Hello,

 

I posted this in my rides thread but ill put it here too,

I have recently put a weber 32/36 on my 4k and fitted extractors at the same time. The carby came off a 18RG? i think.

I can't get it to idle stable. It seems to be very rich at idle. Have attempted to tune according to basic settings and will continue to surge at idle and when backed off from accelerating will drop and nearly stall.

 

I have checked:

1/ Ignition timing - 10BTDC at idle and advance is working on acceleration.

2/ used starter spray to check for air leaks, couldnt find any. when i replaced it i replaced all gaskets including manifold gasket and used aviation sealant on carby and adaptor plate gaskets

3/ Have checekd jets, it has

Primary/Secondary

140/135 mains

160/175 Air

50/55 Idle

4/ it idle very well before carby swap

 

It has an electric fuel pump fitted which worked on standard carby with no problems

 

My questionsn are

1/ Shoud the air jets be larger on the secondary instead of mains?

2/ Do i need a fuel return line, at the moment i have blocked it and i suspect this may be a problem?

The red arrow is fuel in

The green arrow is blocked fuel return

the blue arrow is the vac adavance hose

3/ any other suggestions?

 

Please see youtube video of what it is doing,

You might be suprised how much some back pressure might help once you connect a full exhaust!

oh really? didnt even think of that.... would it make that much difference?

your set up looks very familiar to me. I'm running a 5k though.

 

140/145 mains

165/160 airs

50/50 idle

 

Try running

135/140 main

160/175 airs

Mixture screw 2 turns out, idle speed screw 1 & 1/2 turns out. Timing at 10° btdc.

How much effect do main and air jets have at idle? It seems to rev ok but the idle just keeps surging

Edited November 25, 201213 yr by NinjaMekanik

 

Mains wont affect idle unless the idle is too high.

Havee you set the float level correctly?

Are there any vacuum leaks?

Have not adjusted float level. How is that done?

I can't find any leaks

What sort of electric pump, do you have a pressure regulator? Did the old carby have a return and you've now ditched it??

unsure of what type i scavenged it off another corolla and no i don't have a regulator. It worked on standard with no issues and the standard had no return line.

Is the job of the float to close off the fuel inlet when it reaches the desired level? after i had it running i pulled the top of the carby off and the fuel bowl wasnt overflowing or anything, from memory it was about half full which seemed to be ok?

The float does close it off when it's full, but it can only do so much. Generally they're designed to handle only a few psi of pressure on a Weber, so if your pump is putting out more than that it will overcome the float and cause flooding. Doesn't sound like the problem, but you want to eliminate as many possible problems as you can when trouble shooting.

I would defiantely look at putting the exhaust on before doing doing any more diagnisis as well.

 

Then you are trying to tune the car how its going to drive, or you might get it to idle with the exhaust off, and find it wont idle with the exhaust on!t

The float does close it off when it's full, but it can only do so much. Generally they're designed to handle only a few psi of pressure on a Weber, so if your pump is putting out more than that it will overcome the float and cause flooding. Doesn't sound like the problem, but you want to eliminate as many possible problems as you can when trouble shooting.

Ill pull it off again, check all gaskets again and clean out the carb and reset float while I'm there

 

 

I would defiantely look at putting the exhaust on before doing doing any more diagnisis as well.

 

Then you are trying to tune the car how its going to drive, or you might get it to idle with the exhaust off, and find it wont idle with the exhaust on!t

 

was hoping to drive it to exhaust shop :ninja: to save towing/car trailer hire so was trying to sort it out first (its not that far) but ill see how it is after i take it all off and put back on again. if its still no good ill get the exhaust done before going any further.

Even if you just put a muffler one at the end of the extractors would help. Mine was the same putting a 32/36 on was really hard to make it run with no exhaust put a muffler on at the extractors. Made it easy to tune and ran fairly nicely, plus side once the exhaust is on it should still be fairly close.

rito so i pulled it all off last night. Gave the carby a clean and set the float. It was pretty much spot on anyway. Need to get another manifold gasket as i tore it taking it off Grrr. its stuck to the exhaust pretty hardcore even tho it was only sitting on for a week.

The fuel did look pretty crappy and the tank is really low, so its probably sucking in some crap from the tank. Would it be worth doing a full drain of the tank or just top up with clean fuel?

 

Have to wait now anyway to get a new manifold gasket. Will be couple weeks as ive got few things on the next couple of weekends