CARBY help

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richplezo
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CARBY help

Post by richplezo »

Hi Club folk , my son Willy has 1.3 Sierra , late model . It runs ruff with all sorts of strange fluctuations and bad economy .
Steve Godfrey has suggested returning all settings to factory before we do anything too radical . Good idea .
Is there anyone out there who can tell me what those settings are ? maybe a pic of a workshop manual ,,,,

Thanks heaps in advance

Richard

ps even tough its a coily it has the same carby as my 85 sierra , the one with a wax pellet choke .
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gwagensteve
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Re: CARBY help

Post by gwagensteve »

That makes things a lot easier, I have a ~1987 FSM, I'll have a look and come up with some settings.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
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richplezo
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Re: CARBY help

Post by richplezo »

Thanks Steve ,
muchos graccccos
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gwagensteve
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Re: CARBY help

Post by gwagensteve »

OK, I did a bit of digging with the FSM. The carb/emissions section of the FSM is 31 pages, so I't not really feasible to post them all here.

The key thing is though you need to confirm it's not an ignition timing problem. you can chase carb problems forever, but if your timing is wandering, the coil is breaking down etc you'll go mad.

My first point of call would be to check the throttle cable. The cable should have 10-15mm of play (up down)when the engine is cold, or 3-5mm of play when the engine is hot. This measurement is wiggling the bare cable between the lock nut and the pulley. Adjust to suit.

To set idle speed the car has to be fully up to temperature. The FSM implies this is 77˚C or over.
The car should Idle at 880rpm with All accessories off, ignition timing to spec, and a clean air filter installed, and valve clearance to spec.

If you're running out of idle adjustment (i.e you can't get the idle down to 880rpm even with the screw fully out and appropriate slack in the cable, you have to look elsewhere.

Check the idle mixture adjusting screw. It's on the base of the carb, on the rocker cover side. It should have a aluminium cap over it which sort of makes it tamper proof. adjustment is made by pushing it in and turning it. The primary function of this adjustment is to get the car to ~1.5%CO at idle.

The procedure to set idle using this screw is as follows:
Adjust idle to 880rpm with the main idle speed adjuster.
Close the idle mixture screw until the highest engine speed it attained (it's a regular thread screw - clockwise to close)
readjust idle speed screw to get back to 880rpm
Repeat until the revs don't climb any more when the mixture screw is adjusted.

Idle up:

With the car at temperature, if the blower fan, headlights, or rear demister (if fitted) are turned on, idle should increase "a little higher" (900-1000rpm) There is a two step version of this mechanism, such that if the car is cold, the idle will increase more, 1450-1550rpm. I"m not sure which version the coil car has. Check for blockages or leaks in the vacuum system that could be messing with this operation.

Check the adjustment of the idle up screw such that its' not preloading the throttle when it's off.

Choke:

There's a fairly long and complex process for checking choke function, The key takeout for a misadjusted idle is the fast idle adjustment.
check the choke is fully closed and coolant temp is under 25˚
Start engine and confirm revs are 1500-2500rpm.
Adjust the fast idle screw (which is under the accelerator cable pulley) to get it in that range.

That's mostly the on-car maintenance covered, other than float level.

The other elephant in the room is debris in the float bowl fouling the idle jet. This is super common, it normally comes from a failing fuel pump putting rubbery bits through the fuel system. Pulling the jet requires removing the idle up system off the front of the carb, at which point upon can get access to the float bowl lid and jets. It's not very laborious to do and doesn't involve disassembly that will take the carb out of adjustment. I'd remove and clean the jets, clean out the bowl, and reassemble. With all the other adjustments done, you will know immediately if that's made a difference or not. Most carb problems come down to misadjustment and then junk in the flat bowl. Beyond that the issues become related to physical wear, but that takes lots and lots of km. Luigi on here (Wayne) has ~600,000 km on his carb and the throttle shaft has now worn enough he can't get idle speed down.

See how you go with that.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
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richplezo
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Re: CARBY help

Post by richplezo »

Oh Wow , thats fantastically helpful Steve , we have replaced the cable and checked the timing , so onwards to all the other things.

Should be fun.

Thanks again
steve125
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Re: CARBY help

Post by steve125 »

Could you use your '85 carb as a baseline for settings, or even swap them over to check if it is the carby in the first place?
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richplezo
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Re: CARBY help

Post by richplezo »

Gee that not a bad idea Steve , we had a play with it on the weekend , it looked like the choke wasn't closing properly , made an adjustment and at first it felt a bit better.But Will later reported that the idle was still fluctuating and eratic.
I'm now thinking we'll try taking the bowl off and check for crap.

Thankyou , i appreciate the help.
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