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Engine Specific Info and Questions => IDI Engine => Topic started by: dlorimer on January 09, 2008, 06:59:17 pm
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I just got some major work done on my 85 VW diesel Jetta, N/A, and now I have a smoke problem.
Previous to this, I had almost no smoke -- I would smoke noticably when shifting down to 4th at full throttle up hill (I live in East KY) - that's 55mph in 4th gear (no tach, sorry).
I just had my injection pump and injectors replaced. Now, it smokes MAJORLY. It's light puffs out the back at idle, and just trying to get up to highway speed, it's rolling out clouds. Almost looks like it leaves a dusting on the road, too. It's both black and grey smoke. The only time it's not noticably smoking is at light throttle maintaining speed.
How do I fix this? The new injectors are rebuilt and standard, no fancy nozzles. The injection pump was rebuilt from a MK1 (instead of the MK2 IP it replaced). I know the idle speed and maximum speed screws were adjusted. But, I'm guessing I need to turn down the maximum fuel screw. Is that right? Please let me know where that is. I have been told that a small turn makes a big difference with it.
Might there be anything else that is creating so much smoke? The timing was reset when they installed the new pump. It is set dead center of tolerance range. Power feels about the same. Feels like a little more torque, and a little less HP. Fuel milage is better.
Please advise. Thanks.
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No change in the air cleaner - it's not brand new, but it's ok. No bubbles in the feed line. No leaks from the lines, pump, or injectors (that's why I had the pump replaced). The only leak right now is at the water separator (thanks to USLD). The valves were not adjusted in the process, but have not been checked for some time to my knowledge. Yes, done with cold start lever in.
Just curious - why would you say injector, and not look at fuel screw?
I just had new injectors put in - how can I find out if one is bad? They have to be pulled out to be checked, right?
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Gotcha - I was assuming it was a restricter. How do I check the injectors? Is the only way to pull them out and put them on a tester (which I don't have). I just bought them, and they are BOSCH, so that would really be depressing.
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i've seen cars with really bad compression smoke at idle...
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Yeah I thought about that swap, but I just mailed them back today for the core-charge return ... grr.
Of course, I'm going on the word of the shop that they timed everything dead on. The timing they talked to me about is the 0.90-1.0 or however that rating is (I don't remember the decimal places). But that's pump timing right? I could ask them about crank-to-cam timing ...
The idle is not as smooth as the last pump was. It sounds more "diesely" to me (however, my brother has a mercedes diesel, and it's not near his sound :D ) So, I wouldn't say it's rough, but it's not smooth.
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If all the evidence is pointing to a bum injector you could try the "carefully loosen the fuel nut at the top of the injector while the engine is running, one at a time" approach... this shuts off each injector temporarily and might isolate a bad injector quickly if the smoke suddenly stops. You could then swap in one of your old ones to prove it once and for all.
This is a service-manual approved approach but obviously requires caution.. the fuel is at high pressures... wear eye protection, just loosen each nut enough for fuel to dribble out... have a cloth handy to wipe up spills... etc.
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check the timing for the pump and cam
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Ok, worked on it more today. Seems to have a little less smoke today.
Once warmed up, it did not smoke at idle. It's colder and rainy today, if that makes a difference.
you could try the "carefully loosen the fuel nut at the top of the injector while the engine is running, one at a time" approach
I tried this -- when I loosened the fuel nut on each one, the engine cycle obviously changed, but there was no obvious change in the amount of smoke.
Here's something I noticed today - it does not smoke at all RPM's. Unfortunately, there's no tach, so ...
Imagine the RPM spectrum in quarters. In the bottom quarter, it does not smoke, and in the TOP quarter it does not smoke. In the 2 middle quarters of the RPM range, it smokes badly. So, it stops smoking just about the point when you need to upshift. The smoke is worse when it's going uphill, which is no surprise.
With the previous pump, the car did not have this rapid of response, and it only smoked when it was floored (only the very last 1/2 in of pedal made it smoke). So I'm guessing my previous pump was retarded some?
The next things I need to check are crank-to-cam timing, and compression. Anything else?
Pictures:
(http://i37.photobucket.com/albums/e97/dlorimer/DCAM0003.jpg)
Car at idle (yes, it is running)
(http://i37.photobucket.com/albums/e97/dlorimer/DCAM0005.jpg)
Car revving in neutral
(http://i37.photobucket.com/albums/e97/dlorimer/DCAM0007.jpg)
Soot left on ground after revving for that photo.
(http://i37.photobucket.com/albums/e97/dlorimer/DCAM0008.jpg)
Down the road ...
(http://i37.photobucket.com/albums/e97/dlorimer/DCAM0010.jpg)
Down the road ... these two are between 4-5th gear, 3rd quarter of RPM
(http://i37.photobucket.com/albums/e97/dlorimer/DCAM0011.jpg)
Uphill in 2nd gear
Sorry the pictures are kinda blurry -- but, no, I didn't take them while driving - I at least had somebody else do that! :D
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The one in neutral is floored. The others are not - they are heavy pedal, but not floored.
Where is the pump inlet bolt? Directly across from the inlet stem?
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read my note above -- it's the middle two-quarters of the RPM, the top quarter doesn't smoke.
Of the pedal, it's anything except light pressure - ie, maintain speed on flat ground.
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Fuel Filter is brand new - and I've checked it anyway - it's good. I'll check some of those other things - a mechanic friend of mine is here - I hope he's got a little time :)
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Aaah! Thanks for your help! I ran into one of the problems of working alone. Air in the fuel IS the problem. There is no air in the line at idle, and I hadn't revved it from under the hood (don't ask me why, I temporarily forgot that I could) ...
I tightened the banjo bolt, and it made a noticable difference. Then I revved it from under the hood, and it still had a lot of air in the line (it only gets air under load).
I located a fuel leak at the water separator, so I'm working on that. It may just fix the problem. I'll let you know, and thank you!