Re: teknickle difikulty

["Dominic Sorresso" <surrexi2@home.com>]

Carl,

Your distributor may be ok. Do you have a 2 piece balancer? If yes, check to
make sure the outer ring hasn't slipped giving you a false mark for TDC. A
bouncing timing mark is can also symptomatic of a worn balancer. I went
through 2 of them and finally went with a Fluidamper.

Dominic
----- Original Message -----
From: "Walter Sherwin" <wsherwin@home.com>
To: <gmecm@diy-efi.org>
Sent: Friday, August 18, 2000 2:29 PM
Subject: Re: teknickle difikulty


> Hi Carl,
>
> Distributors of that vintage had more goofy problems (that would affect
> normal operation) than you can possibly imagine, especially once they had
> accumulated a few miles.  Take a good look at the reluctor assembly on the
> mainshaft.  The magnets had a tendency to either swell or crack, and the
> reluctor housing has been known to jump/slip on the mainshaft.  Holding
the
> distributor assembly in your hands, you should be able to feel 8 very
> distinct "tugs" as you rotate the shaft with light effort.  Forget about
> swapping internal parts, the cheaper solution is a complete new assembly
> from GM (1103952).   Below is a little blurb that I sometimes share with
> folks who are faced with diagnosing suspect distributors.  It's pretty
much
> applicable to all the popular SBC and BBC GM HEI/EST external coil ECM/PCM
> setups.  Internal cross-over was a big problem too.  Here goes........
>
> _____________________________________
> 10) Try disconnecting the EST Bypass line (same thing as the set timing
> connector that you disconnect when setting the base ignition timing) and
> driving the truck. If the situation seems improved, then you definitely
> have either a distributor problem or a problem with some portion of your
> EST system wiring.  If the operation does not change, then you also have
> a problem.
>
> 11) Lastly, my favourite pet peev......get on your distributor's case and
> make it prove to you that it is "Okay". Warm-up your engine. With a
> timing light connected to plug wire #1, watch the timing mark on your
> harmonic balancer with the engine at idle speed. Does the mark seem
> relatively steady, give or take a few degrees? If it appears that pulses
> from your timing light drop-out occasionally, or if the mark is wandering
> wildly all over the place, then there is definitely something wrong with
> your distributor. I've seen distributors that intermittently jump 30-90
> degrees out of phase, at or just off idle, that worked "okay" most of the
> time on the road. However, in those same vehicles all of the driveability
> concerns were 100% resolved by installing a known good distributor. What's
> a known good distributor? It's a distributor that has proven to work well
> in a real world truck application. I have one that I guard under lock &
key
> in my work bench. If it works okay in the subject vehicle, then I know
> enough to go buy a new distributor assembly. This test has not been wrong
> to date, and the recent service replacement distributor assemblies that I
> have examined have generally proven to have been adequate. Next,
disconnect
> the EST BYPASS connector to force the control system into backup ignition
> timing mode. Effectively, this gives autonomous control of the ignition
> timing to the distributor module, and bypasses the entire EST feature of
the
> PCM. Again, watch the timing mark on the balancer. With a stock SS chip,
> the timing mark should appear steady at around 4 degrees BTDC (yours may
> differ, depending upon the chip & settings you are running). Now, with
your
> other hand, slowly raise the engine idle speed towards 2000 RPM. The
timing
> mark should hold steady, plus or minus a couple of degrees to account for
> cam chain slack, and then there should be an abrupt shift of 6 degrees
more
> advance (kinda like someone threw a switch). This is the backup timing
> feature of the distributor module kicking in, and is completely normal and
> desirable. What you want to note is the RPM at which this shift occurred.
> If well before 2000 RPM (typically 1600 RPM), and if the previous tests
were
> passed, then your distributor is most likely okay. If the shift was
> nearer 2000 RPM, or yeeeeee gads, past 2000 RPM then your distributor is
> most likely FUBAR despite the fact that the previous tests may or may not
> have passed. If your distributor is FUBAR, you can gamble with replacing
> select internal components such as the mainshaft/pickup, but see earlier
> comments relative to complete assembly replacement.
> _____________________________________
>
>
>
>
>
>
>
> -----Original Message-----
> From: Carl Summers <InTech@writeme.com>
> To: gmecm@diy-efi.org <gmecm@diy-efi.org>
> Date: Friday, August 18, 2000 3:57 AM
> Subject: RE: teknickle difikulty
>
>
> >Hi Shannen,
> >    Verified the 10 degree jump the module provides at ~1600rpm with wire
> >unplugged.....Locked e-brake and loaded throttle with and without the
wire
> >plugged and diacom was accurate with the timing light....This is why I
> >brought up this question....I don't generally do diagnostic stuff so
> thought
> >some of you guys might have seen it and know why....As soon as I get the
> >vacuum leak fixed(next week) I'll delve into it a little deeper....Tried
> for
> >that 80+ million yesterday in the CA lottery....didn't get it...crap,
> >shoulda worked on this truck yesterday.  :)
> >-Carl Summers
> >
> >
> >
> >-----Original Message-----
> >From: owner-gmecm@diy-efi.org [mailto:owner-gmecm@diy-efi.org]On Behalf
> >Of Shannen Durphey
> >Sent: Friday, August 18, 2000 3:27 AM
> >To: gmecm@diy-efi.org
> >Subject: Re: teknickle difikulty
> >
> >
> >Somewhere around 1800-2200 rpm the module will advance timing if it's
> >not getting 5V from the ecm.  It's very sudden.  Disconnect 5V line,
> >start at 800, bring rpm up.  Watch for timing to jump.
> >
> >Timing matching with EST unplugged is a coincidence.  Prolly pretty
> >rare, too.  You might want to buy a lottery ticket since you're
> >beating the odds today.
> >
> >With the EST disconnected  I'd bet it wouldn't take much to find an
> >rpm/vacuum where Diacom and the timing light don't agree, if you were
> >trying.
> >
> >Shannen
> >Carl Summers wrote:
> >>
> >> Hi All,
> >>      Working on a 94 Chev Pu here with Blower and TBI, 7427
4l60E....has
> >> been running well for about 4 years...Runs really poor now...I start
with
> >> the basics and check timing and fuel pressure....fuel pressure is good
> but
> >> timing is 22degrees with est plug disconnected(should be 0)....so I
> >attempt
> >> to move it back and it doesn't like it...dies every time....I notice on
> >the
> >> diacom that the IAC counts down to 0 AND the diacom shows 22 degrees
> >advance
> >> with the EST unplugged....hmmmm....unhook the IAC motor and hook up my
> IAC
> >> tester/driver and close the IAC completely and engine still idles at
> >> 800.....anyway bottom line on the iac stuff is I have a vacuum leak
> >between
> >> the blower and the intake manifold...My question is: Have any of you
seen
> >a
> >> spot in the code that increases timing back to what is in the table if
> IAC
> >> will not lower the rpm enough???? Kinda seems backwards....I was
thinking
> >I
> >> had a bad ecm at first since I had an IAC code, EST code and some
> >> others....The timing with and without the EST wire plugged in always
> >matches
> >> what the diacom says so seems as if all is well with the ECM....Oh well
> >just
> >> checking with Y'all if you have seen this before....ttyl
> >> -Calr Summers
> >>
> >
>
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>
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