Thunderbolt V - No advance

[John_S]

96 1/2 Mercuiser 5.7 Alpha Thunderbolt V without Knock module.

Ignition is not advancing as rpms are increased. Get about 5 degrees of advance, and stops. The following was done/observed:

- Set timing in base mode.
- Observed timing during idle (not in base) and T5 appears to be working.
- Advance throttle to 2K rpms, go to 5 degree advance and stops.
- Rev a little higher, and stays at 5 degree advance.


- Followed service manual T5 flow chart, and everything is fine (flow chart seems to be for non-running engines)
- Gray Tach wire ohmed out from module to coil. Console tach and shop tack work fine, as well.
- Read 7.5VDC on puple/wht wire. Manual says 8-10V but that is for T5 w/knock module. Temporarily provideing correct voltage did not get timing to advance.
- Ground at module good.
- Gray wire tach connection cleaned and tightened.
- Substituted a 5.7LX/Bravo module, no performance change. (did not observe timing)
- During problem, majority of boating has been limited to 1K putting around lake. Can still get on plane, and occaisionally it "feels" like the timing is kicking in. ( a kick in the pants, for a second)
- Removed cover on module and complete circuit board is still covered with clear gunk protector - no corroision at all. No obvious "burn" signs, all small connection wires attached to pins.


Due to the high cost of the replacement module kit (807264A01) ($500) want to make 100% sure the module is bad. I still think there is a strong possibility of it being a bad connection or wire in harness. Outside of attaching small test wires to the pins, to get in-circuit readings, and ohming out each individual wire and ground of harness, not sure if there is anything left. I do plan to retest the Bravo module with the timing light, too. Anyone have similiar experiences or know of anything else that should be checked?

 

[Fun Times]

Re: Thunderbolt V - No advance

First I would make sure all the wires at the module have a good connection in the wire harness where it plugs in to the module, Also try running a new ground to the module if you can, And make sure there is no paint in the area of the grounding of the module, Then try the other module while looking at the timing with a timing light. Also just for the heck of it you could try unhooking the shift interrupter switch with two wires coming out of the switch that is mounted to the shift cable bracket area, Just to make sure that the switch is not cutting any power out some place all while looking at every thing with the timing light hooked up.Good luck with it

 

[John_S]

Re: Thunderbolt V - No advance

While not listed, I did disconnect the shift interupt and timing still did not advance.

I do have renewed interest in that wiring. I noticed that the shift interupt wiring is included on the Merc engine wiring diagram but absent from the T5 wiring diagram. I think if I jumper the shift interupt to the wht/grn wire coming from the distributer, that it should cause the interupt to work with the bravo module. It looks like the T4 were wired this way, where the T5 was done by connecting it internally within the module.

BTW, even though I knew it was likely to happen, when you go to dock and the drive does not come out of gear, it can make your heart jump.

I do plan to take some contact cleaner with me, on the next trip. While the module pins didn't look corroaded, want to clean them up to be sure. I'd like to test the continuity with it plugged in, and that is my intent at the base of the pins.

Overall, it just seems to act like a wiring/ground problem vs bad ICM.

 

[kwoolard]

Re: Thunderbolt V - No advance

Just curious as to what kind of WOT are you reaching with only 5 degrees advance?

Did this just occur suddenly?

If the flow chart checks were good, it's either bad connections or bad module.

Keep us informed on the progress, kind of interested in the outcome as I had a similar problem that turned out to be a cracked coolant temperature sensor. The crack in the temp probe was allowing coolant to be pressurized up through the electrical wire running to the module and was shorting the module out.

 

[John_S]

Re: Thunderbolt V - No advance

Just curious as to what kind of WOT are you reaching with only 5 degrees advance?

I have not pushed it to WOT with this condition. Only have been idling to 1000 rpms putting around lake. I have carefully put it on plane and to 30mph a couple of times, every outing. It takes more throttle to get on plane than normal. When running right wot is 55-58mph.

Did this just occur suddenly?

Started on one outing, ie needing more throttle to get on plane. The mechanical fuel pump went on same outing. That was replaced and found that there were two problems.

If the flow chart checks were good, it's either bad connections or bad module.

If I get the Bravo module to advance I'll be convinced it is the module.

Keep us informed on the progress, kind of interested in the outcome as I had a similar problem that turned out to be a cracked coolant temperature sensor. The crack in the temp probe was allowing coolant to be pressurized up through the electrical wire running to the module and was shorting the module out.

That is an odd one. There wan't a drop or hint of moisture in the module connector or inside the module. According to Merc wiring diagram, the sensors are wired to but not actually connected to module. "NOTE: Tan/blu wire not used at distributer." It is part of the audio warning system.

Certainly will report progress. I will have a little time on Monday AM and have a number of checks planned to perform. Otherwise, probably only have 1 or 2 more weekend chances before pulling it off the water for the season.

 

[kwoolard]

Re: Thunderbolt V - No advance

My problem was the "Yellow" wire running from the temp switch to the module. But I do believe that the "Tan/Blu" wire is also wired into the module as well, because the "Mean-Best-Timing" feature monitors that signal.

 

[dave4151]

Re: Thunderbolt V - No advance

This may help you figure it out.
Well it may have if it wasn't over the size limit.
I have a TB 4 and 5 pdf that may have a different set of testing steps.
PM me and I'll mail it to you.

 

[John_S]

Re: Thunderbolt V - No advance

My problem was the "Yellow" wire running from the temp switch to the module. But I do believe that the "Tan/Blu" wire is also wired into the module as well, because the "Mean-Best-Timing" feature monitors that signal.

I was refering to the switch and not the probe for the dash gauge. The service manual does not show any yellow wire from the temp switch or on the T5 wiring diagram. The manual may be incorrect or yours is a different year, etc. One of the checks I have planned was to trace out the tan/blu to see how it is actually wired.

The temp switch, oil pressure switch, and drive oil switch are all in parrellel. The fail condition is switch closed on any of them. My alarm is definitly working and stops as soon as there is oil pressure. I also had removed the wire from temp switch and there was no change to timing. The temp switch also read open with the meter.

 

[John_S]

Re: Thunderbolt V - No advance

This may help you figure it out.
Well it may have if it wasn't over the size limit.
I have a TB 4 and 5 pdf that may have a different set of testing steps.
PM me and I'll mail it to you.

PM with email sent. Thanks.

 

[kwoolard]

Re: Thunderbolt V - No advance

John,

Did you ever figure this thing out?

 

[John_S]

Re: Thunderbolt V - No advance

Not yet. I did not get the debug time I wanted on the last trip. I will be going back up near the end of the month to bring the boat home. I can get more done there, as well. I will update with whatever I find.

 

[John_S]

Re: Thunderbolt V - No advance

On Thursday, gave up on waiting for the weather, work schedule, and other priorities, and went ahead and completed the winterization. The debug will now have to wait for spring. I will re-activate the thread then.

 

[John_S]

Re: Thunderbolt V - No advance

Final Update and Close-out.

My original T5 module seemed to behave "better" this spring. I was seeing advance while reving on muffs. Performance on the water was better, but still lacked upper RPM power. Broke down and bought the 807264A01 retrofit kit. It requires changing/modifying the connecter harness. The install went fine and now have the upper rpm power back. I was able to purchase the kit for $360, which is somewhat of a savings vs $400-$500 list. Still, I thought long and hard about changing to an aftermarket ignition system. If it wasn't in the midst of boating season, might have gone that way.