RE: IML: the hot starting problem,,,,,,again!!!!

[David Whitney <david.whitney@xxxxxxxxxxxx>]

If your car starts with a couple pumps of the throttle, that is the "shot"
from the accelerator pump.  That means you have fuel in the bowls.

You need three things for combustion:  air, fuel and spark.

Underhood temperature can get high on our cars, even with a proper cooling
system.  Manifold heat radiates into the carb, causing evaporation from the
fuel bowls in some cases.  That is also a main cause of Thermoquad body
cracking.

That said, seldom does fuel evaporate from a properly operating carburetor
in just a few minutes.  More likely the air going into your carb is so hot
it is inhibiting combustion.  If you want to go to the trouble, rig a cold
air intake by running tubing to your air cleaner intake from a cooler
place.

As always, remote diagnosis and troubleshooting makes some assumptions
about your car.  I am assuming no obvious vacuum leaks (including making
sure both halves of the carb are screwed together properly and the carb is
properly attached to the manifold, and all vacuum fittings on the carb have
a hose attached or are capped).  Also that the timing has been set properly
and the plug wires are insulated and the plugs have the correct gap.

I would do the following:

1.  Pull your plugs, inspect and clean or replace if necessary.  Fouled
plugs dry off as the engine cools, allowing a cold start.  When they are
hot they won't spark well.  If fouled, try to figure out why and you will
probably correct the hot start problem.

2.  Try to hot start as before, except pull the distributor vacuum advance
hose and cap the nozzle on the carb.  At low idle (what you expect on hot
start), there should be no vacuum advance anyway.  If that works, check
that hose and the vacuum diaphragm for leaks and make sure you have all the
advance dialed out of the distributor.  Now you have spark.

(For those who don't know, many stock 413/440 vacuum diaphragms have
adjustable advance, anywhere from fully advanced at idle to a 15-degree
advance curve.  It is set with an Allen wrench.)

3.  Same hot start setup as 2. above, except with the air cleaner housing
off.  Is the choke flap fully open?  Is the fast idle screw fully
disengaged from the high idle cam?  Manually prime the carb with some fuel
or carb cleaner, do not touch the accelerator pedal and crank the engine.
If that works, your carb is working fine.  If not, try again but have a
buddy hold one hand over the top of the primary bores to inhibit air flow
while you crank the starter.  If that works, check for vacuum leaks and
make sure your primary throttle plate is fully closed at idle -- if the
transfer slot looks like a square, that's good.  Symptoms of a vacuum leak
are masked during a cold start because the choke flap is closed,
accomplishing the same thing as holding your hand over the bores, and the
fuel/air mixture is much richer when the choke is set.  Now you have air.

4.  Same hot start setup as 3. above, except instead of priming the carb,
firmly press the accelerator pedal to the floor and release (if you have a
buddy to watch the carb while you do this) or pull back on the primary
throttle linkage with your finger and release (if you do not have a buddy
with you).  Does gas squirt into the carb from the accelerator pump
nozzles?  Now you have fuel.  If not, assuming your accelerator pump
actually works, then your carb bowls may well be empty.  Remove the top of
the carb.  If the bowls are empty, then you know what your problem is.
Check your float height and float drop settings and shield your carb from
heat.  If they are full, your accelerator pump does not work but you still
haven't solved the hot start problem.

Out of curiosity, when was the last time you did a compression test?

And don't forget to reattach the distributor vacuum advance hose when you
are done.  The car will start without it, but it will begin to miss and
ping at higher RPMs.

Happy motoring,

David





                                                                                                                                              
                      "DR CHALLENGER"                                                                                                         
                      <drchallenger@xxxxxxxxxx        To:       mailing-list@xxxxxxxxxxxxxxxx                                                 
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                      Sent by:                        Subject:  RE: IML: the hot starting problem,,,,,,again!!!!                              
                      mailing-list-owner@imper                                                                                                
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                      05/18/2005 01:45 PM                                                                                                     
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i have 4 carbureted cars and i have not had to resort to installing an
electric pump. they always start with a couple pumps of the throttle.








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