533i manifold vacuum

E28 technical advice asked and given! Troubleshooting, modifications and more.
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

I've used one of those cheap-O timing lights with a knob in the back to adjust timing, there is only one way to look at it, you need to position yourself a bit towards the driver's side from the engine and try getting a look at it without the upper rad hose in the way.
I had to do it to sync what the megasquirt thought TDC was vs what it actually was in the engine.
Mike W.
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Re: 533i manifold vacuum

Post by Mike W. »

MattC wrote: Sep 14, 2021 2:03 PM
Is it even possible that a component, such as a crankshaft sensor or ECU, could be doing something funky with ignition timing?
The only thing I can think of that could affect it is the fuel quality switch in the ECU.
MattC
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Re: 533i manifold vacuum

Post by MattC »

Thanks Mike and Juan. I'll look into both these items next.
MattC
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Re: 533i manifold vacuum

Post by MattC »

Ok, I bought a timing light that has the dial (used to set the advance).
First, I can confirm it's difficult to aim through the water pump area and actually see the 0|T mark and notch on the timing cover, but it's possible.
Need help interpreting what I saw...

At idle, the 0|T mark was basically lining up with the timing cover notch at 0 degrees of advance on the timing light dial. Sometimes it jumped to the left of the notch (retarded, as I understand it).

I then set the dial to 20-22 degrees of advance, and revved the motor to somewhere in 1500-2000rpm range. (I'll need to retest and get exact rpm). I watched the 0|T mark draw over and align with the timing cover notch, which I think confirms that timing advance value.

Does anyone have any expected values? Does a properly functioning DME advance the timing at idle by any amount? In other words, IS my timing retarded a small amount at idle?
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

If you say that the ot mark was before (to the left) of the mark in the timing cover then that's advanced.
I can't speak for the map in a 533 ecu, but for sure it doesn't idle at 0 degrees in a 059, i don't have the idle spark row handy, but it was near 10 degrees.
In particular I idle at around 20 degrees, and can confirm that it has a big effect on vacuum
MattC
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Re: 533i manifold vacuum

Post by MattC »

I was mistaken. You're right, LEFT of the timing cover notch is advanced. The engine rotates clockwise.

Retested tonight to confirm...
At idle, the 0|T aligns with the notch or slightly to the right (retarded) at 0 degrees advance.
At 2000rpm, I was only getting about 18 degrees of advance.

Juan, as you suggest, I think I should be seeing more advance in both conditions.

I now have 2 spare 008 DME's to test. I'll post anything learned, hopefully tomorrow.

Can anyone educate me on the fuel quality switch? I opened up one of the DME's but didn't see anything that resembled what I've read is a rotary style switch? I just see a circuit board on either side.
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

Ju@n wrote: Sep 14, 2021 9:35 AM Have you used a timing light to measure what's the spark timing at idle?
I don't know much about your particular ECU, but some do have a "rotary switch" which allows the user to retard timing for worse fuels
Image
The switch (if present) should look something like this.
Something that would be interesting is to get the xdf and bin dump of that ECU to know if the ECU actually wants that spark timing or not.
MattC
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Re: 533i manifold vacuum

Post by MattC »

Thanks Juan... sorry, you did post that picture earlier in the thread. :oops:

Anyway, I've now tried the 2 spare 008 ECU's and the basic results are the same as my original. Idle vacuum unchanged. Spark timing checked and basically the same (the 0|T aligns to the timing cover mark at 0 degrees advance). While I had the DME unplugged, I also checked the pins in the harness connector per Bentley. All good there, so DME power/ground/sensor inputs are satisfactory.

Still stumped on the fuel quality switch. Your picture seems to show a 944 Motronic unit, where the cover slides off, exposing the internals. With the 008 (and maybe others?) there's a top and bottom cover that unscrew and reveals a circuit board on each side. It looks like I'd have to unscrew the board from whatever is underneath, but this seems risky.

Image

Image
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

Ahh my bad, that does look a bit more vintage.
I tried searching a bit for someone who had measured ignition timing in a 533/633/733, but couldn't find any data on that. I can try next time I go to the car with the computer 0 degrees of timing at idle and let you know how the vacuum looks :)
Mike W.
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Re: 533i manifold vacuum

Post by Mike W. »

I can't say I've been into a 008 ECU, but a friend did tweak the switch in one long ago to pass smog, so I'm confident it's in there somewhere.
MattC
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Re: 533i manifold vacuum

Post by MattC »

Continued focus on ignition timing...I think that if I can solve the ignition timing, then it might well solve the manifold vacuum issue as a result.

So, I decided to investigate one of the primary inputs to the ECU for ignition timing - the crankshaft sensors. The Bentley Manual shows the x, y axis for the timing map are Engine Speed and Load.

Both sensors were a little dirty, but I noticed the Speed Sensor has a pretty deep gouge in the head. See picture. (Note: Both sensors were new 6 years ago when I installed the rebuilt motor.)

Is this concerning, how could it have happened, and might it influence anything?

Image
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

That doesn't look healthy, still, those sensors either work or not usually. Try swapping them around (also change the plugs on top)
MattC
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Re: 533i manifold vacuum

Post by MattC »

Ju@n wrote: Sep 24, 2021 3:43 PM That doesn't look healthy, still, those sensors either work or not usually. Try swapping them around (also change the plugs on top)
Ok, you were right. Swapped the plugs and connectors - no change. Another item ruled out.

Next up:
1. I'd still like to check cam timing with upper timing cover removed. I want definitive proof that it's either correct or not.
2. Could the reference pin on the flywheel have been oriented wrong or mis-located during the engine rebuild?
  • The pin works with the reference sensor to signal crankshaft position so that initial baseline ignition point can be determined for engine start. My theory is that if the baseline is wrong, then everything would be off from there.
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

If you want definite proof that the cam is correct, you'll need a comparator, a degree wheel, and the specs for your cam (and some time :) )
If not, you can use the method defined in the bentleys, which uses your eyes to confirm that the line that is formed by 2 of the bolts of the sprocket on the cam is parallel to the head.

As for the pin yes, don't remember that exact thread, but I do remember one where a semi-broken reference pin was causing issues. You can check your reference pin is correct if you know how many degrees before TDC it's supposed to be at (and the degree wheel for the previous test).

You are going into a mostly unknown realm though :laugh:
Keep up updated :D
Mike W.
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Re: 533i manifold vacuum

Post by Mike W. »

MattC wrote: Sep 27, 2021 10:17 AM
2. Could the reference pin on the flywheel have been oriented wrong or mis-located during the engine rebuild?
  • The pin works with the reference sensor to signal crankshaft position so that initial baseline ignition point can be determined for engine start. My theory is that if the baseline is wrong, then everything would be off from there.
No, it could not have been moved without serious work, as in the link you posted. If you're really suspicious you could pull the stiffener pan that connects the engine and tranny. NOT the oil pan, the stiffener pan and that would give you a good look at the flywheel. But it's not something that could have been done by accident, it would be a very deliberate action. Not that people haven't done stranger things, but it would be beyond unusual.
MattC
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Re: 533i manifold vacuum

Post by MattC »

Mike, thanks for the reply about the flywheel...I agree, unlikely scenario.

Today I pulled the upper timing cover to check cam position. Here's what I found in 2 pictures:

Picture 1: timing marks on crank are lined up, dowel on cam sprocket at 7 O'clock. I do not believe these bolts are lining up correctly.
Image

Picture 2: lining up the bolts with the mark on timing cover and the 0|T mark does not reach TDC.
Image

Thoughts? Do we think my timing is off 1 tooth?
Mike W.
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Re: 533i manifold vacuum

Post by Mike W. »

You've already got the upper timing cover off so it wouldn't be hard to check, and would do no harm, as long as you're careful and don't move the cam too far and bump valves against the pistons.

A FWIW, I've done a bunch of these and it never seems quite right when I do it. But it always is. Which means nothing except there might be room for confusion.
MattC
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Re: 533i manifold vacuum

Post by MattC »

Mike W. wrote: Oct 02, 2021 3:30 PM You've already got the upper timing cover off so it wouldn't be hard to check, and would do no harm, as long as you're careful and don't move the cam too far and bump valves against the pistons.

A FWIW, I've done a bunch of these and it never seems quite right when I do it. But it always is. Which means nothing except there might be room for confusion.
After further review... it does not seem to be off by one full tooth. Rather, it's more like a half tooth.

Could this be the result of the chain slacked in wrong position when the engine builder engaged the tensioner? Wondering if this scenario would pull the chain tight and move the cam sprocket a smidge relative to crankshaft?
Mike W.
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Re: 533i manifold vacuum

Post by Mike W. »

Are you checking it with the chain tensioned or not? That could make a difference. Installing of course it's not tensioned.
Thecar
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Re: 533i manifold vacuum

Post by Thecar »

If you are going by the position of the vertical cam bolts, keep in mind that one of them is offset towards the dowel pin. They won't both line up with each other vertically. The recommendation is to only go by the position of the horizontal bolts in your picture.

In this pic, you can see how the bottom bolt is offset towards the dowel pin.

Image

MattC wrote: Oct 02, 2021 1:54 PM Mike, thanks for the reply about the flywheel...I agree, unlikely scenario.

Today I pulled the upper timing cover to check cam position. Here's what I found in 2 pictures:

Picture 1: timing marks on crank are lined up, dowel on cam sprocket at 7 O'clock. I do not believe these bolts are lining up correctly.


Thoughts? Do we think my timing is off 1 tooth?
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

Thecar wrote: Oct 03, 2021 4:18 AM
+1
MattC
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Re: 533i manifold vacuum

Post by MattC »

Thecar wrote: Oct 03, 2021 4:18 AM If you are going by the position of the vertical cam bolts, keep in mind that one of them is offset towards the dowel pin. They won't both line up with each other vertically. The recommendation is to only go by the position of the horizontal bolts in your picture.

In this pic, you can see how the bottom bolt is offset towards the dowel pin.

Image
Oh wow this was very helpful, thank you! Strange that they offset that bottom bolt and then Bentley Manual describes alignment as "straight up and down." Anyway, per your horizontal reference, I'd say mine looks correct, right? (I have the level on the upper flat surface of lower timing cover).

Image
Ju@n
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Re: 533i manifold vacuum

Post by Ju@n »

MattC wrote: Oct 03, 2021 8:18 PM Image
That looks alright!
Thecar
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Re: 533i manifold vacuum

Post by Thecar »

Just glad I could help, I have gotten way more info from this site than I have added.
MattC wrote: Oct 03, 2021 8:18 PM
Oh wow this was very helpful, thank you! Strange that they offset that bottom bolt and then Bentley Manual describes alignment as "straight up and down." Anyway, per your horizontal reference, I'd say mine looks correct, right? (I have the level on the upper flat surface of lower timing cover).

Image
MattC
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Re: 533i manifold vacuum

Post by MattC »

Still ruling out problems, but no solution yet.
I was able to measure the cylinder head height with the upper timing cover removed.

Bentley specifies:
129.0 mm +/-0.1mm head height new.
128.6 mm minimum head height allowed after milling
They say: do not shave more than 0.3mm, otherwise a new head is needed.

Using a set of calipers, I measured values in range of 128.8 to 128.9 mm on mine.
It's tough to get it exact, but I never came close to the 128.6 number, so feeling confident it was NOT shaved too far.
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