RV-12iS Fuel Pumps Not Automatically Shutting Down After Engine Shutdown

[Bob Y]

After getting nowhere with Van's support on this subject (they wanted me to tell them how the fuel pumps shut off), I'll reach out to the group to see if any other 12iS owners have experienced their fuel pumps continuing to run after engine shutdown. Yes, I have implemented SB-00058 for the new HIC module, and SL-00072 to replace the start computer. And no, the EMS BBS is not on. I've had them continue to run twice out of five flights after shutting down the engine; it's worked fine for over 2.5 years. This in of itself isn't the end of the world, but we spent a lot of time and money to replace components to force them to shut off in the event of an emergency landing, so I would like to know if something else might be going on. So, am I alone in experiencing this issue?

 

[KEG]

Cannot help with your problem but I just checked Van's online support page for 12iS SB's and could not fine a SB-00085.

 

[Bob Y]

Cannot help with your problem but I just checked Van's online support page for 12iS SB's and could not fine a SB-00085.

Grrr. Thanks for pointing out my dyslexia - SB-00058. I’ve edited my original post. Glad to see someone is reading them.

 

[Tony Kirk]

Sorry, I don't have an explanation for your issue.

It might be helpful if you could capture the HIC Module Diagnostic LED color when the fuel pumps keep running after engine shutdown.

The LED color "decoder ring" is in the WH-0013X schematic in the HIC diagram on page 9.



Let us know what you find.

 

[Bob Y]

Thanks for the suggestion, Tony. You know how tough it is to get back there, and with it being an intermittent issue, not able to predict. I’ll have to see if I could possibly run my borescope through a hole in the avionics shelf and secure it to the harness pointed at the LED to try and catch it. I’ll see what I can do.

 

[mbell]

My pumps run independently of the lane switches. At shutdown they are still running till switched off. This seems like the way it should function. My kit was new enough to not be affected by SB-00058 but if they are supposed to shut off when the lanes are off then maybe it is affected. There's nothing in the POH about this except to turn off the pumps after the engine is shutdown.

 

[Bob Y]

Not sure what to say, Mike. Attached is from SB-00058. Coincidentally, a friend with a 12iS saw my post and called me. He too believes his have always run after engine shutdown, despite having implemented both SBs. He’s going to verify within the next couple of days and get back with me. And yes, even if the pumps automatically shut off, you’re still directed to turn off the switches so the pumps don’t draw high in-rush current when the master is switched on for the next flight.

As I said in my initial post, they worked as designed for over 2.5 years before intermittently remaining on.

 

[mbell]

Not sure what to say, Mike. Attached is from SB-00058. Coincidentally, a friend with a 12iS saw my post and called me. He too believes his have always run after engine shutdown, despite having implemented both SBs. He’s going to verify within the next couple of days and get back with me. And yes, even if the pumps automatically shut off, you’re still directed to turn off the switches so the pumps don’t draw high in-rush current when the master is switched on for the next flight.

As I said in my initial post, they worked as designed for over 2.5 years before intermittently remaining on.

Per my packing list, my kit was supplied with an AV-60009-2. I need to get in there and take a look to see if the unit is actually labeled as such, if in fact they are labeled at all. My connectors looked like the ones in the SB. There's so much detail in the Production Acceptance Procedure it seems like this would be included as something to check.

 

[Bob Y]

If your HIC has the aluminum wire-harness support bracket, it’s the -2 version. It also has the diagnostic LED Tony mentioned earlier. If you have convenient access to the LED, you might try, as Tony suggested, to see what color it is after shutting down. I’m going to figure a way to do that with mine.

 

[mbell]

I have the AV-60009-2 for sure, based on the aluminum bracket. Just got back from flying (and completed phase 1!) and the pumps remained on after both lanes were shut down. The LED was white. I'm leaning towards just replacing it. Not a lot of confidence in a flaky black box that has some control over both fuel pumps. It's easy to check the LED color with a flexible borescope. Just turn off the light and insert it into the unused data port cutout underneath the copilot-side panel.

 

[Bob Y]

No, don’t replace the HIC module…. Tony’s the expert, and will correct me if I’m wrong, but the signals that illuminate the LED are coming from the microprocessor on the ignition module. Remove the ignition module and verify there’s a 7.3 version number printed on the micro. If so, like mine is, there’s something going on in the ignition module that’s causing the FETs on the HIC module to continue in the on state, running the pumps. If not, see SL-00072. That’s where the attached photo came from.

 

[jrtens]

.....SL 00072

 

[Bob Y]

So, I’ve now screwed up the numbers for the applicable SB and the SL. So much for my credibility.

 

[Tony Kirk]

I have the AV-60009-2 for sure, based on the aluminum bracket. Just got back from flying (and completed phase 1!) and the pumps remained on after both lanes were shut down. The LED was white. I'm leaning towards just replacing it. Not a lot of confidence in a flaky black box that has some control over both fuel pumps. It's easy to check the LED color with a flexible borescope. Just turn off the light and insert it into the unused data port cutout underneath the copilot-side panel.

Bob is correct, you probably need to do SL-00072 and swap out the Arduino in the Ignition Module (AV-60007) to the 7.3 version. Here is the link to the part.

The HIC LED should be YELLOW after the engine is started. If it is WHITE then the Ignition Module Arduino is still sending the SBB (Start Button Bypass) signal to the (AV-60009-2) HIC Module. See the LED Color key posted above.

 

[mbell]

Bob is correct, you probably need to do SL-00072 and swap out the Arduino in the Ignition Module (AV-60007) to the 7.3 version. Here is the link to the part.

The HIC LED should be YELLOW after the engine is started. If it is WHITE then the Ignition Module Arduino is still sending the SBB (Start Button Bypass) signal to the (AV-60009-2) HIC Module. See the LED Color key posted above.

My Arduino was not in the affected group and it's labeled "7.3", but no orange dot for what that's worth. Hasn't displayed the behavior noted in SL-00072 but does leave the pumps running at shutdown, and the LED is white. Replace the Arduino?

 

[Bob Y]

I don’t think that would be the fix, since the 7.3 firmware will be the same in a new micro. Seems something else is going on. I believe 7.3 increased the voltage threshold which signaled the start computer that the engine was running, and would then time out. Maybe it’s still a little too low and maybe my voltage it on the threshold? I’d encourage everyone that’s experiencing this issue to let Van’s support know so maybe they’ll investigate if enough of us report it.

 

[rv12is]

I would love to see the source code for this micro. AFAIK it's operation is not well documented publicly. So, for now, all we have to go off of is 3rd party descriptions written by strangers on the internet...

Refer to the below excerpt from a post (https://vansairforce.net/threads/hic-module-rv12is.232043/post-1815733) by rcarsey

On the new and improved SL-000072 module, the arduino takes a snapshot of the bus voltage as soon as MASTER ON.. It then looks for a rise of 0.5v increase - which happens once the alternator is running. Once running, it removed the SBB signal. The only problem this new method has, is that I think its possible that it won't detect a 0.5v increase (perhaps the battery was on a charger, and the arduino was seeing close to the same voltage as what the alternator is outputting) -- and so, the SBB signal won't ever be removed. Not a huge problem, but your fuel pumps will continue to run after engine stoppage/crash.

Are either of you using a battery charger/maintainer that's disconnected shortly before starting?

 

[Bob Y]

No, I don’t leave the charger on my battery. I save my user-data logs after each flight. I’m going to try and find the ones when the pumps continued to run and check the voltages on starting to see what the transition voltage was when the alternator came on line.

 

[mbell]

I would love to see the source code for this micro. AFAIK it's operation is not well documented publicly. So, for now, all we have to go off of is 3rd party descriptions written by strangers on the internet...

Refer to the below excerpt from a post (https://vansairforce.net/threads/hic-module-rv12is.232043/post-1815733) by rcarsey


Are either of you using a battery charger/maintainer that's disconnected shortly before starting?

I don't leave it on a maintainer but have charged it multiple times the past few weeks working on the G3X.

 

[Tony Kirk]

As Rob says in the above linked thread, the Ignition Module Arduino (IMA, I just created a new TLA ) is looking for the 0.5V delta between the voltage measured when the master switch is first turned on until the engine is running and the generators have transitioned to the B-generator powering the aircraft bus. You must run the engine faster than 2500 RPM for a few seconds for this transition to happen. The IMA will stay in this "actively sensing mode" until the 0.5V threshold is crossed. If that condition never happens then the SBB +5V signal to the HIC is never deactivated.

If the initial EarthX battery float voltage is too high to allow the 0.5V delta to be sensed by the IMA, because the battery was recently charged (either by a battery charger or after a quick turn-around and engine restart [fuel stop, YE flight, etc.]) then I would say the system is working as designed. This condition would be indicated by a WHITE HIC LED. Maybe this is not as good as it could be, but it is within the parameters designed into the current 7.3 IMA version.

The previous IMA version (7.0) would time-out after 60 seconds and this caused many "no start" and "my fuel pumps don't work" situations. There was even a student pilot who was "stranded" at a very remote airport and the flight school flew someone out to rescue him, they "saved" him by activating the Emergency Backup Battery switch to start the airplane.

This is one of the reasons I designed the Diagnostic LED into the -2 version of the HIC module. If the HIC LED stays WHITE after the generators have transitioned then, for whatever reason, the 0.5V voltage delta threshold has not been sensed by the IMA and the +5V SBB signal is still being sent to the HIC Module. If this happens then the Fuel Pumps WILL continue to run after shutdown. What was Microsoft's response to this kind of unexpected behavior, "It's a feature, not a bug"

If the HIC LED is YELLOW (indicating the SBB +5V signal is NOT being sent from the IMA to the HIC Module) and the Fuel Pumps continue to run after engine shutdown, I would suspect the MOSFETS in the HIC Module have failed in a Shorted closed-circuit condition and continue to tie the A-generator and B-generator busses together. This has the same effect as having the Emergency Backup Battery switch activated. The fix would be to replace the HIC Module (or the HIC Module MOSFETS). I can't think of another condition that would keep the HIC MOSFETS active when the SBB signal is not present (YELLOW LED). If this happened then the fuel pumps would continue to run EVERY TIME after engine shutdown, not just occasionally as the OP said is happening in the original post.

Note: the EarthX battery has a very low self-discharge rate and doesn't need to be charged as often as a lead acid battery. Unless you are updating the EFIS or testing lights with the master switch on for longer than about 15 minutes I don't think a charger needs to be connected at all. Read EarthX's recommendations here, https://earthxbatteries.com/our-batteries/battery-charging/

Hopefully, this information helps you make an informed troubleshooting decision. Perhaps everything is operating "as expected" and you don't have any failed equipment.

PS, I no longer work for Van's Aircraft and this information is based on my own knowledge and experience.

 

[Bob Y]

Thanks, Tony. I looked at my user logs for the past two months. I was expecting to be able to see fuel pressure with no engine rpm to indicate when they continued to run after shutdown, but everything stopped logging at shutdown. And naturally, I didn't make note of during which flights it occurred. I did check the battery voltage at engine start for the past two months, it was a maximum of 13.1 volts, and it always reached 14 V during every flight, so the SBB signal should be timing out. I'm stumped.

 

[mbell]

Looking through some saved data last night I think the EarthX starts with such a high voltage that the IMA never sees the 0.5V delta. I believe you are correct; the feature/bug is working correctly. I will see if I can catch it with the battery in more of a discharged state and test that. Thanks Bob and Tony!

 

[Tony Kirk]

After getting nowhere with Van's support on this subject (they wanted me to tell them how the fuel pumps shut off), I'll reach out to the group to see if any other 12iS owners have experienced their fuel pumps continuing to run after engine shutdown. Yes, I have implemented SB-00058 for the new HIC module, and SL-00072 to replace the start computer. And no, the EMS BBS is not on. I've had them continue to run twice out of five flights after shutting down the engine; it's worked fine for over 2.5 years. This in of itself isn't the end of the world, but we spent a lot of time and money to replace components to force them to shut off in the event of an emergency landing, so I would like to know if something else might be going on. So, am I alone in experiencing this issue?

One more thing to note, the POH instructs you to shut off both fuel pumps, the fuel shutoff valve, both lane switches and the Master switch in the event of an emergency landing.

 

[Bob Y]

I can’t argue with that. So, the new HIC was intended to act as a backup?