Intermittent missing

[brownni]

I recently got my 1981 1.6 NA caddy up and running really nicely by swapping out an old injection pump with a fresh reman from thedieselstore.com. During the swap I took my injectors to a local diesel shop and had them checked. They said the injectors were working fine - good spray pattern and popping within 2 bar of each other. I set the timing at 0.95mm and it starts fine, and runs pretty nicely when it is warmed up. However, I have been noticing some intermittent misses - or maybe extra clatter is a better description. It is pretty random, and seems most common at high loads and lower rpms/higher rpms. It is very quiet and even sounding at cruise in the mid rpm range.

The only strange thing I see is that there are large air bubbles in the apexes of the return lines - could that be the cause of my issue? Is it possible that there are some bad injectors? Does my description sound like pre-ignition? The sound is very similar to the pinging that I had in a 91 toyota 4runner gasser engine that was worn out. If it is pre-ignition, is that bad?

I really just want this thing running well - I have yet to find a great diesel mechanic around Utah that knows mk1's very well, or IDI's for that matter (brother has a ford IDI) and I really just want some peace of mind that these noises either need to be remedied or are acceptable.

[TylerDurden]

Seeing air in the returns is normal.

I'd back the timing off to .90 and see how it goes.

[brownni]

Thanks - I will give that a try and report back.

[brownni]

I retarded the timing back to 0.90mm.

Result after about 100 miles of driving is that the popping/pinging is less frequent than before, and less loud, however, it is still there. I am not sure how to proceed as I know it is an abnormal sound, but once the engine is warm the power delivery is very smooth and it has what I consider to be very good power.

The most unusual thing about the engine aside from this intermittent pre-ignition (what I have decided to call it) is that at cold start-up (temps in the low 20s F ) it has quite a bit of white/blueish smoke for two or three minutes and then that clears right up and I am left with just the intermittent noises as described earlier.

Is there any chance that the injectors can stick intermittently?

The sound is a lot like the sound of the truck at idle when the timing is way to far advanced - which is why I suspect that.

[Mark(The Miser)UK]

Try a little less timing, ie 0.85 to 0.88 or a little more fuel.

[damac]

Are you sure your timing everywhere is correct and your valves, etc. are good?

Can you really trust this shop?

Are you sure you aren't getting air intrusion at pump inlet?  What about when stabbing the throttle?

I have seen many crazy things happen with injectors.  Sticking, nailing, smoking, etc.  Funny I was able to drive my cars through all of these engines, but if you daily drive them like me you learn to pick up on normal noises.

It gets into the teens here and I time all my cars just a tick below high end spec in bently.  I use idle and advance lever before turning the cars over which do so within a second or two of cranking.  Engines cackle but run smooth.  I also don't get the steady white diesel smoke beyond the initial puff and less than 10 second of running.  Never had so much as a stumble pounding any of my cars, unless of course a fuel filter is clogged

I like to start with each good runner I come across by breaking down pumps to clean and reseal.  And get a workover on injectors from a reputable place.

I have freed up sticky injectors before temporarily by running straight atf through fuel filter on car for a couple minutes then letting car sit for a day, and then doing it again.   I rescued a car once that was left to sit a couple days with a bad wvo/gas blend that caked everything up so much the car wouldn't start.  Got it driving, even though later I pulled pump apart and there was buildup on moving parts still.

[Dakotakid]

I'm not convinced you have a problem....quite frankly.
Can you post a video with good sound qualities?

[brownni]

I daily drive this truck and that's why I am trying to get it just right. I ran it with a bad injection pump (timing didn't advance) for about a year before finally getting a new one. The only other VW diesel I have driven is my wife's 2012 JSW TDi, which doesn't give me a great point of reference for normal sounds for a 1981 idi diesel. So I can't say I know what is or isn't normal sounds.

I am pretty sure (~ 99%) that the rest of the engine is timed properly - the camshaft/crankshaft timing is dead on. Also, I am sure that I am measuring the timing of the pump correctly as well. Also, I have checked and double checked the valve clearances and they all look in spec too.

I retarded back to 0.85mm and aside from being a little tougher to start, it still sounds about the same. The truck fires almost immediately when dead cold after the glowplug light turns off but it doesn't run in a manner I would call "smooth" until I just drive for a minute or two - by the time it is idling smoothly, the white smoke is gone.

I am attaching a link to a video of the truck running. I drove around the block just prior to taking this video so although the engine isn't totally warm, it didn't need glow plugs to start, nor did it have any smoke.

https://drive.google.com/file/d/0ByfxKCNwCdupUFJmcUYtMmVWVkU/edit?usp=sharing


Another note - I saw a thread somewhere where someone mentioned listening to the injectors with a screwdriver, I did that and the #1 injector is quite loud/clackey while the other three are much quieter and have a more gentle ticking through the screwdriver. Maybe I just need to replace #1?

[TylerDurden]

Sounds fine to me. I wouldn't worry about #1.

[Dakotakid]

Ya, really....I thought you said there was a miss in there somewhere!

Occasionally, a delivery valve can be at fault for a very slight miss. Those are those little outlet nipples on the dist. head side of the pump where the fuel lines attach.

There is a spring, washer, and the little plunger (not sure what they are called) in there. Years ago, one of them were at fault for me. And, I never really knew if it was a piece of dirt...or weakened spring....or what. I have a lot of core pumps around and simply swapped one out.
I determined which was at fault by loosening the lines, etc. But, in a massive amount of miles driven...this only happened once for me.

I think a lot of guys would be envious to have one run this good. Perhaps, you should sell the pickup (at a core rate) to one of us to further investigate!

[brownni]

HA! I am thinking of selling the pickup but mainly because my wife and I have a kid on the way and I need a vehicle that can tote the three of us. The truck actually does run pretty nicely if I do say so myself.

Today I as I was looking through everything I checked my coolant tank and found it to be about half full of some black sludge. pretty nasty stuff - just slightly more viscous than grease gun grease. No idea what the issue is. I am assuming the head gasket since that's what most people assume here, but I just replaced the head gasket about 6 months ago. I know there is a slight "crack" in the head from the number 4 cyl. area to a coolant passage, but I am stumped again. I am really hoping I can just buy a new head and replace that gasket again, maybe do the rings while im in there and be good to go with a few coolant system flushes.

When I was in there last time the pistons looked great - very clean and no damage, the cylinder bores looked good to. I have no idea how to diagnose a cracked block either so any advice would be appreciated.

The crack is circled in red:

[brownni]

The image isn't working - I am attaching it to the post this time.

If the image doesn't show up this time, here is a link to see it:

https://drive.google.com/file/d/0ByfxKCNwCdupRGxURC1XTk05T2s/edit?usp=sharing

[TylerDurden]

That head has seen some action. 

I doubt oil is coming from that crack, but if you got crud in the rez, it's coming from somewhere... and that head seems kinda beat.

[Dakotakid]

Damage must have occurred in the trip through the Van Allen radiation belt........

[brownni]

who knows where that damage came from. I almost feel a little guilty for putting it back on, but I couldn't afford a new head at the time - nor did I know how to source a reasonably priced one.

While I have people's attention though, do any of you know where I can source a new PCV breather hose like the one in this picture:?

http://www.mikegabriel.net/vw/dieseltraining/diesel_training-126.html