21V with Assault 325 and MEFI5 - "no start" condition for 2 months

[Nedster]

Hi all,
I have a 2007 21V with the 325hp Assault engine that I haven’t been able to start for 2 months despite lots of troubleshooting and replacement parts. Between me working on it, a few mechanically minded friends and a marine mechanic with a Diacom unit we have still not managed to isolate the problem so I am hoping the wisdom of the forum can suggest some further avenues before I go crazy, and the family disowns me.

Being in Sth Hemisphere we are boating now, so we last used it on Dec 26th and it started and stopped perfectly all morning. It was cleaned, flushed, refuelled and put into undercover storage. 2 weeks later we took it camping to a river and it just cranked and cranked but wouldn't start. Heres what we tried;

• With limited tools we determined we had the fuel pump priming, fuel pressure at the rail, but no spark. We have not yet actually measured Fuel rail pressure (just tested it squirts from the schrader valve).
• Visually inspecting the electrical items we could see the distributor cap and contacts were a little corroded but not cracked or damaged, however the coil looked heavily corroded so concluded it was breaking down and made a mad dash to the closest dealer 30 Miles away to get a replacement. Sadly back at camp and fitting it up - still no start
• Next morning we came back to the dealer to get what we thought was the coil pickup for inside the distributor (now know its the camshaft angle sensor) – sadly still no start
• We gave up on the boat, and towed it home for proper diagnosis. After downloading the MEFI5 manual we started again with multimeter in hand using the step by step guides.
• We found no blown fuses in the engine bay or under the dash
• We found the relays had power either side of them
• We found the ECM had power and ground in and out when testing the 6 pin DLC and their respective ECM pins
• We had power to the coil
• we had continuity between the coil and the module
• We had 5V at the CKP sensor
• We had gnd at the CKP sensor
• We had continuity between the CKP and the ECM
• We tested the injectors with noid lights - all good

At that point we thought it was probably the CKP sensor but decided to send it to the mechanic to scan rather than just throw more random money at the problem.
After restoring all connections we gave it 1 more try and it fired up instantly. Not being on a hose at that stage and being late, we stopped the engine. A day later I set it up on the hose, started it fine, and proceeded to look for loose connections in the CKP wiring. Finding nothing I let it run for 15 minutes to flush then stopped it.

On the next weekend, I decided to do a major check of wiring and clean rust and corrosion around the ECM and relay bank. When I removed the ECM from its plate to clean that I discovered a clot of salt build up between the plate and the ECM which I removed only to find a small hole in the back of the ECM. Looking through it with a flashlight I saw no evidence that anything had entered the hole and affected the boards inside so cleaned the area, sealed it and re-installed it.
The boat however has never restarted. The Dealer has suggested that rarely do ECM's turn out to be the issue but it cant be excluded.
IMG_4660[1].jpg

My mechanic (ex main dealer) who has worked on the boat for the last 4 years had it for several weeks but could pull no meaningful codes and surmised broken wires in the harness somewhere or an ECU, but couldn’t find any wires at fault.
I took it back so I could tow it to the current dealer in case they could try swapping parts in from old stock but was told they don’t have anything left from that era so I would have to buy new anyway.

Just to exclude it as a factor I have now replaced the CKP also – still no start.

Since the harness is neither simple or cheap and the ECU just incredibly expensive out here I want to I be sure before parting with more cash. The codes that did appear were as below, however I’ve had other people suggest that many of those were old codes that were the result of us removing and refitting electrical plugs to test, or low battery could explain SPN66014.

SPN636 - CKP sensor
SPN65541 - IGN coil
SPN65601 - TPS sensor
SPN65602 - TPS sensor
SPN65604 - Pedal Position sensor
SPN65610 - TPS sensor
SPN65701 -
SPN66014 - Power train relay

There is an outside chance that through the importer, I can find someone near me with a similar generation MEFI5 that I can persuade to fit my ECU to their working boat (as if their boat then starts with my ECM we can eliminate the ECM as a factor), but i'm not holding my breath waiting.

Can anyone suggest some other areas to investigate next?

thanks from Australia
Tpnedster