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

[CJD]

I would be prone to blame the ECU. If it got wet enough to eat a hole through the case, it likely had enough moisture to damage the internal circuitry. Add to that the fact you have pretty much replaced every other electrical component...it just seems the most likely problem.

Maybe you can find a similar boat with an owner willing to swap the ECU for a test?

[Nedster]

Thanks CJD,
thats my fear also, yet it supplies signal to all relevant sensors that are needed. Ive just had a chance to measure the fuel rail pressure and primes to the 60psi plus range and stays there while cranking so its getting signal from the ECM at that point, but still no spark from the coil.

[2500HD]

[*]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[/LIST]
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

It would be extremely rare to have the ecm go out, but things happen.
I would bet its in your wiring. Check each component 1 at a time otherwise you won't know which it is for sure.
My money lies on the cpk sensor since there are only a couple of sensors that would not let it start, and you only are getting 5volts to it when you need 12 volts.


When you turn the key and start cranking the engine the crank sensor gets 12 Volts on Circuit A and ground on Circuit B.
A round ‘target wheel’ attached to the front of the crankshaft and positioned so that it rotates above and in close proximity to the crank sensor, starts to rotate.
As the ‘teeth’ on this target wheel pass by the crank sensor, they start to activate the sensor into creating an ON/OFF Pulse.
ON is when a tooth on the target wheel passes directly over the sensor, which induces the sensor to create and send a 5 Volt DC pulse.
OFF is when that same tooth passes completely away from the crank sensor, which causes the sensor to drop the voltage down to 0 Volts.
The PCM uses these ON/OFF 5 Volt pulses to start activating the ignition control module and a host of other things to get your vehicle started.

[2500HD]

Also take a look at your Distributor Mounted Ignition Module

[CJD]

I thought the crank sensor was self generating? If 5v is supplied to it, how does the ECM read the signal from the sensor? It should have a ground wire and a signal wire. Signal would be 0v until the CP sensor starts generating a signal. It would then be a pulsed signal.

Other sensors, like temp and manifold pressure are not self generating, so they need a voltage supplied, and the ECM reads the resistence to that voltage through the sensor.

So, unless I am off base, which wouldn't be the first time, I would still think ECM is providing power to the CP sensor when it should not. Plus, even though ECM's rarely fail...I think it is rarer still that they would have a hole corroded in the case.

[wolff]

I have the same boat and when it was new I would take it to the lake and run it shut it off and it would not start or sometime would not start when we got to lake than haul it home or to the dealer it would start right up not problems. we were getting all kinds of codes that did not make sense they swap around a bunch of electronics not luck Long story short The dealer said were there was a loose ground connection on the motor (something dealing with the computer/electronics would not let it fire) . Boat always cranked but would not start.

[Nedster]

Thanks to all for responses.

I have the boat out the front and will recheck the voltage i noted to see if it was 5V or 12V at the CKP. I am also planning to chase down the ECM earth but am not sure where to find it (is it off the block or does it return the battery?). While i didnt explicitly note where we use our boat, the description of salt may have helped point out that its mainly used in brackish waters so there is corrosion on metal surfaces and a bad earth could be a culprit. This is countered by the fact that there is a good earth being presented on each of the ECM earth points of the harness.

I've also been offered the use of a Diacom unit for a day next week which means i can also try some of the MEFI troubleshooting steps where they ask you to check for certain signals (eg RPM at cranking as indicated from the CKP) so hopefully that may offer further pointers.
Thanks for the suggestions.

[carlossa]

Hey Ned
I've been down a similar road and it turned out to be fuel pressure related. MEFI 5 is very fussy, if you get a +/- 5-8 psi variance of fuel pressure it can frustrate the hell out of you. I had a problem of too higher pressure and the oem fuel pump was tripping the thermal on the fuel pump relay before it even started. The only way I could get it to run was to unplug the throttle body and it sends the rpm to around 1200 and it runs really rich. On the fuel pump mount there is a Bosch component that regulates the fuel pressure. Its weird that it wont throw a code. I have a spare Crank sensor I could post to you if it helps. Where in Aus are you?
Regards Carl

[Nedster]

Hi Carl,
I've been chatting to the Supra guys in Nowra and they mentioned fuel pressure sensitivities also. Yesterday we managed to connect it to a gauge and when primed it was around 60psi, and while cranking it was spiking from about 58 - 65 (?) but not cutting out. This seems to be within spec so am chasing other things now.

I just changed the Crank sensor on Monday this week hoping that would solve it, but it made no difference, and tonight i found the common earthing point on the engine block, pulled all wiring off it, and gave it a good clean with a wire brush and some emery cloth. Still made no difference.

I'm based on the Nth beaches of Sydney and am now chasing a similar boat to try an ECM swap just to eliminate that as an issue. Apparently anything in the range with the 325hp Assault and MEFI 5 would make a viable donor (including Malibus).

Any other ideas I'm all ears
Cheers
Ned