1998 Merc 150 EFI idles fine but stalls when shifted into gear

"I've had this problem sin

"I've had this problem since it was new. The motor will start just fine and will sit on idle forever but once it is shifted into gear or given a little bit of throttle in gear the motor will stall and quit. I have brought it to the dealer 4 different times and they have replaced the spark plugs, wires, and fuel filter but the problem still persists. When the dealer starts the motor they say that there is no cut-out and works properly, but I bring it to the lake and the problem still remains. One thing too the problem only occurs when the motor is cold and after initial start up when I actually get it to keep running the problem dissappears for the rest of the day which includes repeated start ups and cruising. The battery is brand new and completely charged and the gas bulb is hard. Any help is appreciated."

"Gday Danny
There are a lot o

"Gday Danny
There are a lot of things to check with this kind of problem but you should always start with the basics, comp, fuel and ignition it doesn’t sound like this but you want to check anyway just to be sure. Some efi mercs idle at 1000-1100 rpm, i think it was the merc ecu (not motorola) with CDMs (not packs). You may have a faulty head temp sensor (tells ecm engine is at operating temp when it is actually cold) not providing enough fuel for cold start up, a quick test would be to disconnect it, the ecu will add 40% to the base fuel delivery, the sensor should read 2000 ohms at 10 DegC and about 500 ohms at 50 DegC. The other thing to check is your TPS setting it should be at 0.24v-0.26v closed throttle. You will probably have to go through and do a proper efi setup, to do this you would need to grab yourself a workshop manual and go through the entire setup systematically.

Cheers Spanaman"

"Danny,


The fact that it

"Danny,


The fact that it stops happening once you get it to keep running, would cause me to suspect a fuel problem , but I would check the spark also. If you can not get spark to jump a 7/16 inch gap, there is an ignition problem.

It looks like you have a typical stator, trigger, switchboxes and coils, but since I do not have the actual model number I can not be sure. If so, the stator has both a low and a high speed winding. These would be the blue and red wires to the switchboxes; one pair should have a white stripe. Check the voltage (A/C) on these terminals at the switchboxes and see if it meets the specs.

That fuel supply can have quite a few simple problems before the fuel gets to the high pressure pump. Make sure you are getting flow to the vapor separator first as you squeeze the primer, and that the float chamber is filling. Make sure that fuel is getting to the electric pump.

Tony"