[Syty] engine problem

Sun Jan 7 22:42:03 CST 2007

I can only offer what I have done in similar instance. The first thing
is these engines are easily damaged by low fuel pressure. When fuel
pressure is low, the engine will run lean and the excessive heat will
damage the rings and you will end up with low compression. This will
exhibit itself as a rough running engine. There are several major things
to make an engine run correctly but the major items are good rings and
valves, good fuel pressure and injectors, no vacuum leaks, good plug
wires& plugs, electrical system, timed properly, and good computer.  

You can ensure fuel delivery system by checking fuel pressure as you
have already done.

You can check timing with EST lead disconnected in cab as you have done.

The last easy check is to physically check all the lines on the Vacuum
tubes to ensure no leaks

Pull all plugs but ensure you label the plug wires so they get put back
on in the proper order. With all plugs removed check compression around
160 lbs

Replace all plugs and double check the wiring from distributor to each
plug to ensure the wires are in the correct firing order at the
distributor cap and replace the wires if they are suspect or are the
factory originals (as you have done)You should also check condition of
the rotor and cap to see if they need to be replaced (as you have done).

In the past I have simply replaced these (as you have done) along with
the coil just to know I eliminated them as a possible issue.

Wires, Plugs, rotor, cap, coil total cost will be about $150 but worth
it to provide several years of good performance.

I had the issue three times that you are experiencing: 1st time it did
not run real bad but had a noticeable rough feeling due to bad rings on
cylinders 3 and 5 due to low fuel pressure (rebuilt the engine (90,000
miles) rebuilt with race parts so cost was high ($2500). 2nd time was
due to having the engine out of time. I had replaced the intake manifold
gasket material at the rear of the intake because an oil leak that had
developed (the sealer I used at rebuild did not hold up: the GM sealer
designed for this was used this time and it holds up). When I put the
distributor back in I forgot to disconnect the EST wire in the cab when
I timed the engine. The engine would idle OK but when driven and I
pressed the accelerator it would hardly run. I disconnected EST an timed
to 0 Degrees to fix the problem. 3rd time when I floored accelerator
engine would not accelerate well and pinged. I Fixed a vacuum lead that
was disconnected at the tube junction just to the right and slightly in
front of distributor. 

I approach these issues in this manner. If you have fuel, spark, and
timing the engine will run. The first thing I check is Fuel pressure,
next I check for timing and spark at each cylinder using a timing light
on all plug wires. IF I have fuel, Spark, and timing there should not be
an issue so then I go to things like replacing plugs, plug wires, rotor
& cap as you have done.

All this having been said and noting the work you have done it really
does seem you have eliminated all possible problems except a vacuum leak
and a compression test. To me the most often correct answer to your
particular symptoms is timing. I would double check this one more time
making sure the EST wire is disconnected and the timing light is on plug
number 1and also try it on plug wire for number 4.

To go any deeper you should use Diacom software.

________________________________

From: syty-bounces at syty.org [mailto:syty-bounces at syty.org] On Behalf Of
ken & deb rose
Sent: Sunday, January 07, 2007 8:08 PM
To: Syty at syty.org
Subject: [Syty] engine problem

I am stumped!! I put a brand new MCoy engine in my truck two years ago
and it ran fine until I ran the truck almost out of gas.  Shortly there
after one of my new injectors stuck OPEN so I replaced it and all was
well. The following year my son tj noticed that the knock sensor was
broke..must of happened when the engine was put in by my brother n law.
So tj put a new sensor in and the truck would hardly run so he checked
the timing and it was at 40 degrees advanced and yes he unpluged the
wire in cab first. He reset timing to zero and truck idled fine. Now if
you drive it like an old lady it runs ok but as soon as you give her
some pedal it runs terrible. It backfires and misses.We put in new plugs
cap and rotor then drove it for a while and rechecked plugs and they
looked good.We also rechecked fuel pressure and it was fine.. forgot to
mention the old plugs we replaced had to wide of a gap which could of
been from detonation we suspect, but maybe they were not gaped right
when put in. Never heard the motor pinging at all tho. The truck has not
been driven much so the motor has maybe 1500 miles on her and was never
beat on. We still have to check the injectors with tjs noid tester to
see if one or more is sticking. We wonder if the distributer is bad
cause it was the only thing I did not replace on the motor. I bought all
new sensors before motor was put in.Also plugged in code reader and all
was good. But come to think of it me and the kid seem to think the old
motor with a bad rod had more snot to it but hard to say. Could my
computer be bad?? Anyone have any ideas what could be wrong? Also forgot
to mention that the motor revs fine when sitting in park, , No miss..
Idles a bit rough but it does have a cam...almost seems like a slite
miss at idle but could be the cam.. I AM AT THE END OF MY ROPE WITH THIS
MOTOR..KEN.....

kenneth  h  rose  jr   <http://graphics.hotmail.com/emrose.gif>
<http://graphics.hotmail.com/emrose.gif>
<http://graphics.hotmail.com/emsmiled.gif>
<http://graphics.hotmail.com/emsmilep.gif> 

rosekendeb at hotmail.com

________________________________

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