Wiring Kavlico Fuel Pressure Sensor & Capacitor Modification

The Kavlico fuel pressure sensor unit currently being used in the RV-12 is provided by Dynon and is a second generation sensor that replaces the original VDO sensor. The Kavlico unit is a better overall sensor, but not without potential issues which a small modification can eliminate.

Of note to fellow builders: The Kavlico sensor IS NOT a direct replacement for the VDO sensor … in that the Kavlico sensor requires +5 volts to operate. Newer RV-12 kits shipped with the Kavlico sender have the +5 volt wire. Older RV-12’s converting to the new Kavlico sender require an additional +5 wire to the sender, …this voltage can be obtained from the same source as the +5 volts for the manifold pressure module.

The Kavlico fuel pressure sensor is on the right in this photo. There is socket in the top of the sender that receives a molded plug which has three wires connected to it. The three wires are: red (+5volts), green (signal out from sensor) and black (ground) .

Some have experienced issues with the new Kavlico sensor’s readings fluctuating … fortunately there is an easy fix. Dynon support believes this is from electrical “noise” on the green signal wire and suggests placing a 330 microfarad capacitor rated at 25 volts from the green signal wire to ground. To my knowledge, the additional capacitor has fixed the issue of fluctuating readings for all who have installed it. Some builders have had a hard time locating a 330 uF capacitor and have used 470 uF capacitors instead with good success.  Because the DOG Aviation RV-12 is being built as experimental – amateur built, a 330 uF capacitor will be installed now as a preemptive strike. Below is a wiring diagram I made to show how the capacitor is installed.

This diagram shows how the 330 uF capacitor is to be wired to the Kavlico fuel pressure sensor.

The plan is to install the capacitor at the butt splices a few inches from the sender. It is a good location because there are splices here anyway and feel it is better than installing the capacitor on the aft side of the firewall which would require cutting the wires and adding additional splices. However, the engine compartment is a warm environment so the DOG Aviation procurement department took that fact into consideration when choosing which capacitor to purchase.

Friends who know me well, know I have a propensity to over kill a bit at times and this just may be yet another example …as  not all 330 uF electrolytic capacitors are created equal. Knowing the max temperature rating of an electrolytic capacitor is typically around 85 degrees C (which equates to 185 degrees Fahrenheit), I just could not let myself knowingly install a capacitor with a 185 degree max rating in an environment where the heat could potentially easily pass 185 degrees on hot summer days during ground operations. The 330 uF capacitor chosen is an automotive grade capacitor and has a temperature rating of 150 degrees C (which is 302 degrees Fahrenheit). The capacitor was ordered through Mouser electronics … which is a great source for some of the electrical parts used on the RV-12 such as connectors, connector pins, etc.

The Nichicon UBX1E331MHL is a 330 uF electrolytic capacitor rated at 25 volts with a maximum working temperature of 302 degrees F and was purchased through Mouser electronics for a couple of dollars.

Of note … electrolytic capacitors ARE polarity sensitive and care must be exercised when installing them to make sure the negative lead of the capacitor goes to ground. In some applications if they are not installed correctly, they can pop like a firecracker. Some electrolytic capacitors are marked quite well and others like the one in the above photo are not marked very well. Typically, for this style of capacitor, the longer of the two leads coming out of the case is the + lead and the shorter of the two is the – lead. Also, looking closely at the above photo, one can see there is a black box printed to one side of the capacitor, this denotes the – lead is on that side.

Three butt splices have been installed onto the wires from the plug for the Kalvico fuel pressure sensor. The positive lead from the capacitor will be inserted into the butt splice on the green signal wire and the negative lead on the capacitor will be inserted into the butt splice for the black ground wire.

I was hopeful that the leads on the capacitor would be long enough so the capacitor could be heat shrunk on top of the butt splices but unfortunately they are not. So as can be seen in previous photo, the capacitor was covered with a bit of heat shrink to insulate the “can” and prevent chafing of the wires passing by the capacitor. Once crimped to the butt splices, two sizes of heat shrink were used to cover the capacitor, wires and butt splices.

The 330 uF capacitor is now crimped to the butt splices along with the red, green and black wires coming from the firewall forward connector. The positive terminal from the capacitor is attached to the green signal wire and the negative lead on the capacitor is attached to the black ground wire.

The grounding for the Kavlico sensor was to also be modified a bit, in that the black ground wire was to go directly to the ground block on the firewall. However, this did not happen as my efforts to make good connections without messing up the capacitor's polarities distracted me enough that I forgot to crimp to the ground wire going to the ground block on the firewall … instead I ended up using the original black wire that is part of the three wire twisted bundle. Discovered this after all the connections were crimped and the heat shrinking finished. Oh well, not a big deal and certainly not worth the effort to tear back into the butt splices.

Completed wiring of the Kavlico fuel pressure sensor. The 330 uF capacitor and three butt splices are now covered with heat shrink and the whole assembly wire tied for support. The capacitor is the big lump on the bottom and the butt splices the smaller lump above the capacitor.

Primping & Crimping – A “Crimp Fest” Day

It was good to get back to the hangar and make some forward progress on the RV-12 after waiting out the cold snap and also dealing with two vehicles that needed repairs. Gee, what are the odds of having two vehicles and both of them needing sudden repairs simultaneously? Apparently quite good … considering they are 24 and 21 years old.


The first task for the day was to complete the wiring for the oil pressure sensor plug and to provide a ground for the sensor. As mentioned in the previous post, rather than splicing the WH-00096 it was determined the wires were long enough to be connected directly to the firewall forward connector. Normally P-765 (a red wire from pin 6 on the firewall forward connector) would be spliced to the red wire in the WH-00096 wire harness and E-764 (a white/yellow from pin 15 on the firewall forward connector) would be spliced to the white wire in the WH-00096 wire harness. To accommodate the wiring change, the red wire on pin 6 and white/yellow wire on pin 15 of the firewall forward connector were removed and male connector pins were crimped onto the red and white wires in the WH-00096 wiring harness.


After using a pin removal tool to successfully pop the pins out of the connector body, not wanting to cut the green heat shrink covering the wires in the connector, the two wires were plugged into spare wires with a female connector pins and pushed out of the heat shrink. The reasoning behind this was so the old wires could be pushed out and the new wire could follow the same path back through the shrink wrap. Once the new wires were in position, the red wire in the WH-00096 harness was inserted into position 6 and the white wire was inserted into position 15 of the firewall forward connector.  After the wires were locked in place, the connector’s shell was reinstalled and the firewall forward connector was plugged back into the control module.

The yellow wires with the blue and red stripes on the left have female connectors on the end of them and were used to help push the old wires out of the shrink wrap thus creating a return path for the new wires. The new red and white wires in the WH-00096 wire harness are now plugged into the female connectors and about to be pulled back through the shrink wrap on the connector.  This method worked out quite well.


For the oil pressure sensor grounding, the oil pressure sensor was removed from the adapter fitting so a ring connector could be sandwiched between the sensor and the adapter. The new ground wire was run over to the handy ground block (a modification on the DOG Aviation RV-12).


With the wiring for the oil pressure sensor completed, moved on to the wiring for the manifold pressure sensor. There are three wires that connect to the manifold pressure sensor via a Weatherpack connector … pin A is a ground, pin B is the signal wire and pin C is +5 volts. The three wires in the firewall forward wiring harness already come with male Weatherpack pins crimped on them. Wanting to ground the unit directly to the grounding block, I have been keeping my eyes open for male Weatherpack pins to make a short ground wire to connect directly to the ground bock on the firewall. While at the auto parts store getting parts for one of the vehicles, ended up purchasing a wire that had a male Weatherpack pin already on it.


It has been quite a while since the inventory had been done on the engine kit, so I had forgotten that Dynon included male Weatherpack pins along with the Weatherpack connector housing. I had remembered seeing the connector … but not the pins included. So it came as quite a shock to see a package of male Weatherpack pins accompanying the Weatherpack plug housing … especially after having just purchased a wire the day before that had a Weatherpack pin on it.

The Dynon supplied Weatherpack connector body with pins (which normally will not be used because Van’s wiring harness already has male Weatherpack pins crimped onto the wires) and the single wire purchased locally that came with a male Weatherpack pin.


I connected the purchased black wire to position A (this is the ground wire and will run to the ground block).  E-751 (green/red) manifold pressure wire is inserted onto position B and P750 (white/red) power wire is inserted into position C of the Weatherpack plug housing. Here again, similar to the ignition module connectors, it is necessary to hold the wire at the rubber seal while inserting the wire into the connector’s body … when the rubber seal was flush with the body, I used a chunk of popsicle stick to push the rubber seal in a little further until the pin made a “click” sound as the pin locked in place.

About to insert the ground wire into position A. Note on the male Weatherpack pin how the rubber seal is also the strain relief for the wire. While inserting the male pin into the connector’s body, the wire should be held with fingers touching the rubber plug to prevent it backing out of the ring that holds it while the pin is inserted.

The completed wiring for the manifold sensor on the left and the newly attached yellow ground ring attached to the oil pressure sensor on the right can be seen here. Both these units are now grounded to the grounding block under the manifold sensor module.


After the manifold pressure wiring was primped and neatly wire tied, continued on with the “crimp fest” now paying attention to the wires which were routed previously for the left and right cylinder head temperature sensors (CHT) and the oil temperature sensor. The wires were primped and wire tied in position and ES-640903-2 female spade connectors were crimped onto the ends of the three wires. An addition, I used a small piece of heat shrink tubing over the CHT wires where they cross over the metal hose clamps on the water lines they ride on.

Both CHT wires were wired as the one in this photo. Note the addition of a small piece of heat shrink to protect the wire where it passes over the metal hose clamp.

Wiring Of The Rotax 456180 Oil Pressure Sensor Studied

While laying out the wires for the three temperature sensors during the last work session, the two wires for the oil pressure sensor unit (P-765 (red) & E-764 (wht/yel)) were pulled back to the firewall because that is where the oil pressure sensor unit has been relocated. Rotax has begun utilizing a different oil pressure sensor (part number 456180) that has a connector socket built directly into the top of the oil pressure sensor. The new oil pressure sensor is used in conjunction with the WH-00096 oil pressure sensor harness cable. One end of the cable has a molded plug that is inserted into the top of the oil pressure sensor. The red and white wires leaving the plug are covered in what appears to be a heat shrink sleeve long enough to traverse the bottom of the engine and meet up with the main wiring run at the rear of the engine that goes to the instrument bay.

On the left the new Rotax 456180 oil pressure sensor unit, with the molded plug end of the WH-00096 wiring harness attached, is mounted on the custom built dual mounting bracket.


I got to thinking, it may not be necessary to cut the wires on the WH-00096 oil pressure sensor harness cable just so they can be spliced onto the P-765 & E-764 wires that come from the firewall forward connector which plugs into the RV-12's control module. The whole cable appears to be long enough to run through the firewall grommet and routed directly to the firewall forward connector plugged into the RV-12's control module. At this point in time, I see no reason that the P-765 (red) & E-764 (wht/yel) wires can’t be removed from the firewall forward connector and replaced with the two wires in the WH-00096 harness coming directly from the connector plug on the oil pressure sensor unit.

The WH-00096 wire harness for the 456180 oil pressure sensor unit appears to be long enough to be wired directly to the firewall forward connector that plugs into the RV-12’s control module.


The P-765 (red) wire (12 volt EFIS Power to sensor) can be removed from pin 6 of the firewall forward connector and replaced with the red wire in the WH-00096 oil pressure sensor harness cable. The E-764 (white/yellow) wire (pressure signal from the sensor) can be removed from pin 15 and replaced by the white wire in the WH-00096 oil pressure sensor harness cable. This appears to be a sound modification which will eliminate two unnecessary splices … and in the electrical world, less splices = better.


A sticky wicket ... keeping grounded. Because of not seeing a third wire going to the sensor, I became curious about the oil pressure sensor's grounding and looked at section 79 of the Rotax Heavy Maintenance Manual. Based on bullet notes,  it appears the oil pressure sensor units typically receive their electrical ground from being screwed into the oil pump housing. Not being sure if the conductive Teflon hoses will provide enough of an electrical ground for the oil pressure sensor unit (doubt it), or if a ground is truly necessary (would think it is), the logical thing to do is go ahead and provide a ground for the oil pressure sensor. So will ground the oil pressure sensor by crimping a wire onto a ring connector and running the wire over to the grounding block on the firewall during the upcoming “crimp fest” day.

Wiring of Ignition Modules Completed

During the last work session, the wiring of the A1 & B1 connectors was completed leaving the two K-766 purple wires needing to be connected to the ignition module’s A2 & B2 connectors (these wires are used by the ignition module to denote easy start). Having looked the chore over, was not in the mood at the time to deal with what I knew was going to be an exercise in patience …and yesterday I was not disappointed in that regard.


The main task for this work session was to insert the two WH-K766 purple easy start wires into the only vacant slot on each of the ignition module’s A2 & B2 connectors. On the surface this sounds easy enough, but I could tell by looking at the connector’s location this was not going to be much fun. The purple WH-K766 wire is routed along the Pitot tube to the vicinity of the ignition modules where it has a splice that forms a Y … one wire is installed onto the A2 connector and the other onto the B2 connector. Getting the connectors off the bracket by slipping a tiny screwdriver under the locking tab and pulling it away from the bracket while simultaneously lifting up on the body of the connectors to slide them off the bracket is the easiest part of the task …. it quickly goes downhill from there. There is nothing that difficult about this task … the difficulty stems from the lack of space to work on the connectors … the connectors are somewhat buried, have short wires coming from the ignition modules, the fuel lines and coolant reservoir are in the way along with the Pitot tube. Ignoring all that, one must be able to grab onto the connectors to separate them while at the same time releasing the locking tab … a helper would have come in handy for this task.

Both the ignition module’s A2 and B2 connectors are separated. Let the fun begin, the K-766 wires need to be installed into the two connectors buried deep on the right. The wires need to be inserted from the bottom … but not before a couple of rubber plugs are removed from the vacant slot in each of the connectors.


After separating the A2 and B2 connectors, the fun continues … in that, there is a rubber plug in the vacant slot on each connector which must be removed so the K-766 wires can be inserted into the connectors. The rubber plugs are stuffed up inside the connector body so there is nothing to grab onto to remove the plugs … they need to be pushed out from above. At first a tiny jewelers screwdriver was used to try pushing the plugs out … the plugs began moving, but the shaft on the screwdriver was not long enough. There is only a narrow slot in the housing of the connector to work with and I couldn’t seem to find a good tool for the job … finally I got the idea to try sliding a tiny wire tie into the slot on the connector … that worked marvelously. I would suggest fellow builders consider using a tiny wire tie for this task as well.

Discovered a small wire tie fit into the slot on the connector body … so used the wire tie to push the plugs out of the body of both connectors. Looking at the photo, the viewer can see the black wire tie in the slot on the connector and the rubber plug coming out the bottom of the connector.

Both rubber plugs removed from the vacant slots on the A2 and B2 connectors.

With the rubber plugs finally removed, the challenge continues because of the tight surroundings … getting the K-766 purple wires into the connectors is not that difficult, but requires getting hands and connector positioned to get a good grip on the connectors while inserting the wires. Note: Care should be taken to insure the rubber plug on the end of each K-766 wire is fully seated in the strain relief on the connector pin prior to inserting the pin. Holding the wire at the rubber plug while pushing the pin into the body of the connector will insure the rubber plug remains fully seated in the strain relief on the pin.

Both A2 & B2 connectors now have the purple K-766 easy start wires attached.

After both the K-766 wires were locked in place, the A2 & B2 connector halves were mated while making sure to listen for the distinctive snap of the locking mechanism snapping in place. It IS possible for these connectors to look like they are together tightly… yet, they are not locked. This is because of the need to compress a rubber gasket deep inside the connector body which is used to keep moisture out of the connector. Patience is a virtue throughout this whole exercise.

The ignition module’s A2 & B2 connectors reinstalled on the mounting bracket now wired to the purple K-766 easy start wire.


Continuing on with the wiring, the WH-E753 (PRP/YEL) CHT 1 (left), WH-E749 (PRP/BLU) CHT 2 (right) and WH-E754 (WHT/BRN) oil temperature wires were routed to the left and right cylinder head temperature probes and the oil temperature probe respectfully … but the connectors were not crimped onto the wires yet. Figured it would be easier to run all the wires to where they need to go, create small service loops, then cut the wires and add the necessary connectors in one big “crimp fest”. There is nothing exciting here so did not take any photos.

The WH-RV12-IGNITION Wiring Harness Installed

Continued working on the firewall forward wiring but got a little sidetracked doing some research of the wiring schematics and VAF forums regarding a couple of wiring enhancements planned to be incorporated in the coming days. As a result, only completed installing just a few wires … the WH-RV12-IGNITION wiring harness being among them.

The WH-RV12-IGNITION wiring harness ready to be connected to the ignition modules.

The WH-RV12-IGNITION wiring harness is made up of two shielded wires that require some attention to be installed correctly. The plans keep referring to the wires using color references of white/blue for the J-152 and blue for J-153 … however, as can be seen in the above photo, both wires in the harness are white. Fortunately, a yellow heat shrink identification band is placed on both ends of each wire. The J-152 and J-153 wires plug into the only vacant positions on the A1 and B1 plugs with J-153 going to the A1 connector and J-1532 going to the B1 connector.

Looking closely, the vacant connector position can be seen where the connectors are labeled A1 and B1.

Inserting the J-153 wire into the only vacant position on the A1 connector.

There is a portion of insulation that has been removed from both the J-152 & J-153 cables exposing the braided shielding underneath. The bare shielding needs to be carefully positioned under the metal clamp that supports the wiring harness for the A1 and B1 connectors … there should be no insulation under this metal clamp because it provides a ground for the shielding. When the shield for both cables is in position under the clamp, the M5 hex screw securing the clamp is to receive Loctite and be tightened to 22 inch pounds. Also, because this assembly was taken apart during engine preparations for mounting, care must be taken to insure the ground wire is also reattached under the head of the mounting M5 screw as can be seen in the second photo below.

The M5 hex screw securing the grounding clamp and ground wire is torqued to 22 inch pounds.

My finger is pointing to the ground wire and clamp that provides the grounding for the shielding on the J-152 and J-153 cables … only bare shielding should be under the clamp.


Both shielded wires in the WH-RV12-IGNITION wiring harness are to be run down along the main wiring harness for the ignition modules as can also be seen in the above photo.


At the other end of the WH-RV12-IGNITION wiring harness is a Molex connector housing which will interface to J-762 and J763. Here again, the wires are referred to in the plans by color but both wires are white … fortunately, they too have heat shrink identification bands. The both wires need to be inserted into the Molex connector so when the connector halves are mated together, J-762 mates with J-152 and J-763 mates with J-153.

The Molex connector at the end of the WH-RV12-IGNITION wiring harness connected to J-762 and J-763 (wires on the right) … the connector housing still needs to be secured with wire ties.


Still need to tie wrap the Molex connector, but one additional wire will need to pass by this location so will wait until it is in position before securing the connector housing.