Diesel dieseling too much.

[dennis]

I just got my engine (85 1.6TD) back together and running, but it sounds like it has one cylinder with too much pre-ignition. My injectors have around 20k miles as Bosch re man units. Today after the outside temps dropped into the thirties it was sounding worse. So much so that I'm sleeping at the shop tonight. The engine has been bored 1.0mm OS. I replaced the head with a NOS VW unit I got off eBay. (Mexican) Did some port and polish work because the casting was pretty rough. New KS pistons. I have not checked valve clearances warm but they were ok cold. When I last started it I got a fair amount of white unburned diesel smoke which cleared up after about 5 min. Pump timing is set to 1.0mm, and the cold start does affect it. I originally rebuilt the engine because it burned a pretty fair amount of material away between the ring lands (see pic). Im sort of thinkin it might be an injector or a precup with some trash in it. Any ideas?? I have a 180 mile round trip commute and I need this engine to behave.
Dennis

[Quantum TD]

I'd suspecte injectors. Do you have any way to pop test them for variance in pressures? Also, did you sort out what caused the piston problem in the first place?

Those Bosch remans are usually done in India. I've had them bad out of the box. In my case the pressures were fine, but the injectors leaked and one pinged like a biyotch. I ended up rebuilding them myself after I cleaned them and pressure tested them.

Also, at 1.0 mm of advance, the cold start really shouldn't affect how the car runs, unless you have a later (1985-up) pump with the idle advance on it. At 1.0mm, the advance should be beyond what the cold-start can advance.

How long did the car sit while you did the engine work?

Minimally, I'd run some Lubro Moly Diesel Purge through the system and check for air bubbles in the fed line. If it looks good, then run it for a while. But, before really running it, I'd listen to the injectors and see if you can hear anything unusual in them. I use a long screwdriver to each injector and the but end in my ear.

[dennis]

Never did really figure out that piston, but I had been chasing a misfire by swapping out one injector at a time. after that I pulled the head and oil pan with the intent to do rings and rod bearings. I didn't have any issues at the time with noisy injectors. I don't have a pop tester. Also the cold start doesn't affect running, just starting cold. The truck only sat for a couple of months tops, plus I have put around 300 miles on it since the rebuild. No air bubbles. I'll do the screwdriver thing this morning. I still have that injector around here somewhere, plus I have a used set of NA injectors to swap as well. Thanks for the help.

[Mark(The Miser)UK]

Also, at 1.0 mm of advance, the cold start really shouldn't affect how the car runs, unless you have a later (1985-up) pump with the idle advance on it. At 1.0mm, the advance should be beyond what the cold-start can advance.

I'm not one to pick holes, but are you sure?
The cold start is a cheese wedge that twists and pushes the advance mechanism. This rotates the cam plate.
The cam plate on a 1.6 TD maxes out on 2.3mm.
On a 1.9, is it 3 or 4mm?

[dennis]

Well I listened to the injectors and #1 sounded a bit different from the rest. my good buddy who ported my head for me had installed the injectors. Heat shields were upside down. Its better, but still a bit noisy. I think Im gonna revisit pump timing when I check my valve clearances in about 500 miles or so.

[vanbcguy]

Also, at 1.0 mm of advance, the cold start really shouldn't affect how the car runs, unless you have a later (1985-up) pump with the idle advance on it. At 1.0mm, the advance should be beyond what the cold-start can advance.

I'm not one to pick holes, but are you sure?
The cold start is a cheese wedge that twists and pushes the advance mechanism. This rotates the cam plate.
The cam plate on a 1.6 TD maxes out on 2.3mm.
On a 1.9, is it 3 or 4mm?

I'm with Mark on this one... the cold start doesn't add a set amount of lift, it just rotates the cam plate further along.  It will always cause a change in lift.

[rabbitman]

Also, at 1.0 mm of advance, the cold start really shouldn't affect how the car runs, unless you have a later (1985-up) pump with the idle advance on it. At 1.0mm, the advance should be beyond what the cold-start can advance.

I'm not one to pick holes, but are you sure?
The cold start is a cheese wedge that twists and pushes the advance mechanism. This rotates the cam plate.
The cam plate on a 1.6 TD maxes out on 2.3mm.
On a 1.9, is it 3 or 4mm?

I'm with Mark on this one... the cold start doesn't add a set amount of lift, it just rotates the cam plate further along.  It will always cause a change in lift.

X2, excessive internal pressure will disable the cold start too once it's running.

[burn_your_money]

The cold start advance is negated once the internal pump pressures exceed the forces of the spring+shims on the other end of the advance piston

Based on where that damage is on the piston I would not expect a bad injector.

You could back the timing off a bit, new injectors do clack more then broken in ones.

Are all your glowplugs working?

[dennis]

Im pretty sure Im down to one mis-behaving injector. I checked pump timing and adjusted to .99mm. Checked all my valve clearences, and they were ok. Gonna drive it tonight. It sounds like it has one injector hammering at higher rpms. Seems to go away with 10psi of boost and some extra fuel.

[dennis]

The cold start advance is negated once the internal pump pressures exceed the forces of the spring+shims on the other end of the advance piston

Based on where that damage is on the piston I would not expect a bad injector.

You could back the timing off a bit, new injectors do clack more then broken in ones.

Are all your glowplugs working?

Yep the glow plugs are fine. I swapped out one injector this morning and found my buddy had put the heat shields in upside down. I replaced those but I still have some pretty serious clatter at high rpms that will go away at around 10 psi of boost with extra fuel comming in. I hoping thats an injector. 

[Mark(The Miser)UK]

Also, at 1.0 mm of advance, the cold start really shouldn't affect how the car runs, unless you have a later (1985-up) pump with the idle advance on it. At 1.0mm, the advance should be beyond what the cold-start can advance.

I'm not one to pick holes, but are you sure?
The cold start is a cheese wedge that twists and pushes the advance mechanism. This rotates the cam plate.
The cam plate on a 1.6 TD maxes out on 2.3mm.
On a 1.9, is it 3 or 4mm?

I'm with Mark on this one... the cold start doesn't add a set amount of lift, it just rotates the cam plate further along.  It will always cause a change in lift.

For the standard 1.6 pump, @ the operating region, the c/s advance will be about 5 degrees, or 2 flywheel teeth, or 10 thou [0.25mm] on the timing piston/dial gauge

[Powered by Spearco]

Have you tried to time it by ear when fully warm?

[dennis]

I got really sick of chasing this problem down and got 4 new injectors. Problem solved!!

[wolf_walker]

Where'd you get the injectors?  Just curious.

[dennis]

Worldpac. The engine is still noisier than it use to be. At times its fine. Maybe its the pre-chamber design on the new head. They did measure large. Im just gonna continue to drive the darn thing untill its fully broken in or it blows up. Im gonna start looking for a 1.9.