Hard Start Problems

[Dr. Ian McArthur]

Over the last year I have had both cold and hot start problems with one of
my 5TQs similar to those recently posted.

Poor hot start:  leaky injectors.  I installed new injectors in one car and
everything is fine.  The other still has slightly leaky injectors and takes
a while to start when hot.  Its flooded from the leaks.  Starts really well
on very cold days (like the -40 we typically get up here in the mountains)
since the leaks act like a choke that's working even before the cold start
injector pumps much fuel.

Another serious hot start - like no start at all - took me a couple of weeks
to figure out.  It was the check valve on the fuel pump.   I figured this
out by installing the "Big Red Button" posted in the archives.  This is a
momentary switch with long wires to a connector that will plug into the cold
start injector ... got it from a do-it-yourself junk yard.  It took about
ten minutes to make up.  I unplug the connector on the cold star injector
and replace it with my Big Red Button connector.  Now I have a manual choke.
I run the wire through the side window.  When the car would not start I gave
it a short shot from the cold start injector with the Big Red Button.  Fired
right up.  This is why:  the injectors will not fire until a certain fairly
high fuel pressure exists.  With a faulty check valve on the fuel pump there
is not enough pressure build up when first starting.  The fuel pump has to
re-fill the fuel accumulator before the system pressure rises enough for the
injectors to fire.  Since the cold start injector will fire regardless of
system pressure, the Big Red Button provides enough fuel; to fire up the
engine.  Another push or two will keep things running until the fuel
pressure builds up.

Poor cold start: If the injectors are not leaking and the fuel accumulator
and fuel pump check valve are okay, I would first suspect a low battery
voltage during cranking (due to the large current drain from the starter)
is preventing the ECU from functioning properly and therefore no spark.
Another very common problem with starting up here where it gets really cold
is folks who don't know how the system works. They crank the engine over, it
doesn't start, so they do it again.  And again.  Each time pumping more raw
fuel into the intake manifold from the cold start valve until the car is so
flooded it will never start.  Once again, the Big Red Button does the trick.
If one of my cars won't start when its really cold I disconnect the CSV and
install the Big Red Button ... right away, before I crank the engine over
again.  Then I can manually control the "choke."

This Big Red Button is such a good diagnostic tool that I have one in the
trunk of all three of our 5TQs.

The bottom line:  1. Get new injectors.  You can check them for leaks easily
but you risk breaking off the plastic shields inside the injector mounts if
the injectors are really old.  That is a pain.

2. Check the fuel pressure.  During starting the system depends on residual
fuel pressure.  If the fuel accumulator is leaking, the pressure is lost
over time.  If the fuel pump check valve is leaking, same thing only
quicker.  If the injectors are leaking, same thing plus flooding the engine.
On a "good" car the fuel pressure will be maintained over night.  On a "bad"
car the pressure will drop to zero in anywhere from almost instantly to an
hour or so.
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Dr. Ian McArthur, Consulting by Acronym, Cochrane, Alberta
sutul at telusplanet.net