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General Discussions about the 300M and other LHs

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 #392928  by FIREM
Doubt there is a “fuel flooding” issue as time has passed between attempts.
I would pull all the spark plugs, and do a compression test. Throttle wide open, fuel
pump relay removed, battery fully charged, same number of compression strokes / crank time each.
Tool can usually be rented from auto parts storesz
allella liked this
 #392950  by allella
I did a key dance and it immediately shows "done" with no "P" codes or anything else besides the odometer mileage.

I have an Actron compression tester that goes up to 300 PSI, so I'll check the compression.

  • How do you know how many compression strokes have passed? Or, are you just saying the same number of seconds?
  • The Actron manual says to crank until the needle stops going up. Is that equally fine instead of trying to time the # of compressions?
  • I'm assuming I don't need the 14mm extension adapter, correct?
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 #392951  by FIREM
You should hear a different sound during the compression stroke or the cylinder being tested.
Yes, crank until the highest reading is obtained, usually 3-5 strokes. No need to continue cranking once highest reading is obtained.
No need for an extra extender that I am aware of.
Good that there are no codes, still kind of baffled by this one.
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 #392975  by TrepKing95
allella wrote: February 18th, 2023, 1:31 pm No codes on the ODB II scanner, but perhaps I need to try the key dance.

I thought the 10 blinks on the CEL and the ding sound was normal if you wait about 30 seconds with the ignition in ON. Is that not a normal diagnostic signal?
On 2002+ cars the check engine light should come on and stay on at key on, engine off. If it starts flashing with the key on but without cranking the engine, this indicates that the Emissions Readiness monitors have not set and the vehicle is not ready for emissions testing. This is caused after any time that trouble codes are cleared or the battery is disconnected.

Have you had a high level scan tool connected to the vehicle to inspect for pending (not yet active/stored) trouble codes? I can't remember if a pending trouble code will show up on the Key Dance display. Having a good scan tool will also allow you to monitor the cam/crank sensor status and other data that may help point you in the right direction to diagnose this no-start.
 #393002  by allella
Thanks. I only have a small, cheap Actron scan tool and key dance, which both show nothing.

I'm still waiting for good weather and free time to line up so I can check the compression. I'll circle back to this after that test.
 #393166  by allella
I finally got to do a compression test with a brand new Actron tool.

Latest Test Found Low Compression
  • Compression test shows all cylinders are well below the 100 PSI minimum after doing 3 tests per cylinder
  • The PSI range is 45-70 with the average of all cylinders about 60 PSI
  • Battery fully charged, full throttle, fuel pump removed, cranked 4 compression cycles and the PSI is usually peaking by the 3rd cycle
  • For "full throttle open", I held the pedal to the floor, which I assume is the same as if I manually secured the throttle open
  • Cranking it longer, like 5 or 6 cycles, doesn't make the needle go any higher
  • The alternator is not installed, air cleaner is removed, and timing belt covers are all off
  • The timing belt is slightly outside of the "dots" on one cam at TDC, as seen in the photos.
  • FIREM suggested the timing marks looked "okay" based on the photos, but given the low compression is the timing belt back on the list of likely causes?
  • If it's not the timing belt being off, then what else could it be? I can't see how the engine itself could be damaged, given that it was driving perfectly right before it stalled and it still cranks without any unusual sounds.
  • I took a video of one of the tests. Is that worth posting?
Summary of Symptoms and Tests from Previous Posts
  • This 300M Special was running excellent before it stalled while I was putting it in reverse to parallel park.
  • It sat in my yard for many months before I started diagnosing and I found a blown fuse, which I thought was the issue, but that may have just been a coincidence from the oily wires I eventually found shorting the ignition circuit
  • New Cam Sensor, New Crank Sensor, New Spark Plugs
  • Short on ignition circuit was fixed and haven't had a blown fuse in a long time
  • No check engine light the whole time I've been working on it
  • The ECM / computer does the correct things when ignition is turned to ON, so the ECM seems to be good.
User avatar
 #393177  by FIREM
Pressures need to be within 10% of each other.
Very unusual for all cylinders to be that low.
I would almost suspect gauge inaccuracy.
With compression that low maybe try starting fluid to see if it at least kind of runs??
“Leak Down” test next on the list but requires a compressed air source.
 #393178  by allella
The gauge is brand new, but I guess I'll try a different one.

My first thought was if the timing belt is outside the marks, which it is slightly, that perhaps the valves are opening too early. Is that not a possibility?
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 #393180  by FIREM
Very odd all so low, either bent / leaking valves in every cylinder or rings totally wasted in all cyl. Both unlikely unless car has been run with no air cleaner in a dusty environment.
Typically only a few valves get bent affecting a couple of cylinders when the belt fails or slips.
 #393181  by allella
I can't figure out how the car would go from driving fine to stalling and having all the cylinders low unless all the valves are opening early. Or, at least that's the only logical explanation given my limited knowledge of engines.

The timing belt is intact and only slightly, like maybe 1 tooth, out of the markings on the passenger side cam.

If it's not the timing belt causing a leak, then could there be something causing undo drag on the crankshaft, like a bad water pump? I'm assuming the transmission couldn't impact things while in park or neutral, but is there a situation where something in the transmission broke and it binding up the cranking? I add that because I was shifting and trying to go into reverse to park when it stalled and stopped working.

Thanks again.
 #393224  by allella
I did a second set of compression tests with a different test tool and got the same general results of 35-60PSI on all cylinders.

I'm buying a leakdown tester with gauges because the only loaner tools I found are for checking leaks in the cooling system, which requires a running engine and the fluid that changes yellow.

Here is a video of the first tests and perhaps the sound of the cranking will tell something. It's consistent and no grinding or sounds that leave me to believe things are damaged inside the engine block.

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 #393228  by FIREM
This is a real head scratcher, tough to figure out what is going on for sure.
How about a "wet" compression test?
Add about 2 tablespoons of oil to the cylinder and re test compression.
I see you did replace the belt an retimed the engine back in 2012 with no problem, so you are familiar with the process and somehow we will figure this out.
PM me your address in Greenville. I do visit friends in Easley and might be able to swing by when I visit.
allella liked this
 #393354  by allella
I ran more compression and leakdown tests. The results "dry" vs "wet" (after adding oil down the spark tubes) were drastically improved.

The "dry" compression, as previously noted, were in the 45-70 PSI range. After adding oil the tests immediately jumped to 3-4 times , and they got better the more I cranked. All "wet" cylinders eventually registered in the 150-210 PSI range. Also, the leakdown went from 85% (red / high zone) leakage on all cylinders to all being in the green "low" leakage range on a Milton tool, immediately after adding the oil.

Before adding oil, the leakdown was losing a lot of air, but I could not identify a single notable exit points. The air intake, tailpipes, dip stick, PCV, oil filler, coolant tank were all basically quite and with no tangible feeling of moving air. The only place there was a slight draft, and not even enough to move a piece of paper or register with the compression gauge connected, was between some of the spark plug tubes. I started thinking it was a head gasket, but as soon as oil went into the cylinders even that slight leak went away.

I put the plugs, coils, and fuel relay back in and hoped it would start, but still no luck. Before going off on this tangent checking the compression I still hadn't seen spark after fixing the ignition short. So, I'm wondering if the root issue is still the spark and the low compression was the result of the cylinder and rings drying out from sitting still for 10 months.

I did briefly get codes P0562 and P0700, but I believe these were due to me cranking the first few times with battery that had sat for weeks since the last attempt to crank. I cleared those codes, topped off the battery, and they didn't come back during the additional compression cranking tests.

  • This thing sat outside for 10 months before the compression tests started. Is it possible the cylinders just lost all lubrication from sitting around that long and adding oil is giving a more realistic test?
  • The accessory belt, timing covers, and radiator fan are still removed. I figure it should still start even with those removed, but should I bother putting any of them back to continue on with the spark testing.
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 #393355  by FIREM
WoW this is really a tough one to figure out.
Low compression dry/good compression "wet" is rings sealing in the cylinder.
There is a good chance sitting for 10 months rings may have gotten stuck. Oil sealed things up and I'm betting once we get this engine to fire up there will be no issue with the rings.
Engine will run with the covers and radiator out however I would put the upper rad hose on and fill the system with water or coolant. (if the water pump is run dry for a little as 30 seconds the water seal can be damaged)
We must verify spark for sure.
If spark is present a little whiff of starting fluid may be needed to overcome the low compression.
Must verify spark !