Mystery low power highly modified alh

Calling modified alh experts! Been chasing a low power issue on my alh setup. I will list off the mods and what I have diagnosed/changed so far.

ALH engine with 17/22, r520's 11mm pump, lift pump, race pipe intake, 2.5in exhaust straight through, fmic, software, etc.

Problem began about 6 months ago, when it felt down on power. Also egt's were excessive, reaching 1600 in under a 1/4 (It could go a 1/4 and then some before this temp was reached before this issue). Camshaft was then upgraded to a colt stage two and lifters were changed, but no significant increase in power or lowering of egt's happened. Everything I have checked has come out positive.
Timing is perfect, iq is set at 3.8, boost is at what the chip calls for (27 psi).

I believe the issue lies somewhere in the fueling system, as the air is there. Changed filter and inspected lines, no change. No leaks on injection pump. Injectors seem fine, no symptoms of a bad one. New case pressure valve in injection pump. N108 gave acceptable ohm readings. Occasionally when giving it a hard run, an error code will be thrown, 00550- Start of injection Regulation
17-10 - Control Difference - Intermittent. However, this code is unpredictable in terms of you can not force it to happen by doing one particular thing.

Only discrepancy I could find this the start of injection timing on a hard pull, as graphed here



One shows expected and one shows actual degree of the injection, this data came from measuring block 4 if I do recall correctly. Other than the error code and this graph which I cannot make any meaning out of, I have no other leads. But there is an obvious problem when your trap speed goes from 98 to 74 mph! Thanks

Based on your symptoms, your pump is dying. I just went through the same symptoms and spent a lot of time chasing my tail. I ordered a replacement pump from Frans at DAP, and will get it installed tomorrow. I haven't gotten the "timing" code in a while, but now I have an un-resettable QA error that prevents my engine from starting.

What is DAP if you don't mind me asking as im trying to learn all the places to buy parts for my race BEW build

gibbswrecker said:

What is DAP if you don't mind me asking as im trying to learn all the places to buy parts for my race BEW build

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Dutch Auto Parts, you can google it or there is a thread here somewhere

Replace qa

Nevada_TDI said:

Based on your symptoms, your pump is dying. I just went through the same symptoms and spent a lot of time chasing my tail. I ordered a replacement pump from Frans at DAP, and will get it installed tomorrow. I haven't gotten the "timing" code in a while, but now I have an un-resettable QA error that prevents my engine from starting.

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Thank you for the input, but I am trying to avoid the common process of just sucking it up and buying a new pump, I want to learn what is actually wrong with my current one.

mk1-83 said:

Replace qa

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You say replace quantity adjuster for what reason? Possibly not working correctly, or output readings are off? I have a ahu 10mm pump quantity adjuster assembly, would this work or do I need a specific alh 11mm one? Thank you.

For erratic "dynamic" timing check the "cold start solenoid" (aka timing advance solenoiod). I say "dynamic" timing to distinguish from "setting the timing" in basic settings, which is merely a mechanical setting as opposed to actual advance while the engine is running under load.

As the pumps wear out, they develop leaks around the timing advance solenoid seal internal to the pump and won't hold the dynamic advance.

Might get by with a new timing solenoid but if its leaking really bad then you need to go deeper with the machining.

Generally not considered fixable, even for official Bosch authorized rebuild facilities with millions of dollars of specialized equipment. Thus why most will just say just get a new pump, because it will cost more to fix by a shop than a whole new pump costs. So not worth it to try.But that probably won't deter someone who is really determined to show they can do it no matter what the experts say, regardless of the effort involved or the cost. "Not fixable" is a challenge to some.

To fix it you would need strong machinist skills and a bit of innovation. In theory, you could perhaps hog out the bore and sleeve it or if it's too deep perhaps weld it up and machine it very carefully, but I can't recall where I've ever heard of anyone doing that successfully.

So there you go, that's how you fix it if you really want to.

KERMA said:

For erratic "dynamic" timing check the "cold start solenoid" (aka timing advance solenoiod). I say "dynamic" timing to distinguish from "setting the timing" in basic settings, which is merely a mechanical setting as opposed to actual advance while the engine is running under load.

As the pumps wear out, they develop leaks around the timing advance solenoid seal internal to the pump and won't hold the dynamic advance.

Might get by with a new timing solenoid but if its leaking really bad then you need to go deeper with the machining.

Generally not considered fixable, even for official Bosch authorized rebuild facilities with millions of dollars of specialized equipment. Thus why most will just say just get a new pump, because it will cost more to fix by a shop than a whole new pump costs. So not worth it to try.But that probably won't deter someone who is really determined to show they can do it no matter what the experts say, regardless of the effort involved or the cost. "Not fixable" is a challenge to some.

To fix it you would need strong machinist skills and a bit of innovation. In theory, you could perhaps hog out the bore and sleeve it or if it's too deep perhaps weld it up and machine it very carefully, but I can't recall where I've ever heard of anyone doing that successfully.

So there you go, that's how you fix it if you really want to.

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So here is graph of the cold start valve percentage (blue) specified start (green) and actual start in yellow. This is fully warm, at idle then a mild first gear acceleration, to a full second gear acceleration, and a bit into third.

some interesting notes about the above graph that leap out as questionable to me are the creeping of the cold start value on the left side (far left was just after I stopped), and then the far mismatch in spec'ed vs actual advance at wot.

Tdipickup said:

So here is graph of the cold start valve percentage (blue) specified start (green) and actual start in yellow.

Click to expand...

Yep that's what I'm talking about.

the pump can't make the timing advance it needs to

Tdipickup, at this point you have two options: order a rebuilt from DAP w/o a core charge for $850.00 delivered, or you can send off your pump to DFIS and wait for them to rebuilt it at a possibly, significantly higher cost. Plus shipping both ways of course. I installed my pump from DAP yesterday, and asked permission to adjust the IQ as it was quite low, likely from my large nozzles.

EDIT: The DAP price is for an 11mm IP, not the standard 10mm head.

Case pressure readings would be definitive. You are losing advance, that much is clear.

Could be fuel supply (you want some positive pressure at inlet at all RPM and fueling range, given that you're running a lift pump), could be the solenoid/seat, or could be advance piston sealing/wear as kerma suggests.

If you don't have the parts to check case pressure, at least check fuel inlet pressure while getting on it real hard. Might be you're just asking too much of whatever lift pump you're running, or the feed lines themselves.

Thanks for the feedback. I suspect something electrical like the timing advance solenoid, keeping in mind that as of less than 1000 miles ago this thing worked fine. I would have trouble imagining it wearing that quickly.

Could this be caused by the I.P. case pressure valve poppet sliding out?

Search "keystone" mod.

http://forums.tdiclub.com/showthread.php?t=206384&highlight=keystone

No the case pressure valve has been checked and is fine.

Change for 10mm manuel use pump and make autopsy of the bad one.
If the head are good, swap head on 10mm pump, dont forget to check the K clearance.



Dieseleux

Picked up a donor car yesterday, going to swap pumps around and see what happens. I believe the only issue with the current pump appears to be related to the values given by the cold start valve.