Weird fuel smoke issues...

[crazybushman]

Hey all,
My 1985 TD Jetta just recently developed a new issue. On start up it only runs on 2 (ish) cylinders until after I've driven it around for a while. The exhaust is whitetish blue and stinks of fuel. It hasn't really been consuming any oil. I re-ringed and installed new bearings and seals last year and it's been doing pretty good ever since. The timing belt has apx 25 k on it, camshaft timing dead on, injection pump timing was at 1.17mm so I adjusted it back to 1.0 and still no difference (no clue how it got so far out of whack!?!). Today I just tested the compression with my trusty princess auto tester and I'm showing between 375 and 395 psi across all 4 cylinders(412 minimum according to book). I really don't know how accurate my guage is so I'll take it to work tommorow to test it. Here's the weird part, when I first start it and it's running on 2, if I crack the 2 inward injector lines it makes no difference in the engines running, outward cylinders just about kill it. I swapped injectors and still no difference. If the compression is relatively even (although apparently low) across all 4 it should run poorly on all 4. I know that the injection pump is putting out as I get fuel spray from all 4, put at what presssure I don't know.

Any advice would be awesome, I really don't have the money to fix too many of the engine internals right now, I was thinking of pulling the head this weekend and then maybe getting the valves ground and everything done properly in the head.

ideas????

Thanks!

[Fatmobile]

I didn't see glow plugs mentioned.
Did you test those?
Since it's a new problem it's probably not timing related... unless the crank pully is coming loose from the crank.
Grab the crank pully and see if it feels loose.
Make sure everything timing belt related is tight.

[rwest1]

You’ve done some good work troubleshooting. From info you’ve provided sounds like 2 inner cylinders are getting fuel (smoke at exhaust) but not firing. Since they start firing after warm-up, would lead one to think that heat/expansion improves condition (rings??). You need fuel, pressure/heat and correct timing to fire cylinder. Bad glow plugs are a question but in my experience even low compression engine near your numbers (need to be verified as your doing) will usually fire even in cold weather after you have them started (higher engine speed more pressure/heat). Might try squirting some heavy oil into questionable cylinders, cranking engine w/IP off to get oil spread around, button all up, then start cold engine and see if cold miss is gone or lessened. DON’T ADD OIL W/COMPRESSION TEST, CYLINDER COULD FIRE AND TESTER BLOW UP IN YOUR FACE!!! A leak down test on the cold engine would likely point you to the problem area. There’s lots of info on using LDT’s on I-net and elsewhere so I won’t go into specifics of uses/tests. Also, these engines like lots of advance for good starting & run-up. Your pump setup sounds OK, but you may want to temporarily advance pump to make sure its not part of problem. Rings, valves (adjustment?), head gasket, timing, are most likely candidates, keep group posted on your progress. Regards.

[tawney]

Here's two simple things you could do to try to figure it out: first, a cold compression test; bet you'll find really low compression on the two cylinders in question, hence no fire until it warms up and gets better compression. If, as it seems from your description, it turns out that compression is the issue, check valve clearances. It's not the most likely problem, but you installed new rings last year, so presumably it's valve related as you suggested. Checking and adjusting valve clearance can be done with the head on the engine; anything else and the head has to come off. When hot, the intakes should be around .25mm, exhausts around .45mm. (plus or minus .05mm) Cold, intakes should be .20mm, exhausts .30m, both plus or minus .05mm.

[Vincent Waldon]

Sounds like my beloved 84 caddy... and yes the trick was that compression was terrible on two cylinders when cold, but got better (in my case within a couple of minutes) such that doing the warm test as described by VW didn't show any real problems. Your numbers are low but even... engine should run fine normally.

A Leak-down test is an excellent idea as follow-up because it should help you figure out if pulling the head will be enough or perhaps a ring or two has broken.

In my case I sold the beast before I had a chance to pull it apart and find the smoking gun (pun intended) so I never learned what was causing the poor compression when stone cold.


Vince

[crazybushman]

Tested the compression tester at work today and it's bang on.... I have a spare injection pump, so I will try that out first, I have been running a lot of Jet fuel through this car in the past few years and although I add lube, it may be taking it's toll, it's just all so sudden... I probably should check my valve clearances one of these days though...... its' been a LONG while.

Cheers!

[tawney]

If loosening the injection lines on #2 and #3 made no difference, and you were getting fuel at both, then it's not your pump. There's only one injection plunger in the pump, and it provides the fuel pressure to all four cylinders; I can't imagine the pressure being significantly different from one to the next.

Best thing to hope for is a valve clearance issue, but my guess is it's worn exhaust valves, assuming your new rings are not damaged.

Good luck; let us know what you find.

[jasonsansfleece]

I bought a parts Jetta that ran on less than four cylinders.
I took the injectors out in order to rebuild with new nozzles and set the breaking pressure to use in a Golf.
Just for interest i checked them before their rebuild.
The break pressures ranged from 1600psi to 2100 psi and one nozzle squirted an almost strait stream of fuel with no atomisation. No doubt the reason it was not firing on all four.

Guy

[crazybushman]

I think that I may have figured out the 'mystery problem'.... I was about to pull the injection pump so I lined it up to #1 TDC, cam is looking good but injection pump is now out 1/2 a tooth and lock pin doesn't fit.... That's odd.... I had all of that stuff off of the engine a couple of weeks ago when I changed a water pump (without removing the coolant housing from the block). The belt was too tight, I figured that it had stretched so I walked to the parts store to get another one. When I went to loosen my crank bolt I got a little surprise... It didn't need a 4 foot breaker bar and the starter to break it loose, it was already loose! I had tried to wiggle the pulley as fatmobile had suggested earlier, but it didn't feel loose.

I took it off and found that the key on the timing sprocket had left a little pile of metal dust in there as it had been pounding back and forth for the last 3000kms Anyhow, I am really hoping that the crank material is harder (as it should be) then the timing sprocket (appears to have taken the 'beating'), I think that I have one of those kicking around here somewhere, I will post again to let you all know, but I think that if it's not the culprit it certainly isn't contributing to a good running engine.

If anyone has some good tightening tips for the bolt (ie how to safely lock up the engine) that would be great, I will install the next one with loctite!!

Cheers!

[rwest1]

The crank snout is not as hard as you might think. Check keyways and everything else carefully, any slop left in this system will probably come back to haunt you. Pretty sure there is a torque bar tool in tool section for holding crank still. I use Loctite 40 hi-temp retaining compound liberally, torque to spec., then hit it briefly with impact wrench (this is touchy feely part) to make sure everything is cinched up tight. Regards

[surfcam]

After doing what rwest1 suggested. Check to see if you have the right key. Make sure everything is real clean and you have no burrs. Using the IP lock-up tool it easy to torque to 33 ft. lb. I haven't had any problems do this but sometimes my rewiring goes up in smoke but I learned from it. We all have are flaws. If you don't have another sprocket PM me and I could drop one off on Sunday morning a coffee donut charge may apply. I'm going through Calgary to the Great White North.

[rwest1]

Be sure to check current torque spec.'s, I beleive 33ft.lbs. is pretty light if were talking about the bolt holding the small cogged pulley to the crankshaft snout. What a guy... to hand deliver the part at such a bargain price!!

[crazybushman]

If anyone has one of these sprockets kicking around....

I couldn't seem to find the one that I had and surfcam has the injection sprocket but not the crank sprocket so I guess if no one else here in Calgary has an extra laying about, I'll run down to pick and pull and see if a vw gas sprocket is the same or not.... This is assuming that there are no diesels there of course.

Cheers!

[Fatmobile]

I think the gasser timing belts aren't as wide.