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AHU with Cummins MTDI pump.. Pump timing help
by
shortysclimbin
on 09 Sep, 2015 21:06
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OK so I am getting close on the kubvan project and am running into some timing configuration questions for the cummings pump experts.
Background: AHU motor with AHU injectors, and Cummings 12mm pump modified with Governor spring, tdi timing advance, and an IDI pulley modified to fit the snubshaft.
Currently I have the cam and crank set at perfect TDC between the two thanks to a borescope. Now the pump is a little more tricky. It is set as advised by libby to have one tooth off from getting the timing pin for the pump in place (for clarity I need to rotate the pump 3 flywheel teeth in the clockwise direction looking at the harmonic balancer (advance?)). I read that this is about 2.73 degrees per tooth so roughly 8.19 degrees [REF:
http://www.vwdieselparts.com/forum/viewtopic.php?t=10351.
If I do the mechanical timing check I am reading .28mm on the gauge at the current setup. Where I am zeroing the gauge (basically when the pump cam is at zero lift) we are at 8 flywheel teeth in the same direction (21.84 degrees). Ideally I keep hearing for 12mm pumps on TDIs people are running around 1.43mm lift and 12 degrees Before Top Dead Center? Where are others setting these pumps? What are you reading as far as flywheel teeth for the zeroing point on the gauge and max lift points? I would prefer to go by the flywheel as this is more accurate than reading pump readings since they would vary by pump cam configurations. Any help would be great.
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#1
by
shortysclimbin
on 09 Sep, 2015 21:22
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hmm.. I am thinking I am actually ATDC by 8.19 degrees... I think I may need to go the other direction with the pump teeth.. its late, ill need to play with this tomorrow...
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#2
by
libbydiesel
on 10 Sep, 2015 00:37
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Your post is confusing and overly complicated. Without a diesel pulse adapter, you have to ignore the 12° BTDC recommendation and any other degree value. You need to set the timing using the plunger lift. I would recommend setting it to 1.30-1.35mm as a starting point. Without the pulse adapter, you will need to fine tune it from there based on ear and performance. So, set the engine at TDC, install the dial indicator with a couple mm of pre-load, rotate the engine CCW until the dial indicator stops moving, rotate the face so the big hand is at zero, look at the small hand and note its value. Then rotate the engine forward back to TDC and see what the reading is on the dial indicator taking note of the small hand to see if the indicator has rotate more than a full turn. If the reading is less than desired, then loosen the pump mounting bolts and rotate the pump top toward the cyl head. If you run out of adjustment before you reach the desired value, then you need to jump the sprocket and additional tooth CW relative to the crank and cam. Lather, rinse, repeat until you get the correct reading.
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#3
by
shortysclimbin
on 10 Sep, 2015 07:03
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Things get overly complicated when your on hour 19 for the day.... after thinking it over I believe I moved the pump sprocket CCW one tooth initially. I'll check tonight and most likely move it two teeth CW while I am at it. That should get me close to 1.28mm. The Kubvan is not something you want to screw with timing adjustments as it has almost no room to play in.
Thanks again Andrew. I'll set it at around 1.35mm to start. Ideally I would like to find someone with a pulse adapter on the east coast to borrow / rent. The pump piston size, pump cam size, and injector breaking point all change depending on the parts. I was trying above to identify the flywheel tooth location of TDC for the pump cam and BDC for the pump cam. The 12 degrees BTDC should be a datapoint in between on a curve. I'll build a chart for others future reference once I get it figured out. All my parts are new or rebuilt condition so this should be a good one to reference.
Sidebar: If anyone has an AHU ecu and the connectors for the harness they are looking to sell let me know. I could also use the AHU sensors and Vagcom to fine tune.
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#4
by
vanbcguy
on 10 Sep, 2015 08:05
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One gotcha I see above is you mention using the TDI timing advance. Be aware that the TDI pump did not control timing the same way as a mechanical pump, it had an electronic pressure modulator controlling things. As a result the timing spring is extremely soft and will go to full advance early when used on a mechanical pump.
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#5
by
libbydiesel
on 10 Sep, 2015 08:54
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Vanbcguy, I agree with you in theory, but in practice, it should be fine. The timing difference that the engine management accomplishes is minimal. In looking at timing graphs, it is unusual that the electric control can even meet the desired timing advance and drops off the map on the retarded side at higher rpms, especially on older pumps.
Things get overly complicated when your on hour 19 for the day.... after thinking it over I believe I moved the pump sprocket CCW one tooth initially. I'll check tonight and most likely move it two teeth CW while I am at it. That should get me close to 1.28mm. The Kubvan is not something you want to screw with timing adjustments as it has almost no room to play in.
It usually needs to be 1 tooth clockwise from the stock sprocket hole relative the crank/cam.
Thanks again Andrew. I'll set it at around 1.35mm to start. Ideally I would like to find someone with a pulse adapter on the east coast to borrow / rent. The pump piston size, pump cam size, and injector breaking point all change depending on the parts. I was trying above to identify the flywheel tooth location of TDC for the pump cam and BDC for the pump cam. The 12 degrees BTDC should be a datapoint in between on a curve. I'll build a chart for others future reference once I get it figured out. All my parts are new or rebuilt condition so this should be a good one to reference.
the 12° BTDC is for when the injector starts squirting fuel. Without a pulse adapter, you cannot find what that correlates to WRT plunger lift without knowing the injector break pressure, area of the plunger, camplate lift curve, leakoff of the plunger and some extremely complex math that would still be at best a guess. Ignore the degree specs unless you have a pulse adapter.
Sidebar: If anyone has an AHU ecu and the connectors for the harness they are looking to sell let me know. I could also use the AHU sensors and Vagcom to fine tune.
A pulse adapter would be a lot cheaper and a heck of a lot easier.
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#6
by
shortysclimbin
on 15 Sep, 2015 09:27
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Ok after playing with it for quite a few hours I have come to the conclusion I may not know I am in the right cycle for cyl one injection. Is there an easy way to make sure your in the right cam cycle on the pump? This pump sprocket has two timing pin locks 180 degrees out from one another and neither of them seam to want to start the motor when set at 1.35mm lift.
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#7
by
libbydiesel
on 15 Sep, 2015 09:46
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Do you have the woodruff key in place? (I had to ask)
When you had the sprocket machined for the larger shaft, was the woodruff key cut in the same place?
You completely disassembled to pump in order to change the dynamic advance parts. Are you sure you installed the camplate facing the correct direction?
The correct timing pin hole is the one that is directly opposite the woodruff key slot. It is not the one that is on the same side as the slot. There should be a timing mark on the inner rim of the sprocket by the teeth. That mark should align with the top center of the pump when the lock pin is in place.
Did you return all of the settings when reassembling the pump? Are you getting fuel spitting at the injectors?
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#8
by
shortysclimbin
on 15 Sep, 2015 20:52
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Andrew thank you for the rechecks! It is now starting fine and I am onto the next few issues (shutting it off with the key, fuel leaks, Minor oil leaks, and assembling the exhaust, axles and transmission cabling). It is amazing how such small things make a huge difference. I am extremely tedious on stuff and just needed a little push to point me in a direction. FYI for others below is what I did and found. I also found by setting it dead nut on where the factory cog key is the belt doesn't like to ride on the groves and will jump one tooth. So right now I have the pump set at one tooth retarded. I need to recheck timing and play with it a bit after everything else is up and running.
Do you have the woodruff key in place? (I had to ask) (yes, double and tripple checked that! good point though!
When you had the sprocket machined for the larger shaft, was the woodruff key cut in the same place? This is unknown as I bought it "all ready to go" from another member a few years ago.
You completely disassembled to pump in order to change the dynamic advance parts. Are you sure you installed the cam plate facing the correct direction? yes, I was like a surgeon pulling this thing apart in the kitchen on the granite with spots marked and laid out in order and orientation... its really hard to screw it up when you do that.
The correct timing pin hole is the one that is directly opposite the woodruff key slot. It is not the one that is on the same side as the slot. There should be a timing mark on the inner rim of the sprocket by the teeth. That mark should align with the top center of the pump when the lock pin is in place. Thanks! this was good to know and I did check this, I had it correct.
Did you return all of the settings when reassembling the pump? Nope! This was one of the two issues, I had the piston collar screw backed out three turns as I was worried I would over fuel the single turbo setup with the 12mm and 764 injectors. Turns out I had it way to far out. I turned it back into the oem spot for the 12mm pump and BAMB! it started.
Are you getting fuel spitting at the injectors? Yes lots of fuel, although, after it started the pump was leaking at the timing advance plate on the front of the pump. Turns out the screws were too loose and fuel was leaking by. It could also have caused some starting issues too.
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#9
by
libbydiesel
on 15 Sep, 2015 21:00
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Nice. I'm glad it's running.
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#10
by
shortysclimbin
on 16 Sep, 2015 20:38
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#11
by
libbydiesel
on 16 Sep, 2015 22:15
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Right on.
You need to adjust your belt tracking. Pull the pump, loosen the bracket mounting bolts, rotate the pump CCW (sprocket DOWN - lines UP), torque the bolts, and reinstall pump and belt.
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#12
by
shortysclimbin
on 20 Sep, 2015 18:50
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Andrew, I tried this sadly not much movement in the mk3 ahu bracket and the bolts assembly. Have you ever slotted the bolt holes a bit to allow more play to move the pump inward a bit? I need to move it in about 3mm for it to track dead nut on. I oddly think the sprocket may have been machined too much hence the issue. Option two would be to find a whole new sprocket setup.
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#13
by
libbydiesel
on 20 Sep, 2015 23:39
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It is not a matter of moving the bracket toward the pulley end of the engine or toward the flywheel side of the engine. You need to rotate the bracket so that the sprocket goes down and the metal lines end of the pump goes up. I have not ever had to slot the bracket more than the stock hole size but I do know one other person who did so and was successful after enlarging the holes to get the belt tracking correctly.
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#14
by
shortysclimbin
on 18 Oct, 2015 06:54
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Well fixed the alignment issue and was able to get it timed to right about .058". I also installed a return spring as the stock location for the cummings spring doesn't return the pump to rest on the idle screw (this is what normal 4bt pumps have on the trucks). Now it idles and starts and shuts off great but I am getting idle hang much like Matt described here:
http://www.vwdiesel.net/forum/index.php/topic,35659.0.html Im scratching my head a bit here as I suspect the issue isn't the same as Matt's since I am down to the one spring inside the assembly. I'm going to play around with the fuel quantity screw a bit and the idle adjustment screw. I may also move the lever arms off from there stock position to see if that helps. Right now the aneroid boost isn't connected, so I suspect the fuel pin shouldn't be an issue?
