High RPM stalling problem

[gldgti]

Hey guys, its been a while since i posted here.

I did a search already to no avail, but I will try to engage the collective mind :-)

I've recently done a 1Y (similar/same as aaz) conversion into my wifes 1991 cabriolet, with the standard aaz GT-15/K03 sized turbo.

Its got a big FMIC, i've put 273 nozzles in it, I had to rebuild the injector pump, and so it has a 1.9TD camplate, 10mm head and a brand new vane pump.

THe thing runs like an absolute dream honestly, has great power and is getting good economy. Runs nice and smooth too - however, I am having a stange problem - and it can't be that common, I've been tinkering with vw diesels for years and never some accross it ever before.

Basically what happens is, when the engine is cool - or rather, not really really warmed up - if you give it full throttle, when you get to say.... above 4000, maybe up to 4500, the engine will completely stall. This is not the governor kicking in. Its sudden and severe. Also, it makes a slight nailing noise as this happens. Extra smoke will come out of the exhaust too.

Usually, I might be in 2nd or 3rd gear when this happens, so I keep the clutch engaged and back off the throttle - momentum keeps the engine turning over, and after a second or two it runs like normal again.

To be honest, this problem is pretty scary when it happens. Its not a good noise.

To try and give some extra information:

Timing is set at about 1.15mm lift at TDC.
The 273 nozzles are new
New injector hard lines
No air leaks
No boost leaks
It has a good fuel filter

To top off the weirdness, it only happes, like I said at the start of the post, when the engine is not good and warm.... e.g. - within the first 20minutes of driving. Even if the temp gauge shows fully warmed up, if I've only been driving for 10-15 minutes it will still do it. If you sit in traffic and idle for a little while, its usually hot enough to negate the problem.

I can't figure out what the heck it is, so I'm asking for any ideas. Surely someone has come accross something similar ?

Thanks for any help you can give me in advance - kind regards
Aydan

[CRSMP5]

hydro valve?? if yes.. whats the oil temp vs oil pressure say?

[gldgti]

yes - they are hydraulic lifters.

I put new lifters in it when I rebuilt it, about 12,000km ago. I don't have oil temp gauge, and oil pressure gauge not connected at the moment (only have the warning light). I run good quality semi synthetic 5W-40 diesel engine oil, which is VW approved, and also I ran this oil in my old mk3 aaz for about 150,000km with no problems.

I might try hooking up the oil pressure gauge.... I've been putting it off since the sender is big and will stick out near my intercooler plumbing - and I have no oil leaks from this engine at all :-) plumbing in a T for the sender always seems to create an oil leak... and right above the bellhousing :-(

[CRSMP5]

ok here is my theory... its not a good one... but oil pressure is key...

the pressure releif valve in oil pump i hanging up.. pumping the lifters full so much things hit and stall it..

oil temp is the varable.. takes longer then water to warm up... once warm no issue.. but under a certin temp its got too much oil pressure... why the differance in operating/slow to go away..

[gldgti]

OK, so I guess I can check that fairly easily by plumbing in the oil pressure gauge.

How much oil pressure is too much at 4000 rpm? Anyone got any ideas? I would think it should be around 80psi max....

[colhel59]

I have a similar problem but I think mine is due to air getting into the pump and then works its way out. Do you have air bubbles in your return line when this happens?

[burn_your_money]

On a completely different train of thought, try running a constant 12v power to the stop solenoid straight from the battery. I had a strange engine cutting out issue once and it was the stupid battery cables were loose. Everything else was fine except when I pushed the clutch in, it would stall sometimes.

I realize it's not very probable but it's worth trying if you can't find the problem elsewhere.

[CRSMP5]

my  worry is knock noise... electrical on pump or anything would be like killing via key... no knock noise supposed to happen...

fuel is always a great guess.. but it would no reseal its self IMO for his engine temp change..

hmmmm how much pressure.... sadly my only hydro engine is my tdi-m... no accurate tach to guess... but 4k is like 2500rpm.. rotella 5-40 synthetic.. ~85*c on oil temp it runs 35psi...

for your oil pressure issues... you will be trying to exceed 8bar.... aka bury a 10 bar gauge no issue... buries 5bar/80 psi at idle w/cold...

the idea when cold.. rev it till gauge drops.. this drop is the oil pressure valve... no drop = stuck pressure valve... usually they blow up the oil filter... aka big leak/mess... but ive seen this happen on a personal car i owned... not diesel thank god... but 1st start of day it woulf fire then boom... 0 compression on all 4 holes... neetest wtf just happened...

im thinnking he loses compression.. stlls... pistns hit things closing the lifter.. all of sudden lots of nonn burnt fuel = smoke... 

[gldgti]

I'm not sold on the oil pressure being the problem... mainly since I "rebuilt" the engine so recently:

> Fully diss-assembled block and head. Pressure clean and full degrease. Checked and cleaned all oil passages and coolant passages in head, block and crank, oil squirters etc.
> dis assembled, cleaned, reassembled and checked gear backlash and clearances in oil pump. fully cleaned/degreased filter housing
> like i said before, 8 new hydro lifters... OEM brand (febi)

The knocking/nailing noise sounds just like way too advanced timing. Could it be something like needle float in the injectors or something? Perhaps too much fuel going in, or residual fuel causes pre-ignition in the next stroke?

I have an EGT gauge, I havent seen any scary temps (i did a track day a couple of months ago, highest I saw was 1200F)... on the road usually I only see up to 1000F on a very hard pull.

My gut feeling is that the problem has something to do with fuel supply being somehow way too much in this particular circumstances.... but it just seems so strange that it goes away when the car is nice and warm.

Keep the ideas coming, thanks guys. :-)

here is a vid of the engine in the car (the engine is warm in this vid)
http://www.youtube.com/watch?v=5cHeEI2kRks&feature=plcp

and in this one too

http://www.youtube.com/watch?v=tGF6Bk2Qr7U

[CRSMP5]

did you take apart the valve?? its built into the oil pump pick up.. its cover is the goofy freeze plug looking thing... basically drill across it for a cotter key, then use small slide hammer to pull the plug out.. valve and spring should fall out with ease... if not its stuck..

gotta drill first.. so you know the holes line up... the cotter ke is the saftey that it does not fall back apart..

the one i had issues with was on a fresh rebuild too... but who takes it apart..

[gldgti]

Hah, no I did not do that..... now I'm worried.

I will definaltely be fitting the oild pressure gauge to check this weekend and if it looks at all sus the sump will be coming off.

Thanks 

[lloydbiker]

You know, this seems really funny, but I had an old 1.6TD which had a new head installed, and in the winter it would do really weird things. It would start, try to run to 'High Idle', and immediately stall. Then it would spin like 0 compression.
If left for a while, it would do a repeat performance, over and over.
As I had bought a '97 AAZ Mk3 and my grand-daughter was fed up with an unreliable car, I sold the mk2 and a NA parts car to a friend. He sold it to someone else, and he scratched his head for a while over it. He eventually found out the problem was high oil pressure pumping the lifters just enough to crack the valves, and dump compression (it doesn't take much).
Also, I can see where, on restart, you could have a bunch of unburned fuel in the exhaust, resulting in a lot of white smoke.   

[CRSMP5]

thanks for sharing.. its something i only seen 1 time... on my own car at that on pumping lifters up too much.. ive seen it blow oil filter gaskets a few times though.. just the lifter pumps up too much not common..

[gldgti]

Well, after some more testing, I'm pretty certain its not to do with oil pressure.

We would all agree that, if oil pressure was the problem, the colder the engine was the worse the problem would be.

So last night, I left from work and after only 4 minutes of driving, I rev'ed the engine to 4600rpm. In the past I see this problem from 4000rpm onwards.

So, this did not replicate the fault - why? Because I rev'd it out using only about 1/3-1/2 throttle. 3rd gear, coolant temp only just off the bottom, I allowed engine speed to pick up (going down a slight hill) until 4600. Ran smooth as anything.

Thinking back, this problem only happens when I am really gunning it (lots of throttle), and when cool, and at high rpms.

Since acellerator position has no effect on the oil pressure, I would think that my experiemnt last might would have ensured replicating the problem, if it was due to oil pressure.

So, I think it is related to the injector pump.

Any ideas on this tack?

[theman53]

But the injector pump is still spinning that fast???

One good thing I can tell you is unless you are in danger of getting ran over by a train there is no need to ever take the engine over 3,000RPM when it is still cold. I think if you stop beating on it when it is  cold this may have a way of fixing itself over time. I put an oil temp gauge in mine and sometimes when it was cold outside it took 15minutes of driving for the oil to get up to running temp.