2-for-1 and possibly related: Bucking and unstable/nonidle

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Ronin10
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon May 18, 2015 7:03 am

Was able to get some time in the garage yesterday and did a diode test as well as checked out my voltage regulator. Both passed. I also started down the alternator tests suggested in this video, but didn't get beyond the negative voltage drop test.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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Amskeptic
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Mon May 18, 2015 7:28 am

Ronin10 wrote:Was able to get some time in the garage yesterday and did a diode test as well as checked out my voltage regulator. Both passed. I also started down the alternator tests suggested in this video, but didn't get beyond the negative voltage drop test.
Your diode test cannot specify all six diodes. It just tells you that the diodes are overall doing their job. Usually, it is an excitor diode that drains the battery down.

Field test at the negative battery terminal. Do you have a tiny little spark with all lights and radio off?
a) Remove alternator B+ wire from starter. Does spark go away?
b) Remove voltage regulator plug and blue wire connection. Does spark go away?

A) main diode leak
B) excitor diode leak

Well, that is how I discovered the Road Warrior had a weak charging system and a battery that would go flat. Replacing the alternator after some fifteen years of that, cured it for good.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Ronin10
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon May 18, 2015 6:48 pm

Okay, disconnected negative battery cable and brought it ultra close to the negative battery terminal and got a minuscule spark.

Set the cable aside and went under the bus and disconnected the heavy red wire leading to the starter solenoid. Reattached everything else and the the red wire dangle in space, not contacting anything. No spark.

Set aside the battery cable again, reconnected wire at starter solenoid and unplugged the plug at the voltage regulator, unplugged the blue wire to the dash light, and touched the battery cable to the negative terminal again, sparked.

So by your logic above and assuming my procedure was correct, I have bad main diodes, but my exciter diodes are good. What really sucks is this alternator is only a couple of years old.

Question...I've seen tales of other replacing their diodes themselves, some simply having the alternator rebuilt, and most people just replacing the alternator as a whole. I have two alternators sitting on the shelf in unknown states (salvage). Is it worth the effort to do the diodes myself?
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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Ronin10
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Sat May 23, 2015 3:41 pm

Pulled my alternator yesterday and disassembled it to check the diodes individually. They all seem to check out.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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Amskeptic
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Mon May 25, 2015 5:31 am

Ronin10 wrote:Pulled my alternator yesterday and disassembled it to check the diodes individually. They all seem to check out.
There are leakage tests that put running voltage on one side of the diode. I don't know that a 1.5 volt ohmmeter is going to "load' it up enough.
Colin?
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Ronin10
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Wed May 27, 2015 10:29 am

Sucked up my misgivings, bit the bullet, and sprung for a new alternator. Got a 70 amp version as down the line I'll be putting in a BA6 heater and dual batteries. The only issue was the pulley. The correct ones seem impossible to find although the rebuilder I purchased from offered me his last one...for the princely sum of $200. I found an early vanagon pulley from a junkyard which looks very similar, but it's a 2 piece pulley with the fan not welded to the pulley. I'll also need to figure out the proper stackup of spacers to get the offset correct. If it doesn't work, I can run for the time being with the 55 amp pulley as I won't yet be pulling current beyond the ability of a 55 amp alternator. That should giving me time to find a reasonably priced 70 amp core or pulley.

I'll get that sorted in the next week and should be able to verify if my 55 amp alternator was genuinely shot, only part not in hand is the round boot to the fan shroud, but it's on it's way.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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Ronin10
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Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon Jun 01, 2015 6:16 pm

Got the alternator installed. Let the engine warm up for about 20 minutes before doing any testing. The running voltage at (rough) idle was 13.3V. I ran up the RPM to about 2500 and it was 13.0V. Voltage after stopping was 12.3V. I'll check it again tomorrow to see if it runs down further.

I also took a video of the engine running with the timing light going to show the firing on cylinder 1. The thin yellow line indicates firing position for #1 and #3 (if you can't see the notch) and the wide yellow band is the approximate firing position for #2 and #4 (it's not exact).

https://youtu.be/_L-DOYTa-5M
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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asiab3
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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by asiab3 » Tue Jul 19, 2016 7:11 pm

I looked at this engine just this morning. A few observations:

1- The AAR was not as open as it could have been. Cold starts previously REQUIRED a feathered throttle and now hold on two cylinders.

Before:

Image


After:

Image


I even managed to get the AAR a hair more open after I put the camera away before buttoning up the hoses. :cheers:

2- This engine has larger-than-stock valves and a cam much like JR's performance engines. With JR's fuel injected turn-keys, he machines a hole in the throttle plate according to a dated Samba post. This sounds to me like "more metered air" is a verifiable solution for us here. Of course Xevin (who now owns the bus) is his own R&D department now, but he is willing and able to experiment, as his fuel injection knowledge is growing.

3- The engine responded VERY well to an idle timing of 14-16* btdc. Xevin is working on procuring a "mule" distributor that we can bend the tabs on to achieve a slightly higher idle timing. Right now, it "idles" at 7.5*btdc and maxes out at a 28* bfdc, hose off. If only I still had my Mallory to offer, from like page three of this thread…… :pale:

--

I know Andrew and now Xevin have been the point of much speculation around beers regarding this engine. At this point there are a few solutions that I see, each having merit.

A- AAR. Modify (drill?) the existing AAR plate to allow more air. The engine needs more air at warm idle too, possibly more than the idle speed screw can give us.

B- Secondary air supply. Incorporate something like Luftvagon's microsquirt air bypass solenoid. Something like the idle air valve on air-conditioned cars to keep the idle speed up could work here and be activated by a switch, relay, or temperature sensor. Caveats include the fact that multiple people will drive this bus, and they might not like/remember a switch. My suggestion was a second AAR, tee'd off the AAR intake hose and plumbed into the EGR port, which is currently blocked off by a nice flat piece of metal just WAITING to have a nipple grafted onto it.

C- Timing. Once we attempt a narrowing of the advance curve with FULL attention to CHTs and engine sounds, we will have a better idea of what is possible. Andrew, do you know the compression ratio of this engine? Xevin, get your DD gauge hooked up schnell.


I say "we" because we're all in this together, right? " :drunken:
--

…Whew… had to get that out while the WiFi was good!
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Ronin10
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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by Ronin10 » Tue Jul 19, 2016 8:20 pm

The calculated compression ratio from measurements should be/might be/I hope is in the spreadsheet I gave Kevin, but I don't exactly remember it off the top of my head. I won't have access to that spreadsheet until I get home from this business trip. The target was stock compression though and I don't recall it being far off.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by asiab3 » Tue Jul 19, 2016 10:47 pm

Thanks for the quick reply. I look forward to hearing the numbers from Kevin. I hope he tries a quick stint at 32* total advance, hose off, to see how the idle improves. I don't think longterm misfires or two-cylinder idling is benefiting any part of the engine, with the gas filling the cylinders and all… Plus I'm not a fan of belching hydrocarbons, emissions exempt or not. :)

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

Rusty Sub
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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by Rusty Sub » Tue Jul 19, 2016 11:30 pm

Well look what I stumbled on. Didn't know this thread existed. Nice.
Surprisingly no compression test in the spreadsheet except for the old engine.
I did find this in the Samba "Greta" thread.

I just completed my compression test and all looks good:

#1 150 (no oil) / 150 (w/oil)
#2 140 (no oil) / 145 (w/oil)
#3 150 (no oil) / 150 (w/oil)
#4 140 (no oil) / 150 (w/oil)

Given that this engine only has about 2000 miles on it since the rebuild those numbers seem pretty reasonable.
a.k.a Xevin

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asiab3
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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by asiab3 » Tue Jul 19, 2016 11:38 pm

Hey hey, nice of you to join us Kevin!

Compression ratio anyone? Bueller? Bueller? :blackeye: (In all seriousness, let me know if we need to discern the differences.)

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Amskeptic
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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by Amskeptic » Tue Jul 19, 2016 11:44 pm

Rusty Sub wrote:Well look what I stumbled on. Didn't know this thread existed. Nice.
Surprisingly no compression test in the spreadsheet except for the old engine.
I did find this in the Samba "Greta" thread.

I just completed my compression test and all looks good:

#1 150 (no oil) / 150 (w/oil)
#2 140 (no oil) / 145 (w/oil)
#3 150 (no oil) / 150 (w/oil)
#4 140 (no oil) / 150 (w/oil)

Given that this engine only has about 2000 miles on it since the rebuild those numbers seem pretty reasonable.
That is the serious compression of high CHTs noted in years past as we strafed I-90 outside of Renton WA.

Now, unfortunately, NaranjaWesty's factory compression ratio (7.3:1) is also yielding 145 psi readings, and I too enjoy some serious CHTs on the Columbia River Headwind Highway, today, 421* at 67 mph straight into the wind. At 55 mph, I was 403*.

What is your average fuel economy, Xevin?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by Rusty Sub » Tue Jul 19, 2016 11:59 pm

Just went through my first tank, 10.48 gal is what I put in. (Still getting comfortable with fuel gauge)
16.53 mpg. Half of milage was on freeway at approx 65mph.

Robbie, when I pulled Greta into the driveway from a cold start tonight she didn't die. But rather a shaky bewrap bewrap bewrap.

Big thanks to all three of you still working on the puzzle.
a.k.a Xevin

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asiab3
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Re: 2-for-1 and possibly related: Bucking and unstable/nonidle

Post by asiab3 » Wed Jul 20, 2016 12:22 am

Well.. brap brap is certainly better than death... I think we're heading in the right direction. Come camping. Bring your spare AAR and all the hoses with it. I'm going in.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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