For about the fifth time in three or four months, my 99 5.7 has backfired
out the evap canister while cranking. Today, I went to start it hot, I it
cranked for about a half-second then backfired. A ton of smoke came from
under the hood. (Almost as much smoke as in a message from Snoman.) I
cranked it again and drove away.
No MIL and otherwise runs great. Where do I start?
Start with the ignition system.
The distributor cap on this style ignition is notorious for
cross-firing between cylinders when the cap gets some age on it.
Use only a genuine Delco cap, no aftermarket cap will last more
than 2 months. Make sure the vent screen in the bottom of the
distributor bowl is clear.
Insulation breaking down on plug wires will also allow
cross-firing between cylinders, use quality Belden or Delco wires.
Now, how is the backfire getting to the canister??
Only way would be a leaking vapor purge solenoid AFAIKS.
Thanks Neal. I didn't think to start with the ignition. You're right that
the unexpected spark is there somehow. Now on that cap, I put a cap and
rotor and cleaned the distributor last winter when I changed the lower
intake gaskets. (You might remember the problems I had with the P1345 code
after stabbing the distributor.) I did put a new cap. I think I had to
settle for a Borg-Warner...but I'll have to double check. I'll also check
all the wires, etc.
Now let me tell you one ASSumption. The few times it has done
this...especially yesterday. Smoke bellowed from under the front left corner
of the hood. I'm ASSuming the smoke is coming out of that canister. The air
intake is over on the other side. Could the smoke be coming from somewhere
else? and let me tell you, that smoke stinks. First time I thought it was
all the wires and the power distribution box that sits on the left front
tire. Scared the crap out of me.
Alright, time for NASCAR with the kids.
Everytime this has happened, the engine did not start so the fan didn't turn
much but certainly could influence.
Where do you think the smoke is coming out? Upstream of the filter? out one
of the clamps / flex hoses to the TB?
Thanks...and I'll check those wires tomorrow night.
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