


.

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? :confused:

How long did the 380 sit?

Did you get the 420's ECU to go along with the 420's engine or are you using the 380's ECU?

That's the other issue, wrong KE in there (and wrong FD). It's the last piece I need for my 560 swap into the 420

Also check and make sure that the airflow sensor plate is central and not jamming on the side of the air intake. It should sit higher than the thinest part of the air intake before cranking.

Are you doubting my veracity ?


.

lol no . I have the 420 engine in the 380 body. The 380 fuel injection and complete intake manifold is on the 420 engine. BUT i HAD to use the 420 distributor. So i dont think i would NEED a 420 comp or fd if i was keeping the 380 injection. Am i correct?
Thanks again

You need the 420's computer and timing unit (I forget the names, it's 5am). Not to worry, they're common and maybe $50 total in parts.

im just curious, WHY do i need the computer and timing unit from the 420????
If i am using the 380 intake manifold and Fuel Distributor shouldnt it still work???. The ONLY difference is the size of the block and the distributor. I just dont understand what you are saying, and im swear im listening. But i would think you would need ONLY that 420 comp and timing unit ONLY if i had the 420 injection setup on it. Remember, the car is an '85 380sel. I understand i would need that 420 timing unit and ECU if i had the intake and sensor setup from the 420. All i want to do is make my motor work with my current 380 equipment and sensors. The ONLY thing i have that is from the 420 is the distributor (which shouldnt make a difference it hooks up the same way. All i know is the damn car floods itself the INSTANT u try to crank it. I mean, WHOOSH!!!. Flooded in 2 cranks. It is getting spark. Im about to give up, but i knew there were very knowledgable people here. Please any thoughts or suggestions would help me.
Patrick

380
 

if you are using the injection setup from the 380, i presume you have installed the 380 in take manifold together with the warm up regulator and 380 fd. Then you dont need the brain from the 420. if i where you i would stick the ignition distr. from the 380 in the 420, and hook it up to the ecu from the 380.

the flooding on both banks means that the injectors are are letting in to much gas. this can only happen if your fd is faulty, but if it worked just fine while it was on the 380 perhaps the plunger piston is stuck.

if you depress the air plate does it move with a resistance to the touch, if i where you i would remove the fd, and check the piston for movement.

just my 2c

well. When the key is on, the plunger has resistance instantly. You dont even need to crank it. It takes effort to push it down. The piston is inside the fd correct??? i mean it is like a variable resistor and adds fuel according to the plunger position. I am sorry for bugging people about this, but i would HATE to give my baby up to charity and i swear im almost to that end....