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Bob Blaylock

Reged: 04/24/01
Posts: 379
Loc: N38°35' W121°29'
“Also never pump the gas before you start it…”
#69509 - 10/25/02 08:08 PM

  With regard to a statement made in a separate thread:
In reply to:

Also never pump the gas before you start it either .
  On old-fashioned carbureter-equipped cars, you were supposed to pump the gas pedal once, to set the choke, before you cold-started it.  Modern fuel-injected cars don't have a choke, so no need for this.

  Also, on older, carbureter-equipped cars, there was a pump that would squirt extra fuel in when you pressed the gas pedal.  With most of such cars with which I was ever familiar, it was often useful to pump the gas a few times to prime the engine.  Again, this doesn't apply to modern fuel-injected cars.

  I've seen, in numerous places, statements like the above, saying not to pump the gas on a fuel-injected car before you start it.  The reasons why you would want to do so on a carbureted car don't apply, so there is clearly no need, and no good reason to do this.  But does it actually hurt anythng?  I can't imagine that pumping the gas pedal on a fuel-injected car, that is not running, would do anything at all, good or ill.

  Is there really a good reason not to pump the gas pedal before you start a fuel-injected car?

Hyster E60XM-33
1996 Mercury Mystique GS, Zetec, ATX
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Hard-core CEG'er

Reged: 03/11/01
Posts: 1603
Loc: Westchester Co., NY, USA
Re: “Also never pump the gas before you start it…” new
#69537 (Re: Bob Blaylock) 10/25/02 08:29 PM

Originally posted by Bob Blaylock:
Is there really a good reason not to pump the gas pedal before you start a fuel-injected car?


During the early 80s when fuel injection was coming online, the PCMs
that monitored your engine management controls were slow.

Pumping the gas and then cranking the engine would set the bandwidth of the injectors to FULL TIME,
because the last thing the PCM saw as you turned the key from on to start,
was a TPS setting close to Wide Open Throttle.
This in-turn would FLOOD your engine very easily.

In today's PCMs I doubt that pumping the gas would do any harm, since the speeds of today's PCMs are
quickly approaching real time calculations and adjustments.

But what do I know ?
Go out to your car, turn the ignition to ON and give the accelerator pedal
a few quick stomps and then crank her up !!!

Let us know what color your exhaust is...


2004 Mercury Marauder 300A
Black Clearcoat/Dark Charcoal LEATHER
DOB 10/31/2003
DOP 1/2/2004

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