Fuel or air supply trouble 4Y Engine

[Jay6]

Firstly Hello to everyone!!

I am new.

I Drive a old 1985 Hilux that I converted from 2.4 Diesel to the 4Y...

I recently reinstalled a Ignition module and changed the base and top gasket of the carb. Now after I managed to get the timing perfect, he pulls well when I drive on the open road, but when I drive traffic light to traffic light there seems to be a fuel or air shortage.

I have attached a image to show the carb. If anybody can tell me what model the carb is or have a service manual for it, I will appreciate it a lot.

Please help

Thank you in advance

[Jay6]

[LouisZ]

That's the Chinese version of the Niki carb. Hard to fix.

[Jay6]

I have a complete kit to replace all parts the weekend, but need to know why it is doing what I described in the post... Have any suggestions please?

[Mars]

You say it seems to have a fuel or air shortage but you do not actually say what it is doing? Under powered, not picking-up revs, jerking? The more specific you are the easier it will be for the guys to provide you with assistance.

Generally speaking those Chinese knock-off carbs are total rubbish. And this does not only hold true for the Toyota replacements. I know of a carb specialist who refuses to touch any Chinese carbs.

[Jay6]

It jerks when you start accelerating after you have stopped and it has idled a bit... for example stopping at a red light and trying to take off at the green light, I have to pump the accelerator otherwise it is jerks and stalls.

[LouisZ]

Disconnect the fuel supply line on the carb. Take off the dizzy cap, put the Hilux in neutral and swing the engine. Look if the fuel pump give constant burst of fuel, if not you got a pump problem. You might need a assistant inside the Hilux.

Could be the fuel pump too.

[Mountain Man]

It sounds like the idle mixture is too lean.

[Jay6]

okay the carb does get a constant supply of fuel.

Sorry Mountain Man, what do mean by a lean idle mixture?

[Mars]

Have you always had this issue since the conversion or did it start recently after making the changes? That is one of the known issues with the Chinese carbs is flat spots. It seems as if you have a large flat spot way down in the rev range.

[Jay6]

it was fine in the beginning of the week, the issue started this morning when I left for work.

[Haboob]

Welcome to the Forum Jay...

[Mars]

Well if it wasn't doing it before then it would not be the carburettor being inherently bad. Start looking for your problem where you made the last changes.

[Mountain Man]

Hi Jay6,

There are 2 adjusting screws on the exterior of the carb, one is for the idle speed, and the other one adjusts the idle mixture. Neither of these 2 adjustments makes any (or hardly any) difference in the actual performance of your vehicle once it is accelerating as the internal jetting of the carb is at work. However both of them are very much in play at idle and as you are about to pull of i.e as you touch the accelerator. The rule of thumb is to turn the idle mixture screw in one direction until the motor idles rough and then in the opposite direction until it idles rough. you need to count the turns and set it more or less in the middle. A carb center use a CO meter to measure the exhaust carbon monoxide level to adjust the screw but the rule of thumb works to a reasonable degree. After you find the middle you will then adjust your idle screw, from memory the 4Y should idle at about 800rpm at normal operating temperature.

The other problem could be related to your accelerator pump (Not the same as the fuel pump). This is a diaphragm on the carb which comes into play when the accelerator peddle is depressed and it squirts a bit of fuel into the carb as you depress the accelerator. This does not squirt if you hold the accelerator in one position even full throttle as the jetting of the carb come into play for this. However, as you accelerate to overtake or pull off that is when it adds a bit of fuel. If this is not working correctly the car will jerk and stall when the accelerator is depressed, and the more vigorous it is depressed the more chance it will stall/jerk. Changing the diaphragm is very easy and not expensive.

The pros will probably have more info for you but these are some of the issues I found when I had my 4Y.

I hope it helps.

(Sorry I forgot to say that you need to make sure your hoses etc are connected correctly and that there are no air leaks at the base of the carb/manifold)

[Jay6]

Thank You Mountain Man...

I got rid of the jerking, I played around with the carb and retighten it.. Then I also played around with the distributor. After that the jerking was gone.

I just want to thank everybody for the advise and tips, it was very help full.