740 - B230k idle woes

[islipaway]

It is, haha. Maybe the amp thing will help you if not me

[islipaway]

[Bumping this comment as it got knock back a page, don't want it missed]

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.

[Prufrock]

[QUOTE=islipaway;2336148)How difficult to fit/set up is the weber carb?[/QUOTE]

Not difficult at all, It is a replacement - usually - with a manual choke and the cost is £299 hence my previous comment, I am fortunate in that I have nearly new spare carbs - 1 x Weber, 1 x Pierburg.

Some might suggest you source a carb from another make/model, but given carbs all but disappeared 30 years ago it isn't really an option.

Jon


N.B choke flap should move of course, when starting a slight dab on the throttle will get the car started.

[islipaway]

Originally Posted by Prufrock

N.B choke flap should move of course, when starting a slight dab on the throttle will get the car started.

What I am trying to get some clarity on is should the choke flap move along with the throttle, or does it just remain in this fully open position once warm. It seems to be stuck in the fully open position, this is definitely a new development as it wasn't stuck like this when I inspected the carb last week.

While idling should the choke be fully open as it is now?

With regards to the weber carb, I assume is also uses the vacuum system hoses so any issues with the idle related to vacuum hose leak wouldn't be solved. Does it have any electronic components as the pierburg does?

[aardvarkash10]

Originally Posted by islipaway

What I am trying to get some clarity on is should the choke flap move along with the throttle, or does it just remain in this fully open position once warm.

Should be fully open at all times once warm.

[Laird Scooby]

I think you may have cured 90% of it and found the other 10% - cleaning the jets again was the 90% and the other 10% sounds like the servo vacuum hose. From your description it sounds perished - this will leak allowing air in almost on a random basis but always some.

As a temporary fix/confirmation of fault you could cut an inch or so off the end of the servo hose if there is enough hose to do that with. If not it needs replacing anyway, your local motor factors/auto parts store should keep it in stock. Get enough to replace what's on there and a few inches more just in case it's already been shortened, it should be slack but not loose to allow for movement of the engine.

When you come to remove the old hose from the servo and non-return valve, slit the ends of the hose with a Stanley knife to make removal a lot easier and reduce the risk of breaking the plastic banjo on the servo and the stubs on the non-return valve.

While you're in the local parts shop, buy some carn and air intake cleaner, preferably one with a long nozzle. If you can see the top of the air correction jets without dismantling the carb, get the nozzle in each one at a time and give a good squirt through - this will clean the air correction jets, the main jets and if you're really lucky, the idle jets as well. If not you'll have to dismantle the carb again and clean each jet individually with the carb cleaner.

Might also be worth checking your float level and needle valve, to help the needle valve seal on its seat, use some cheap toothpaste and applying light pressure to keep them together, rotate the needle valve back and forth to lap it into the seat, stopping every few motions and rotate the valve through 90 degrees before repeating the lapping motion.
When you have an even contact mark on both parts, wash the toothpaste off and rebuild, checking the float height again.

Assuming you have some carb cleaner left once all is clean inside, clean the outside including all the linkages between the auto-choke unit (those flaps are in the right place for a warm/hot engine by the way, they should close when the engine is cold and the accelerator pedal is pumped once prior to starting), the accelerator linkages and so on and lightly lube with a thin oil, something like 3-in-1 or similar. Also give the throttle cable a squirt of the oil and operate the accelerator pedal to help distribute the oil along it.

[islipaway]

Gotta be worth a shot!

I will replace that hose and see if there's any improvement.

I'm not sure I'll be able to do the float adjustment, not sure how to access it, I've some experience with simple motorcycle fully manual carbs but this thing is much more complex.

I have been spraying carb cleaner down the jets I can access from the top, and down the holes they come out of. I think these are the aux air/fuel jet, the idle air/fuel jet and the air correction jet.

Seems there's an o-ring missing from between the carb and the black air intake that looks like a shower head too.

[Laird Scooby]

Can you get a photo of the "shower head" please? I suspect it may well be you LPG mixer ring.

[islipaway]

I just mean this thing at takes the air from the filter box. I don't know the proper name, it looks like a shower head to me. The LPG mixer is inline on the tube that feeds into this, just a metal ring. I want to update the LPG system with a BLOS style mixer but until it's idling properly that's not really gonna be worth looking at.

(not my car in photo but but same part for illustration)

[Prufrock]

Tried to upload a file on the Weber - failed !

Jon