Hello people! I am a proud owner of a scirocco mk2 '83 model, 75 hp with a pierburg 2E fitted... I recently completed a restoration and I have one more stubborn problem to fix... The problem is that, when I'm in low revs, below 2000, if I push hard the accelerator pedal, in the initial stage of acceleration I feel a hesitation... I was thinking that the problem is the carburetor, but after thorough investigation and complete rebuild, even testing another carb, I'm sure is not this to blame. What I also have observed is that, when I push the acceleration pedal, the 3/4 point unit does not retract - it remains in the idle position. Should n't it retract completely in the idle cut off position? Is that relative to the problem? Any ideas? Thanks in advance!
Hello there! First off, have you been thru this thread: https://clubgti.com/forums/index.php?threads/1-6-1-8-pierburg-2e2-carb-faq.124945/ from memory the 3/4 should only retract during over-run, i.e. when you lift off the throttle. even if it should retract during acceleration and yours does not, I cant see it causing this particular issue as the throttle lever will be nowhere near it... there is a relay to control the operation of the 3/4 unit so thats worth a look, its clipped on top of the fusebox. could try unplugging it in case its somehow causing an issue. first thing that pops into my head is the accelerator pump, plus maybe check the 2nd butterfly vacuum valve is working properly. then obvious checks like ignition timing, full ignition system check over, look at the fuel pump and reservoir too. quick thing you can check there is remove the reservoir and block the return, see if this helps. there should be a fuel restrictor in the return port but it often goes missing, a welding tip pushed into the return line does the trick if this is the case.
Good morning and thanks for the quick answer. The accelerator pump was the first thing I suspected but it operates normally, as the second butterfly vac valve does also. The ignition timing is in the correct setting. I suspect that the distributor is to blame but it seems to operate normally. Is there any way to check it? Does anyone know how exactly the “hal” is working? What’s its function? Also, is there any available electrical diagram about ignition connection and carburetor electrical connections?
the hall sensor is probably fine if the car runs, will either be ok or it wont usually. any part numbers on the distributor? just to double check, timing for the carbs is set to 18 degrees BTDC with vacuum line on dizzy connected. you can use the big diamond mark on the flywheel with a basic timing light no need for an advance version. usually you can dial a bit more advance though just use the diamond for base reference. wirign wise you should have ignition live to the carb heater, the autochoke and inlet heaters should get voltage when engine is cold then cut out as the thermoswitches in the front flange turn them off. make sure the earth strap from the top of the carb to the rocker cover is there else the carb and choke heaters wont work very well.
The advanced is set aligning the two marks in the flywheel, it seems like that: I think this is the original setting...
yep thats all good, see if you can spot any VW part numbers on the dizzy then I can check if its right
Is the engine advancing when you bring the revs up ? if you suspect the distributor disconnect the vacuum advance line and suck on it to see if the advance plate moves, very common issue for this plate to stick up over time in Bosch units,good luck.
On the cap of the distributor there is the number "1235 522 056" Watercooled your idea is very interesting... I suppose that to check this I have to disconnect the vacuum line from the distributor and tap it, then connect a hose to the distributor and suck in while the engine runs on idle? Then I should see the "diamond" mark on the flywheel going to the right - "advancing"?
Need to check part numbers on the dizzy itself, if its plain then its not a genuine bosch/duciellier unit and could be the cause of the issue
You can do it without the engine running first,you are testing the movement of the advance plate and the vacuum units ability to hold vacuum,or with the engine running pull the hose off and plug the vacuum point with your finger ,the idle will change if everthing is right. I used to repair VW/Bosch dizzys as a sideline job,80% of the advance plates I found were seized or sticking up and some had advance weight issues,things get rather dirty inside there. Good luck.
- Watercooled I tried what you describe and the vacuum unit seems to hold the vacuum perfectly. Also, when at idle, I pulled off the hose as you describe, the idle revs got lowered and then as I sucked the pipe they went up again. If I suck the pipe to the dizzy, shall I see the arm of the dizzy moving? -Rubjonny the dizzy is the genuine OEM BOSCH, never replaced. It has the number "1230 500 147" typed on it. -Anyway, I suspect the dizzy, but the problem may be somewhere else... If someone encountered the same problem on a carburated mk2, he could help us. Also, I didn't mention that, its difficult to start when the engine is warm and turned off for about 10-15 minutes. Actually, It takes 5-7 seconds to start and once it does, it has low idle revs (300-400) until I push hard the accelerator pedal. I don't know if this is related to the problem I've described...The strange fact on that is, if I take the air filter box off then it starts as it should... the air filter is new, the carburetor doesn't seem to overflow and, by the way, I've tried three different carburetors...Fuel evaporation?
Ok think the dizzy is ok,whats your fuel pump like ? you do have a good rubber mount under the carb ? sure you have checked that right? . Removing the air cleaner makes it start better that's odd,trying to get my head around that ??? strange. You did time the motor with vacuum line off @ correct idle speed? sorry to ask all these questions but I'am half way around the world and don't really know all you have done,what I do know is the Pierburg is a troublesome bugger when they get old,worked on one years ago and got mixed results on a Jap import Jetta. FI generally with an air leak will cause a high idle,carbs tend to idle low due to poor vacuum signal with air leaks,check that and see how you go,cheers
Yeap, it’s really strange! Fuel pump replaced with a new pierburg one. The carburetor rubber mount is also replaced. The advance set at correct idle speed but with vac line on, I think that this is the correct manner... as far as the airleaks are concerned, I’ve thoroughly checked all the system... By the way, is any special way to connect the vac lines (on the carburetor and generally) for this specific car (scirocco mk2 ‘83 1,6)? Any guide for this?
how about with airbox fitted but breather pipe disconnected and hole on airbox blocked, does that make any difference? also when airbox is removed, are you blockign the vacuum lines to it or leaving them open, as that would give a small air leak if left open
No, I tried all these, no difference. If I leave the vac line to air box removed and unblocked then it is better, but then I have air leak... The vac line from the distributor where exactly shall be connected? Mine is connected with a “y” connector to the brake servo line and to the fuel consumption gauge ( a line comes from the brake servo hose, then with the y connector it splits, one line goes to the distributor and one to the fuel consumption gauge). Is that right?
that will be fine yep. if its better with a small air leak, then maybe you just need to adjust the mixture a touch?
I’ve tried a lot of mixture settings! Leaner, reacher... what happens with the air leak is the same when I remove the air box. That’s why I suspect fuel evaporation, because when I have the airbox open , vapors find an exit...
have you checked to see if the autochoke and inlet heaters are correctly switching off when engine is warm?
the inlet heater is only thing I can think of which could cause fuel to evaporate as you suspect, worth a look anyway. Years back on my old 1.6 driver one of the thermoswitches went bad and I bridged it, the car certainly ran worse when I did that anyway
