EFI "Case History"
EFI "Case History"
HESITATION ON ACCELERATION.
SO LET'S SOLVE A PROBLEM:
In a carburettor car you would look at the accelerator pump
or other fuel enrichment device. Maybe check the diaphragm on a constant
depression carbi. In system with a fuel pressure regulator working off
the manifold, the drop in manifold pressure causing a corresponding increase
in fuel line pressure and more fuel is injected. Or the injection pulse
width widens to jet more fuel into the cylinder. You can see the injector
pulsing by connecting your INTER-JECT LB-291/2F
into the fuel system by using the INJECTOR FLOW-METER for diagnosing the
INJECTOR PULSE and INJECTOR FUEL FLOW.
Watch the injector flow indicator staying steady on one set place at a
pressure setting of say 150 kpa. The computer puts this indicator regardless
of pressure changes to its set level at idle, then rev the engine slowly
up and you will see the flow and the time of the pulse increase by the
INJECTOR FLOW METER INDICATOR. The computer is told to do this by the MAP
sensor, the AIR FLOW METER or/and the THROTTLE
POSITION SWITCH.
The THROTTLE POSITION SWITCH sends the same signal as the throttle linkage
in the mechanical ACCELERATOR pump. "Foot
has gone down. Enrich mixture".
If the mixture is not enriched the car will behave as if it has a faulty
accelerator pump. If it has these symptoms you know where to look. As the
throttle position sensor is a moving part it is most likely the culprit.
MAP sensors don't give much trouble, but pressure regulators are very commonly
damaged by over pressurized servicing technique from aerosol rail cleaning
equipment such as RAM or others with air pressure.
A blocked fuel filter will NOT cause
these symptoms. In that case the car will go perfectly at all times but
it simply will not go fast. The oxygen sensor will hold the mixture exactly,
right up till the last drop. It is a common problem with cars having water
in the fuel which causes contamination and resin build up in the whole
system causing restrictions in the injectors. It
pays to check every car with the LB-291/2F in your TUNE UP services. Back
wash the filter after the service is completed and keep the rubbish in
a jar or in a INTER-JECT TEST BEAKER to show the customer.
This INTER-JECT guide plus the following hints will assist you in tracking
down the odd problems that are NOT covered in a normal general reference
books that you probably already have. See under section CONSULT1 (Your
Computer consultant Disk which come with the Equipment or | DOWNLOAD
from here now free |
and see under Air flow meter out of calibration
and air flow meters all types in general).
It comes more and more to our attention, that most mechanics in dealer
ships cover up faults by tampering with air flow meters and temperature
sensors to fool the computer with fitted resistors in the temperature wiring
circuit by not having the right equipment. Also squeeze pressure regulators
in a vice for higher pressure settings to remove hesitation. Remember,
if the engine does not have its free momentum at 100 kpa pressure and stalls,
do a full INTER-JECT service as you
have been trained for and then do calibrations last.
ANOTHER PROBLEM:- A VN COMMODORE has a slight miss or rough spot just over idle but it goes away at speed and does not occur under load during a road test.
QUESTION:- What is different about
these conditions?
LOGIC:- One is under 1200 RPM and one
is over.
The difference is, if you look at the PROGRAM (OPEN
LOOP AND CLOSED LOOP) "CONSULT1".
The most likely cause of such a problem in any car is SPARK.
If you know that you can get a spark showing outside the engine but
it still won't work inside the engine. (Holden
Rodeo, Mitsubishi, Holden VN, VR, VS and others) That's because
it is harder for it to jump the spark gap through the added resistance
of the compressed air. Mixture will also affect the spark. A lean mixture
offers a higher resistance and can destroy Distributor caps, rotor buttons,
leads and coils or coil-packs on VN's. So the slogan " THE WETTER
THE BETTER " is true up to a point. However, an excessively rich
mixture will cause the fuel to cover the entire plug and short the current
out such as happens when the engine is flooded. Alternatively the mixture
is so rich that there is not enough oxygen to burn it all and it goes through
into the exhaust. In the VN COMMODORE at the moment of going into closed
loop the mixture is quite lean. This does not normally cause a problem,
but if the coil is weak, the leads old and burned the slight miss comes
in. In other vehicles with distributors the spark has to jump the cap between
the rotor button and the spark lead point first and secondly the gap of
the spark plug. So you need a lot of energy to overcome the first obstacles
and there is the lean mixture still to overcome.
CHECK THIS WITH THE INTER-JECT POTABLE IGNITION MODULE PART NUMBER: 2632.
A new coil will fix it. Better put new genuine leads on too. (
Holden Rodeo, Mitsubishi, VL Commodore change the rotor button and Distributor
cup as well! ) We have had many reports via the INTER-JECT NET-WORK
of faulty non genuine leads on VNs. They run on 40,000 volts and the non
genuine ones won't do the job.
TRADE TIPS:
I have personally experienced this problem in some cars on trade
and training nights as we had to swap over to a back up car which had proper
leads fitted. This problem could occur with any other car and model. The
fact that it didn't break down under load was a bit of a false clue to
the students which may have thrown them off to look for an EFI problem,
as the evidence shows up in the INJECTOR FLOW METER that it is not an EFI
problem. Given enough load it may have broken down. Please read in section
"S" under SPARK PLUG TESTER (home made).
TRADE TIP:
Just because a coil or high voltage lead shows OK with a resistance
test doesn't mean that it is going to be all right when 100,000 volts are
going through it. The multi-meter only tests for ohm using a reference
voltage of probably 3 volts. It does not check for high voltage insulation
leakage's or conductivity. Use your SPARK PLUG tester or the INTER-JECT
portable ignition module or an OSCILLOSCOPE.
TRADE TIP:-
A short to ground in a tachometer wire or the instrument itself, may cause
a loss of ignition which may be also only intermittent.
More
case history of Injector leaking after an farmed out ULTRA
SONIC cleaning Job. Find out all the flustration of a customer
and how YOU can gain reputation in
your EFI servicing Business in YOUR Town!