Starting Tips

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Page created by T Apr 14th 2009:

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Jumpstarting. Photo by Ashley186. Click to Enlargen.
 

Starting Tips:

When the Battery is weak these tips improve the chances of getting the Engine running.If the Battery is in normal condition these steps are not needed.  

Reducing The Load On The Battery:

Closed Throttle Cranking (Foot Off The Accelerator):

Cranking the Engine with the Throttle closed produces a vacuum in the Inlet manifold which causes
the least Compression in the Cylinders.  

Least Load Most Spark:

Because the Compression is least it makes it easiest for the Starter and Battery to turn the Engine.
With the least Load on the Battery there is more Spark output from the Ignition.
Simultaneously the Plugs need the least Voltage because the Spark will be jumping across the thinnest Air.  

Open Throttle Cranking (Foot To The Floor):

Cranking the Engine with the Throttle wide open produces no vacuum in the Inlet manifold which causes
the most Compression in the Cylinders.

Most Load Least Spark:

Because the Compression is greatest it makes it hardest for the Starter and Battery to turn the Engine.

With the most Load on the Battery there is less Spark output from the Ignition.

Simultaneously the Plugs need the most Voltage because the Spark will be jumping across the thickest Air. 

Best Voltage Best Chance:

Cranking with the Throttle Shut (Foot Off The Accelerator) gives the best chance of continued Cranking
and the strongest Spark. However with the Throttle closed the least mixture gets through.

Crank Then Pump:

For Carburettor Engines this simple method greatly improves the chances of getting an Engine started if the Battery is weak.

1. With the Ignition off so the Engine doesn't Crank, Pump the Accelerator all the way to the floor and back 5 times. This will inject sufficient Fuel into the Inlet Manifold to charge all the Cylinders.

2. Take your Foot right *off* the Accelerator. This gives the Battery the least load. Crank the Engine for  5 Seconds without touching the Accelerator Pedal.

 
3. Repeat steps 1 and 2 until the Engine fires. If no joy leave the Car alone for half an hour. The Battery will recover slightly. 

Flooded Engine:

A wide open Throttle is the best bet for Starting a Flooded Engine. It provides an abundance or Air so that a combustable mixturecan be produced. Only works with a good Battery. If the Battery is weak  leave the car with the Throttle jammed open for half an hour then try again.  

Cap Priming:

If a Carburettor Engine is being Started when the Float Bowl is empty a Capful of Fuel poured down the Carburettor Throat will make the Engine Start quickly and save a lot of Cranking. 
Cap Priming a Carburettor Engine is a fast way to get the Fuel System primed and to prove that the Ignition System is working properly. Photo by Ashley186. Click to Enlargen.
 This is also a quick way of eliminating a lot of variables if an Engine won't start without Cap Priming. For instance an Engine that fires from a Cap Ful of Fuel must have good Ignition, workable Valve Timing and Compression.If the Engine won't start without Cap Priming then the Fuel Pump may have failed meaning that the Float Chamber is empty.Alternatively it may mean that the Choke has failed or the Float Level is too low.  If the Engine won't start *with* Cap Priming it may be Flooded, have dead Ignition or some major Mechanical Problem like a stripped Cam Gear. 

Slow Crank Rate When Hot:

This can be caused by a low octane rating of the Fuel.

Workaround:

1. Force flood the Engine by cycling the Accelerator Pedal to the floor and released a few times and without cranking the Engine.  Then crank the Engine with the Throttle shut until the crank rate returns to normal.  This quenches any heat source in he Combustion Chambers. Then crank the Engine with the Throttle wide open and the Engine will start OK. 

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