Fuel System Troubleshooting - SuperFlow Dynamometers and ...

Service
Procedure

Fuel System Troubleshooting

The purpose of this document is to help you understand how the dynamometer fuel system works
so you can troubleshoot the fuel system and perform a basic calibration routine to increase your
fuel measurement system’s accuracy. This document is written with the SF-901 dynamometer
system in mind, but the basic theory applies to all SuperFlow engine dynamometer systems. The
photos were taken from an SF-901 system.
The standard engine dyno system provides its own fuel system for the engine being tested and
contains two fuel measurement channels, designated A and B.

Fuel System Basic Components

• An electric fuel pump to move fuel from a customer-provided fuel cell to the dyno fuel
system
– A standard Holley Blue fuel pump or
– The high-volume MagnaFuel pump (previously known as the SuperFlow Performance
pump or MagnaFlow pump)

• A fuel accumulator to reduce fuel aeration and pulsation to the flow measurement turbines
• Two FloScan 100CS type mechanical flow turbines to measure the fuel flow (one for each

fuel channel)
• Two sets of FloScan optics—one on each turbine, modified to fit the electrical connections
• Two fuel regulators for regulating fuel pressure to the carburetors (typically 6—9 psi)

– Standard Holley type or
– Anodized MagnaFuel type

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SuperFlow Technologies Group Service Procedure

• Two fuel pressure gauges attached to the regulators, used for observing fuel pressure
• A fuel pressure switch attached to the A-side fuel regulator (set to activate a low-fuel

pressure indicator light on the console when pressure is below 3 psi; this switch is only used
on SF-901 systems)

• Two –6 fittings on the engine stand panel to connect the fuel supply to the fuel system on
the engine

The system is capable of flowing a very high volume of fuel. Although FloScan rates the 100CS
flow turbines only to 50-gallons-per-hour flow, SuperFlow has successfully flowed 95 gallons per
hour (nearly 600 pounds per hour) simultaneously through each fuel turbine. This was
accomplished using the MagnaFuel pump (the Holley pump will not flow that amount of fuel)
and the Holley regulators set to 6 psi at that flow.
The measurement turbines are quite linear (generally less than 2% deviation from 10 to 95 gallons
per hour flow). Additionally, the –6 lines provided from the pump to the carburetor are more than
adequate for most engine fuel flow requirements.
With the two channels, you can obtain the following information from the system:

• Fuel A
• Fuel B
• Fuel A+B
• Fuel A–B
You can also obtain any derivative calculation using the information from the above channels.
However, as delivered, the derivative equations use either Fuel A, Fuel B, or Fuel A+B. No default
derivative equations exist using the Fuel A-B value. To use that value in derivative equations, you
must alter or add the term to the proper equations in the system configuration file.

Consult the WinDyn manual for proper procedures to change a configuration file.

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Troubleshooting System Components

Fuel Pump

The standard Holley Blue fuel pump is self-regulating and produces a
system pressure of about 12–14 psi. It requires no external bypass.

The MagnaFuel pump has an external bypass line that must be used to
return fuel to the fuel cell. The bypass may be an adjustable type or the
more common spring-type bypass which is not adjustable without
altering spring pressure.

Typically, SuperFlow sets the MagnaFuel bypass to regulate the pump
output to ~12–15 psi for gasoline engines in the 200–700 hp range. For
high-flow applications (methanol), SuperFlow recommends checking
the pump output pressure to ensure it is adequate for your engine’s
fuel requirements. To do this, insert a pressure gauge in the fuel line
after the pump and before the fuel pressure regulators. Remember,
pressure drops with increased flow rates.

Figure 1. Holley Blue

The MagnaFuel pump can deliver a tremendous amount of fuel when set up properly. Often, on
systems equipped with the spring bypass, you can switch to an adjustable bypass type and make
simple adjustments to accommodate a variety of engine fuel requirements. Both MagnaFuel and
Barry Grant offer adjustable bypass valves for these pumps.

SuperFlow recommends a –8 or –10 size fuel
return line to eliminate any restriction in the
line which would raise the fuel pump
output pressure. For the same reason, fuel
return lines should also dump fuel into the
top of the fuel cell—not push it in from the
bottom. Because the fuel amount bypassed
can be significant, this may cause fuel
aeration in the cell and create cavitation
problems for the fuel pump. Thus, we
recommend using either a splash guard in
the fuel cell or routing the return fuel along
the fuel cell side wall to prevent excessive
aeration.

Figure 2. MagnaFuel Pump

The battery (customer supplied) on the engine stand provides power for the fuel pump. On an
SF-901, this power travels through the engine box under the tool tray on the engine stand. A 30-
amp fuse on the side of the engine box provides current overload protection. Fuses on newer
systems (SF-902) are located on the engine control panel on the sensor box. Typically, the Holley
or MagnaFuel pumps require less than 15 amps current (AC) for normal operation.

Higher current draws may be caused by a jammed pump due to debris or a shorted pump motor.
Because the 30-amp fuse on the SF-901 also supplies voltage to the ignition and starter solenoid
circuits, if this fuse blows, both of those circuits will fail to operate. Often, a blown fuse may be
caused by an ignition system over current rather than a problem with the fuel pump. It is best to
troubleshoot a blown 30-amp fuse through a process of elimination and with the use of an
inductive current clamp and multimeter.

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If the fuel pump cannot energize and the 30-amp fuse is good, check the voltage at the two-pin
Molex® connector at the fuel pump for +12 VDC when the fuel pump switch on the console is on.
If +12 VDC is at the connector but the pump still does not energize, the pump has failed. If you do
not get +12 VDC, check your battery for good voltage.
If the battery is good but you still do not get +12 VDC at the Molex connector when you turn on
the fuel pump switch at the console, check whether a Limits file is loaded that tripped a limit
function to turn off the fuel pump relay. If this is the case, reset the limit through the software. You
can also reset the limit by pressing the Stop Program or Power ON/OFF buttons on the console. If
the limit continues to trip, check your limits file to see why.
A bad relay in the SF-901 engine box can also cause the fuel pump not to turn on. Four relays are
in the engine box under the tool tray. Three of the relays are the same type (fuel, ignition, and
starter). When standing behind the engine stand, the relays are Fuel, Ignition, and Starter from left
to right as you look into the engine box. They may be swapped for troubleshooting purposes. The
relays are standard Bosch relays and may be purchased from local auto parts stores.

If further troubleshooting is required, contact SuperFlow for assistance.

On newer systems, the engine control panel uses Polyfuses on the circuit board inside the sensor
box. If tripped, this type of fuse resets after several minutes. A Light-Emitting Diode (LED) on the
panel indicates red if the fuse has tripped.
The Holley and MagnaFuel pumps are designed to push fuel and work best when the fuel cell
provides some gravity flow to the pumps. Therefore, SuperFlow recommends raising fuel cells
slightly above the fuel pump height to help prime the pumps.
The MagnaFuel pump has its own built-in filter screen. The Holley is typically fitted with an
external filter.

IMPORTANT: Keep the filters clean to prevent flow restriction. We recommend periodic cleaning
or replacement.

Fuel Accumulator

The accumulator is generally trouble-free. It is in the system to provide a dampening effect to the
fuel before it enters the measurement turbines. Without the dampening effect, fuel flow readings
may become erratic, especially at low flow rates.
Older SF-901 systems (pre-1990) had a smaller volume version of the accumulator. If you are
encountering consistent erratic fuel flow readings or have switched to the high-volume
MagnaFuel pump, you may want to upgrade to the current style accumulator.

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Fuel Flow Turbines

The fuel-measurement devices cause most problems associated with the fuel system on the SF-901
systems. These devices are located under the engine and oil drip tray, which is a harsh and dirty
environment. Most fuel-measurement devices are completely ignored and receive no routine
maintenance until a problem occurs. Frequent inspection and general cleaning can significantly
extend their usable life and prevent problems from occurring during engine testing.
On new systems, the turbines are located under the tool
tray and generally sustain fewer problems than
turbines on the SF-901 systems.
These devices work by sending a beam of infrared light
through the turbine lens; the optical sensor on the
opposite side of the turbine then reads the beam. A
small propeller interrupts the beam of light when fluid
passes through the turbine and spins the propeller. The
system sees those broken light beams as pulses and
computes the amount of fuel that passes through the
device by counting the number of pulses per second.

The design of the suspended turbine mount on the SF-901
requires the electronic optics to receive a direct ground. This
is provided through a ground cable with a spade connector
that attaches to a spade lug on the fuel turbine housing. It is
very important to make this ground connection and keep it
clean to avoid high resistance. A bad ground connection
causes the fuel turbine electronics to cease functioning.
On newer systems, the ground is provided through the fuel turbine electronics cabling. No
separate spade ground connection is necessary.
The two fuel measurement circuits contain two separate electrical connections for the two
channels; this makes troubleshooting a single failed fuel channel easy by using the functioning
channel:

Fuel A Channel not Working; Fuel B Channel Working

1. Place the Fuel A channel optics 4-pin amp connector on the Fuel B channel wiring
2. If Fuel B now reads, the problem is in the wiring to the console or the circuitry inside the

console on the Central Processing Unit (CPU) card for Fuel channel A.

If further diagnosis indicates the problem is not on the engine stand, contact SuperFlow
Technical Support for assistance. You may be required to send the console CPU card to
SuperFlow for repair.

3. If Fuel B does not read, the problem is with the Fuel A mechanical turbine or the optics. Try
swapping the optics from the working turbine to the malfunctioning turbine.

4. If the malfunctioning turbine now works, the optics are bad. Purchase a new set from
SuperFlow.

5. If the malfunctioning turbine still does not work, the mechanical turbine is bad; remove it and
inspect. Often, debris will jam the turbine; you can sometimes dislodge it through careful
examination. Another problem can be the lens is no longer clear.

IMPORTANT: Using high-pressure air to clear debris or clean the lens will damage the turbine
propeller bearing. If you cannot repair it, purchase a new turbine assembly from SuperFlow.

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Figure 3. SF-902 Fuel Flow Block Diagram

Figure 4. SF-901 Fuel Flow Block Diagram

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Fuel B Channel not Working; Fuel A Channel Working

NOTE: Repeat the above steps for channel B.

The electronics on the turbines require +5 and +12 VDC supply voltages. These can be measured
on the 4-pin amp connectors where the optics connect. The pinout is:

• Pin 1 = ~10–12 VDC
• Pin 2 = The output signal (must measure with an oscilloscope to see the pulses)
• Pin 3 = +5 VDC
• Pin 4 = 0 VDC (ground)

NOTE: If you are measuring these voltages, use the engine stand chassis as ground.

If you are missing the +5 VDC on an SF-901 system, check whether the airflow and engine speed
readings were generated because these also use the same +5 VDC circuit on the 822 card inside the
engine box. Try disconnecting the air turbine cable and see if the +5 VDC returns. Often, the air
turbine cable burns and shorts the +5 VDC circuit.

If that does not solve the problem, contact SuperFlow for additional help. The 822 card inside the
engine box may require repair.

If you are missing +12 VDC on the SF-901 (it should read ~10–12 VDC), check the 1-amp fuse on
the side of the engine box. The fuse is the over current protection for the fuel turbine electronics. If
it blows, both fuel measurement channels will fail.
The +12 VDC on an SF-901 also passes through a couple of current-limiting resistors on the 822
card. These may fail individually, causing loss of a single channel.

Contact SuperFlow for additional help. The 822 card inside the engine box may require repair.

If the optics or the mechanical fuel turbines failed, you must replace them because they are not
repairable. According to FloScan, if a turbine is stuck and debris cannot be removed, it is not
repairable. However, a more common failure is contamination of the window where the optical
sensor transmits and detects the infrared light beam. It becomes contaminated with a film from
fuels passing through it. FloScan recommends pouring (not spraying) carburetor cleaner in the
window with one end sealed; then seal the other end, shake it around, let it sit for ½ hour to 1
hour, then shake it again and pour it out. This should remove anything covering the windows and
eliminate failed readings.
If you are experiencing an incorrect flow reading instead of no flow, first check that the proper
fuel-specific gravity was entered for the fuel you are using. Although the flow measurement
turbines initially produce a volume flow value, the system calculates the flow as a mass amount
using the fuel-specific gravity in the calculation. Thus, it is critical to use the proper specific
gravity value.
You can obtain specific gravity in several ways:

• Get the value from the fuel supplier.
• Use a hydrometer (one is supplied with every SuperFlow dynamometer).
• Weigh 100cc of fuel in a container. Whatever the fuel weighs in grams, place a decimal point

in front of the value for the fuel-specific gravity.

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If the fuel-specific gravity is correct but the flow numbers still seem incorrect, check the fuel
turbine calibration coefficients in the SF-901 Sensor Calibration file (or Z screen on DOS systems)
for the proper values. For newer systems, SuperFlow supplies 6 points to use in an interpolation
table to linearize the flow values. Make sure those values are correct for your system, using the
configuration viewer on the WinDyn tools menu. The interpolation tables are typically 138 and
139 for fuel channels 1 and 2. These calibration numbers are sent with every dynamometer system.

If you have misplaced the numbers, contact SuperFlow for assistance. You can also perform the
simple calibration check under “Calibrating Your Fuel System” on page 9.

Fuel Regulators

Fuel regulators are generally problem-free and can be replaced with a regulator of your choice
with no consequences. The standard Holley regulators will flow an adequate amount of fuel for
most applications (SuperFlow has flowed up to 600 pounds per hour through them).
To properly adjust the regulators, fuel must flow through them. An engine at idle may not always
flow an adequate amount of fuel through the regulators for proper adjustment.

IMPORTANT: Do not adjust the regulators when no fuel is flowing through them.

Many customers prefer to relocate the pressure gauges to allow viewing from the front of the
engine stand. Others prefer to use higher quality liquid-filled gauges. The new SuperFlow dyno
systems include high-quality liquid-filled Autometer gauges as standard equipment.
One SuperFlow customer switched to different regulators and then had excessively high fuel flow
readings. He reported hearing a “hammering” noise from the regulators. When he switched back
to the Holley regulators, the high fuel flow readings subsided. If you suspect this has happened on
your system, SuperFlow suggests running a flow test (use the weighted method described under
“Correcting Calibrations on an NGE System” on page 11) before and after the regulators to
determine if they are causing erratic fuel flow numbers on your system.

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SuperFlow Technologies Group Service Procedure

Calibrating Your Fuel System

WARNING: The following procedure requires you to work with fuel flowing into an open
container. Extreme fire hazard exists. Take all appropriate precautions when performing
this procedure.

The fuel flow turbines produce pulses as fuel flows through them when running the engine. The
dyno system electronics interprets those pulses and produces a fuel flow value in pounds per
hour.
The SF-901 uses a simple single point coefficient to compute the flow rate for each fuel channel.
The coefficients are stored in the SF-901 Sensor Calibration file (accessed through the fourth
option on the WinDyn>>Calibrate menu or through the Z screen for DOS systems). The data in
the Sensor Calibration file is then permanently stored in the Non-Volatile Random Access
Memory (NOVRAM) chips on the CPU card in the back of the console.
A typical coefficient would be:

125.0 hz = 300 lbs/hour fuel flow
In this example the coefficient is 125.0 which means when fuel (of specific gravity .750) is flowing
at a rate of 300 lbs/hr, the frequency from the fuel turbine will be 125 pulses/second. Fuel flowing
at that rate through each turbine would support the needs for a gasoline engine of 1200–1500 hp.
Your fuel turbine calibration coefficient for each turbine may be different than 125.0, but that
value is a good starting point if you do not know what the coefficient should be. To calibrate each
channel, you will need:

• Two empty, clean 5-gallon containers
• A scale capable of measuring to within a 10th of a pound
• A watch with a second hand
• A suitable length of –6 AN-type line to connect to the fuel outlet on the engine stand panel

(long enough to easily reach to one of the containers)
• A –6 AN-type cap to place on the end of the line and any adapter needed to put the cap on

the line
• A second –6 AN-type cap for the unused fuel channel
• An .080" to .100" drill bit
• A second person to assist

Calibration Procedure

1. Install the correct fuel-specific gravity into the system.
2. Connect the –6 line to the fuel channel to test.
3. Place one of the –6 caps on the fuel channel not being tested to block its fuel flow.
4. Use the .080" to .100" drill bit to drill a hole in the end of the other –6 cap.
5. Place that cap and any required adapter on the end of the –6 line. This will be the flow orifice

(representing a jet in the carburetor).
6. Place one of the empty containers on the scale and zero the scale.
7. Place both containers on the floor near the dyno.

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8. Use the container that you did not place on the scale as a catch can. Place your –6 line with the
drilled cap on it into the catch can.

9. Have your assistant turn on the fuel pump and begin flowing fuel into the catch can. While
fuel is flowing, set the regulator to ~6 psi. Once set, turn off the fuel flow.

10. If the catch can is rather full, empty the contents back into the fuel cell. You are now ready to
start a timed calibration check.

Timed Calibration Check

1. Set the display function on the SF-901 to show Fuel and set the fuel channel selector on the
console to display the channel you are flowing.

2. Instruct your assistant to monitor fuel flow on the console (or on a WinDyn screen object).
3. Place your –6 line with the drilled cap into the catch can.
4. Turn the fuel pump on and begin flowing fuel into the catch can. Watch the fuel flow number

on the display. It will take approximately 15–20 seconds for the flow number to stabilize (to
within a pound or two).
5. Once flow stabilizes, check your watch and start a countdown to begin a timed 60-second flow
into the container zeroed on the scale in step 6 in the “Calibration Procedure” above.
6. At the end of the countdown, quickly move the flowing fuel line from the catch can to the
measurement container.
7. Flow fuel into the measurement container for exactly 60 seconds.
8. Monitor the fuel flow on the console or in WinDyn and make note of the value. Write it down.
You can also manually record lines of data while the fuel is flowing and then look at the data
from the dyno.
9. At the end of the 60 seconds, quickly move the flowing fuel line back to the catch can.
10. Turn off the fuel pump.
11. Place the measurement filled container with fuel on the scale and weigh it.
12. Multiply the amount weighed in pounds by 60 to get pounds per hour.
13. Compare this number to the number observed on the console while flowing fuel. If they are
the same, your calibration coefficient is correct. If they are different, perform the flow test
again and see if your numbers repeat (to within a pound or two).
14. If the coefficient appears incorrect (fuel weighed does not match fuel flow displayed on the
console), make the following adjustments to the coefficient:
• Fuel Observed divided by Fuel Weighed = Error Factor
• Error Factor * Fuel Turbine Coefficient = New Coefficient
15. Enter the new coefficient into your SF-901 Sensor Calibration data screen.
16. Repeat the flow test with the new coefficient to verify the new coefficient produces a correct
flow value (to within 1–2 pounds per hour).
17. Repeat the procedure for the second fuel flow channel.

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Example:
Fuel turbine coefficient: 125.0
Fuel displayed on the console during flow test = 95 lbs/hr
Fuel measured in the measurement container = 100 lbs/hr
ErrorFactor = -1-9--0-5--0-- = 0.95
New coefficient = 0.95 x 125.0 = 118.8

The key is remembering that to increase fuel flow displayed by the console, you must decrease the
fuel turbine coefficient.
To decrease the fuel flow displayed, you must increase the fuel turbine coefficient.

Correcting Calibrations on an NGE System

Because the newer engine dyno systems use a six-point interpolation table, correcting these six
points can be more time consuming. However, you can use the method described above and then
derive a simple offset to adjust the fuel flow numbers.

Fuel displayed on the WinDyn Screen 3 during flow test = 95 lbs/hour
Fuel measured in the measurement container = 100 lbs/hour
ErrorFactor = 1--9--0-5--0-- = 1.053
Edit the appropriate fuel flow equation (channel 127 or 128) using the WinDyn Configuration
Editor.
Add a multiplier of 1.053 to the fuel flow equation to correct your fuel flow reading for that
channel.

Example:
Fuel1m = (Ful1hz T138 * 8.3378 * Fuel SG) * 1.053

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SuperFlow Technologies Group Service Procedure

Using the Air Turbine as a Frequency Generator

Parts Required

Part # Description Qty

E4230P-0061531 Connectors 2 ea
E4230P-661029 Pins 6 ea
E4230P-060621 Strain relief 2 ea
Red 18-gauge wire 6” 1 ea
Black 18-gauge wire 6” 1 ea
Green 18-gauge wire 6” 1 ea
Blank 3/8” wide 2” long labels 2 ea

By building the cable shown above, you can connect your air turbine to your fuel flow turbine
cables and then blow through the air turbine to see if you get a fuel flow reading on WinDyn or
the console.
This verifies the circuit is good and points to the fuel turbines, the +12VDC circuit, a grounding
problem on the SF-901 fuel turbines, or the fuel turbine optics.
You at least know your cabling and the circuitry in the dyno or the sensor box is functioning
correctly.

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