Help, seize when cranking on cold starts

[someotherguy]

Long shot here but as long as we're guessing, here's something you can test. Next time it does this.. pull the distributor cap, see if there's any indication of moisture. Shoot it with WD40. Re-install and try again. Be careful with the cap screws; it's very common for the tabs on the distributor body to already be cracked, if not broken. If one of them does break or strip out don't panic. You can easily zip-tie the cap around the distributor body for a tight fit.

Richard

 

[Road Trip]

@Schurkey 's "voltage drop while cranking" test is well worth doing.

I was asked to troubleshoot a '70 Chevelle that cranked very slowly on a cold start,
and even slower on a hot start? Previous mechanics had thrown a big (high CCA) new battery
and a new starter at it, and were now telling the owner that there must be something wrong
inside the engine itself causing excessive drag? (There was a high compression 383ci
small block installed.)

The first thing I saw was the relatively tiny original battery cables being used. The car was
originally manufactured with the low compression 307-2bbl, so smaller battery cables made sense.
I told the owner that an original set of heavy gauge battery cables for the LS-5 454 would be a
much better match for the high compression 383. (More than enough battery cable doesn't hurt, but too
little definitely does!)

After purchasing the big block battery cables & upgrading the car with them, the problem was instantly
solved. Although the Chevelle's battery cables failed a visual inspection, if I had used Schurkey's
'voltage drop during cranking' check it would have certainly confirmed the inadequate wiring diagnosis.

****

Long shot here but as long as we're guessing, here's something you can test. Next time it does this.. pull the distributor cap, see if there's any indication of moisture. Shoot it with WD40. Re-install and try again. Be careful with the cap screws; it's very common for the tabs on the distributor body to already be cracked, if not broken. If one of them does break or strip out don't panic. You can easily zip-tie the cap around the distributor body for a tight fit.

Richard

@someotherguy 's scenario:

Another time I was troubleshooting a slow/erratic start was on a high compression
'66 Olds 425ci. This one had me stumped, for the engine had been starting reliably
for quite some time prior to the symptoms suddenly showing up. And this time it
was a fast AND slow thing. It seemed to run through several cylinders at normal
speed, and then almost come to a complete stop...and then back to full speed, only
to repeat, as if there was a mechanically bad cylinder?

I pulled all the spark plugs and cranked the motor over, and it spun faster (expected) and
also completely smooth with no more near-seizing behavior. (unexpected) A compression test
showed all 8 cylinders were evenly matched & well within specification, so there was no
physical issue with the engine, starter, and battery? Since the only thing I had done
was remove the spark plugs (ignition system) from the equation, it had to be in there
somewhere?

Sure enough, a careful look at the inside of the distributor cap showed a carbon track
had developed between 2 adjacent cylinder contacts? So what was happening was that
(via the carbon track) I now had a cylinder where the spark plug was being fired 90°
too early, causing that cylinder's combustion pressure to go high too early, trying to
force that piston back down the cylinder in the opposite direction, and causing the
engine to nearly halt once every 2 revolutions. And then once we got past that point
the engine would spin smoothly through the next 6 cylinders no problem before
hitting the bad spot (carbon track) and repeating the stall symptom.

****

So, in these 2 examples of "slow cranking", the only difference between them was
that the engine with the 'too small' battery cables was 'smooth/consistent, but too
slow.' On the engine with the bad ignition/carbon track, the engine spun at full speed,
almost came to a full stop, and then back to full speed. Way more erratic behavior.

****

Just some food for thought. If this engine bay is completely stock, and all the
individual high-amperage connections are in new condition, then I'd pay close attention to the
spark distribution stuff. When high voltage creates unexpected short cuts to ground you can
get some really counter-intuitive symptoms.

Good luck -- and let us know what you discover.

 

[L31MaxExpress]

GM has a TSB for a bad crank sensor causing kick back on the starter. It will break the starter, tear teeth off the ring gear or even break the block.

 

[L31MaxExpress]

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 00-06-04-014

Date: April, 2000

TECHNICAL

Subject:
No, Hard, or Slow Start, Backfire or "Kickback" During
Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338
(Replace Crankshaft Position Sensor)

Models:
1999-2000 Cadillac Escalade
1995-2000 Chevrolet and GMC S/T Models
1996-2000 Chevrolet and GMC C/K, M/L, G, P Models
1996-2000 Oldsmobile Bravada
with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine
(VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29)

Condition:
Some customers may comment on one or more of the following conditions:

^ Backfire during crank/start
^ "Kickback" during crank/start
^ "No" start
^ "Slow" or "hard" start/crank
^ "Grinding" or unusual noises during crank/start
^ Cracked or broken engine block at the starter boss
^ Broken starter drive housing
^ Broken starter ring gear on flywheel
^ Any combination of the above

Cause:
A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss.

Correction:
Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear).

Notice : When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel.

Important : Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal.

Parts Information:

Parts are currently available from GMSPO
Crankshaft Position Sensor, P/N 10456607

 

[CumminsFever]

You didn't say what transmission you have. If it is automatic, there is a chance something malfunctions internally when the oil is thicker.

 

[Mossback]

These are all good thoughts thank you guys.

It’s an automatic btw

 

[HotWheelsBurban]

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 00-06-04-014

Date: April, 2000

TECHNICAL

Subject:
No, Hard, or Slow Start, Backfire or "Kickback" During
Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338
(Replace Crankshaft Position Sensor)

Models:
1999-2000 Cadillac Escalade
1995-2000 Chevrolet and GMC S/T Models
1996-2000 Chevrolet and GMC C/K, M/L, G, P Models
1996-2000 Oldsmobile Bravada
with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine
(VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29)

Condition:
Some customers may comment on one or more of the following conditions:

^ Backfire during crank/start
^ "Kickback" during crank/start
^ "No" start
^ "Slow" or "hard" start/crank
^ "Grinding" or unusual noises during crank/start
^ Cracked or broken engine block at the starter boss
^ Broken starter drive housing
^ Broken starter ring gear on flywheel
^ Any combination of the above

Cause:
A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss.

Correction:
Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear).

Notice : When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel.

Important : Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal.

Parts Information:

Parts are currently available from GMSPO
Crankshaft Position Sensor, P/N 10456607

I wonder if something like this, was the problem on my Burb, that made the starter and flexplate get messed up. I have replaced the crankshaft position sensor on it, back in 2018. This was a couple of years after the flexplate and starter were replaced.

 

[Mossback]

@Schurkey 's "voltage drop while cranking" test is well worth doing.

I was asked to troubleshoot a '70 Chevelle that cranked very slowly on a cold start,
and even slower on a hot start? Previous mechanics had thrown a big (high CCA) new battery
and a new starter at it, and were now telling the owner that there must be something wrong
inside the engine itself causing excessive drag? (There was a high compression 383ci
small block installed.)

The first thing I saw was the relatively tiny original battery cables being used. The car was
originally manufactured with the low compression 307-2bbl, so smaller battery cables made sense.
I told the owner that an original set of heavy gauge battery cables for the LS-5 454 would be a
much better match for the high compression 383. (More than enough battery cable doesn't hurt, but too
little definitely does!)

After purchasing the big block battery cables & upgrading the car with them, the problem was instantly
solved. Although the Chevelle's battery cables failed a visual inspection, if I had used Schurkey's
'voltage drop during cranking' check it would have certainly confirmed the inadequate wiring diagnosis.

****



@someotherguy 's scenario:

Another time I was troubleshooting a slow/erratic start was on a high compression
'66 Olds 425ci. This one had me stumped, for the engine had been starting reliably
for quite some time prior to the symptoms suddenly showing up. And this time it
was a fast AND slow thing. It seemed to run through several cylinders at normal
speed, and then almost come to a complete stop...and then back to full speed, only
to repeat, as if there was a mechanically bad cylinder?

I pulled all the spark plugs and cranked the motor over, and it spun faster (expected) and
also completely smooth with no more near-seizing behavior. (unexpected) A compression test
showed all 8 cylinders were evenly matched & well within specification, so there was no
physical issue with the engine, starter, and battery? Since the only thing I had done
was remove the spark plugs (ignition system) from the equation, it had to be in there
somewhere?

Sure enough, a careful look at the inside of the distributor cap showed a carbon track
had developed between adjacent cylinder contacts? So what was happening was that
(via the carbon track) I now had a cylinder where the spark plug was being fired 90°
too early, causing that cylinder's combustion pressure to go high too early, trying to
force that piston back down the cylinder in the opposite direction, and causing the
engine to nearly halt once every 2 revolutions. And then once we got past that point
the engine would spin smoothly through the next 6 cylinders no problem before
hitting the bad spot (carbon track) and repeating the stall symptom.

****

So, in these 2 examples of "slow cranking", the only difference between them was
that the engine with the 'too small' battery cables was 'smooth/consistent, but too
slow.' On the engine with the bad ignition/carbon track, the engine spun at full speed,
almost came to a full stop, and then back to full speed. Way more erratic behavior.

****

Just some food for thought. If this engine bay is completely stock, and all the
individual high-amperage connections are in new condition, then I'd pay close attention to the
spark distribution stuff. When high voltage creates unexpected short cuts to ground you can
get some really counter-intuitive symptoms.

Good luck -- and let us know what you discover.

As for the pre-ignition causing high compression, I unhooked the coil to the disty and the symptom remained.

 

[HawkDsl]

I'm so happy I have a pre 94

 

[someotherguy]

I'm so happy I have a pre 94

pre-1996, sir.. the gmt400's were OBD1, TBI, all the way thru 1995.

Richard