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  #11  
Old 09-26-2020, 10:26 AM
ngoma ngoma is offline
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So with the non-intact Pressure Control Valve in the IP like that-- means no dynamic timing advance, correct? Excess smoke, loss of power at mid to high RPMs?
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  #12  
Old 09-26-2020, 11:11 AM
v8volvo v8volvo is offline
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Quote:
Originally Posted by ngoma View Post
So with the non-intact Pressure Control Valve in the IP like that-- means no dynamic timing advance, correct? Excess smoke, loss of power at mid to high RPMs?
Yes those were the symptoms. Presumably resulting from not enough timing advance at high engine speed because with the valve fallen apart like that and in effect running full bypass all the time, it couldn't crank up the pressure to move the timing piston and give the required dynamic advance.

Surprisingly it did not set a check engine light on my engine, which sometimes this issue will, if the injector needle lift sensor reports that the timing is retarded and the computer realizes it is unable to add enough timing advance to bring it to the desired value. I suspect that was because on this engine I happened to set the static injection pump timing set at the high end of the acceptable range, so that even without the benefit of full ability to control dynamic advance, the final timing was still close enough not to trigger a fault. But it was obviously off enough to affect the way the engine ran, fault or no fault, which is funny. The primitive onboard diagnostic functions of these early engines presumably allow for more error / wider tolerances than a modern system would, especially for something like injection timing that has a very large impact on tailpipe emissions.

As you pointed out before also, on a mechanically controlled IP like on D24/T, simply tapping the valve back together like I did on this pump would not necessarily achieve a satisfactory result for restoring the dynamic timing curve. That would have to be done theoretically on a calibration bench for our engines I suppose. Whereas with these TDI pumps less precision is demanded from the mechanical systems, since the computer has control over a solenoid valve in the IP that can fine-tune the timing advance with feedback control. Thus as long as the mechanical systems can get the timing to within any kind of reasonable ballpark range, the computer will be able to take it from there and hit the desired value. So what's "good enough" for this IP, in terms of shade-tree methods, would not necessarily be good enough for a D24/T.

I see my pictures aren't showing in the earlier post, I'll fix those.
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  #13  
Old 09-27-2020, 03:18 PM
DieselScout DieselScout is offline
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Where can a pressure gauge sender be installed for the D24 NA VE Pump?
And what gauge sweep would be needed?
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  #14  
Old 09-27-2020, 04:05 PM
ngoma ngoma is offline
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NA IP is apparently a little easier.

"I used a pedestal from a n/a diesel and drilled and tapped a standard compression fitting in order to use a mechanical oil pressure gauge. The pedestals are readily available. Two stacked together would allow easy fitting to a TD pump. One works fine for a n/a pump."

Talking there about the IP OUT fitting.

"Pressure in pump MUST be 43.5 Psi at 1000 RPM engine "
"Pressure at 2000 Rpm -about 75.4 Psi"

There's also a flow rate that is important to test.

All the information here:
internal injection pump pressure
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  #15  
Old 09-27-2020, 05:54 PM
DieselScout DieselScout is offline
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So I'll need a reading up to 300 PSI to cover all RPMs?
The largest gauges I can find is 0-100 PSI for most all makes, except for an odd couple that go up to 200 PSI.

What is the pedestal referenced in the first quote?

Best place to connect a gauge is at/after the "Out" fitting on the pump?
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  #16  
Old 09-28-2020, 09:14 AM
ngoma ngoma is offline
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Interesting questions. Where did you get the 300 PSI figure?

I am not the expert on this subject. Sometimes I surf the vwdiesel.net site to try and learn new things. Our same basic engine had a much larger and longer production run in the VWs so there is a naturally larger population of gearheads there and a more extensive knowledge base.

This fairly recent post caught my attention:
Gov mod AND timing mod??

Which lead to this one:
internal injection pump pressure

Quite a lot of info there, and not always so cut and dried. It will take some time to study all that info and arrive at a clear testing method but the results could be worth it.

My current thinking is that the first test to perform is the outflow test which seems to not require specialized equipment.

Your questions could probably be better answered if you posted them in the Gov mod AND timing mod?? thread. Some of those recent contributors were also active in the older, more extensive internal injection pump pressure thread.

Please report back and tell us what you find!
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