[jimmyjimny]

Hi all, I rebuilt my carb due to the car not idling when cold, and now it's not only still doing that, it's now surging after the rebuild. Originally the car would stall cold and I'd have to hold my foot on the pedal until warm then it'd idle fine. Now it's surging badly I'm afraid to run it for too long. I was wondering if anyone new the specs for the float level? I didn't adjust it during the rebuild and assume that's what's causing the surging. With the cold start I was told it's the fuel passages in the base of the carb, I replaced every jet but wasn't aware there were more passages in the base I need to remove it and use carby some cleaner.

I found a guide on youtube, the carb looks slightly different but was wondering if I could use it as a guide? This is the video https://www.youtube.com/watch?v=6mJHc3YjwPQ

I also have a video of it running with the cold start issue https://www.youtube.com/watch?v=6mJHc3YjwPQ it's been sitting in the garage ever since!

Any help would be greatly appreciated! Cheers

[Marko_SJ]

jimmyjimny wrote:

Hi all, I rebuilt my carb due to the car not idling when cold, and now it's not only still doing that, it's now surging after the rebuild. Originally the car would stall cold and I'd have to hold my foot on the pedal until warm then it'd idle fine. Now it's surging badly I'm afraid to run it for too long. I was wondering if anyone new the specs for the float level? I didn't adjust it during the rebuild and assume that's what's causing the surging. With the cold start I was told it's the fuel passages in the base of the carb, I replaced every jet but wasn't aware there were more passages in the base I need to remove it and use carby some cleaner.

I found a guide on youtube, the carb looks slightly different but was wondering if I could use it as a guide? This is the video https://www.youtube.com/watch?v=6mJHc3YjwPQ

I also have a video of it running with the cold start issue https://www.youtube.com/watch?v=6mJHc3YjwPQ it's been sitting in the garage ever since!

Any help would be greatly appreciated! Cheers

Before you go any further, what work did you do to the car before you tore into the carb? I say this because often the carb gets the blame for things that aren't always its fault.

Did you verify the lines were clear? did you make sure the pump was good? did you change the fuel filter? As for the hard cold starting, did you make sure the choke was adjusted as per manual? if you live in a cold part of Aus?

My car's idle gets erratic and hunts when something is amiss in the fuel system. Most of the time its been a blocked filter. On my other sierra it was a crudded up fuel line or return or something.

All specs are in factory manual.

Edit: also, vac leaks can cause a bog/hesitation/surge too.

[jimmyjimny]

Hi Mark, thanks appreciate the reply currently I've got the carb out and apart on the desk now!

I replaced the fuel filter when I was doing it all last year, I also removed the tank and cleaned it, sprayed carby cleaner and compressed air through the fuel lines etc. The fuel pump is ok, the choke I adjusted and was apparently fine (the butterfly was closed at cold, and opened correctly when warm). When I first bought the car I swapped the head gasket, I can't remember if the cold start problem existed before I did the head gasket. As I only drove the car once before (when I bought it and the previous buyer had warmed it up beforehand), only other possibility I could think of is the valve timing but I double checked the gaps and I'm sure I did it all correctly.

I just took apart the base of the carb (I didn't do that when rebuilding it last time) and found a badly blocked jet which might have something to do with it. Not sure what it does but hopefully it solves the problem!

Regarding the float level my manual is a Haynes it doesn't list the float specs unfortunately. Some searching tells me the float should be set to 7mm or 7.5mm. I'm willing to take a guess, but where are you supposed to measure the gap? Is it 7mm between the top of the float and underneath the top piece/lid of the carb??

The other thing is I noticed if I push the float valve upwards it sticks... it's a new valve and seat not sure if this is normal or will it be a problem? When in the car fuel would come through the inlet line and push the valve back down back down I'd imagine and it's normal.

The float sticking:


The fuel passage that was blocked solid and is now clear!

[andrew]

Im having very similar problems with my car..
What's that fuel thing ...like a return line from the carby. ?
Did that fix the problem ? Did you just belt carby cleaner and compressed air into it ?

[Marko_SJ]

jimmyjimny wrote:

Hi Mark, thanks appreciate the reply currently I've got the carb out and apart on the desk now!

I replaced the fuel filter when I was doing it all last year, I also removed the tank and cleaned it, sprayed carby cleaner and compressed air through the fuel lines etc. The fuel pump is ok, the choke I adjusted and was apparently fine (the butterfly was closed at cold, and opened correctly when warm). When I first bought the car I swapped the head gasket, I can't remember if the cold start problem existed before I did the head gasket. As I only drove the car once before (when I bought it and the previous buyer had warmed it up beforehand), only other possibility I could think of is the valve timing but I double checked the gaps and I'm sure I did it all correctly.

Its been a few days since your reply, how'd you go?

Sounds dumb but is the choke operational?

Quote:

I just took apart the base of the carb (I didn't do that when rebuilding it last time) and found a badly blocked jet which might have something to do with it. Not sure what it does but hopefully it solves the problem!

Going by your last pic, looks like one of the breather/vac lines IIRC, one goes to the charcoal can, one goes to the dizzy, one goes to the front of the intake?

Anything being blocked wouldn't help. If I had one of those unplugged it would cause the car to hesitate slightly.

Quote:

Regarding the float level my manual is a Haynes it doesn't list the float specs unfortunately. Some searching tells me the float should be set to 7mm or 7.5mm. I'm willing to take a guess, but where are you supposed to measure the gap? Is it 7mm between the top of the float and underneath the top piece/lid of the carb??

Thats what I did but 8mm height. 8mm drill used as thickness gauge.

Quote:

The other thing is I noticed if I push the float valve upwards it sticks... it's a new valve and seat not sure if this is normal or will it be a problem? When in the car fuel would come through the inlet line and push the valve back down back down I'd imagine and it's normal.

The float sticking:


The fuel passage that was blocked solid and is now clear!

My float didn't stick. Does it stick hard?

[jimmyjimny]

Marko_SJ wrote:

jimmyjimny wrote:

Hi Mark, thanks appreciate the reply currently I've got the carb out and apart on the desk now!

I replaced the fuel filter when I was doing it all last year, I also removed the tank and cleaned it, sprayed carby cleaner and compressed air through the fuel lines etc. The fuel pump is ok, the choke I adjusted and was apparently fine (the butterfly was closed at cold, and opened correctly when warm). When I first bought the car I swapped the head gasket, I can't remember if the cold start problem existed before I did the head gasket. As I only drove the car once before (when I bought it and the previous buyer had warmed it up beforehand), only other possibility I could think of is the valve timing but I double checked the gaps and I'm sure I did it all correctly.

Its been a few days since your reply, how'd you go?

Sounds dumb but is the choke operational?

Quote:

I just took apart the base of the carb (I didn't do that when rebuilding it last time) and found a badly blocked jet which might have something to do with it. Not sure what it does but hopefully it solves the problem!

Going by your last pic, looks like one of the breather/vac lines IIRC, one goes to the charcoal can, one goes to the dizzy, one goes to the front of the intake?

Anything being blocked wouldn't help. If I had one of those unplugged it would cause the car to hesitate slightly.

Quote:

Regarding the float level my manual is a Haynes it doesn't list the float specs unfortunately. Some searching tells me the float should be set to 7mm or 7.5mm. I'm willing to take a guess, but where are you supposed to measure the gap? Is it 7mm between the top of the float and underneath the top piece/lid of the carb??

Thats what I did but 8mm height. 8mm drill used as thickness gauge.

Quote:

The other thing is I noticed if I push the float valve upwards it sticks... it's a new valve and seat not sure if this is normal or will it be a problem? When in the car fuel would come through the inlet line and push the valve back down back down I'd imagine and it's normal.

The float sticking:


The fuel passage that was blocked solid and is now clear!

My float didn't stick. Does it stick hard?

Hey Marko cheers mate she's running good atm Still has the problem where it won't idle on cold (I adjust the idle screw on the wax pallet and this fixes it, but then over revs once warm). But once warm I back down the screw and it drives pretty smooth. The valve was definitely sticking, I cleaned some of the rubber off with methylated spirits and it seats pretty good now

I've been sick all week with the flu once I recover I hope to get out there and give the idle a crack!