S.L.O.W. Mode

[Incorrigible]

Can anyone tell me if the alarm is supposed to sound when the engine goes into S.L.O.W. mode?

My understanding is that S.L.O.W. mode is caused by overheating, and this is determined by the temperature switches on the cylinder heads. I am assuming this is the same switch(es) used to trigger the warning alam (constant sound)

Engines are J225TXESS - 1990

 

[ezeke]

Re: S.L.O.W. Mode

Overheat closes the circuit on one of the temperature switches (tan wire) in the cylinder heads. This activates S.L.O.W. and sounds the constant alarm at the same time.

 

[Rick.]

Re: S.L.O.W. Mode

Please correct me if I am wrong but I though SLOW would also happen it your oil tank went empty and if your oil quit pumping as well. Rick.

 

[ezeke]

Re: S.L.O.W. Mode

No, in fact the system has a blocking diode specifically to prevent interference from the VRO/OMS warning system. [See the wiring diagram and/or the function tests in the ignition section of your service manual]

 

[boobie]

Re: S.L.O.W. Mode

As was said SLOW meaning speed limited over heat warning. Back in those days the only warnings you'd get if you had no oil was 1/2 second beep on and off or low oil a beep every 40 seconds. These came from your warning horn. SLOW was for mainly overheat.

 

[d.boat]

Re: S.L.O.W. Mode

Please correct me if I am wrong but I though SLOW would also happen it your oil tank went empty and if your oil quit pumping as well. Rick.

I can't remember ever reading that or seeing it in my manual. The SLOW mode is only triggered by overheat, the low oil and no oil alarms are just different intermittent alarm patterns. I'll double check.

 

[Incorrigible]

Re: S.L.O.W. Mode

Last nights testing shows:

Both overheat switches, when grounded, activate the warning horn.

When running at WOT and having the primer bulb pumped, the problem goes away and she runs well.

Oddly enough, the first two times up to WOT the warning horn went off intermittently. It would sound, then sound again, as though it was just on the verge of overheat.

The rest of the times it was tried, the engine would still sputter at higher rpms, but there was not warning horn noted.

Water coming from the telltale was hot.

 

[ezeke]

Re: S.L.O.W. Mode

While it should not cause S.L.O.W. to activate, your vacuum switch will cause a constant alarm to sound if you have a fuel obstruction. A fuel obstruction will be before the fuel pump and could also be the cause of your instability at higher RPM.

 

[Incorrigible]

Re: S.L.O.W. Mode

I plan to clear the fuel filters tonight, and run the engine on a portable tank directly attached to the fuel filter to determine if this makes a difference. That would lead me to believe that there is a fuel obstruction and allows me to start that search.

The fuel system is comprised of two fuel cells, each running to a fuel selector valve, one for each engine. This allows me to run each engine on either the same or different tanks. I have tried every combination of tanks (one on each, both on the foreward, both on the aft, etc) with no change in performance. From the valves, a fuel line runs to a fuel/water separator, then to the fuel filter, then into the VRO2.

The problem was more pronouced, until I removed the anti-siphon valves. This brought the engine RPM where the problem occured from roughly 3500 rpms to 4200ish. Prior to removing them, the primer bulb would be completely collapsed when running above 2400rpms, leading me to believe that the fuel pump is trying to draw fuel with at least some strength.

Thank you to everyone who has replied to these posts. This is an EXCELLENT resource when trying to troubleshoot!!!

 

[ezeke]

Re: S.L.O.W. Mode

Redundant fuel filters may contribute to the problem and are not necessary. The water separating filters alone are adequate.

The more frequent problem is the pickup screen, just because they are at the bottoms of the tanks where most of the debris is.

Sometimes the vent screens on the outside of the hull corrode and can cause problems.

 

[Incorrigible]

Re: S.L.O.W. Mode

Do you have any suggestions for how to:

Find an air leak in the fuel system (at a connection point or along a fuel line)

Clean out the bottom of a fuel tank permanently mounted in the bilge (I can access the fuel level senders and the fuel fill/taps on each tank) and the pickup screens?

I'll double check the fuel vents. They are newly installed within the last month, but I've had wasps start building mud nests on an airplane over the lunch hour.

Again, thank you very much.

 

[ezeke]

Re: S.L.O.W. Mode

On the engine side of the primer bulb you can apply a little steady pressure and look for leaks that will become air leaks when the fuel pump is working.

Some use clear hose temporarily to look for bubbles.

The hardest problem to detect is degraded pickup tube that allow air to enter when the fuel level drops as on turns.