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NH Carb
Posted: Mon Aug 30, 2021 11:10 pm
by Professor Fate
How does one blow out a NH Carb that has a full bowl, but is not passing fuel to the intake?
Alas, I'm ignorant and need to learn.
I think I sucked some crud/rust into the needle and seat. My NH knowledge is not great.
Car ran poorly on 1.25 turns open and would run worse or stall if mixture was moved in either direction. Now it will run 2-3 seconds and die....
Could the needle be deformed from closing it and reopening? I have gone gently when turning to close and reopen. I've read that they can be easily damaged.
You guys are always great to me. Thanks for your help in advance.
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Re: NH Carb help
Posted: Tue Aug 31, 2021 7:25 am
by Ruxstel24
Almost sounds like the main jet is loose or has some crap in it. The needle valve only lets fuel into the bowl or not....
Re: NH Carb help
Posted: Tue Aug 31, 2021 8:46 am
by Professor Fate
Any tips on how to clean?
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Re: NH Carb help
Posted: Tue Aug 31, 2021 8:49 am
by Scott_Conger
To clarify some:
some people call the float valve a "needle valve", which is what Dave is referring to
In fact it is the float valve which allows fuel into the bowl, and yours may be stuck closed or mostly closed, severely limiting the fuel flow into the bowl and thus the fuel height at the jet
The actual needle valve, the thing you twist, changes the amount of annular clearance on the jet and meters the fuel flow into the air flow, thus adjusting the "richness" mixture. If it is in fact this part which is the problem, then Dave may be correct in that some junk has been sucked up into the jet. In that case, removing the needle valve while the carb is on the car, inserting a WD-40 plastic tube down in there and giving it a blast, will push the crud out. Re Install the needle valve; gently bottom it on the jet; open it 1 1/2 turns and try the car again.
Re: NH Carb help
Posted: Tue Aug 31, 2021 8:53 am
by Professor Fate
So needle will just turn out easily and go back in without little bits flying off when the needle comes out? My eyes are not the best working with micro parts. That's why I ask.
The fuel line setup may be contributing too. I'll get a pic of that for you guys to look at shortly.
Re: NH Carb help
Posted: Tue Aug 31, 2021 9:21 am
by Scott_Conger
If the NH is fitted to an '09-24, the richness needle on top will simply unscrew after the clamp nut on top is loosened. No springs, no surprises, no drama
If fitted to '25-'27 with the integral choke mechanism on the richness adjuster, the needle will easily come out without loosening anything, as there is no clamp nut, just the grip/fingers dragging on the brass fitting on top.
I suspect you have the earlier version?
Re: NH Carb help
Posted: Tue Aug 31, 2021 9:33 am
by jab35
Re: NH Carb help
Posted: Tue Aug 31, 2021 10:11 am
by TRDxB2
Re: NH Carb help
Posted: Tue Aug 31, 2021 2:16 pm
by Professor Fate
'26-'27 NH setup with the sliding choke on the mixture rod
Re: NH Carb help
Posted: Tue Aug 31, 2021 4:20 pm
by Scott_Conger
OK, then the needle simply screws out. Nothing to it.
WD-40, carb cleaner or anything with compressed gas and a long plastic nozzle...insert down until it bottoms and give it a blast...anything blocking the jet will be pushed back into the bowl and you'll either see an immediate improvement (proving the jet blockage has been at least temporarily displaced) or not. If no improvement, time to look for other things
Re: NH Carb
Posted: Tue Aug 31, 2021 7:02 pm
by Professor Fate
Thanks Scott.
Did as you said. Car still won't run.
I'm covering it up and moving it off to a dark corner.
Moving on to other things as winter is approaching. I've got a list to get thru for the house..... no more time or patience for the T.
Re: NH Carb
Posted: Tue Aug 31, 2021 7:07 pm
by speedytinc
Professor Fate wrote: ↑Tue Aug 31, 2021 7:02 pm
Thanks Scott.
Did as you said. Car still won't run.
I'm covering it up and moving it off to a dark corner.
Moving on to other things as winter is approaching. I've got a list to get thru for the house..... no more time or patience for the T.
If it runs a short time, might be a sticking/stuck needle/seat. Open the drain into a glass jar. check for dirt & actual fuel flow.
Re: NH Carb help
Posted: Tue Aug 31, 2021 7:45 pm
by Professor Fate
Fuel is clear no debris or H2O.
Fuel flow is good.
Re: NH Carb help
Posted: Wed Sep 01, 2021 8:38 am
by speedytinc
Ruxstel24 wrote: ↑Tue Aug 31, 2021 7:25 am
Almost sounds like the main jet is loose or has some crap in it. The needle valve only lets fuel into the bowl or not....
Nh carbs are so trouble free, how bout the unusual? Its worth a try to check the jet for being loose. Easy enough. Drop the bowl. Check that big brass screw under the bowl mounting screw/drain. If loose, back off the mixture needle before tightening.
Re: NH Carb
Posted: Wed Sep 01, 2021 8:46 am
by Ruxstel24
Maybe it’s not the carburetor at all...
Have you checked spark and compression ?
How about the timer ?
Re: NH Carb
Posted: Wed Sep 01, 2021 8:49 am
by TXGOAT2
When you crank the engine several rounds with the ignition off and the choke full on, does fuel drip out of the carburetor air intake? It should. If it does not, it points to a carburetor issue. If fuel does drip out when cranking as described, it's very like you have some other issue, such as an air leak in the intake tract or an ignition problem. Have you done any checks to see if the system is delivering proper voltage to the spark plugs?
Re: NH Carb Nightmare
Posted: Wed Sep 01, 2021 5:38 pm
by Professor Fate
-Never drips or dribbles.
-Ignition voltage is good.
Re: NH Carb
Posted: Wed Sep 01, 2021 8:03 pm
by TXGOAT2
It should definitely drip gas at the carb air intake when you choke it while cranking with the needle adjustment open about one turn. Is it possible that the carburetor adjustment rod isn't actually turning the needle, leaving it seated or very nearly so? I once had a car that refused to run. After a lot of fiddling, I discovered that a red harvester ant had somehow gotten lodged in the float needle seat fitting. I have no idea how it got past the fuel pump. It made a very effective plug.
Re: NH Carb
Posted: Wed Sep 01, 2021 11:27 pm
by Professor Fate
Thanks....
The needle is firmly attached to the top that connects to the turning mixture rod.
I was able to blow out the carb using the straw of a wd40 can. WD40 came freely out of the breather hole that faces the motor just above the bowl.
***previously the carb float was sticking causing fuel to pour out. I had to tap the bowl gently to get the float to release and rise thus cutting off fuel flow to the bowl.
Now the float is rising fine and no fuel overflowing.
Re: NH Carb
Posted: Thu Sep 02, 2021 7:36 am
by Ruxstel24
I think since you have no fuel dripping when choking...it’s time for a compression test, dry then with a little oil in each cylinder.
Also check for a good seal at the intake manifold.
Good luck !
Re: NH Carb
Posted: Thu Sep 02, 2021 9:15 am
by TXGOAT2
Did WD 40 or gasoline ever run out of the carburetor air intake which faces to rear of the car? WD 40 escaping from the small bowl vent that faces the block does not necessarily indicate that the spray jet is clear. When you crank the engine for several seconds with the choke pulled shut, and the adjustment open one turn, gasoline should drip freely from the air intake. If it does not, and the bowl is known to be full of gasoline, the spray jet is almost certainly clogged.
Re: NH Carb
Posted: Thu Sep 02, 2021 2:49 pm
by Professor Fate
Carb is on the bench.
The float needle is sticking all the way up against the seat. The rubber tip is not letting it move freely up and down. Why is it sticking? The sides of the float needle travel freely up and down. It's the rubber tip sticking up not allowing the float needle full travel .
Also, the bottom of the spray needle has a ridge or slight groove around it. Not sure if you can make it out in pic..
Spray needle is clear as I can see right thru it
Thoughts?
Re: NH Carb
Posted: Thu Sep 02, 2021 2:55 pm
by Ruxstel24
Dan, the spray needle groove is from bottoming out but shouldn’t be an issue.
The float needle sticking is probably gum from the wonderful gasoline we get today.
Some carb cleaner and an old tooth brush on the needle and spray some on the seat, might take care of things.
Re: NH Carb
Posted: Thu Sep 02, 2021 3:01 pm
by Scott_Conger
Well, with the float valve sticking, it sure won't run.
The needle has been bashed into the jet one to many (hard) times and needs refurbishment before you'll get good control of richness and performance once the thing is running.
If the float valve has been forced into its seat, which can happen as the float is a great force multiplier if pressed on with a finger, then there will be some small damage/distortion to the Viton. Small amounts of varnish can also make things sticky, too.
I will stop with this advice: Float valves as bought from vendors, have a through-put of FAR less than the original valve. If there is any reluctance of the needle to release from the orifice, the pressure exerted on the needle by the fuel does not have the same area of pressure (compared to the original) to unseat the valve if it is anything less than perfect.
Re: NH Carb
Posted: Thu Sep 02, 2021 3:38 pm
by speedytinc
There was a common problem of a sharp edge on the seat. Recent parts dont seem to have that sharp edge. Another example of a part that missed the mark. The fuel hole is too small also & effects performance @ high demand. The fix, if you have the equipment, is to drill out the hole in a lathe to .120". If the seat develops a bur. Tap a 5/32 or 3/16 ball bearing with a pin punch to debur the seat.
If you cant modify yourself, Scott C. sells one already modified ready to go.
Re: NH Carb
Posted: Thu Sep 02, 2021 4:41 pm
by speedytinc
A good needle & seat has to pass 2 tests. The suck test as illustrated in the service manual. The tongue should stay stuck until you pull it off. That tells you it is not leaking. There is also the blow test. After the suck test, turn the carb back over & blow. If the air doesnt easily flow, the needle is stuck. If you get a pop before air flows it sticks some. Each cycle of tests should have a solid tongue stick (inverted position) & free air flow when in normal position. Now, lets try to be adult about the subject.
Re: NH Carb
Posted: Thu Sep 02, 2021 4:51 pm
by DanTreace
Just to keep the proper visual with your description of the carb tests
Re: NH Carb
Posted: Thu Sep 02, 2021 5:55 pm
by Professor Fate
Carb will not drip fuel when choked.
I cleaned it all and put it back together with little success. Will not run. It pops nicely back thru the carb though
Thanks everyone for trying to help.
Re: NH Carb
Posted: Thu Sep 02, 2021 6:15 pm
by speedytinc
Did you test it, as I suggested, before putting back on? suck & blow.
When you crank & choke, you should hear the "slurp" of fuel. When you stop cranking, the excess fuel you just sucked up will leak out the back of the carb if you are getting fuel.
Re: NH Carb
Posted: Thu Sep 02, 2021 6:41 pm
by Professor Fate
I didn't get the suck and blow tip until after i had reinstalled the carb. My carb is not a dribbler or leaker of fuel at all. I held the choke for 6 seconds plus while cranking and only got it to pop. No fuel exiting carb at all. So my float needle is probably stuck again.
Re: NH Carb
Posted: Thu Sep 02, 2021 6:47 pm
by speedytinc
Professor Fate wrote: ↑Thu Sep 02, 2021 6:41 pm
I didn't get the suck and blow tip until after i had reinstalled the carb. My carb is not a dribbler or leaker of fuel at all. I held the choke for 6 seconds plus while cranking and only got it to pop. No fuel exiting carb at all. So my float needle is probably stuck again.
I agree. that sharp edge on the seat locks on the viaton edge. A ball bearing tap might do it. Then test several times. If the needle is not stuck too tight, a light tap on the fuel inlet casting may free it now. Open the bowl drain to confirm. Even if a tap frees it up, you will still need to fix the inlet needle/seat.
Re: NH Carb
Posted: Thu Sep 02, 2021 9:44 pm
by Professor Fate
so much for my "rebuilt" nh. What a mess.
Carb Fix
Posted: Fri Sep 03, 2021 11:36 pm
by Professor Fate
Carb fixed!
Swapped out the mixture needle for a new one, fixed double firing coils, and stopped coils from grounding out on coil box cover.
No wonder it wouldn't run.
It's all good now!
Thanks to all for kind help.
Re: NH Carb
Posted: Sat Sep 04, 2021 10:33 am
by Scott_Conger
always nice to hear "the rest of the story".
thank you for that and have fun!
Re: NH Carb
Posted: Sat Sep 04, 2021 5:35 pm
by Professor Fate
In addition to carb issues, I had a coil box cover shorting coils, three out of four coils were out of tune and double firing, and my ignition switch is still on the blink.
We fixed it all and ran a jumper to bypass the switch. My Al Clark rebuild runs like a sewing machine. It ran last night beautifully.
"HAPPY DAYS ARE HERE AGAIN!"
Re: NH Carb
Posted: Sat Sep 04, 2021 6:31 pm
by speedytinc
Professor Fate wrote: ↑Sat Sep 04, 2021 5:35 pm
In addition to carb issues, I had a coil box cover shorting coils, three out of four coils were out of tune and double firing, and my ignition switch is still on the blink.
We fixed it all and ran a jumper to bypass the switch. My Al Clark rebuild runs like a sewing machine. It ran last night beautifully.
"HAPPY DAYS ARE HERE AGAIN!"
CONGRADULATIONS! Now you got a lot of other nigglin stuff to attend to.
