heat soaked engine gets idle surge on restart.

[destin]

I agree that the soapy water method won't help you find a vacuum leak. The method I was taught involves a little bottle of propane and a hose to direct it around the manifold gaskets and base of the carb, where most leaks occur.

How to Find a Vacuum Leak With Propane | eHow.com

Other spots are around the brake booster when present and the vacuum shifter mechanism for the low gear.

Could I have a vacuum leak and have 20 inches of vacuum at idle ?

If so I find someone with propane to test it. They would have to test it cold correct.?

Still feel although I have done nothing but go in circles for three years with this

 

[destin]

Ok deep breathe

So seeing I have a good vacuum at idle, but a stumble when cold and heat stoked restart...
And the plugs show lean.

Could this all equal a week accelerator circuit, or plunger?

 

[destin]

Well I discovered the one of the springs on the choke is s***e and does not work properly.

It wii stay lock open fine ( knob in ). But if you pull the knob out It seems to not do s*** half the time.
I fix this and see if it resolves the cold start.

Does everyone use the choke on a cold start until it warmed up to prevent stumbles? ( see my video )

 

[IDave]

You might have a vacuum leak in a hot engine that you don't have when it's cold. Our older engines have cast iron manifolds and they may change a lot with temperature. You can test it hot and cold. Just get one of those little propane cylinders for brazing/welding/plumbing at the hardware store. I think they're 10 bucks or something with a valve. A handy thing to have around anyway.

I really don't know if that's it. 20 inches is great and I'll never achieve it at my elevation of 5100 feet. I'm happy to see 16.

But I think your stumble is too much air or not enough fuel for whatever reason it turns out to be.

 

[kurtnkegger]

I have read in other threads about their Cruisers running like s*** when the dwell is set to factory specs.

This comes to mind....https://forum.ih8mud.com/40-55-seri...no-start-pic-where-i-set-gap.html#post2720126

HTH

 

[vegasfj40]

My 79 has the exact same problem. Starts and runs great cold but on hot starts intermittently has idle surges that usually lasts about 30 seconds or so after I have revved the engine a couple of times. It doesnt do it everytime though so its hard to pinpoint. I have wondered about the EGR circuit. Not sure if that could be the cause.

 

[Pighead]

Could I have a vacuum leak and have 20 inches of vacuum at idle ?

No, 20 inches is fabulous.

I have read in other threads about their Cruisers running like s*** when the dwell is set to factory specs.

Do not try to set your dwell to factory specs. Forget the dwell. Set the points gap and run it.

 

[fj404life]

Mine acts the same way cold with no choke on. 1/4 pull on the choke smooths mine out. Only takes maybe 30 seconds till it will run pretty good no choke in this weather.

 

[IDave]

20 inches is fabulous.

I'm tempted to say "unbelievable".

Where ever I look up acceleration stumble or hesitation, they seem to say something about air/fuel mismatch. I believe that acceleration stumble is what I'm hearing in Destin's video (and my truck has done that too, Destin). Obviously, vacuum leak is only one cause of air/fuel mismatch. But based on how the plugs look, I'm leaning to a lean condition. Vacuum leak would be one cause of that.

 

[destin]

It has 18 inches at idle cold, 20 warm...

Ok so I have a vacuum leak somewhere?

So it is either an intake leak or a carb leak somewhere ?

Does this need to done cold?

Is this just a goose chase and my carb is a piece of s***, with some weird warped internal vacuum leak that I will never find?

Lol sorry, this has been pissing me off or years

 

[destin]

actually i bought this cruiser originally in colorado, mayeb the jets are set up for higher elevation.

1) what number is the _idle jet_ and _metering jet_ supposed to be at sea level?

2) what diameter metering rod ( does the metering rod ever vary for elevation or just the jet )?

3) does the metering jet control richness overall?

4) does the acceleration jet change sizes?

thansk fellas

d

 

[destin]

ok

was careful not to pull the trottle linkage before i disconnected the carb.

carb had a leaked a puddle of gas into the intake :

pulled the carb over the tray and tried to pump out the gas via the accelerator pump.

s*** would only spray have the time if at all, badd accelerator pump yes?

video:

VID 20120808 092752 - YouTube

.

will be tearing it down here and posting photos. and videos as necessary.

I will likely be using the old plunger, with a thin white lithium grease to seal the plunger, and thin coat on the gaskets when i reassemble.

Anyone know what size meter jet, idle jet, and metering rod i shoudl be using?

thanks

Destin

 

[destin]

idle and metering jets are clean and clear, both apparently size 30, is that correct for sea level?

both check valves clean and moving free

this is the metering rod i have in the carb, there was no spare in the spare slot
correct?

blew out all passage ways with compressed air

 

[destin]

so i popped in the old plunger, ( which seem to fit tighter ) added some light white lithium grease to seal

plunger action was better for sure.

BUT

popping on the air horn, and look at this gap at the back of the air horn

i took 2 videos, one with the gasket in and one without so you can see the gap.

gap is big enough where you can move the gasket.
I am assuming this would cause me to run lean?

Put the car on because i have no other carb working, seems to ironically run better, could be the better plunger masking that big ass air leak.

no gasket video

with gasket video

so new carb in my future eh?

 

[fj404life]

Im no carb expert so wait for someone who is to chime in...but I wonder if you can "re-surface" that carb body. Using some sandpaper and a sheet of glass or other very flat surface? Like I said dont do it unless a pro says you can!

 

[destin]

Im no carb expert so wait for someone who is to chime in...but I wonder if you can "re-surface" that carb body. Using some sandpaper and a sheet of glass or other very flat surface? Like I said dont do it unless a pro says you can!

it was hand filed before because it was so warped, when it was rebuilt, but I did not know it was this bad lol.

anyway, on the look out for a non fawked single barrel carb, small window, big window, it does not matter

 

[destin]

maybe i should get mad ghetto and throw some heat vent metal tape on it lol
Ya know until i find a non knackered carb.

 

[destin]

To be clear, a vacuum leak on the back of the air horn WILL cause lean issues and erratic power deliver i would imagine, as there is more pull through air could come through weird correct?

 

[miker]

that is pretty warpped. likey a major contributor to your issues. and yes, I'd say that would cause air to bypass the venturi, meaning unmetered air is entering the carb and intake. "unmetered air" means there is no associated fuel entering with this unmetered air, therefore it will cause a lean condition. just like a vacuum leak at the intake

BTW, the accelerator pumps only purpose is to add extra fuel when the throttle is actively being opened to compensate for the extra air entering the intake/engine before the engine vacuum has a chance to increase. Basically, fuel is drawn into the intake from the carb because of the vacuum created by the engine running and the design of the carb's venturi. When you open the throttle, a larger amount of air is immediately allowed to enter the engine and the vacuum drops (for a short period of time) until engine RPM increases. The accelerator pump compensates for the extra air by adding extra fuel and keeping the air fuel ratio optimal. When the engine is at a steady throttle position, whether idle or high RPM or anywhere in between, the accelerator pump does nothing and it should not be supplying fuel to the engine.

surfacing the carb faces seems like a reasonable idea to me. Assuming that there are no 'features' you will be removing by doing this, and no height, or distance issues with rods, linkages, etc between the top and bottom halves of the carb.

You could try a temp thing like you suggested (tape?) just to confirm it makes a change for the better.

 

[destin]

that is pretty warpped. likey a major contributor to your issues. and yes, I'd say that would cause air to bypass the venturi, meaning unmetered air is entering the carb and intake. "unmetered air" means there is no associated fuel entering with this unmetered air, therefore it will cause a lean condition. just like a vacuum leak at the intake

BTW, the accelerator pumps only purpose is to add extra fuel when the throttle is actively being opened to compensate for the extra air entering the intake/engine before the engine vacuum has a chance to increase. Basically, fuel is drawn into the intake from the carb because of the vacuum created by the engine running and the design of the carb's venturi. When you open the throttle, a larger amount of air is immediately allowed to enter the engine and the vacuum drops (for a short period of time) until engine RPM increases. The accelerator pump compensates for the extra air by adding extra fuel and keeping the air fuel ratio optimal. When the engine is at a steady throttle position, whether idle or high RPM or anywhere in between, the accelerator pump does nothing and it should not be supplying fuel to the engine.

surfacing the carb faces seems like a reasonable idea to me. Assuming that there are no 'features' you will be removing by doing this, and no height, or distance issues with rods, linkages, etc between the top and bottom halves of the carb.

You could try a temp thing like you suggested (tape?) just to confirm it makes a change for the better.

hehe I posted a WTB in the classifieds for a good one barrel carb.
Sick of this one lol, bane of my existence lol!

I might look into using the aluminum tape in the meantime of you guys do not forsee that causing problems. Not sure how long it will take me to find a good carb. Maybe trollhole will start selling single barrel carbs

::dreams::