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Old 08-08-2021, 06:22 PM   #1
jwolf90
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2001 SC2
Default 2001 SC2 Slow Crank After Rebuild

Hello All,
Wanted to share my experience in hopes of helping someone else as well as get your thoughts on the matter. As subject suggests, in the process of getting my 2001 SC2 engine operational following a rebuild. For initial start procedure I added 2 tablespoons of oil to each cylinder, disabled ignition system by unplugging spark plugs and removing fuel pump relay and fuse and cranked engine with spark plugs removed until oil light on dash went out indicating presence of oil pressure. Cranked a little slower than pre-rebuild without plugs. Here's where it gets interesting. After I vacuumed oil out of cylinder, reinstalled plugs, reinstated ignition system and allowed fuel pressure to build up I attempted to start the engine. It cranked over but very slowly. Sounded like it would crank over to the next compression stroke and pause for about a second until it overcame the compression resistance and repeat. At this point I realized the issue could be electrical or mechanical. My battery and starter had been sitting unused for 4 months while (slowly) rebuilding engine so I thought it could be a weak battery. I also pulled the plugs and turned crank by hand with torque wrench and registered 28 ft-lbs maximum torque required to turn crank through 2 rotations. After researching this torque value seemed maybe a little bit high but not crazy high. I had battery tested at Orielly and it passed whatever test they used. Checked and cleaned/dielectric greased ground points: front top engine mount, starter to transmission and transmission to block bolts. Cleaned and dielectric greased starter terminals. Still slow crank. Replaced starter with re-manufactured starter thinking that starter could be getting tired. Rebuilt starter not only didn't noticeably improve crank over speed but also made a click noise with no cranking at all sometimes. Tried briefly using battery charger start function to crank engine. Would crank over but not fast enough to fire. Put battery on trickle charge overnight thinking that a low battery might be interfering with battery charger starter. No significant improvement in crank over speed. Tried the battery in my other vehicle to see if it would crank over and it cranked over and started the other vehicle just fine. At this point all the evidence seemed to say that the issue was not electrical. I removed accessory drivebelt and made sure all pullies turned freely. Max torque to rotate crankshaft with accessory drivebelt removed was 24 ft-lbs. At this point decided to dig deeper to see if there was something wrong mechanically whether it be the crank and connecting rod bearing oil clearances or a timing issue. Dropped oil pan and checked all main and connecting rod bearing oil clearances with plastigauge. Clearances were all within specs. I did notice that gaps on either side of the center thrust bearing between the crankshaft and thrust bearing surfaces were not equal. Thinking that the crankshaft might have been contacting one side of the thrust bearing, I loosened the main bearings slightly and tapped on the end of the crankshaft with a mallet and was able to thereby even out the gaps on either side of the thrust bearing surfaces. Re-torqed the crank bearings following Haynes procedure. Added 3 tablespoons of oil to each cylinder and turned crankshaft by hand for several minutes to make sure there was plenty of lubrication. Removed valve cover and verified that cam timing marks were at 12 o'clock position when cylinder 1 was at TDC of compression stroke. Torque to rotate crankshaft at this point was under 20 ft-lbs, right around 19 or so. Didn't change camshafts or camshaft caps so didn't see point in checking camshaft oil clearances. Haven't checked the pistons/rings since I don't know how I feel about pulling off the timing cover/chain and head just yet. Was very careful when installing piston rings to make sure the upward marks were facing up and that the ring gaps were all within specs. I'm wondering if anyone has had a similar experience and if so if you would be able to share your thoughts. Does the 20 ft-lbs seems like a reasonable value for crankshaft hand rotation without accessory belt and spark plugs removed? I mistakenly followed the Haynes manual and filled oil pump with petroleum jelly. Could this be cause of any excessive rotational resistance? Is there an obscure ground point that I am missing that could be corroded? Could the newly rebuild engine tightness be revealing a tired battery needing replacing? Should I consider connecting multiple batteries in parallel with starter and see what happens???
Any input/thoughts/help on this matter is greatly appreciated!
Thank you in advance!
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Old 08-08-2021, 08:26 PM   #2
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Default Re: 2001 SC2 Slow Crank After Rebuild

That 20-30 ft-lbs to rotate an engine with new rings sounds OK to me.

Take compression readings!

The crank floats around between those two thrust bearings. You did no harm forcing it in one direction, but accomplished nothing. The crank will seek its own "happy spot" with the engine running, but will be tight against the passenger-side bearing when the clutch on a manual trans is disengaged (pedal down).

If in any doubt about the power to the starter (battery, cables, ground, whatever), simply connect a voltmeter between the starter case and the stud on the starter solenoid where the cable/strap going into the starter connects. That voltage should not drop under 10V when cranking.
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Old 08-08-2021, 09:03 PM   #3
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Default Re: 2001 SC2 Slow Crank After Rebuild

I'd suspect electrical.
...
Bryan Cotton
'99 SL2, 5SP bought new
Rebuilt at 204,067 September 2017
Engine, subframe, diff pin mod, brake lines, headliner, alternator, and so on!
'98 SC2, 5SP bought 2018
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Old 08-08-2021, 09:58 PM   #4
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Default Re: 2001 SC2 Slow Crank After Rebuild

Quote:
Originally Posted by billr View Post
That 20-30 ft-lbs to rotate an engine with new rings sounds OK to me.

Take compression readings!

The crank floats around between those two thrust bearings. You did no harm forcing it in one direction, but accomplished nothing. The crank will seek its own "happy spot" with the engine running, but will be tight against the passenger-side bearing when the clutch on a manual trans is disengaged (pedal down).

If in any doubt about the power to the starter (battery, cables, ground, whatever), simply connect a voltmeter between the starter case and the stud on the starter solenoid where the cable/strap going into the starter connects. That voltage should not drop under 10V when cranking.
That's what was gathering from what numbers/others' experiences I could find WRT crank rotational torque.

Just curious as to what the compression test would tell. I guess if the compression is excessively high it would mean potentially the wrong rings or valves not opening when they should?

That makes sense about the crank floating. Was kinda searching for anything I could find that could be a friction issue.

I'll try checking the voltage difference between starter solenoid terminal and starter body.
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Old 08-08-2021, 10:01 PM   #5
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Default Re: 2001 SC2 Slow Crank After Rebuild

Quote:
Originally Posted by Waiex191 View Post
I'd suspect electrical.
The battery is right around 3 years old so it might be on its way out, plus with the added resistance of new rings it might be time to replace it.
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Old 08-08-2021, 10:28 PM   #6
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Default Re: 2001 SC2 Slow Crank After Rebuild

The compression test will tell you if the compression is abnormally high, and that is the cause of slow cranking; nothing to do with the starter system. Taking compression is so easy to do on these engines, you should get that out of the way, before fussing with anything else.

If compression is way high, it won't be from new rings or valve operation. Any problem with either of those will show up as lower compression, not higher. Has the head surface been shaved a lot? If not, the mostly cause of too-high compression is all that oil you dumped into the cylinders.
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Old 08-08-2021, 11:19 PM   #7
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Default Re: 2001 SC2 Slow Crank After Rebuild

Quote:
Originally Posted by billr View Post
The compression test will tell you if the compression is abnormally high, and that is the cause of slow cranking; nothing to do with the starter system. Taking compression is so easy to do on these engines, you should get that out of the way, before fussing with anything else.

If compression is way high, it won't be from new rings or valve operation. Any problem with either of those will show up as lower compression, not higher. Has the head surface been shaved a lot? If not, the mostly cause of too-high compression is all that oil you dumped into the cylinders.
Head surface has not been shaved at all to my knowledge. How do you recommend getting the oil out of the cylinders? Used vacuum line taped to shop vac hose to vacuum most of it out, but was having trouble getting all of it around the edges of the piston head. Do you think 1/16" - 1/8" layer of oil on piston create abnormally high compression?
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Old 08-09-2021, 12:34 AM   #8
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2001 SC2
Default Re: 2001 SC2 Slow Crank After Rebuild

Best way to get the oil out is to put paper towels over the spark plug holes to limit the oil spray on everything (but don't plug up the holes) while you crank it over.

If you do get around to a compression check, you need a fully charged battery and block the TB fully open. A new engine should be 205-210psi, service limit is 180psi.


Based on the symptoms I'd start with fully charging the battery (should come down to 12.7-12.8v after 30-45min). While it's charging I'd clean up all the battery cables and the fuseable link to the alternator.
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Old 08-09-2021, 10:20 PM   #9
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Default Re: 2001 SC2 Slow Crank After Rebuild

Without jinxing myself wanted to share the good news that I think I found my issue. Picked up compression tester from AutoZone this afternoon and did compression test. Had battery on charger all day while at work. Battery seemed good at 12.91 volts. Checked voltage between starter solenoid terminal and starter chassis while cranking engine without plugs and registered 8.8 volts. Then performed compression test just to see if compression was doing something wonky. Came back with 175 175 175 170 with crank rotating slower than normal. Used battery booster and got 180 185 185 175 with crank still seeming to be turning abnormally slow. At this point I remembered seeing one more ground point under air box. Long story short, turns out I realized that I had a complete brain-toot and totally missed the ground wire coming from the negative battery terminal to the front stud on top of transmission. When putting engine back in I had tucked it under the frame behind the drivers headlight and subsequently forgotten about it. Buffed and dielectric greased the frame ground point below airbox and buffed/greased and connected the negative battery terminal ground to the stud on the transmission. Put plugs in, turned the key and she cranked over like a freaking champ. Planning to put the oil pan back on and attempt initial startup tomorrow. The lesson for me is to post on this forum and ask for help/ideas sooner rather than later. Also if you think you took care of all your grounding points, go ahead and check again for good measure. Thank you to each of you for taking the time to read and share your thoughts and advice.
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Old 08-10-2021, 12:11 AM   #10
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Default Re: 2001 SC2 Slow Crank After Rebuild

Excellent job. We had an electrical checklist we used at Sikorsky.
1) plug it in
2) go back and plug it all in
...
Bryan Cotton
'99 SL2, 5SP bought new
Rebuilt at 204,067 September 2017
Engine, subframe, diff pin mod, brake lines, headliner, alternator, and so on!
'98 SC2, 5SP bought 2018
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