740 - B230k idle woes

[Prufrock]

Originally Posted by aardvarkash10

The carb itself is a nest of vipers. It was a horrid piece of kit when new regardless of what it was fitted to, and age hasn't improved it. Parts are almost unobtainium as I understand it, so regardless of the cause, its well worth considering a swap to something more common, simpler, easier to get bits for and reliable. Like a Weber ( the carburettor, not the barbeque).

Comments like the above both amuse and irritate me. I have two 1986 700s, one still has it's original carb and the car runs fine, starts and idles well, the carb may well be 31+ yrs old but I have no concerns.

My other car (again a 1986 700, 31+ years old and been in the family from 1986) has a Weber conversion (in 1993) this was mainly because the original owner (Wife's Dad) couldn't find someone to get in running correctly.

I am also fortunate in having a near new Weber in my cache as well as a low mileage Pierburg - I'll wager most 700s with the B230k will die simply because owners will not have funds to replace the carb.

Apologies for being a little off topic.

Jon

N.B perhaps I ought to add that all hoses etc, are no longer 1986 vintage, all OE Volvo with OE clips !

[Laird Scooby]

Still useful input Jon - reminded me of the GM Varajet and Ford VV (Sonic Idle) carbs that were born from the same idea, essentially reducing emissions while still delivering good power and economy.

When they were working they were good bits of kit but it didn't take much to get them working incorrectly. If that happened, any fiddling would generally make them worse as certain adjustments were factory set, the throttle butterfly idle position on the Varajet for example was set to a specific vacuum setting from a small port just above the butterfly, 8-10" of water if i remember correctly.
I believe the Ford VV was similar and fairly sure the Pierburg is the same as well in as much as there are certain things that shouldn't be touched.

[Prufrock]

Thanks, Dave.

We had a Passat B2 wagon years ago, that was an '86 on a C plate, bought around 1993 with 80k on - that had a Pierburg and again never an issue. Sold with nearly 200k on it...France, Scotland, Spain...

One of the most reliable cars we ever had, a very well made, simple car.

Jon.

[Laird Scooby]

Originally Posted by Prufrock

We had a Passat B2 wagon years ago, that was an '86 on a C plate,

from a time when VW made proper cars and didn't have their fingers in too many other pies.

I'd make a guess your Passat had been dealer serviced and MoT'd as well. The troubles seemed to come when they went to independent garages that weren't aware of the idle bypass screw to alter the idle speed and a car would fail the MoT on emissions. The tester would alter the mixture screw to get it to pass then the idle speed would be wrong so they'd adjust the throttle butterfly position instead of using the idle bypass screw.

This would be the first kiss of death for the carb - it would perform for the idle test but then become unreliable in terms of mixture and generally throw more fuel in than was needed. Subsequent MoTs would exacerbate the problem and certainly with both the GM Varajet and the Ford VV, both were made of "dubious" materials and would often wear quickly after the uneducated fiddling of the various MoT testers.
It's not all the MoT testers fault of course, much of the blame has to lie with the owners who probably only thought of maintenance and servicing when the MoT was looming.

The inevitable happened and it failed the MoT so a replacement carb was fitted or the car was scrapped.

[Prufrock]

Right there, I've had a few 80s VWs, the Passat had the classic two previous owners (both vicars - true).

And I forgot to mention I also have a BMW that was 40 last month, and still running well on it's original four-barrel Solex - that's been in the family most of that time too...don't get the impression I'm a car hoarder...oh dear four Volvo's as well !!!

Jon.

[Laird Scooby]

In the mid 80s i very nearly bought an 83/Y reg VW Santana GX5, the "flagship" Santana that later became the Passat, not sure if the 5-pot engine was used in the Passat or not though.

Had a couple of BMW 728s many moons ago, both had the Solex DVG4A1 4-barrel carb. If i didn't know better i'd say the GM Varajet was one of those cut in half!

[Prufrock]

Passat B2s with the 5 were badged GL5 - also had what is now super rare: a Passat B3 GTI 16V.

Never had a big six with a carb'.

Jon.

[islipaway]

So! Today, I did a few things. Cleaned the jets/carb a bit better, checked for vacuum leaks again, renewed the paste on the ignition amp and replaced the inline filter before the carb as it was pretty gross looking.

After just cleaning the jets again I was able to get the car to drive around without constantly stalling, though the rpm would still keep dropping to the bottom line then picking back up. All other jobs didn't improve the running.

I cant find any vac leaks but I guess without a smoke machine or something I can't be 100% sure. I did see the hose from the brake booster seems to have kinda crumpled/caved in on it's self at the non brake booster end, so I'll replace that. It didn't seem to have any effect on the idle when I manipulated the hose. Checked the vac check valve, and all the elbows I could find, all seems fine.

One thing I have noticed is the choke seems to be stuck fully open (see attached picture) when should this flap move? I have cleaned the carb since this picture.

Also seems to idle better facing up hill but it might be my imagination.


How difficult to fit/set up is the weber carb? I dont really want to put a lot more money on it as this car has a huge list of things that need doing and probably isn't worth it overall as it's had a lot of welding and is fairly rotten in parts. I picked it up as the idea of an LPG 740 for doing road trips in the summer was very appealing, but I didn't inspect it properly and got stung on the price, needs new calipers all round, front strut legs, all bushing look bad, clutch need replacing, slave is welded to bellhousing, rear shocks are super soggy heater core is leaking (now bypassed)... Don't know how it ever got through mot.

[cpjitservices]

Jay is that you? Following this mate, mine idles rough.

[cpjitservices]

Actually, if I start mine without putting foot on the accelerator pedal, my battery light stays on as the revs are that low - then put some revs on it ticks over fine albeit roughly. Better when warmed up but not perfect.