Author Topic: 1.6TD max fuel screw question.  (Read 1142 times)

June 21, 2019, 08:52:34 am

BajaVWCamper

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1.6TD max fuel screw question.
« on: June 21, 2019, 08:52:34 am »
HI All,

I just finished a rebuild on 1.6TD JX engine and am now in the process of dialing it in.

When i accelerate i get a huge puff of black smoke for the first 1-2 seconds.
Running and under boost (ie under load)  it seems to be at about normal smoke levels.

The previous mechanic who worked on the car before i bought it moved the Max fuel screw on the IP as the seal was broken (the paint dot) but the original wraparound clamp is still on it.

in a effort to reduce this initial black smoke puff i drastically reduced the max fuel screw (like 3-4 turns OUT if not more) but it seems to be even worse now.
Its important for me to get rid of that smoke puff (or minimize it) as the car must be smog tested because i live in Germany.

My question is can screwing the max fuel screw OUT actually increase fuel injection for the instant when the throttle is opened at low RPM?

And if not what other things can it be?...

Thanks!
« Last Edit: June 21, 2019, 08:55:11 am by BajaVWCamper »



Reply #1June 22, 2019, 10:38:05 am

sgnimj96

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Re: 1.6TD max fuel screw question.
« Reply #1 on: June 22, 2019, 10:38:05 am »
Have the Injectors been tested for proper function?
 
3 or 4 turns is way too much for a normal running pump to be adjusted.    Just for ***z,  take the out bolt out the pump and check that the TINY hole is not plugged.    All the fuel flow going out of the pump goes through that tiny hole.

Maybe someone who knows turbo setups can add something.   More fuel needs more air.
81 Scirocco 1.6D (conversion)               86 Gofl 1.6D                          1985 300TD

Reply #2June 24, 2019, 01:21:02 am

BajaVWCamper

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Re: 1.6TD max fuel screw question.
« Reply #2 on: June 24, 2019, 01:21:02 am »
After burning my brain after to much thinking of what could the problem be it simply occurred to me what if when i got the car the pump already had very messed up settings...  I decided to screw the Max fuel screw a long way out (ca 6 -7 tuns) and to my absolute pleasure it seems that was it! ;D
i had to turn up the idle screw up considerably also but now on accel i get a nice reasonable puff of black instead of a whole smoke screen.

The only issue i seem to be having now is that the #4 Piston (closest the Flywheel) dosen't seem to be working as hard as the others. When i crack open the each injection line pistons #1-3 give me RPM drop as they should but with #4 there is hardly any difference at all other than the sound (you can defiantly hear the clak clak clak from the injector and the detonation stop as soon as the line is cracked open)

On driving thought it does feel like its running on all 4 normally (powerwise)

Tips suggestions???

Thanks!

Reply #3June 25, 2019, 04:15:46 am

BajaVWCamper

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Re: 1.6TD max fuel screw question.
« Reply #3 on: June 25, 2019, 04:15:46 am »
On further test driving i noticed something else. I have poor throttle response for the first 2\3s of the pedal. Can this have something to do with the max fuel screw? or where should i start looking?

it is like at 2\3's pedal i'm only getting 30% power and from there on is a sharp increase in power. (so full pedal is 100% power).
Sort of feels like its only running on 3 cylinders up to 2\3's pedal then on all 4 from there on.

Throttle linkage is working properly full pedal opens the pump all the way.

i am aware the pump hasn't been runned for at least a good 3 years. i do plan on running a good lubricating and cleaning additive as soon as i fill the tank.
maybe it just needs a good running in?...

thanks!

Reply #4June 26, 2019, 11:11:38 pm

ORCoaster

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Re: 1.6TD max fuel screw question.
« Reply #4 on: June 26, 2019, 11:11:38 pm »
Sounds more like timing issue to me.  Once it gets rolling the advance gets over far enough that you come near normal and it starts to run right.  Have you done a timing check on it?  Got the tools?  You may just be able to loosen the IP for starters and see if you push it towards the head it picks up RPM and smooths out for now.  Very tiny movements are all it takes. 

Mark a line across the IP and the bracket it is secured to so you can come back to that adjustment if moving the pump makes things worse.

Best I can think of for someone with a new to them Rabbit and no manual or specific tools.
Rabbit repairs to body damage need attention before trying to sell it in the spring

Reply #5June 28, 2019, 02:06:34 pm

Dakotakid

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Re: 1.6TD max fuel screw question.
« Reply #5 on: June 28, 2019, 02:06:34 pm »
If you truly want an engine which cleanly grunts off the bottom and rips right to the top with minimal smoking, etc., then, put forth the effort to thoroughly port the intake and exhaust ports. Air in....air out....quicker rotation of the turbo vanes.....cleaner burning  with all or almost all of the turbo lag gone.

It certainly works well for me in multiple engines...and I live between 3500 and 5500 feet elevation here in the greatest country in the world.

For me, running one of these NOT ported is like trying to win a 5-gallon bucket of liquid drinking contest, while using just a straw. Makes very little to no sense.

The same principle works extremely well for my later ALH engines as well. I've got two stock alh Beetles which will quickly creep up to 100 mph on the open road if not careful.
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Reply #6July 01, 2019, 05:48:04 am

BajaVWCamper

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Re: 1.6TD max fuel screw question.
« Reply #6 on: July 01, 2019, 05:48:04 am »
Sounds more like timing issue to me.  Once it gets rolling the advance gets over far enough that you come near normal and it starts to run right.  Have you done a timing check on it?  Got the tools?  You may just be able to loosen the IP for starters and see if you push it towards the head it picks up RPM and smooths out for now.  Very tiny movements are all it takes. 

Mark a line across the IP and the bracket it is secured to so you can come back to that adjustment if moving the pump makes things worse.

Best I can think of for someone with a new to them Rabbit and no manual or specific tools.

Thanks! I set my timing with a caliper as i don't have the proper dial tool yet (eyeballing it to about 1mm). Someone sometime did scribe a line across the bracket and i used that as my initial start point. ill play with the timing a bit more eventually then ;) .


If you truly want an engine which cleanly grunts off the bottom and rips right to the top with minimal smoking, etc., then, put forth the effort to thoroughly port the intake and exhaust ports. Air in....air out....quicker rotation of the turbo vanes.....cleaner burning  with all or almost all of the turbo lag gone.

It certainly works well for me in multiple engines...and I live between 3500 and 5500 feet elevation here in the greatest country in the world.

For me, running one of these NOT ported is like trying to win a 5-gallon bucket of liquid drinking contest, while using just a straw. Makes very little to no sense.

The same principle works extremely well for my later ALH engines as well. I've got two stock alh Beetles which will quickly creep up to 100 mph on the open road if not careful.

Ill do porting and polishing sometime down the line. I've done this in air-cooled VWs before and i know it makes a huge difference.

But yea those later 1.9TDIs haul ;D I daily drive a 2003 VW Touran (basicly a golf with a minivan body) with a totally stock AVQ 1.9tdi PD engine (nearly 200,000 miles on it already only normal service and timing belt changed at interval) in it and i regularly drive over 100mph but i've pushed her up to 125mph on a few occasions. No speed limits on the autobahn are a blessing ;D

Reply #7September 21, 2019, 06:17:18 pm

F.O.R.C.E.

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1 6TD max fuel screw question
« Reply #7 on: September 21, 2019, 06:17:18 pm »
For a while i ran my MZ Ynamar wihout the max set screw i lost it and id spend lots of thought while driving about not to overfueling. So a while back i replaced it with a dumb screw  It works like a charm, just give it some throttle and away you go, no worries about cokeing the rings no more. Ill never go back to driving without a means of setting max fueling.

Reply #8December 18, 2019, 12:30:01 pm

rabbitman

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Re: 1.6TD max fuel screw question.
« Reply #8 on: December 18, 2019, 12:30:01 pm »
On further test driving i noticed something else. I have poor throttle response for the first 2\3s of the pedal. Can this have something to do with the max fuel screw? or where should i start looking?

it is like at 2\3's pedal i'm only getting 30% power and from there on is a sharp increase in power. (so full pedal is 100% power).
Sort of feels like its only running on 3 cylinders up to 2\3's pedal then on all 4 from there on.

Throttle linkage is working properly full pedal opens the pump all the way.

i am aware the pump hasn't been runned for at least a good 3 years. i do plan on running a good lubricating and cleaning additive as soon as i fill the tank.
maybe it just needs a good running in?...

thanks!

That is caused by the max fuel screw being out too far. I've noticed I have to move my foot more either way to get the same response if the screw is out too far. Try threading it in a half turn and then thread the full throttle limit screw in a little. The go pedal won't depress as far so you can adjust the stop under the pedal to save the cable.
'82 Rabbit, I put on a euro vnt-15, 2.25" DP, 2.5" exhaust, the result.....it whistled.

I removed the turbo, made a toilet bowl 2.5" DP, the result....it was deafening. Now it has a homemade muffler up front and a thrush in the rear, the result.....less loud.
Watch: AGENDA, GRINDING AMERICA DOWN

Reply #9January 31, 2020, 10:22:00 am

BajaVWCamper

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Re: 1.6TD max fuel screw question.
« Reply #9 on: January 31, 2020, 10:22:00 am »
On further test driving i noticed something else. I have poor throttle response for the first 2\3s of the pedal. Can this have something to do with the max fuel screw? or where should i start looking?

it is like at 2\3's pedal i'm only getting 30% power and from there on is a sharp increase in power. (so full pedal is 100% power).
Sort of feels like its only running on 3 cylinders up to 2\3's pedal then on all 4 from there on.

Throttle linkage is working properly full pedal opens the pump all the way.

i am aware the pump hasn't been runned for at least a good 3 years. i do plan on running a good lubricating and cleaning additive as soon as i fill the tank.
maybe it just needs a good running in?...

thanks!

That is caused by the max fuel screw being out too far. I've noticed I have to move my foot more either way to get the same response if the screw is out too far. Try threading it in a half turn and then thread the full throttle limit screw in a little. The go pedal won't depress as far so you can adjust the stop under the pedal to save the cable.

I clearly understand Screw the Max Fuel screw in (more fuel) but when you say "full throttle limit screw in" do you mean Screw in towards the Throttle arm (less Max throttle) or Screw in away from the throttle arm (More Max throttle) ?
« Last Edit: January 31, 2020, 10:32:04 am by BajaVWCamper »