MK1 Golf K-Jet Ramblings...

In the process of doing the modification to make the basic (not vacuum enhanced) control pressure regulator adjustable... waiting on different bits to appear in the post.

In the mean time opened up a spare and as you can see below the heating element is marked as 22 ohmns.

Noticed too that the rating is to +/- 3 percent and not as you sometimes read ohmns.

3% equates to 0.66 ohmns either side of 22 which is a much, much narrower band than the 19 to 25 ohmns you'd get if that measure is used instead.

Would be useful if anyone else has opened up a control pressure regulator, not just a VW one, and we could create a list of heating element ratings.

To kick things off -

Bosch 0 438 140 118
VW 026 133 403
22 Ohms (+/- 3%)

 

I did mine last month and on an 86 mk2 GTi WUR it has exactly the same markings

 

0 438 140 118's listed as suitable for certain B2 and B3 Audi 80/90's, the 1.8 GTI MK1 Golf / Jetta, a couple of MK1 Cabbies, 2 x MK2 Golf / Jetta GTi's, 2 x B2 Passats and a 53B Scirocco... Not that many really, but interesting that they're all 1.8's.

 

Harping back to that odd / modified control pressure regulator of a few posts earlier...

Now finding out there's quite a few different body casting types, depending on the functions being carried out and their different applications.

The one pictured below is for an early Porsche 911 SC 3.0 according to the seller, currently on ebay for around £450!

You can see that it's maybe what the modified one is trying to emmulate... done by adding the top mounted atmospheric vent and closing the original rear one that's solid in the Porsche version.

They both do the exact same thing, just positioned differently. I'm thinking on a 911 the regulator is perhaps fitted somewhere that the vent won't work if it's on the rear?

I've also no way of checking what the Porsche regulators bi-metal strip ohmns rating is, it may be that the MK1 1.6 GTI and 911 SC had by chance the same one and why they chose it to convert?

Even if not, Bosch doesn't appear to have used many different rated ceramic elements, maybe just 3 or 4 whose various ohmns overlapped to cover all the different regulator needs.

Alternately it wouldn't be a big job to someone who already appears to have known how to do the modification to also change out the incorrect element if they weren't the same rating.

The modification to the non-Porsche one may just be to allow easier adjustment or it may have been a solution to compensate for the wrong rated element?

If you're looking at big money for the genuine article it might explain why using / adapting a presumably much cheaper / easier got VW one was the motivation?

 

Saw this on ebay.de... the box lid shows the example of an early 1.6 MK1 GTI, even the kit for sale is to suit a BMW.

Bearing in mind K-jet was primarily designed to improve emissions / economy, seems odd it wasn't fitted as standard.

 

Picked up a mid '80s Volvo 240 set up to dissect / experiment with rather than risk expensive VW parts that are also going to be needed later on.

For no other reason than I'd recently opened another Control Pressure Regulator, started with the one here.

It's the bog standard type, without for example the enhanced vacuum feature, so should basically be the same fundamental unit as that on 8v MK1/2 Golfs in layout.

And so it was, save for the ceramic element being 18 Ohms and not the 22 Ohms of the VW's.

Not too bad inside, just some oxidation starting to seep in via the atmospheric port on the rear.

With the exception of breaking open the actual fuel cell, this is it down to all of its various parts.

At the moment there's nothing to suggest the cell isn't working fine, the ports / filter are spotless and cleaner passes through it freely,.

If however that turns out not to be the case it's easy enough to dismantle, but no point tempting fate needlessly.

As it stands, other than my time it can all be reassembled at no cost.

Going to look into setting up a way of bench testing the various K-jet components, so in this case being able to remove the fuel cell will help when setting up / adjusting it in a controlled way.

 

The Volvo Fuel Distributor's turned out to be a pretty good one...







Up to now I've been opening the casings, initially just out of curiosity, but more so now to check on condition.

(That's one of them in all the remaining images)

So far stuck plungers have been the main issue, with the rest of the inards quite often being in perfect condition.

Got me wondering if there was a way to free a stuck plunger (as with the Volvo's) without having to needlessly dismantle a distributor that's otherwise OK?

A common cause of the sticking seems to be due to fuel lacquering rather than say dirt ingress or physical damage.

Since the plunger is intentionally such an exact fit in it's barrel (to prevent fuel escaping), putting anything into the bottom of the casing, where the plunger exits, won't have any effect as it'll not be able to penetrate.

The plunger however has a lubrication system when in normal use.

Ironically it's possible this also contributes to the cause of it sticking when not in use for long periods as it lets fuel reside inside portions of the plunger barrel where it can later lacquer.

There's variations of the fuel distributor, I'm concentrating on the iron, 4-cylinder type here, so this may not be applicale to them all.

I'm also doing this with the distributor out of the vehicle and detached from the Air Flow Sensor as in the pics. below.

Take out the large banjo bolt for the fuel tank return line.

Remove the Primary Pressure Regulator.

The ports for these intersect.

If you shine a light into the now empty fuel tank return line port you'll see a large hole about half way in, then a smaller one an equal distance just beyond it.

That smaller hole takes a direct line to the center of the (lower part) of the casing, the bit the plunger and its barrel sit in.

There's a distinct groove that runs around the circumference of the barrel and it sits where the hole exits.

There's another single, small hole within the groove.

That hole in turn leads to the plunger.

If you look at a plunger it'll have thin channels cut into it, one on the lower part and three near the top.

The bottom one will pass back and forth over this exit during operation, pulling in fuel

Look too at the piston / tip of the Primary Pressure Regulator.

It has a similar single broad and single thin channel.

Not only does the petrol in the system act as a hydraulic it also acts as a lubricant.

When the engine is running / fuel distributor is flowing fuel the piston / tip of the Primary Pressure Regulator is forced back by system pressure.

The large groove will be centred with the return to tank line port on one side and the channel to the plunger / barrel on the other.

Fuel can go both ways simultaneously, that going to the plunger / barrel eventually gets smeared up and down the lower portion of the barrel by the single thin channel.

The top half similarly gets lubricating petrol from its 3 x thin channels but from a different source as it passes into and out of the fuel going to the injectors.

When the engine is off and the fuel pressure can no longer hold the Primary Pressure Regulators piston / tip open it'll move to the end of it's port and seat.

This in turn brings the thin channel to the same position that the larger channel occupied so fuel / pressure can be kept within the plunger barrel ready to lubricate immediately the engine starts up again.

This is why I'm guessing the same stored fuel that's captured around the plunger is what eventually lacqurers and sticks it.

If you insert an aerosol carb. cleaner pipe right up the channel to the plunger barrel it'll flood the plunger cavity and quite quickly disolve the lacquer... well it did in this case, I'd imagine there'll be different success rates depending on condition, but at least you've something to try now.

Likely haven't explained things all that well and missed high lighting important points that you'd probably need to know in order for the rest to make sense...

 

Up to now I've been gathering up Fuel Distributors / Air Flow Sensors suitable for 1983 and earlier MK1 GTI's.

This particular Volvo 240's is date marked late 1988, so a bit out of character.

Looks like there might be potential for an 'upgrade' of sorts to those earlier VW ones if you swap over the arm / adjustment screw pictured below from this apparently later version.

Not sure if it's exclusive to Volvo's, but I'm going to speculate not and likely found in other later Sensors too, be interesting to know.

From the first Fuel Distributor available for the MK1, there have been a succession of replacements / part numbers.

These seem to tally with improvements Bosch made to the basic set up, sometimes quite minor things and sometimes more fundamental, so it shouldn't be a surprise the Air Flow Sensor was similarly improved over time.

The arm itself is the same casting on both the old and the new so interchangable, however the threaded collars / screws are not.

The later ones are to a much finer thread, presumably allowing for far more precise / accurate adjustment.

Just a rough calculation, but the later one will turn 36 times to cover the same travel that takes the earlier one 24 turns, so an approx. 1/3 improvement.

It's probably also worth bearing this in mind if your screw has rounded out and you've got a replacement from a different sensor in case they're not compatable... you'll need the associated arm along with it to make the substitution.

 

Here's a link to a 2010 thread that I keep going back to... lots and lots of interesting comments.

https://www.clubgti.com/forums/inde...ng-metering-heads-air-weighing-valves.220566/

Dave's shown a scan in the very first post, and it's copied below...




I've found that there's distinct castings of the alloy air flow sensor... on the whole if it's for a 4 cylinder fuel distributor to be attached to it differs from those that are for 6 cylnder distributors and above.

Principle difference is the pattern / placement of the 3 x attachment holes, means a 4 cyl. distributor cannot physically be attached to a 6 cyl. air flow sensor and vice versa.

However there seems to be a few exceptions and I think it's those that are high lighted in the document. The references to cylinder number is I think is a nod to the hole pattern and not the cylinder count itself.

It mentions 'Handel' and 'Fabrik', the literal translation seems to be 'Trade' and 'Factory', but I'm thinking it's more nuanced than that and maybe along the lines of 'standard' and 'special'

If correct, it'd mean there's some 6 cyl. air flow sensors that have the hole pattern for 4 cyl. distributors, that'd allow sneaky old VW to fiddle / mix and match many more air volume profiles and fuel rates than if they were limited to the off the shelf components.

'6 Zyl. LMM mit bahrbild fur 4 Zyl. mengentelier' - roughly means '6 cylinder airflow sensor for 4 cylinder fuel distributor'

LMM is short for 'Luftmassenmesser', or air flow sensor and 'mengentelier' is fuel distributor.

In relation to the pair of Motorsport distributors - the 066 and 067 denote the year and month of manufacture.

066 is June 1990 and 067 is July 1990.

 

Volvo Air Flow sensor came up well also... something that they all seem to have in common is the steel tube for the 3mm adjustment screw corrodes badly.

Cleans up easily enough, but'll probably do it all over again.

Time'll tell if it works... shrink wrap.

 

Said this elsewhere, but repeating it again here... Tim Stiles, in his 'Haynes Golf GTI Performance Manual', makes a brief reference to the benefits of putting early MK1 'Metering Heads' on later cars, if done in conjunction with other modifications.

In his words ' ...they flow more fuel because the fuel pin is different'.

All very vague and because he uses his own terminology elsewhere and not that of Bosch to describe Kjet components, it leaves things slightly open to interpretaion.

Anyhow, got me looking into it a bit more and not surprisingly there's a few other references supporting this, though some simply repeat / trace back to what he states rather than add anything of their own.

Got to restress what I said at the start of this thread, this is just me mulling over things, so nothing is confirmed and could very well even be completely changed as more is discovered.

So far then this is what I believe to be the chronology of MK1 GTI Hard Top 1.6 110hp / 1.8 112hp fuel distributors (the component I suspect he is referring to as a 'metering head'), please note there are other distributors listed for MK1 Golfs that aren't shown here, for example found on Cabrios or 1.5 / 1.7's from other markets -

All are the Bosch numbers -

0 438 100 005 - 1.6 from 06/1976 to 07/1977

0 438 100 023 - 1.6 from 08/1977 to 10/1978

0 438 100 059 - 1.6 from 11/1978 to 07/1980

0 438 100 079 - 1.6 from 08/1980 to 07/1981

0 438 100 100 - 1.6 from 08/1981 to 07/1982 and 1.8 from 08/1982 to 07/1983


There are also Bosch factory refurbished numbers, for example F 026 TX2 021 is substituted by them when a 0 438 100 005 has gone back out, but rather than complicate things at this stage, I'll try and list those later.

From what I've seen so far the progressive change over the years of the distributor number seem to tally with material changes to the distributor itself, Bosch improving on the design.

Some of those changes appear to be quite minor and some others are quite fundamental, again I'll try and go through them one by one and list what I think those are.

So back to why I looked into this... the supposed increased fuel flow on older distributors.

Again all unconfirmed, but I was sent a list of figures by someone with a Bosch Microfiche.

It shows all of the above listed distributors have matching flow rates for idle and part load while 005 / 059 and 079, (doesn't mention 023 unfortunately, but going to assume at this point it's included falling as it does within that range) are 160.0 ml at full load against the later 100 that is 110.0 ml.

So seems to bear out what Mr. Stiles was hinting at, not that I'd doubt him!

 

Carry on from an earlier post, updating the list -

"Would be useful if anyone else has opened up a control pressure regulator, not just a VW one, and we could create a list of heating element ratings."


Bosch 0 438 140 118
VW - 026 133 403
22 Ohms (+/- 3%)

Bosch 0 438 140 004
Volvo - U/K
18 Ohms (+/- 3%)

 

Far too much for one post, so in no particular order will start /add further differences over time rather than swamp you with them in one go.

Going to commence at the beginning with 0 438 100 005, the initial fuel distributor VW used when MK1 GTI's (1.6) were introduced in 1976.

Kjet was already being marketed by Bosch from 1973, Porsche were early adopters I believe?

Have used a 0 438 100 100 for comparison in some of the images, it being the last distributor variant fitted to the 1.8 GTI's (and 1.6's in 1982) at the end of MK1 production in 1983... Gives the starkest view of the changes / improvements made over the years.

Have kept the orientation the same when both types are shown together, hopefully helps highlight the positional differences of the various ports on each.







This last image is of the Primary Pressure Regulator on each, it's one of the components that appears to have received the biggest improvement quite early on.

You can see it's become vastly more complex, the original was more of an on / off valve to allow excess fuel to return to the tank.

Pressure control was also very basic, that little disc pictured between the spring and washer is a shim. Increasing or decreasing its depth adjusted spring tension. If you reached the point that you needed to do away with it altogether and still required more adjustment that was done by adding to the copper washer instead.

You'll notice 005 only has the two lower ports, one is for fuel supply and the other is fuel return to tank, no dedicated port for a 5th injector or the return line from the control pressure regulator seen on 100.

The top portion has the port that goes to the control pressure regulator, just as you see on later versions.

Return from the control pressure regulator simply tapped into the tank return line further along, using a non return valve.

My understanding is this set up was prone to leeching pressure and causing problems, particularly on hot starts.

I can't confirm this on the Golf, but other marques using these early distributors seem to supply the 5th injector via a double banjo fitting, in effect simply tapping into the fuel supply line.

Those additional components you see on the later primary pressure regulator of 100, the pin / second, smaller spring etc. combine to make a push valve.

It allows for the addition of a dedicated return port into the fuel distributor, for the return line from the control pressure regulator.

It'll open / close along with the main piston when the system's operating / shuts back down, idea is that it'll allow excess fuel from the control pressure regulator to flow back to the tank when open but seal that return when closed, maintaining pressure in the contol system at the same time and fixing the earlier weakness.

 

Getting back to Mr. Stiles and his different 'pins' (plungers).

There's two obvious areas of difference, the first (and I'm going to speculate the less important), is the machined shape of the tops, that's the end that's hidden out of sight inside the distributor when it's re-assembled.

On 005 it's a squared profile (from side on) whereas on 100 it tapers conically.

I believe that's solely to do with the later addition of a spring in this area to 100 that 005 doesn't have, which was intended to counter momentary drops in system pressure that would potentially allow the plunger to be raised too far / cause overfuelling.

The spring acted as a buffer and ordinarily doesn't come into play, the conical plunger top merely acted as a secure seat for it and wouldn't I think have played any part in flow rates.

I think the plunger differences that are probably most relevant are those found to the narrower, machined mid-section.

(Excluding these two areas, the top spring seat and profile of the mid-section, the plungers on either distributor are otherwise identical.)

Easiest way of explaining is to look at the image with the dimensions marked on it, you'll see the earlier plunger is actually stepped at it's bottom plus narrower for the rest of its length than the later one.

Because the early / late distributors flow rates are supposedly only different at full load, it may be that the 1.5mm 'step' which is the main influencing factor?

If the plunger is moved up to the highest point that would be possible if it were the air flow sensor acting on it, that step coincides with the fuel channels in the lower chamber, which coincides with max. slit opening / full load

So far (but bearing in mind it's a small sample) the barrels of all 0 438 100 100's have been etched 087 with the ones previous to it that are found in all the earlier distributors being 74.

My old, cheapie vernier gauge never gives the same two measurements twice in a row, the ones shown are a rough average and not to be taken as exactly right, just close!

 

Made a reference in a previous post about the lack of a dedicated 5th injector port and (apparently problematic) return set up from the control pressure regulator on the early distributors.

Good old 7Zap has helped confirm some of what we were speculating at... flow to the 5th injector piggy backs straight into the fuel supply from the filter using a double banjo arrangement while the return line from the control pressure regulator does something similar but instead using a T piece and non-return valve into the return to tank line.

 

Been looking a bit more at Thermo-Time Switches.

Wanted primarily to know if mine is working as it should be, but not having a running engine means I'm relying on bench tests instead.

I've got car electrics blindness, I just can't get my head around the schematics / terminology etc., you could explain something to me a hundred times over and it'd still make no sense.

So for anybody that's similarly afflicted the below are hopefully two simple tests which when combined will show your switch is both not only working but also within spec.



Initially you don't use the connection at 'A' (between terminal 'G' of the switch and the postive of the battery) but instead with everything else connected as shown that in-line bulb should stay on indefinitely. This indicates the switch is earthing correctly.

You can then further test by including the connection at 'A' (you are now supplying power to the bi-metal strip inside the switch allowing it to heat up), doing this will cause the earth path to be broken after a short period of time and the bulb will extinguish.

If you want to repeat this part of the test you'll have to let the switch cool down for around a minute or so before retrying... lets the strip close once again, thereby completing the earth path.

The above test will only let you know the switch has a proper earth and that the bi-metal strip is capable of turning it off /on.

With all the switches I tested, the bulb turned off on each after exactly 3 seconds, no variation between them

If you've a multimeter you can then check the approximate points at which the bi-metal strip activates and that the ranges it does so are within spec.

Problem is I can't find anything definitive stating what those specs. are for a MK1 GTI, just those for several other marques that use the same switch.

Having said that the figures I've been getting, taken across a sample of four separate switches (all the correct to my car Bosch 028130214 / VW 043906163A) not only come in at virtually the same readings (maybe 0.2 ohms variation at most, which in itself suggests they are working correctly) let alone also tallying with the readings for those other marques I've found on line... if you've a switch of your own and can check, it'd be very useful for building up a bigger sample base, the more we can find with similar readings, the better it'll bolster the case that those we already have are accurate.

So... it's as simple as taking the ohms at cold, all 4 of mine were 35.8, then getting a cup of boiling water and immersing the thinner part of the switch entirely into it.

It'll take a minute or two, but you'll see the ohms suddenly jump from 35'ish to the high 60's / low 70's. All mine had higher readings that ranged from 68.9 to 70.03ohms... again very little variation between them.

If you then let the switch cool (or run it under the cold tap) it'll do the reverse and react by suddenly dropping back down to whatever point it started at.

All mine were 100% consistent throughout these tests in both bulb on / off time and their cold / hot ohms over repeated tests.

 

A strange one on my early mk2 kjet is that it doesnt have this. There is a black wire with spade connection hiding behind the inlet manifold, but no bracket that anything would fit to. Unsure if someone has previously removed it or it never had it.