R Addiction

Mats, You said you hooked up a scan tool.....Was it your tool or did you have a Merc certified tech do it? Do they show codes? I'd love to have one but was told that you have to be a certified Merc Tech to get one

Could be a ignition coil heating up and like Insptech said possible module heating up and breaking down.

mats

Hi. I borrowed the scan tool from a local merc shop here. It is a very simple tool, basically a processor that communicates with the ECM, a display and a few buttons. It shows trouble codes if any as well as some 20 parameter values (rpm, vaues from all the sensors, ignition advance, knock retard, etc) The tool is self explanatory. I would say that a wrist watch is more complicated. If you want one I think the main problem is the outrageous price the will most likely charge you. http://216.230.203.183/marine/mtspec.htm

R Addiction

Thats not too bad....Considering the cost of a Snap On Modis, or a GM Tech 2 Thanks for the link. I'm headin' out to the bay. I'll get some pics of the fittings for the fuel pressure.

Dave_N

R Addiction,
Did you know you can get trouble codes with just a 12 volt LED and a paperclip? I can give you the details if you want.

mats,
I think we have been over this before, but if you have a MEFI1 computer and Keihin (1993-98) injectors, you should be running a 36PSI regulator (860349A1), not a 43PSI.
Dave

mats

Hi Dave. Yes, we have been over this one before. Based on what we concluded the last time I put in the 860349 A1 (which Mercury claims is 30 psi). But then the engine started to misbehave as described in this thread and I thought for a while that it might have been the wrong regulator. I then threw in a 861126A1 (43 psi). However the problem persists. Now I know for sure that it is MEFI-1 SW and the regulator should most likely be the 860349A1. But the question remains , what makes the engine lose power? I beginning to think that it is ignition related. When I hammer, the tach shows that the rpm is going down while the engine and boat slowly picks up speed. It feels like the engine is running on maybe 4 cylinders during the acceleration?! What drives the tach, is it the ECM ? can the ECM supress eg each other pulse to the primary side of the coil and tach in certain situations?

Dave_N

One thing you might check it you have not already, is check for Knock Sensor wire or Ignition Control circuit wire touching a plug wire. Also, have you tried it with the tach disconnected?

Dave

mats

I have tried with the tach disconnected. I will take a look at the Ignition Control circuit. I guess you suggest that the plugwire could induce a current/voltage in the Ignition Control circuit.

Thanks for all your input. This was a tricky one......

R Addiction

Mats, Here are the pics....Hope they help

mats

Thanks for the pictures R Addiction. Now I know how it has been done. Great.

Pismo10

This is a perfect example of the downside to EFI, if this were a 1980 motor with points and a carb you could diagnose and fix it in about an hour.