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RV-12iS Fuel Pump issue

S

SmokinF15E

I'm New Here
Weird one for the crowd. I'm having a problem with one of the two fuel pumps (the main, I'll call it Pump1) not operating with the switch on. Here are the details

2023 RV-12iS S-LSA
Pump 1 doesn't come on with the switch after Master-ON and before a start attempt.
Pump 2 will come on.

Swapped electrical connections between pump 1 and pump 2. Pump 1 operates on Pump 2 switch. Pump 2 does not operate on Pump 1 switch. (both pumps are good)
Returned the connections to normal.
Swapped electrical connections between switch 1 and switch 2. Pump 2 operates on switch 1. Pump 1 does not operate on switch 2. (both switches are good)
Returned to normal.
Wired both pumps to operate from switch 2 and both operated normally (the wiring from the switch to pump 1 is good).
Returned to normal.
HIC LED indicates normal power.
Swapped HIC (suspecting a logic or board problem in HIC A) with an HIC from an identical RV-12iS. (same problem, HIC is good).

So I'm pretty much out of ideas, unless the power wire from the HIC to the Pump 1 switch is bad... Anyone seen this problem before?
 
SmokinF15E said:
Weird one for the crowd. I'm having a problem with one of the two fuel pumps (the main, I'll call it Pump1) not operating with the switch on. Here are the details

2023 RV-12iS S-LSA
Pump 1 doesn't come on with the switch after Master-ON and before a start attempt.
Pump 2 will come on.

Swapped electrical connections between pump 1 and pump 2. Pump 1 operates on Pump 2 switch. Pump 2 does not operate on Pump 1 switch. (both pumps are good)
Returned the connections to normal.
Swapped electrical connections between switch 1 and switch 2. Pump 2 operates on switch 1. Pump 1 does not operate on switch 2. (both switches are good)
Returned to normal.
Wired both pumps to operate from switch 2 and both operated normally (the wiring from the switch to pump 1 is good).
Returned to normal.
HIC LED indicates normal power.
Swapped HIC (suspecting a logic or board problem in HIC A) with an HIC from an identical RV-12iS. (same problem, HIC is good).

So I'm pretty much out of ideas, unless the power wire from the HIC to the Pump 1 switch is bad... Anyone seen this problem before?
Click to expand...
Im not an electrial guru like a bunch of our friends here, but if you swapped the switches and the pumps run, that tells me that everything from the switch to the pumps is fine, and its probably switch 1. Check that with the electrial guru department here at VAF.
Tom
 
Don't forget, your ignition module AV-60007 does a little "thinking" of its own at start up (turning the usual Rotax iS 3-handed start into a 2-handed maneuver).

My bet is on the ignition module. Perhaps it just needs the software update per SL-00072...

SL-00072 - Van's Aircraft Total Performance RV Kit Planes

Optional installation of microcontroller with updated firmware for RV-12iS aircraft ignition module, if the behavior described in the service letter is observed.
www.vansaircraft.com www.vansaircraft.com
 
If either fuel pump runs the AV-60007 Ignition Module "Start Button Bypass" feature is active and the HIC Module diagnostic LED should be White. That rules out the Ignition Module and the HIC Module as the problem.

Note that the HIC Module does NOT actively switch the fuel pump circuits - it is simply a pass-through from the Rotax ECU to the Aircraft harness.

A little tidbit - HIC is an acronym for "Harness Interface Connector". ;)

Be sure to check the Green HIC Module 8-pin connector for proper wiring and security - the fuel pump switch wiring passes from the ECU harnesses to the aircraft harness through pins 1-4 on the 8-pin connector.

SB-00058 has a great table identifying the wire numbers in the green 8-pin connector on the HIC Module, as does the Schematic, both shown below.

. https://www.vansaircraft.com/wp-content/uploads/2022/10/SB-00058-RV-12iS-HIC-Module-Replacement.pdf
.
ES-796859-8 Pinout.png

HIC.png


HIC Fuel Pump Wiring.png
This is Garmin, Dynon numbers will be different.
 
Tony Kirk said:
If either fuel pump runs the AV-60007 Ignition Module "Start Button Bypass" feature is active and the HIC Module diagnostic LED should be White. That rules out the Ignition Module and the HIC Module as the problem.

Note that the HIC Module does NOT actively switch the fuel pump circuits - it is simply a pass-through from the Rotax ECU to the Aircraft harness.

A little tidbit - HIC is an acronym for "Harness Interface Connector". ;)

Be sure to check the Green HIC Module 8-pin connector for proper wiring and security - the fuel pump switch wiring passes from the ECU harnesses to the aircraft harness through pins 1-4 on the 8-pin connector.

SB-00058 has a great table identifying the wire numbers in the green 8-pin connector on the HIC Module, as does the Schematic, both shown below.

. https://www.vansaircraft.com/wp-content/uploads/2022/10/SB-00058-RV-12iS-HIC-Module-Replacement.pdf
.
View attachment 86050

View attachment 86051


View attachment 86052
This is Garmin, Dynon numbers will be different.
Click to expand...
I took his write up that it was a flying plane that just started having this issue. So I guess I mispoke on my extremely limited electrical troubleshooting capabilities.
 
Yeah, it was a flying plane with 400 hours on the engine already. It failed on one flight. We troubleshot the pumps and when we re-connected the wiring after one of the evolutions mentioned above, the pump came on. It flew once uneventfully (normal start), then repeated the failure.
Tony, since the pump 1 power runs through the HIC A connector, I thought there might be an interface failure, which is why I tried the other HIC board.
My next move is continuity between PIN 4 on the 8-pin power connector on the HIC and the pump 1 switch. Since it was an intermittent failure (sort of), I wonder if it's chafing of that power line. Will also check the Ground on PIN 3 (I believe that one is Engine Ground, not Airframe Ground).

As a hypothetical. If I started the engine using the #2 pump, then completed the B->A power transition, the power source for the pumps should move from the battery bus to the A generator. What would it mean if pump 1 worked after the B->A transition? Would that indicate a power logic problem in the Start Computer?

Thanks for your help folks. I'm obviously still a novice of RV-12iS electrical system lore.
 
I assumed from the first post it was a new build, not a flying aircraft, my bad.

According to the electrical schematics in the POH (and the Rotax Installation Manual) the Fuel Pump Switches only switch the ground side of the Fuel Pump circuits. There is no "fuel pump power" going through the HIC connectors from the ECU or to the FP Switches.

POH Schematic Fuel Pumps.png
POH pg 7-11

Rotax IM Fuel Pump Switches.png
Rotax IM 24-00-00, pg 37

The Fuel Pumps are powered from the main Rotax Harness (connectors #19), these wires are passed through the firewall by the builder, perhaps the Fuel Pump 1 wire is chaffing on the firewall passthrough or where it goes through the F-01202B Avionics panel into the tunnel.

Rotax Harness.png
Rotax MMH 76-50-00, pg 5

The Fuel Pumps each have a 10A fuse in the Rotax Fusebox, perhaps F5 is loose in its socket or blown. We have also seen the main fuse F20 or F21 come out of their sockets in the past.

Rotax Fusebox.png

And the other possibility is the Fuel Pump itself is failing. Have you checked the FP serial numbers against the multiple Van's and Rotax Service letters, see SD-00083.
 
Tony Kirk said:
I assumed from the first post it was a new build, not a flying aircraft, my bad.

According to the electrical schematics in the POH (and the Rotax Installation Manual) the Fuel Pump Switches only switch the ground side of the Fuel Pump circuits. There is no "fuel pump power" going through the HIC connectors from the ECU or to the FP Switches.

View attachment 86073
POH pg 7-11

View attachment 86074
Rotax IM 24-00-00, pg 37

The Fuel Pumps are powered from the main Rotax Harness (connectors #19), these wires are passed through the firewall by the builder, perhaps the Fuel Pump 1 wire is chaffing on the firewall passthrough or where it goes through the F-01202B Avionics panel into the tunnel.

View attachment 86076
Rotax MMH 76-50-00, pg 5

The Fuel Pumps each have a 10A fuse in the Rotax Fusebox, perhaps F5 is loose in its socket or blown. We have also seen the main fuse F20 or F21 come out of their sockets in the past.

View attachment 86075

And the other possibility is the Fuel Pump itself is failing. Have you checked the FP serial numbers against the multiple Van's and Rotax Service letters, see SD-00083.
Click to expand...
Again, I certainly am NOT an electrical guru, but Paul indicated that they switched pump 1 to the pump 2 switch and everything works. So, to me anyway, that indicates that the pump, and the assorted wiring, including breakers or fuses, were intact. Dont know if the switch contacts are open, but thats easy enough to test---and yo have the pump 2 switch to verify the results.
 
Elegant puzzle and troubleshooting effort. Thanks to Tony K for the diagram.
Logic points to this area of the diagram:
1745706577308.png
 
The problem with the POH schematic is, it is a GROSS oversimplification of the installed system.

That tiny link between the switch and the fuel pump that you have identified encompasses at least 7 different connections, the HIC Module, the Rotax ECU and the Rotax fusebox. So yeah, it's not quite as simple as it seems.

Here's the list I can think of.
  1. the fuel pump switch connectors
  2. the HIC Module 8-pin connector
  3. the HIC Module Rotax HIC_A 12-pin connector
  4. the Rotax ECU
  5. fuel pump 1 ground connection on the A-bus ground stud on the bottom of the Rotax fusebox (documented below)
  6. the fuel pump wiring connector in the tunnel behind the Power Module (#19 above)
  7. the fuel pump connector itself
  8. and probably something else I forgot ;)
Rotax Schematic.png
This is from a Rotax "internal use only" schematic.

SmokinF15E Please be sure to post the solution when it is found.
 
Thanks for the data, guys. I'm at the hangar now and will run down as much as I can in the next couple hours. I'll let you know how it goes.
Cheers.
 
SmokinF15E said:
Weird one for the crowd. I'm having a problem with one of the two fuel pumps (the main, I'll call it Pump1) not operating with the switch on. Here are the details

2023 RV-12iS S-LSA
Pump 1 doesn't come on with the switch after Master-ON and before a start attempt.
Pump 2 will come on.

Swapped electrical connections between pump 1 and pump 2. Pump 1 operates on Pump 2 switch. Pump 2 does not operate on Pump 1 switch. (both pumps are good)
Returned the connections to normal.
Swapped electrical connections between switch 1 and switch 2. Pump 2 operates on switch 1. Pump 1 does not operate on switch 2. (both switches are good)
Returned to normal.
Wired both pumps to operate from switch 2 and both operated normally (the wiring from the switch to pump 1 is good).
Returned to normal.
HIC LED indicates normal power.
Swapped HIC (suspecting a logic or board problem in HIC A) with an HIC from an identical RV-12iS. (same problem, HIC is good).

So I'm pretty much out of ideas, unless the power wire from the HIC to the Pump 1 switch is bad... Anyone seen this problem before?
Click to expand...
Good troubleshooting so far. The problem is farther upstream. I'm assuming you have the newer HIC modules with the green terminal blocks (the old modules used a connector that had vibration problems and caused pins to fail). Check the fusebox's 10A fuse for Pump 1. Also check the wires going through the firewall. If you have the garmin setup, the wires can rub against the thumbscrew for the GEA24 mounted on the aft side of the firewall behind the PFD. Possible the Pump 1 power wire shorted out and blew the 10A fuse in the fusebox.
 
Well the problem fixed itself all of a sudden.
After reviewing all of the troubleshooting previously accomplished and verifying it again (with no change to the outcome), I directed our A&P to look into a difference in voltage between the pump 1 and pump 2 circuits (at the pump connector Pump 1 showed 12.2V and pump 2 showed 13.4V). He was checking the voltage at HIC 8-pin connector PINS 1 and 2 (pump 2 voltage) and when he touched the probes to the screw terminals, pump 1 began running... (power had to be on and pumps connected to their circuits for a valid measurement). Since that moment, the pumps are operating normally with equal voltage (13.4V). We started the engine multiple times and are cautiously returning the aircraft to service with restrictions while we see if this problem reappears just as magically...
Super strange... Any ideas why that might be?
 
SmokinF15E said:
Well the problem fixed itself all of a sudden.
After reviewing all of the troubleshooting previously accomplished and verifying it again (with no change to the outcome), I directed our A&P to look into a difference in voltage between the pump 1 and pump 2 circuits (at the pump connector Pump 1 showed 12.2V and pump 2 showed 13.4V). He was checking the voltage at HIC 8-pin connector PINS 1 and 2 (pump 2 voltage) and when he touched the probes to the screw terminals, pump 1 began running... (power had to be on and pumps connected to their circuits for a valid measurement). Since that moment, the pumps are operating normally with equal voltage (13.4V). We started the engine multiple times and are cautiously returning the aircraft to service with restrictions while we see if this problem reappears just as magically...
Super strange... Any ideas why that might be?
Click to expand...
You have an intermittent connection somewhere. No way I would fly that thing till I have positively identified where that bad connection is. It could be a connector crimp, a broken wire under the insulation, a poor connection at a screw or pin, pins that are not properly seated, PC board trace issues, cold solder joint on a PC board, etc. etc.

One thing is for sure, if you don't find it, it will show up again and likely at a really bad time.
 
SmokinF15E said:
Well the problem fixed itself all of a sudden.
After reviewing all of the troubleshooting previously accomplished and verifying it again (with no change to the outcome), I directed our A&P to look into a difference in voltage between the pump 1 and pump 2 circuits (at the pump connector Pump 1 showed 12.2V and pump 2 showed 13.4V). He was checking the voltage at HIC 8-pin connector PINS 1 and 2 (pump 2 voltage) and when he touched the probes to the screw terminals, pump 1 began running... (power had to be on and pumps connected to their circuits for a valid measurement). Since that moment, the pumps are operating normally with equal voltage (13.4V). We started the engine multiple times and are cautiously returning the aircraft to service with restrictions while we see if this problem reappears just as magically...
Super strange... Any ideas why that might be?
Click to expand...
I agree with Brian, somethings is loose. If it magically started working while messing with the HIC connector that is where I would start. Double check everything is tight and taut in that 8 pin....
 
So, continuing the story. The problem came back. Still just the Pump 1 not starting with the Pump switch on the ground at power initiation. Found the A and B regulators have slight (14 KOhms) continuity. As soon as we physically touched the B regulator wiring connection between the generator and the fuse box, the pump activated. We switched out the Fuse Box (the old one was all green LEDs with power on the airplane and later bench tested with no continuity between A and B regulators) and have had no issues since. Still scratchin my head though as to what would cause the issue. When the issue presented itself again this last time, we were able to start the engine on the number 2 pump, then make the B to A transition. After the transition, pump 1 worked. After shutdown and power cycle, pump 1 would not initiate. Whenever the pump was running, it never stopped or stumbled until the pump switch was turned off (so I don't believe it's an intermittent power connection). Anyone care to explain that behavior? I'm stumped and a little daunted by the "random not random" nature of the issue.
 
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