Pliant

Well I told you 100 posts back the 4 has 3 ground and the 3 has one.

nunnink23

I know but I counted all three grounds coming out of the 4 connector. All three attached to that loop connector and all the had cotinuity. I just don't know wtf that other 10 pin connector is for. Esp since it only has one active pin and that's not the pin that connects to that strange other harness

BUP

I do not have any instructions about the conversion that I am able grab. Most of my stuff is in storage.

Mercruiser, Indmar and more have the same conversion to.

Volvo used MEFI 1 , MEFI 3 and MEFI 4 then went to E controls ECMs in that order.

The Mefi 3 is NLA for many years now thru all of the OEMS - hence the reason for the MEFI 4 Conversion.

What I remember

your pics 428 that ground wire first pic as I asked before - needs to mount actually on the flywheel housing bolt where no other ground is connected. Its needs to be all by itself. Next Clean paint off for good connection. Use dielectric grease.

all power completely off and or unhook batteries if needed. NO power

Mount the MEFI 4 the same as MEFI 3 with bracket

connect the J1 and the J2 connections on the crossover harness

Mount the coil driver bracket to relay bracket - do you have this ???

mount coil driver - do you have this ???

connect coil driver harness to crossover harness then to coil driver - again do you have this ???

route Y harness next to cool fuel now this is the part I am not sure of but I guess disconnect engine harness from the fuel pump which one ???? check connectors and follow this next step to help.

Connect male connector of the Y harness to the fuel pump and then connect the female connector of the Y harness to the male engine harness connector.

Next I take it your IAT sensor is mounted thru the flame arrestor is this correct ??? most likely back side is this correct ? then you need to find the correct connector for the IAT sensor and plug that in.

I think this should cover it - I THINK

Your plugs in and that ground need to be properly installed and well connected.

I will think if I forgot something.

Most people are not doing the conversion lately because the expense of it about 2500 to 3300 K OEM pricing. then the labor for the install.

BUP

Hate to tell you all OEMs require a cranking battery only of the proper cranking amps MCA to start and run the engine. They also have been listing no wing nut connections for the battery terminal connections to the battery. This has been common knowledge for years now with EFI / MPI engines on the marine side. Just saying. With service and new boats we always had to follow this and to keep all warranties in effect thru the marine OEMs.

Also never ever turn your battery selector switch / perko switch when the engine is running - have you done this or turn it while cranking the engine over ?

ECM's like proper steady voltage plus being unrestricted and not interrupted.

nunnink23

BUP - I'm not sure what you mean by the coil driver, or the Y harness to the cool fuel pump. I have the original harness powering the fuel pump. The only connector without a home is that one I took a picture of. I don't think it actually has a home, but who knows.

I've never switched the batteries off or from one to another with the ignition on. That I can be sure of.

The ground strap you were talking about is connected to the flywheel housing stud, along with the negative battery lead, and a few ships system grounds. The ground was checked between the stud and the battery, and .2 ohms recorded. I'm not sure if there is any way for that reading to be misleading, as I am not an electronics guy. I know with voltage you can read 12v on a wire, then put a load on it and it could drop to 3v, etc. if the wire has a short or high resistance.

Not sure if the same applies to grounds and checking for resistance.

nunnink23

Wait a minute.... I think we just found the problem. And its operator ignorance.

I still want to know what you mean by the external coil driver, but the thing I posted a pic of is the Y harness you are talking about. I KNEW that thing had to have a home, but the fact that it only had one active pin made me suspect. I just found this: http://river-service.ru/uploads/pdf/...formatsiya.pdf

That document states how to connect the Y harness to the cool fuel pump! That one pin must be a ground wire, or maybe even a 12v IN wire to the ECM, and its just tapping into the fuel pump for power. I am so excited. The front of my engine is off right now so I cant test it tonight, but that must be the problem!!! I need to trace that wire back to the ECM and see what its purpose is.

If this was the problem, then this case is going to really exemplify the point that its "always something small and stupid" that cause these massive perplexing problems.

In the meantime, does anyone know what the external coil driver is?

28Eliminator

You can't always measure a bad ground with an ohm meter. Take the wires off and clean them all, put dielectric grease on them and reattach..02ohms could just be the meter. I think the 2 fuel pump style connectors you posted those pictures is the Y that BUP is talking about and should be inserted between the harness and your fuel pump, but we'll let BUP confirm that! This whole mefi 3 -4 conversion is very messy, and it sure would be nice to see the documents for the conversion. I suppose you didn't take pictures of all of this while you we disassembling?

nunnink23

I had a bunch, but not of the wiring because I thought it was standard mefi III. I will document this very well when I am finished and leave no confusion.

SB

Also (this just popped into my head as I'm diagnosing an ill running Buick) I believe a while back you mentioned it was grounded to the main ground stud thru the bellhousing with the other grounds.

Computers, and other delicate electronic components (like MSD ignition boxes and etc) should have their own seperate ground.

nunnink23

I will do that as well then. I have plenty of spots I can bolt it to. I will use a brand new bolt, and make sure it's a Clean ground. I'll clean up all the grounds again