Can't get an easy cold start #2

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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 17, 2017 7:21 am

Andy,
Flywheel is 60-2 with the sensor at about 2 o'clock.
clutch 15d.jpg
clutch 15d.jpg (40.58 KiB) Viewed 294 times


The Clewett cam sensor is on the front of the LH camshaft and is triggered by a bolt in the end of the camshaft.
eng assy 048a.jpg
eng assy 048a.jpg (38.67 KiB) Viewed 294 times
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billr » Sun Sep 17, 2017 10:19 am

What resistance is the VR coil (disconnected from the harness)? Maybe somebody can advise if there is an obvious problem with it.
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Re: Can't get an easy cold start #2

Postby DaveEFI » Sun Sep 17, 2017 10:54 am

Personally, I'd be looking at the output of the sensor with a 'scope to make see where the problem arises.
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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 17, 2017 9:00 pm

billr wrote:What resistance is the VR coil (disconnected from the harness)? Maybe somebody can advise if there is an obvious problem with it.

Bill,
I vaguely recall checking the sensor resistance some time ago and it checked out OK. Can't remember the details though.
I just can't imagine that the sensor is the problem if it works OK once the engine is running.
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Re: Can't get an easy cold start #2

Postby billr » Sun Sep 17, 2017 9:06 pm

Yeah, but... low speed is where a VR works poorest. Throwing a new sensor at it is just a "Hail Mary" play (does that mean anything in Australia?), before you have to dive into the 'scope learning adventure.
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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 17, 2017 10:12 pm

Fair enough. Anything to avoid the 'scope learning.
We do a lot of powdercoating for the local Porsche shop. I have just borrowed one from them to play with tonight and ordered a new one (which I should have in a day or two).

Skip forward a few hours ... the sensor from another running engine did not make any difference. :(
Just to be 100% sure, I still have new one on the way, but the problem doesn't seem to be with the sensor.
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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 24, 2017 6:17 am

Installed the new crank sensor today and ran temporary wiring outside the car directly from the sensor to MS3 separate from all other wiring.
As I expected, it didn't make any difference, so I am confident that there is no problem with the external sensor circuit.

Just to focus back on the problem again, it might help to restate the symptoms ...
- engine won't start when cold (due to low cranking rpm?)
- there is sync loss when cold cranking (but is this a cause or effect?)
- after first start of the day, subsequent starts are easy
- sparking is quite random due to weird tooth log
- problem is only during cranking, engine runs fine
- R56 has been adjusted from end to end with no effect

It still seems logical to me that the sync loss could be occurring because of slow and pulsating cranking speed.

I haven't put a 'scope on the sensor yet. If I do this, what is this going to show us?

Is it likely that adjustment of R52 could help? I can't find any explanation of its purpose.
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Re: Can't get an easy cold start #2

Postby billr » Sun Sep 24, 2017 7:53 pm

Where are the pots now, are you leaving them at full CCW except during the tests noted?

What is the cranking compression pressure?

I would like to see a tooth-log taken with compression, but no spark. Maybe both ways... with and without fuel, too.

Have you tired with one set of coil drivers disconnected? I know you aren't eager to dig into that coil driver box and disconnect six of the FET gates, but are you eager to continue this chase forever?

Besides verifying where the pots work best, the scope will let us see what the CKP sensor looks like. I can't guarantee the scope will be the "magic bullet", but it will give us much more understanding than will ever be possible without it.

It seems there are two different symptoms here. First is the hard cranking, which I suspect is because one of those coils is firing too soon. Second is the weird tooth-logs, where your 60-2 wheel starts looking like a 4x-x. The scope is the best (only?) hope for resolving that. Are these in fact different symptoms of the same problem? I don't know, but feel we must address both as being possibly different issues.

I do not think the sync-loss is causing the hard cranking. If there is sync-loss, I would expect that all spark and fuel events are immediately terminated; no sparking at wrong time to cause that hard cranking.
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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 24, 2017 9:19 pm

Bill,
I cranked R56 up about 8 turns CW and R52 by 1 turn CW for the most recent logs that I uploaded and they are still set that way.
Do you know what R52 does? I can't find any info in the manuals.

I haven't done a compression test for some time, but I would expect it to be around 11 times atmospheric pressure (150 - 160 psi) for a motor with 11:1 compression.

Later today, I should get some time to do a bit of testing, so I will run the logs you requested. So far, all the tooth logs have been run with no fuel as I don't want too much fuel sloshing around in the cylinders, and I didn't want any wayward misfires interfering with the logs. With fuel on, the cranking speed just becomes a bit more erratic as the spark occasionally coincides with a compression event.

I tried starting and running on only one set of coils several weeks back and I posted that it didn't make any difference to logs, starting or running. I have since reconnected all coils.

I have been putting out feelers for someone local to help me with the scope, but no joy yet. I just can't envisage how this exercise will work. It's not like I can record for you what the scope is displaying other than by trying to take a picture of it.
If I connect the scope to the disconnected sensor and crank the engine, I presume we would get some kind of trace that has 58 bumps and a gap?
If the sensor is connected, there is nowhere to connect the scope without cutting into the harness or dismantling the DB37 connector.
Even if I can pickup the sensor wires somewhere near the MS3, I don't see how the scope trace would look any different because its signals are still being measured before its signals get into the MS3 box.
Do steer me in the right direction if I am not understanding the basics here.
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Re: Can't get an easy cold start #2

Postby billjam » Mon Sep 25, 2017 6:46 am

Compression test = 155psi. No surprises there.

This log is with no compression, spark or fuel.
I ran two more logs with no compression, one with spark and one with fuel. They are exactly the same as above.
The main spike is at 58 even though there are gaps in the log.
Log 1.jpg
Log 1.jpg (49.23 KiB) Viewed 213 times


This log is also without compression, spark or fuel but with R56 at 4 turns CW.
The only difference is that the gaps that were in the first log have disappeared. Spike is still at 58.
Log 3a.jpg
Log 3a.jpg (56.12 KiB) Viewed 213 times


The next log is with compression. R56 is still at 4CW.
Again, the logs with or without spark and fuel are exactly the same.
Log 4.jpg
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MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billjam » Mon Sep 25, 2017 6:59 am

Next, I fitted the new starter I have had waiting in the wings. It is a HiTorque 2kw model.
Cranking speed is noticeably faster and the log looks like this.
Log 7.jpg
Log 7.jpg (60.85 KiB) Viewed 210 times

The spikes at 58 are still there but are now taller than the interference at about 40 spacing. The engine felt like it wanted to start, but just couldn't quite get there.

Just for the hell of it, I enlisted some extra hands and ran a log as I turned R56 from fully CCW to at least eight turns CW. I'll attach it for you.
It shows R56 having some effect over the first few turns, thereafter the log doesn't change. I can't tell exactly how many turns were made at specific points in the log ... the intention was to see what effect R56 was having, if any.
Attachments
2017-09-25_8.csv
Log with R56 varying from 0 to >8 turns
(72.92 KiB) Downloaded 10 times
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby Marty Wagner » Mon Sep 25, 2017 12:34 pm

In my opinion, Log 3a looks like a normal 60-2 trigger wheel pattern. The tall 'spikes' are actually the -2 gap in the trigger wheel. The height of the bars is the TIME ()in milliseconds) between trigger pulses. Notice however that the tall 'spikes' are slightly different in height. The taller spike means the engine is turning slower.

In Log 7 you can still see the -2 gaps but they are somewhat obscured by elongated humps where the engine is turning slower. The -2 gaps are the over 10ms spikes.

To me the interesting thing is the 2 humps on one engine revolution and only 1 hump on the next. I would expect 3 humps per engine revolution ( 6 per engine cycle ) for a 6 cylinder engine. This makes me think something is causing extra drag/compression on 1 bank of the engine.

I would like to see a Log 7 run on a warm engine to see if the humps are the same.

Log 3a actually shows the 2 hump followed by 1 hump situation if you look close at the short spikes around the 4.9ms line.
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Re: Can't get an easy cold start #2

Postby Dennis930 » Mon Sep 25, 2017 2:22 pm

I agree with Marty. There has to be 3 compressions( or humps) per engine revolution so why is there a spike in between. It is almost like there are 2 places per revolution where there is a missing tooth.
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Re: Can't get an easy cold start #2

Postby Dennis930 » Mon Sep 25, 2017 2:53 pm

I just counted the interval of the spikes, they come up every at 58, so this is just odd. There should be three slow downs as three cylinders come up on compression.
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Re: Can't get an easy cold start #2

Postby billr » Mon Sep 25, 2017 4:47 pm

We are all expecting to see three "compression humps", but there seems to be only one. I think that one dramatic hump isn't from compression at all; it is a cylinder firing at the wrong time.

Those tooth-logs taken with the R56 not full CCW are meaningless to me, I would like to see one with both pots full CCW and no spark. When coils were disabled before, was drive to the FET gates removed? That is the only way I would trust that the dual-plug system isn't still a problem.
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Re: Can't get an easy cold start #2

Postby billjam » Mon Sep 25, 2017 5:25 pm

Dennis930 wrote:I agree with Marty. There has to be 3 compressions( or humps) per engine revolution so why is there a spike in between. It is almost like there are 2 places per revolution where there is a missing tooth.

The single spikes are the missing teeth and occur every one revolution (spaced at 58).
The humps are compression strokes and for a six cylinder four-stroke engine, I agree, there should be three of them per revolution, not three per two revs.

Keep in mind, that when the engine is running (not often lately!), it runs and idles just fine. It even starts easily after the first start of the day.

The log seems to indicate that half the engine doesn't have compression. I will do a compression test on all cylinders tonight to check this possibility. I ran a test yesterday but only on one cylinder. Maybe one camshaft has mysteriously disconnected itself with all valves open?

There are some things that can now be safely discounted ...
Crank sensor ... three different sensors, one new, all give same logs.
Sensor wiring ... temporary external wiring direct from sensor to MS3 (avoiding all other wiring) gives same logs.
R56 ... adjustment makes only small changes to the log up to about 3 turns CW.

It is also clear that without compression, the logs are OK (see log 1). As cranking speed increases, the missing teeth spikes become more prominent (log 4 vs log 7).
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billjam » Mon Sep 25, 2017 5:48 pm

billr wrote:We are all expecting to see three "compression humps", but there seems to be only one. I think that one dramatic hump isn't from compression at all; it is a cylinder firing at the wrong time.

Those tooth-logs taken with the R56 not full CCW are meaningless to me, I would like to see one with both pots full CCW and no spark. When coils were disabled before, was drive to the FET gates removed? That is the only way I would trust that the dual-plug system isn't still a problem.

Bill,
To disable the spark and fuel, I have been pulling the relays so that the signals from MS3 are not driving the coils or injectors.
Pulling the ignition relays (one for each bank) removes the 12v power supply to the coils and the 5v power supply to the FETs (but not the 5v spark signal from MS3).
I have just run logs with all combinations of fuel, spark and compression and in every case, there was no difference between having fuel or spark on or off. This means that random ignition events outside the expected firing position are not happening and are not the problem.

The position of R56 has almost no effect on the logs.
Log 8 that I posted is continuous cranking for 10 seconds or so as I slowly turned R56 from 0 to about 8 turns CW, so I don't believe that R56 is the problem. It helps clean up the signal marginally, but it isn't the problem.
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billjam » Tue Sep 26, 2017 4:28 am

Tonight's report ...
As I expected, all cylinders have good compression ... 157, 155, 160, 155, 160, 160.
Therefore, we can safely exclude compression, or lack of, as a cause of the strange patterns in the logs.
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Re: Can't get an easy cold start #2

Postby Dennis930 » Tue Sep 26, 2017 10:25 am

Bill,

Just for kicks, could you post a composite tooth log of the engine cranking with no spark/fuel?
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Re: Can't get an easy cold start #2

Postby turbo conversion » Tue Sep 26, 2017 6:20 pm

Have you actually tried r56 and r52 at full CCW?

I'm just curious as it has been mentioned and you haven't responded.

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