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bobbybrown
04-08-2014, 12:46 PM
Hi all,
this engine (1641 vw) is one headache after another. Had running problems for some time and as such fitted a fuel regulator to bring down the pressure from the electric fuel pump, after fitting this and adjusting it to 1.75psi (from memory) which my carbs run well on (according to google), I had to increase the pressure a little as it wouldn't run. I haven't refitted the pressure gauge to check what the pressure is now but, I put yet another set of plugs in and it ran absolutely perfectly for two days, covered probably 10-15 miles and now it's jumping and missing again.

I'm yet to take the plugs out again but when I do I would expect them to be black again.

Can anyone throw anymore ideas at me to get this sorted?

KEITHCANFIXIT
04-08-2014, 03:52 PM
Yep, they are an absolute pain, pressure should be in the region of 3psi I am told, carb balancing is critical and tappets and timing must be spot on.
The thing is you balance the carbs with linkage detached and then make sure that the linkage does not alter it when reattaching which is easier said than done, found trial and constant error is the only way.
Balance the carbs using a flow meter helps somewhat but in the end I completely stripped and rebuilt them checking float levels and all jets blown through with compressed air as the slightest bit of crude takes you back to square one.

bobbybrown
04-08-2014, 05:52 PM
Need to find some time to check it all out again. The carbs were stripped and cleaned with new float needle valves and diaphragms recently, need to invest in some more kit for balancing them I think!

Gmacz
04-08-2014, 07:05 PM
Try some hotter plugs.

MicksRedNova
04-08-2014, 07:22 PM
Dan
If your engine has been running fine and you've only done a few miles, not changed or adjusted anything, then it's unlikely to be anything significant. Assuming the dual carb linkages were all tight the balance wont have suddenly been lost.
It's more likely an ignition fault (ie duff ht lead, or dizzy cap tracking in damp) or dirt being sucked into the carbs blocking slow running jets. You may clear a blockage by whacking a a thick bunched up cloth over the carb inlet whilst blipping the throttle by hand. It sucks small blockages through due to the vacuum created.
But my money is on ignition. Are you running electronic ignition?

Mick

bobbybrown
04-08-2014, 07:46 PM
It's had new points, new dizzy, new plugs and new coil, it was running absolutely perfectly for two days then today it's juddering again, it's when trying to speed up you can feel it missing. Exactly what it was doing before and this set of plugs cleared it for two days.

The plugs that are in there now are the NGK BP5ES, I could always try the NGK BP6ES, I believe this is a hotter plug?

MicksRedNova
04-08-2014, 09:26 PM
With NGK plugs higher numbers are colder plugs. Cold plugs suffer from fouling as the carbon doesn't burn off if your burning some oil but a hotter plug can cause local overheating ie melted piston. If your plugs look black its probably running rich which can cause misfiring until hot.

See this link

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp?mode=nml

If you can get to a section of dual carriageway without too much stop start its probably worth giving it a good blast. It takes my 1600 about 5 miles at 70 mph to get up to temperature.

Mick

bobbybrown
04-08-2014, 09:48 PM
Thanks Mick, I'll give it a go down the local dual carriageway later in the week and see if it behaves any better, I've had two days of perfect engine running since I've had the car and I want them back. It was an absolute pleasure to drive the last two days and was gutting when it started again today.

Once I've checked the fuel pressure again is there much more that can make it run rich? Feels like I'm coming toward the end of the list of things to check off lately.

KEITHCANFIXIT
04-08-2014, 10:59 PM
What carbs are you running, at what revs does this occur, about 3000 I guess, and did you not change the petrol tank or just thought about it.
Sound like air correction jet size, have you always had this problem?

MicksRedNova
04-08-2014, 11:42 PM
If you know a friendly garage ( is there such a thing?) You could ask them to shove the O2 probe up your exhaust for an emissions check. This will show if its running rich.

If the car starts and idles OK but doesn't pick up well when you hit the throttle it could be an air leak (vacuum pipe off if you have them), valve clearance wrong, blocked jets, ignition fault (auto advance / retard jamming), fuel level low or high in float bowl or intermittent electrical connection to ignition or carb fuel cutoff.
Theres probably more too.

Mick

KEITHCANFIXIT
04-08-2014, 11:52 PM
Ok, forgive the rambling of an old man, here is a scientific theory that is so far out of the ball park you may have to get a bus to get your ball back.
You are running those carbs with your innovative scoops on top...correct.
Those scoops face backwards, now if those scoops do not have a hole in the rear of the scoop or do but only a small hole it could be that at certain revs or speed they are creating a vortex which instead of supplying the carbs with more air the faster you go you are actually starving them of air due to the action of the vortex therefore causing the engine to run rich and fouling the plugs up.
Clean the plugs , turn the scoops to face the front or if you cannot do that remove them and try it for a few days.
It may be you car ran ok for a few days only until the plugs got sufficiently sooted up.
One thing to be aware of, if you run the carbs without them you must cover the tops with plastic bag or sometime when at a standstill or overnight to stop them filling with rain ( don't ask me how I know , the drain pipes where missing ),but remember to remove bags before starting and driving off:thumbdown:.
Give it a try, you never know, it is amazing what I can think of while laying in the bath contemplating my naval.

bushboy
05-08-2014, 12:10 AM
When you say you changed the dizzy, was it a new, complete dizzy? Check the points gap & then chuck them in the bin & fit hall effect or similar electonic points replacement. I have seen the heel wear off the points cam follower & give erratic misfires & head aches. Same with worn dizzy shaft bearing/bushes. That is why i asked if the dizzy was brand new.

As for the carbs, strip them out of all floats, jets etc and throw them in the bin, & use the remaining parts as throttle bodies for EFI.

In fact you can then also throw away the dizzy & wonder why you persevered in the first place.

So endeth lesson 102.1

bushboy

Alzax3
05-08-2014, 07:38 AM
Give it a try, you never know, it is amazing what I can think of while laying in the bath contemplating my naval.

Heads-up alert: Keith keeps a Navy in his bathroom! :giveup:

Peter
05-08-2014, 09:02 AM
To me it sounds like float levels, valves need a thicker shim washer 2mm makes a big difference. too much fuel would make the engine run rich and soot up the plugs.
Run at 3 PSI.
Change to Pertronix ignition, no points, no condenser no black box and std coil, once fitted and timed against the static marks it is fit and forget.
What filters are you running inside those covers, you need at least 4", (100mm)?
Do you have velocity stacks fitted, (a must)?

KEITHCANFIXIT
05-08-2014, 05:11 PM
Ha Ha Ha Ok Alzax, Navel to you, my excuse is it was late and I could not find who sunk my Bismarck.

Very astute of you so early in the morning though,well done.

bobbybrown
05-08-2014, 08:55 PM
Ok guys a lot there to look at.

What bugs me is that it was fine for two days then back to square one. I like the scenario of the plugs sooting up which has caused the issue again, I will remove the plugs and clean them up and try moving the scoops to face the opposite way, worth a try.

After that will be electronic ignition, Peter has recommended this countless times over PM for it's range of benefits, I will try to dig out the messages with the links but with almost 3,000 PM's that could take some time.

I will also attach the pressure gauge again and get it pumping out at 3psi, hopefully with all of this done we should be somewhere towards finding the cause of this problem.

Just to be double sure, I will also use my rubber tape to seal around all vac hoses and the manifolds incase of any sort of air leak, if one should be found new gaskets will be installed.

Not sure if this could be related but the gubbins inside the fan shroud is noisy on this car when the engine is running, having never taken this apart I am unsure of exactly what is inside but it is noisy, will try to get a video as that will say a lot more than I can. A drive along video may also assist as it will capture the noise of the engine when accelerating.

MicksRedNova
05-08-2014, 10:21 PM
Not sure if this could be related but the gubbins inside the fan shroud is noisy on this car when the engine is running, having never taken this apart I am unsure of exactly what is inside but it is noisy, will try to get a video as that will say a lot more than I can. A drive along video may also assist as it will capture the noise of the engine when accelerating.

Mine was making a nasty scraping / rattling noise after I replaced the fuel pump with blanking plate. Turns out the inlet manifold was pushing the fan shroud against the fan because the support bracket needed a couple of washers under it because the blanking plate was a few mil thinner than the mechanical pump.
Mick

bobbybrown
05-08-2014, 10:27 PM
Sounds similar! Will look at that thanks Mick.

steve_d
05-08-2014, 10:41 PM
Couple of things to think about.
Air leaks would cause lean running not rich so air leaks are unlikely to be the issue.

If the fuel pressure is too high the carb will either deal with it or it will flood. You have not mentioned flooding so I doubt fuel pressure is the issue.

Far more likely is that the float levels are set too high.

Steve

bobbybrown
05-08-2014, 10:45 PM
So another washer under the float needle should resolve that?

steve_d
06-08-2014, 12:44 PM
I don't know the specifics of the engine/carb setup but others on here should be able to tell you a specific setting for the float level and how to adjust it.

Many folk don't know how critical the float level is. In most carbs the fuel level will be just below the top of the main jet aperture in the carb throat so that the air rushing past sucks the fuel out. If the level is too high the engine will run rich and the fuel can actually dribble out if even higher. If too low the engine will run lean.

Steve