MACS Monthly Newsletter - 2019 - APR3

NOTHING TO DO WITH HVAC, BUT EVERYTHING TO DO WITH YOUR SHOP OPERATION
The vehicle was a 2012 Ford F-350 that was getting major
work on its transmission, mated to a 6.2-liter gasoline V8. After
removing the flywheel, the ignition pulse ring (Figure 3) just sits
there on the end of the crankshaft. But with that flywheel out,
there's nothing really holding the pulse ring in place, and it fell
oﬀ, down to the ground (Figure 4). The job was being done with
a jack, so the distance it fell was perhaps something over a foot.
The technician looked at it, saw no apparent damage, and continued with the job.

Paul Weissler

motorcraftservice.com

The short distance to the ground and the absence of really
obvious damage to a pretty solid iron part produces this caution: when you drop a part, even one that looks pretty robust,
and even just a very short distance, don't just give it a cursory
look for damage. In this case, it had to be put on a flat surface
and checked very carefully against a ruled straight edge, which
showed the bends.

Figure 4: The pulse ring falls perhaps a foot to the floor, and the
beefy cast-iron part (placed on a work table) looks none the worse
for it. But Ford service material warns that if the part is dropped, it's
likely necessary to replace it. When the reassembled engine failed to
operate properly, the technician removed it and checked it.

Figure 3: With the transmission out, the ignition pulse
ring rests on the end of the flywheel of the 2012 Ford F-350
with the 6.2-liter gasoline engine. But there's nothing holding it there.

Paul Weissler

Finally came the time to reassemble, and when the job seemingly was done, the technician tried to start it. It ran for a few
seconds then stalled out. This unhappy result was repeated several times, at which point the technician began the usual round
of checks. Good spark, good fuel delivery, good compression.
At this point, the shop's senior technician remembered that
the pulse ring had fallen and decided, that although removing
the transmission and flywheel was not a happy prospect, it had
to be done. He took the pulse ring, put it on a flat surface and
checked (Figure 5). Sure enough, there was an ever-so-slight inward bend in a couple of the teeth. New pulse ring installed,
reassemble the job (now unprofitable but at least solved) and the
engine starts and runs.
We decided to check the Ford F-350 shop manual (online at
www.motorcraftservice.com) and in plain English, above a drawing of the pulse ring, it says "Note: inspect the ignition pulse ring
for damage. If the ignition has been dropped or has any visual
damage, it must be discarded."

Figure 5: He put the pulse ring on a flat surface and placed
a straight edge against it as shown. Careful inspection
showed that a few teeth on the ring were dented inward,
something that could not be seen with cursory inspection.
And some parts that seemingly couldn't be damaged, such as
something relatively light in weight, made from plastic, might
have developed a hairline crack. Takes maybe an extra minute
to check now, could save hours of miserable labor later. ■

IT'S FIXED? ARE YOU SURE?
The 2006 Dodge Durango with the 4.7-liter V-8 and the manual A/C was blowing 65°F air from the registers. Ambient temperature was in the low 80's, so a temperature drop of under
20°F indicates something's wrong. The refrigerant charge was
tested and verified with a certified SAE J2788 RRR machine. So,
the technician clamped oﬀ the heater hoses, and the A/C register temperatures dropped into a near normal range, which
convinced him to pull the dashboard for a close inspection, con-

April 2019

fident the problem was going to be something obvious, likely
with the blend air (temperature) actuator or door. No dashboard
R&R is a fun job, and this one was no exception.
Once he had the dash out, he couldn't see anything particularly apparent that was malfunctioning. The actuators worked and
the doors seemed to move normally. But because he was into
the job this far, he replaced the temperature actuator, and noting it was adjacent, the evaporator temperature probe too. And

MACS Service Reports

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MACS Monthly Newsletter - 2019

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