I installed a new fuel quantity transmitter and the system is still not working. What is wrong?
There are several other components in the fuel indicating system which could be the issue or are causing the indication problems:
- Ensure that your aircraft fuel indicating system utilized Stewart Warner style transmitters.
- Even if your aircraft originally came with that style, there were many Cessna Service Bulletins to replace them with the Rochester style. Our transmitters will not work with those components if they have been changed. This was a very common SB when Cessna switched over to Rochester.
- Transmitter Identification shows the difference in the Rochester style and the original Stewert Warner transmitter.
- McFarlane transmitters and Cessna Stewart Warner transmitters have an electrical resistance range of about 32 ohms when in the full position and 250 ohms in the empty position. This can be measured with an ohm meter connected between the wire terminal and the metal body. Note that the gold dichromate corrosion treatment on the zinc plating is a poor conductor. The metal body must be scratched a little to get a good electrical connection. The Rochester transmitter has a much different resistance pattern than the Stewart Warner or McFarlane transmitter.
- Consult your log books and check the part numbers of the fuel gauges and transmitters. Do not rely on Illustrated Parts Catalog or eligibility.
- With the age of most of the general aviation fleet, the possibility of corrosion in the wires or grounding is very likely. The gauge (indicator) may not be working correctly or properly calibrated.
- Since the transmitter gauge system works with very low voltage and very low milliamp electrical flow it is very sensitive to proper grounding and high resistance in electrical connections. Most problems are related to electrical connections.
- Excess resistance in the transmitter circuit can be detected by measuring the transmitter resistance with the transmitter being installed but without the wire connected at the terminal, and then measuring the resistance at the transmitter wire at the back of the gauge with the transmitter wire connected to the transmitter terminal and the transmitter wire disconnected from the fuel gauge and the other ohm meter connection to a ground at the back of the gauge. The resistance readings should be very close to the first resistance reading. In other words, you are measuring the transmitter resistance first without the airplane circuit and then comparing the reading with the airplane electrical circuit.
- If the preceding wiring check shows good, the problem is likely in the gauge. The fuel gauge has a brass grounding strap that grounds the internal electrical coils to the gauge case. With years of service this grounding strap can develop a thin layer of corrosion that restricts electrical flow. When this happens the gauge will show more fuel than what is in the tank which is not good! Cleaning this ground strap should fix the problem. Refer to the Cessna service manuals for detailed trouble shooting and maintenance information.
Caution! Never short the battery power to the transmitter wire! It will take only seconds before the stainless steel resistance wire in the Cessna transmitter will glow red hot in the fuel tank. The hot wire could explode the tank! Never have power on when trouble shooting the fuel gauging system.
Electricity in the Fuel Tank. Is it Safe?
Always check the fuel gauge system for proper calibration per the Cessna maintenance instructions.
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Can I use a McFarlane transmitter on a Cessna 152 aircraft?
No, the fuel indicating system on a Cessna 152 is unique and McFarlane has not designed a transmitter for them yet.
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Are templates required for Piper seat rails?
No, McFarlane does not provide templates for installing seat rails on Piper aircraft because the rail is riveted to the floor of the airplane, making installation easy by riveting directly from under the airplane.
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How do I know if my universal joint needs to be replaced?
A universal joint attaches to each control yoke shaft behind the instrument panel. Universal joints are very precision. Replacement of the universal joint is required if any free motion or rust around the joint pivots is detected or if the joint fails inspection required by the Piper AD 2010-15-10.
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Should I use a sealer or lubrication for my Viton gaskets?
The Viton gasket and screw seals do not require any sealer and must not have any lubricants. Do not over tighten the attachment screws as over tightening can extrude the gasket out from under the transmitter and tear the gasket in the screw holes. This will cause a leak. Tighten the screws evenly until you see the gasket just start to extrude a little. Any lubrication will aggravate the tearing of the gasket.
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How do I keep contaminants out of my fuel system?
The fuel selector valve works in unscreened fuel. Contaminated fuel can cause selector valve seal damage. When fueling from possibly contaminated fuel sources McFarlane recommends the use of a fuel filter, such as Mr. Funnel or another filtering device, to reduce trash in the fuel system.
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How do I know which Piper seat adjustment spring to purchase?
Aircraft make, model and serial number are not sufficient to ensure the correct replacement spring as many aircraft may have been originally equipped with either one or retrofitted with a conversion kit. If the spring you are replacing is marked with a brand name (e.g. P.L. Porter or Stabilus) the correct replacement is readily identified. The coil spring/hydraulic style are also identifiable by a 1¼" diameter visible coil spring. The thread may also be measured to verify the correct identification.
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What is causing my fuel pressure to fall below the “green arc”?
The most common reasons for low fuel flow/pressure are the following:
- A worn or broken O-ring on the inlet side fuel fitting can cause an inlet suction leak. An inlet air leak will result in low Fuel Pump output pressure.
- A weak operating spring in the Fuel Pump diaphragm assembly
- A worn fuel pressure gauge
- A clogged fuel vent or fuel cap
- A constriction in a fuel line either externally (a kinked hose), or internally (due to a collapsed hose lining)
- Wrong fuel pump for the installation
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What is causing my fuel pressure to fluctuate?
Fluctuating fuel pressure can be the result of the following:
- A worn fuel pressure gauge
- A worn or broken O-ring on the inlet side fuel fitting
- An obstruction in the induction system (air intake)
- A clogged or dirty fuel strainer
- Foreign material inside the fuel body (such as fuel cell sealant, thread sealant, or a drill shaving)
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How do I know when to replace or service my fuel selector valve?
The most common indication of external fuel valve leaks is the smell of avgas in the cabin. Most valves are located under the cabin floor. Fuel stain on the valve and drain plug or drain valve or on the belly of the aircraft can also indicate external leakage. External leaks are generally around the actuation valve stem. Internal leaks are detected when the fuel is turned off and fuel continues to drip during fuel system maintenance. Inner port leakage will allow fuel from one tank to leak into another fuel tank. This type leak is difficult to detect. Fuel transfer from one tank to another with the fuel valve selected to one tank only will indicate inner-port leakage. An extended period of time is needed to detect fuel transfer from one tank to another. Generally if internal leakage is detected when servicing the fuel system, it is likely there is also inner-port leakage.
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I installed the correct fuel vent line per your eligibility and it isn’t fitting, what is the problem?
Do you have aftermarket Monarch fuel tanks installed? We have received customer feedback stating that when Monarch or other aftermarket fuel tanks are installed, McFarlane’s fuel vent line does not fit. There is nothing we can do to solve that issue. McFarlane’s fuel vent lines fit well when OEM fuel tanks are installed. Please review the Installation Tips for McFarlane Fuel Vent Lines.
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I have just installed my new Fuel Pump and my engine will not start. Why?
A common cause for this problem is fuel starvation due to improper installation of the fuel pump. Make sure that the fuel lines are not crossed; that is, the inlet line should be connected to the inlet side of the pump (marked “IN” on the top of the port) and the outlet line should be attached to the fuel pump outlet port. Fuel should be present at the inlet side of the fuel pump.
Improper installation of the fuel pump may result in a misalignment of the operating lever with the operating plunger in the accessory case. If so, there will be no movement of the lever and no pumping motion to provide fuel flow. If misalignment is found upon removal of the pump, the lever is probably damaged or broken. If misalignment of the operating lever has occurred, it will require inspection and repair by a qualified technician.
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Which fuel cap washer will fit my fuel cap?
We have three types of fuel cap washers. In order to know the correct washer, the fuel cap part number must be known. It can usually be found at the bottom of the fuel cap assembly.
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What is causing the fuel (or oil) to leak from my Fuel Pump drain line?
Leaking fuel or oil through the fuel pump overboard drain line indicates the rotary seal is running dry or contamination happened in the field. Your fuel pump should be replaced before further flight.
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Can ACF-50 be used inside light aircraft fuel tanks to provide a corrosion inhibiting coat?
This is not recommended to be used inside light aircraft fuel tanks. This is not an area wehre ACF-50 was designed. It would mix with the fuel and can cause other issues.
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What causes carbon fouling on my spark plug?
Carbon fouling is indicated by dry, fluffy, sooty deposits. The plug is operating too cold to burn off combustion deposits. This may be fuel related or ignition related. Fuel related causes include rich fuel mixture, faulty carburetor adjustment, excessive idling or improper idle mixture. Ignition causes could be related to a worn spark plug ignition lead, improper magneto timing or running too cold of a spark plug.
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How is the fuel primer sold?
The McFarlane primer is available as a complete fuel primer assembly and knob assembly only, and replacement seals for the knob assembly are available. In many cases, where the old primer bore is still good, the McFarlane knob assembly can be used for a FAA-PMA approved quick fix for your existing primer.
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What is SEB99-18R1 about?
Cessna SEB99-18R1 describes periodic checks of the fuel gauging system.
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Do I need to remove the Cessna fuel strainer standpipe to clean the fuel screen?
Yes. The fuel screen is removed by removing the standpipe. The rubber tipped plunger must be unseated before the standpipe is loosened. Failure to lift the plunger off of its standpipe seat can damage the plunger. Pull the strainer drain knob as if you were draining the fuel bowl. Block or clamp the knob in this position. Insert a smooth round tool such as a screw driver or punch in the standpipe cross-hole and un-screw the standpipe.
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Do you have any advice for installing a McFarlane fuel vent line?
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