Floscan Series 9700/97000 Standard Flow GPS Interface System (twin engine model) - Manual (Page 38)

8/30/2004 7000-074-00D
FloScan Instrument Company, Inc. Tel: (206) 524-6625 Fax: (206) 523-4961
3016 NE Blakeley Street, Seattle, WA 98105 Email: [email protected] Http://www.floscan.com
1. Check continuity of the YELLOW and VIOLET Tachometer signal wires, (Section VI). Verify that the tachometer signal wires
are connected at the correct signal output point.
2. Disconnect either the YELLOW or VIOLET Tachometer signal wire from the Tachometer Sender. Connect an Ohmmeter to the
two sender wires and measure its’ resistance. AC Signal Generators should measure approximately 180 Ω, (±) 10%. Magnetic
Pick-ups can measure between 100 to 800 Ω depending on manufacturer.
3. Next connect an AC Voltmeter to the sender wires. Both AC Signal Generator and Magnetic Pick-up senders should produce at
least several volts at idle.
4. If the voltmeter reads “0” on an AC Signal Generator, it may not be properly attached to its drive port. Verify that its’ drive shaft
and tang are installed correctly.
5. If the voltmeter reads, “0” on a Magnetic Pick-up sender, it may not be installed correctly. With engine stopped, loosen its’ lock
nut. Turn the sender clockwise until it bottoms out. Back the sender out 1/8 th to 1/4 th turn. Turn the engine over by hand, or slowly
jog it to verify adequate clearance.
6. Engine alternators tend to be an inaccurate Tachometer signal source, especially at low Rpm’s. The engine may have to be revved
up before the Tachometer will read.
B. HIGH OR LOW READINGS.
1. Verify that the Tachometer is calibrated correctly.
C. FLUCTUATING READINGS.
1. Listen to your engine(s). If engine speed cycles up and down, (when idling or underway) the tachometer reading will follow.
This does not indicate a problem with the Tachometer, but may indicate engine problems.
2. Verify that wiring connections are tight, clean and dry. Check continuity while shaking the wires. Ohm readings should be
near zero and remain steady while shaking.
3. Verify that the tachometer signal wires are connected at the correct signal output point.
VIII. PULSATION PROBLEMS
A stiff anti-siphon valve(s) or miss-plumbed Pulsation Damper(s) can cause fluctuating GPH readings. These are most pronounced at
low Rpm’s and tend to disappear around mid throttle. They are annoying, but won’t affect totalizer accuracy. To eliminate, repair or
replace any defective valves, or re-plumb dampers according to the Fuel Flow Schematic Instructions.
IX. FINDING FUEL SYSTEM VACUUM LEAKS
Fluctuating GPH and High Totalizer Readings are usually caused by a small vacuum leak between the fuel tank and fuel pump inlet.
Fluctuations tend to be between 2 and 4 GPH. These vacuum leaks also affect totalizer accuracy, causing it to read 15 to 100% high.
Larger leaks produce greater fluctuations and higher readings. They generally do not affect engine performance.
Finding suction leaks can be time-consuming. When approached properly, they can usually be found and repaired quickly. Two
common places for suction leaks to occur are at the primary fuel filter - water separator, and/or a loose valve stem packing nut.
Remove the filter housing and coat all o-rings, gaskets and sealing surfaces with a medium to heavy grease, (Do not use oil) and
reassemble. Grease all valve stem packings and gently tighten gland nuts. Don’t over tighten, valve handles should turn freely.
Tighten all hose clamps and compression fittings. Don’t over tighten. Run the engine for 5 to 10 minutes observing GPH readings. If
you’ve found the problem, fluctuations should be reduced to less than ½ GPH.
If the problem persists, temporarily install a clear piece of fuel resistant hose downstream of the forward flow sensor. Run the engine
and watch for a stream of small bubbles in the clear hose, or an occasional larger bubble. Sometimes shining a light through the hose
makes bubbles easier to see.
Observe the clear hose while shaking the fuel lines. If the bubble stream continually increases or decreases you’ve found the leak area.
Repair or replace as needed. If this occurs one-time, you probably dislodged some trapped air.
If the leak hasn’t been found, the last step is to inspect each pipe joint. Thread sealant should be visible around each joint. If not, that
joint is suspect and must be resealed. After resealing run the engine for a few minutes to purge any remaining air. There should now
be bubble free fuel running through the clear hose. If bubbles are still present a leak was missed. Recheck your work. After all the
leaks are stopped, remove the clear hose.