M.2.b. Fuel-Related Starting Problems
Note:
When diagnosing a fuel system problem, a fuel pressure gauge will be needed.
•
With the ignition key switched on, the fuel pump should run for a few seconds. The fuel pressure
should then increase to the rating of the fuel pressure regulator (typically 43psi).
o
If the pressure does not rise to this pressure, there is either air in the line, or the fuel pump or
regulator is malfunctioning.
Air can be relieved from the fuel line by running the fuel pump for a minute or two.
o
If the pressure stays at 43psi but the engine will not start, look to the fuel injectors. With a
stethoscope (or a screwdriver placed against the ear), listen to the fuel injectors while
cranking the engine. A loud clicking sound should be heard. If none of the injectors are
clicking, there is a wiring problem.
Check for +12volts on one injector terminal with the ignition turned on. If +12volts
is present on one terminal, check the continuity between the other terminal and the
injector channels of the
TECgt
. If an oscilloscope is available, look for a +12 Volt
square wave at the injector connector
If the electrical test shows no problem, but the injectors are still not clicking, look to
the injectors themselves. A stuck injector will not click. An injector that is stuck
closed will not flow fuel, and an injector stuck open will flood a cylinder in short
order.
•
If the fuel system passes the above test procedure, look to the engine tuning calibration file.
o
Too much of a starting enrichment will flood the engine. A flooded engine will have spark
plugs that are wet with fuel.
o
Too little starting enrichment will keep an engine from starting and running properly.
o
A coolant temperature enrichment that is too low or too high will cause an engine to have
cold starting problems.
M.2.c. Spark-Related Starting Problems
•
The crank sensor is the first thing to check when an engine will not start.
o
Crank the engine. The LED on the
TECgt
ECU should flash red-green-red-green in a fairly
steady fashion (see
Section A.4
). If the light is not functioning in this manner during
cranking, and there is no RPM reading when viewed on a laptop, there is likely a trigger
problem.
Check the crank sensor alignment and air gap with the trigger wheel.
Check the crank sensor resistance (should be between 600 and 700 ohms across the
red and black wires).
o
If the LED is functioning normally, check for spark at the coils. Remove the two spark plug
wires from the coils, and watch for a spark between the coil towers during cranking. BE
EXTREMELY CAREFUL NOT TO TOUCH THE SPARK!! It will really be painful, and
can be deadly to people with pacemakers!
If there is no spark, check the wiring to the DFU and to the
TECgt
. Pin D on the
DFU should have +12volts with the ignition key on.
If the wiring is good, and the coils are still not firing, look to the software. Make
sure the appropriate calibration file is loaded.
If there is spark across the coil towers, but the engine will not run, check the plugs
and plug wires. Also be sure that the coils are firing the appropriate cylinders (see
Section C.3.
)! An engine will not run (or will run very rough) if the plug wires are
not going to the appropriate cylinders.
______________________________________________________________________________________
TECgt Manual Version 2.0
- Page 112 -
©2008 Electromotive, Inc.
