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GL1100trike

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Dec 12, 2009
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Something I've thought about for a while is for someone with a little more expertise than myself to create a sticky about what should be happening when an old wing is started and then running. I've seen and used such a post on a Corvette Forum and found it very useful when trying to diagnose problems. It should begin from the time the key is turned. What do ya think? Respectfully.

PS, Dan..sorry for your recent misfortunes with this Forum, but glad to see you are getting past it.


83 GL1100 Trike Conversion
 
Thanks for the warm welcome but I was a member before the incident. What I am refering to is not necessarily a starting proceedure but what happens within the mechanics and electrical of the bike ring startup. The key turns which supplies power to the coil, then when the starter button is pressed it engauges the starter which turns the motor over and activates the fuel pump etc......
I am sure I am missing may other aspects of what needs to hppen within the system in order for the motor to suscessfully start and continue running. It may seem sort of elementary but it may help those having simple or not so simple problems as a sort of check list.
 
I'm envisioning a video clip, al-la CSI, where you turn the key on, and you get to see the electricity flow down thru the wiring, to the starter rely, out to the starter, around the windings, and out to....a timer with a bomb attached! :smilie_happy:

This is good idea for folks that basically know where to put the fuel and oil, but not much else. It would help them understand a little more about what is going on, or what should be going on.
I ain't all that up on 'Wing mechanicals at this point, so I'm out. :read:
 
I like the idea of a video Joel, but I am gonna keep a look out for any timers just in case!! :smilie_happy:

Roady has done some real good tutorials with pictures. (I'm not volunteering him, just using his posts as a reference.)
 
Oh MAN! This is gonna be fun! Thats "fun" as in stay up late, lots of coffee, red eyed, banging your head against the wall. it will be a living post, almost done then "BAM" someone will notice something we forgot... and 80-81's may not be exactly the same as 82-83's, then there is the Standards vs Interstates vs Aspencades... :smilie_happy:
You are gonna make me dig out the schematics (compliments of Sidecar Bob @ NGW) and try to remember what that diode in the neutral switch circut does.... aren't you!
The neutral switch illuminates a light on the cluster and is tied to the "Starter Magnetic Switch" (relay) through a "Silicon Rectifier" (diode) and the clutch switch. This prevents you from starting it in any gear other than neutral.
 
This is a sample of what I have found using the Corvette Forum:


L-98 Engine Start Sequence

knowing whats going on and WHY can help

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

Fuel Rail Pressurization:

When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.

Engine "Catches":

When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).

The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time” or less “on time”) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

Note that prolonged idling can force the computer back into open loop mode.

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.

Summary:

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.
 
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