Power loss Woes!!!

[klittle]

OK, I've reached the end of my teather, I've tried everything I can think of so hopefully someone can help.

Basically the car in general runs great (now), but the symptoms are this, when putting the engine under load, ie, going up a steep hill and putting the power on it will pull fine for a few hundred yards then it will start to cough & splutter, if I lift off it will settle down and go back to normal. It's almost like fuel starvation, but I can't find anything wrong with that side & now I'm wondering if it's actually ignition related. But in the mean time, this is what I've done so far.

Weber carb fully cleaned & rebuilt with a genuine Weber carb overhaul kit (not much in the way of dirt in it when stripped)
Dizzy cap, rotor arm & spark plugs replaced
Fuel pump was also replaced & found that the old one had a smaller pickup port which I thought may have been the cause of the problem, the new one has improved things, but not cured it.
The rubber carb mount is new & double checked it when I removed the carb for overhaul & I made sure that all the bolts were secure.
I also pulled the sender/pickup unit from the tank and inspected all that side of things & it all looks nice & clean, no rust or anything that I could see. The inline fuel filter under the bonnet was changed recently too & it's nice & full when the engine is running & stays that way if I rev the engine when parked.

That's basically all I can tell you, I was convinced that it was fuel starvation as before I changed the pump the car would sit & idle all day just fine, but as soon as it was under load it would get about 100 yards & die and the carb would be dry of fuel. The new pump seems to have cured that, but like I said above, under heavy load it is still threatening to do the same which is why I'm wondering, could it also be ignition related. The only thing I haven't tried is changing the swirl/regulator pot, do these ever cause any problems? I was considering putting in a bypass 'Y' connector to see what would happen just to see if there was a restriction going on at this point. Oh & all the hoses & pipes are in good order & seem to be clamped nice & tight at all connections.

If anybody has any ideas I'll be most happy to try them all as this is starting it bug me big time.

[Mr Funk]

Have you physically checked the Fuel Neck? If that's gone it'll cause no end of trouble.

[MacColl]

Sorry I'm on my phone and can't link you but there is a thread if you search weber and my name you'll find the thread where I had unknown issues when I converted to the weber, constantly cutting out but sorted in the end.

Any contamination in the float bowls all the way back through to the filler neck can cause these problems plus blocked gauze in inlet tube. Keep checking your jets where a particle can intermittently block.

I'll give you the link later this eve.

[klittle]

Thank so far, yes I have checked the dreaded filler neck & it's all in good order, I pulled the lifter out the top of the tank yesterday & actually replaced the flexible lifter pipe on the end & put a new gauze on it although there didn't seem to be anything wrong with the old one. I also checked the state of the inside of the tank & saw nothing in the bottom that would cause any flow issues.

I have disconnected the pipe that goes into the regulator pot from the pump & turned over the engine to check the pump flow & it pump nicely, although before I changed the pump when I disconnected the pipe from the carb & turned it over nothing came out. Now that I have changed the pump it has been ok so far turning it over in the drive, this is why I'm suspecting a partial/intermittent block in the regulator pot, it's ok at idle & low flow, but when the power is increased there is a restriction on the fuel flow. Or could it be something as simple as load on the coil? grr I hate these intermittent problems when everything looks ok when it's idling!!

[the edmundator]

It is easy to swap in a new ignition amplifier to see if this is the cause, as these can cause this kind of problem when they're on their way out.

[klittle]

Addition

Ok, done some more reading & it makes sense (should be working but Scirocco more important LOL) have read on a few web pages that when a Weber is fitted that there was an additional restrictor put on the return from the fuel seperator regulator thingy. I must admit that when it's running there seems to be a constant flow (expected) through this line (as it's clear) but if the return flow is too much this could cause my starvation problem? It ran ok on the Pieburg, well it didn't have fuel starvation anyway. I have read that some people have removed the separator unit completely, but I'm loathed to do this as where does the excess fuel go? I can quite easily put in an additional restrictor I just wanted to run this thought past you folks. One more thing, I put the Weber on as a second hand unit (it is a good one) & it came off a 1.8 so jets are ok, but if it had a restrictor on the line & I didn't then this might account for it.

[klittle]

I had considered the Ignition Amplifier as the next route to take, but at the moment I'm convinced it's still fuel starvation as I've seen nothing obvious to confirm that I'm not getting a constant spark, even when it died the other day I was still getting a spark (and timing is pretty bang on), I can confirm it purred 25 miles to work this morning without a hitch since the new pump was fitted, it's only under heavy load that I get the problem, ie overtaking and going up steep hills, I live in Scotland & they are pretty common unfortunatley
I'm going to put a bulldog clip on the fuel retrun line before I leave work just to restrict it a bit (not block it) & see what happens on the way home, I'll deliberately put the foot down a bit & see if it threatens to die on me. Will let you all know, fingers crossed & thanks so far for the replys so far, much appreciated.

[ianaudia4]

The fuel return line should be fitted to the smaller pipe from the Y or T piece, has yours been changed for a non standard one?

[klittle]

That's what got me thinking about the restrictor as the regulator/swirl pot thing looked original & I wondered if it had grud in it from years of use. I noticed that basically the return connection & supply to the carb were pretty much the same size (externally at least). I was under the impression that the return had the restriction on the inside, but as it's a sealed unit I can't tell. So as I said in my earlier post I found that the original Weber kits come with a restrictor piece to connect. So tonight with tools in hand I went out & disconnected the return line from the pot & I fabricated a restrictor to push into the hose connector, Obviously I'm guessing at the size it should be, but I have reduced it to approx 2.5-3mm & reconnected the hose. Car started no problem & ran fine, no petrol being forced out where it shouldn't be, now before the return had a constant high flow through it, now it has reduced to a trickle. The test will be tomorrow going to work on the hill outside my house, it's going to get gunned up there & see what happens when the second choke kicks in, cause that's when the trouble started before. I'll post in the morning to update everyone, but thanks so far for the input from you all.

[MacColl]

Some pictures would be good of your carb and fuel lines etc without the air filter.

Here is that thread where I had issues..
http://sciroccoregisterforum.co.uk/carf ... er+maccoll

It seems there are a number of people on here with what I think are very similar problems from the outer reaches of the fuel system to the carb. The Weber simplifies things a lot but there can still be inner rust that you can't see. Obviously with the inner fuel filler neck, tank, fuel lines supply and return which can be old and rusted. Then the swirl pot can be rusty internally. Other issues can be tired old rubber fuel lines that can collapse under revs even vent air/fuel. Look at replacements.

Other important things are vac hoses, have you got correctly blanked and routed? nice and new ones?

I'm considering binning the Pierburg I have because I am having rough starts, bogging down/flat spots especially when cold and intermittent idling

There could be other electrical issues but this is where I'm out of my depth.

Here are other helpful links..
http://www.clubgti.com/showthread.php?1 ... TML-refurb
http://www.clubgti.com/showthread.php?1 ... d-air-flap
http://www.clubgti.com/showthread.php?1 ... t-location

[whiteshark]

Other issues can be tired old rubber fuel lines that can collapse under revs even vent air/fuel. Look at replacements.

This problem nearly caused me to take a sledgehammer to the car. After tinkering around with the car for weeks, the problem was the fuel line from the filter to the carb collapsing under pressure / heavy load. Yes my car would idle fine all day. Up a hill it would struggle. Hard to detect. If you have old fuel line rubbers that are cracking on the outside or look slightlyn perished the chances are on the inside they are not much better, replace them to rule it out if this is the case.

[go-for-it1]

Hi mate,
See my previous post about the swirl pot and the return restrictor size (1.2mm)
http://sciroccoregisterforum.co.uk/carf ... pot#p42501

My experiences after car didn't just stutter but completely shut down on acceleration are:
1. Old rubber fuel lines in engine bay collapsed internally even though they looked ok on the outside, (cheap to replace),
2. Ignition amplifier breaking down under load
3. Coil breaking down under load

I replaced both coil and Ign Amp at the same time so don't know which one was duff!
I have also put an inline fuel filter between the fuel swirl pot and the carb because as you can see from the photos the inside of the swirl pot corrodes badly and the small flakes of rust are not prevented from getting into the carb except by the internal nylon mesh filter.

One other thing to check is the vacuum advance is working. Take the dizzy cap off and also disconnect the vacuum pipe from the tee piece in front of the carb. Suck on the pipe whilst watching the inside of the dizzy and you should see the rotor arm rotate. If it doesn't then the vacuum advance is not working which it needs to do when under load.
Hope this helps?
Rob

[klittle]

Thanks for the additional info folks, it's all good stuff, but I think it's cured!! I had the Pieburg sitting so I pulled one of the brass vacuum plug out & it pushed perfectly into the end of the return port on the pot thereby restricting the flow. The existing hose pushed back on & clamped nicely, I didn't manage to take it for a test drive last night, so this morning on the way to work was it's test & it ran perfectly, I even managed to overtake a car & hit second choke to about 4500rpm & it didn't even hesitate. I'll keep an eye on things over the next few days, but it's looking good.

On the subject of the dreaded rust in the lines, I'm lucky in that every pipe was replaced for the last MOT, from front to back & everything under the bonnet & the tank was cleaned out at the same time. The filler neck I suspect was replaced about then or shortly before as it looks in excellent condition, so I was pretty confident that dirt wasn't the cause which was confirmed when I stripped the carb & found nothing that would cause a blockage in there either, although it got a major clean just to be sure (which didn't cure it).

So there we have it for now, looks like the jobs a good one, anybody else converting to a weber I recommend the restrictor in the return line. Oh and if your petrol pump is a good few years old I would recommend changing that at the same time for all the cost, mine was £30 & it's a genuine VW bit, certainly looks better quality than what was on before. If there are any more developments I'll post em, but for now I'm away to

[ianaudia4]

Glad it's sorted and was a simple fix.

[klittle]

Just thought I would post & say that it's now been 24hrs & no sign of any problems, pulling like a train through the whole rev range & not missed a beat. Hope anybody else with similar problems get's some help from this thread.

One thing I would like to ask, would it be worth while binning the swirl/regulator pot & putting in an adjustable after market one? some pretty good one's out there, it would be a bit better than my narrow sleeve shoved in a hole situation at the moment even if it is working. With this mod in mind can anyone confirm what the pressure should be? I have read somewhere that somewhere between 3-3.5psi, but just wanted to confirm. I want a regulator with a gauge if it's going to work, piece of mind more than anything.