Choke issues I think

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RollinCajun
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Choke issues I think

Postby RollinCajun » Tue Dec 04, 2018 5:51 pm

So removed the entire pollution pump setup and all hoses, etc going to it today and truck actually seems to be running better from what I can tell plus they don't check that stuff around here so no reason to have it. The only issue I'm having is it doesn't like to idle when first start up when it's cold.

I have to keep pumping the peddle to keep it running till it warms up a little then it runs perfect. I looked down the carb a couple days ago when the engine was cold and the choke never closes all the way. The furthest it closes has a 1/4" or so gap. I feel like the electric choke is causing the problem by not closing enough at cold temperatures to keep the engine running.

Most vehicles I've had over the years with carburetors the choke could close completely off during super cold starts and gradually open as it warms up. I've read this truck has a choke relay I'm wondering if I should try replacing that to see if that fixes this problem. It's such a pain in the ass to keep running in the mornings it's driving me nuts. I can't take off for several minutes.

I've checked connections on spark plug wires, I checked under the cap for moisture, don't have any vacuum leaks and the EGR valve was taken off with the pollution stuff so that can't be an issue either. I believe it's the choke but wanted some insight from the good mechanics out there.
1987 Isuzu Pickup Gas (Short Bed)

fasteddie
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Re: Choke issues I think

Postby fasteddie » Tue Dec 04, 2018 10:02 pm

I don't classify myself as a "good mechanic" but for what it's worth, my truck has had the same problem for many years. It will get a little better after new plugs cap and rotor but after a while it goes back to it's same old used to be. I think these trucks just don't like the cold. Fortunately the pedals are close together so I can cover the gas and brake with one foot to keep it idling at a stop. My truck has always run very cool. Great in summer, not so much in winter, takes a good 10 minutes of driving to move the needle. And this post reminds me, I have a corrugated plastic poster board that I stick down between the condenser and radiator, covers about 75% of the rad. I keep it behind my seat, time to install that.
1989, 2.3L, 5 speed pickup, original owner

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Re: Choke issues I think

Postby FiatSpider2 » Wed Dec 05, 2018 7:13 am

The choke closes completely when the engine is cold after you depress and release the accelerator pedal to engage the fast idle before you start it however the moment the engine starts its supposed to be unloaded/opened about 1/4 of an inch by a vacuum pot or on some a solenoid just like it should when you operate the choke manually with a cable.

More likely you have left a vacuum port open (causing a lean condition that may give you a few more rpm at idle when warm along with the false impression its running better but will ultimately lead to a burnt valve or piston top along with let dirt into the intake) when you yanked the EVAP components which are also part of the system that keeps acid due to unburnt fuel and condensation from forming in your crankcase which reduces the effectiveness of your engine oil and can lead to shorter engine life.

I don't have inspections where I live either however I do like clean air, a clean crankcase and engines that last a long time so I keep it all working as it left the factory and have no problems whatsoever. I keep my vehicles for 20 to 40 years, rebuild my own carburetors (been doing so for over 50 years) when needed and have never had a problem because I left the EVAP system in place however a lot of people have a multitude of issues from removing them some of which may not become apparent for years.

Its time to backtrack and figure out what was removed and not rerouted properly along with check to see if you damaged any of the parts that control the choke and fast idle. The manual for adjusting the carburetor will be needed to ensure the unloader, etc are all still set correctly however none of that should be touched until the routing of the vacuum lines and PCV system are verified correct for running without the canister, catalytic converter and air pump.
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RollinCajun
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Re: Choke issues I think

Postby RollinCajun » Wed Dec 05, 2018 8:54 am

FiatSpider2 wrote:The choke closes completely when the engine is cold after you depress and release the accelerator pedal to engage the fast idle before you start it however the moment the engine starts its supposed to be unloaded/opened about 1/4 of an inch by a vacuum pot or on some a solenoid just like it should when you operate the choke manually with a cable.

More likely you have left a vacuum port open (causing a lean condition that may give you a few more rpm at idle when warm along with the false impression its running better but will ultimately lead to a burnt valve or piston top along with let dirt into the intake) when you yanked the EVAP components which are also part of the system that keeps acid due to unburnt fuel and condensation from forming in your crankcase which reduces the effectiveness of your engine oil and can lead to shorter engine life.

I don't have inspections where I live either however I do like clean air, a clean crankcase and engines that last a long time so I keep it all working as it left the factory and have no problems whatsoever. I keep my vehicles for 20 to 40 years, rebuild my own carburetors (been doing so for over 50 years) when needed and have never had a problem because I left the EVAP system in place however a lot of people have a multitude of issues from removing them some of which may not become apparent for years.

Its time to backtrack and figure out what was removed and not rerouted properly along with check to see if you damaged any of the parts that control the choke and fast idle. The manual for adjusting the carburetor will be needed to ensure the unloader, etc are all still set correctly however none of that should be touched until the routing of the vacuum lines and PCV system are verified correct for running without the canister, catalytic converter and air pump.


All lines that needed to be there are still on the ports they were already on. Such as the vacuum line to the distributor, etc. I will check to see if any of the hoses may have cracked and I didn't notice or I left a port open. As far as evap systems I've never used them on any vehicle I've ever owned I've always removed them. I've never had an issues with engine life I've had engines going over 400k miles without evap systems. I've been working on my own vehicles for about 25 years myself. These little trucks with 4 cylinders are already low on power because of small engines. Having all these restrictions to take away horsepower is non-sense in my opinion. Anything that helps give it a little more power I'm all for as long as it won't damage an engine and I've never had that happen. Thanks for the info though.
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Re: Choke issues I think

Postby oldestisuzuist » Wed Dec 05, 2018 9:08 am

It's very possible you just need to lube the moving parts. Spray everything down inside & out liberally with carb cleaner while running, turn off, then lightly lube every moving part with something like WD-40 while cycling the throttle fully. Watch for slop in the choke & throttle plate pivot bushings, they can wear over time & cause things like vacuum leaks & other problems.
You may also need to re-adjust the idle mixture to account for the lack of the smog input.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
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RollinCajun
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Re: Choke issues I think

Postby RollinCajun » Wed Dec 05, 2018 9:34 am

After checking everything just now there are no lines left off and no vacuum leaks. The engine runs great once warmed up. Plenty of power at all rpm ranges and idles perfect also once its warm. The only issue this vehicle has is starting on cold mornings. I believe its more of a fuel issue. I never liked manual fuel pumps they always let the fuel bleed back down the line over night. I think electric fuel pump would do the trick. After checking the fuel level sight glass on the carburetor it isn't showing any fuel in the carb at this point in time. I already have an electric fuel pump designed especially for carbs so I'll probably install that soon. Never liked manual pumps anyways.
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RollinCajun
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Re: Choke issues I think

Postby RollinCajun » Wed Dec 05, 2018 9:38 am

oldestisuzuist wrote:It's very possible you just need to lube the moving parts. Spray everything down inside & out liberally with carb cleaner while running, turn off, then lightly lube every moving part with something like WD-40 while cycling the throttle fully. Watch for slop in the choke & throttle plate pivot bushings, they can wear over time & cause things like vacuum leaks & other problems.
You may also need to re-adjust the idle mixture to account for the lack of the smog input.


Yeah I checked all that stuff when I pulled the carb off and cleaned it really well when I first got it. The jets and all that were completely clogged up. Spent a couple hours cleaning the carb real good and checked all the linkages and all for loose parts and such. I didn't find any issues with any of the parts everything looked good and moved freely.

The choke itself it stops at 1/4" or so open and it doesn't go any further closed. I checked it several times and if I try to push it close it is like a brick wall its not closing anymore than that. It's too far open for a super cold start so I don't quite understand it. When I used to run manual chokes on carbs I'd close it all the way start the engine then back it off about 1/8" or so till it warmed up some then open the choke all the way up. The choke fully closed on this thing is around half the distance that the choke can even open or close so I'm a bit confused on that.

I know fuel is an issue it always is with manual fuel pumps I've never had a carbed engine with a manual pump that I didn't have to pump the peddle to get it started in the mornings. I've always ended up getting annoyed and replacing with an aftermarket electric pump which I'm going to do soon I already have one ready to go.
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Re: Choke issues I think

Postby puttputtinpup » Wed Dec 05, 2018 1:48 pm

May you ought to consider doing the Weber carb upgrade with manual choke and enjoy more power amd economy. That's one of the 1st things I'd do if I ever bought a gasser again.

I had a 74 Dodge Colt and an 81 Luv w the Jap Hitachi carb. Always had a problem. Then again, that was before this forum came along.

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Re: Choke issues I think

Postby RollinCajun » Wed Dec 05, 2018 5:19 pm

puttputtinpup wrote:May you ought to consider doing the Weber carb upgrade with manual choke and enjoy more power amd economy. That's one of the 1st things I'd do if I ever bought a gasser again.

I had a 74 Dodge Colt and an 81 Luv w the Jap Hitachi carb. Always had a problem. Then again, that was before this forum came along.


I've thought about that till I seen the prices $300 is what I paid for the whole truck. lol After putting the electric fuel pump I have on the truck I just started it up it wasn't complete cold but it was barely warm to the touch and it idled perfect. I had a feeling it was a fuel issue. I absolutely hate manual fuel pumps. Worst invention ever. lol
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Re: Choke issues I think

Postby FiatSpider2 » Thu Dec 06, 2018 7:24 am

You need to read the spec book on the carburetor and go through each item in its specific order to verify the choke adjustment and pullback. This data is presented as a check list so you can copy it and check it off as you go through each step. If the linkage is not adjusted correctly or the vacuum pots that articulate it are not connected to the correct ports then you will hit the fast idle stops like a brick wall and the choke will not close all the way however you won't know if in that application the 1/4" gap is considered correct unless you read the spec book and adjustment procedure. The preferred gauge set for choke adjustments that many of us who rebuild carburetors use is a good and complete set of drill bits incremented in 64ths. Note that some of the adjustments are done by bending the external linkages or stop tabs where adjusting screws are not practical. On many vehicles from the 70's and 80's you also needed a propane enrichment tool and gas analyzer to adjust the carb along with a good tachometer.

An electric fuel pump will many times be masking the root cause behind the dry fuel bowl. Yes it will make starting easier since it will refill the dry bowl of the carb before you start the engine however you really need to find out why the bowl is dry since once fuel is in there it should not siphon back out through the fuel line even if the mechanical pump lets fuel drain back to the tank and it should be well over a week before it evaporates enough to cause an issue. Fuel can be weeping out through one of the gaskets or down inside the intake due to a bad check valve or forced through the venturie by a stuck or plugged vent valve allowing pressure to build up inside the bowl while the engine is still warm which can cause dilution of your motor oil however it won't get siphoned out by a faulty check valve in the fuel pump.

Mechanical fuel pumps give you a more disaster proof engine since they will still run even with limited electrical power available to the engine. In critical applications a magneto and mechanical fuel pump are the preferred setup making it so the engine if you can turn it will still run without any battery power available.

BTW: Did you also remove the catalytic converter or just plug the air pipe going to it from the pump? The cat will eventually clog if its left in place with no air being pumped in allowing it to burn off what it collects.
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Re: Choke issues I think

Postby oldestisuzuist » Thu Dec 06, 2018 9:14 am

No fuel visible through the carb sight window or at the wrong level means the float level is incorrect, this is not a fuel pump issue but internal to the carb. This is a separate problem from the choke function but can definitely cause starting & drivability problems & needs to be corrected.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
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Re: Choke issues I think

Postby FiatSpider2 » Fri Dec 07, 2018 6:15 am

oldestisuzuist wrote:No fuel visible through the carb sight window or at the wrong level means the float level is incorrect, this is not a fuel pump issue but internal to the carb. This is a separate problem from the choke function but can definitely cause starting & drivability problems & needs to be corrected.


All part of going through the adjustment check list in the correct order. Whether you are breaking down a carburetor for cleaning or rebuilding you should use the check list to ensure its reassembled along with adjustments checked/corrected in the proper order to ensure correct operation. No voodoo or missed adjustments when you use the checklist. I had my guys circle each step when they started it and slash it when they were finished so even if they got interrupted they would know at a glance where they had started a step and not completed it leaving it part way done or had only finished the previous one.

Some of the simple carburetors may have 50 or less specific steps to assembling and adjusting them while some of the more complex may have over 100 steps to follow.

Motors Manuals even back in the 1920's had the checklists and time has proven them to be best practice when tearing down and reassembling carburetors.

The Carburetor Refactory has the carburetor rebuild kits for the Hitachi carbs commonly used in the 1987 Isuzu pickups.
https://www.carbkits.com/catalog/pr/c5/3/ISUZU
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Re: Choke issues I think

Postby RollinCajun » Fri Dec 07, 2018 1:38 pm

oldestisuzuist wrote:No fuel visible through the carb sight window or at the wrong level means the float level is incorrect, this is not a fuel pump issue but internal to the carb. This is a separate problem from the choke function but can definitely cause starting & drivability problems & needs to be corrected.


It's definitely not a float issue i checked all that when I had the carb out of the truck and cleaning it up really well. The truck has only 98k original miles on it. Everything was super tight no loose linkage or anything like that. I don't like how the choke is not adjustable. After taking a further look at it today I'll have to drill out the choke rivets so I can adjust the choke properly how it's suppose to be.

I drilled out the mixture screw today and adjusted it by ear and it's running way better than before. It actually idles when cold although it's not perfect yet. I need a vacuum gauge to set the mixture right but I don't have one at the moment. Hopefully I'll get one for Christmas this year.

The only 2 issues I'm having at the moment is the choke not working correctly although it idles now it barely does because the choke is not closing enough and its not adjustable thanks to them using rivets on the choke housing instead of screws I'll be fixing that soon. The other issue is when under load driving if I put it to the floor it has plenty of power until it reaches the higher rpm bands and at that point it starts to stutter a little. I'm sure once I get the mixture right with a gauge that should fix it. I rarely doubt the electric fuel pump isn't putting enough fuel at the higher rpms although that is a possibility also.
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Re: Choke issues I think

Postby puttputtinpup » Fri Dec 07, 2018 3:03 pm

If I'm not mistaken, there's a secondary plate that opens with vacuum when conditions are right(speed and rpm and vacuum). I gets its vacuum from below the carb and up through to the upper half of the carb then pulls the secondary open. On my Dodge colt (mitsubushi engine), there was a bad gasket between the 2 halves and vacuum was lost goung to the the secondary diaphragm. It wouldn't open. Ran okay as ling as i didnt need a lot of high end throttle. If i did, it would run badly and starve for the added fuel fuel.

With right much throttle, reach around the carb and try opening the seconday and see if that engine comes to life. The diaphragm may even have a hole in it

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Re: Choke issues I think

Postby oldestisuzuist » Fri Dec 07, 2018 4:19 pm

-"It's definitely not a float issue i checked all that when I had the carb out of the truck and cleaning it up really well"
The float level is what determines the fuel level in the float bowl. If the fuel level is not correct- centered on the sight window bullseye- the float level needs adjusted no matter how clean & tight everything seemed. You adjust the float & fuel level by bending the float tab very slightly until you get the fuel level correct. Have you checked the carb sight window since changing to the electric pump? It may be that the new pump has changed the fuel level.
-"The other issue is when under load driving if I put it to the floor it has plenty of power until it reaches the higher rpm bands and at that point it starts to stutter a little"
This could very well be caused by low fuel level in the float bowl starving the engine for fuel at higher rpms.

The "mixture screw" you drilled out & adjusted is the Idle Mixture Screw & should have very little if any effect on anything above idle. As far as I know this screw & the Idle RPM are the only adjustments on these carbs. Per every FSM I've seen the Idle Mixture & Idle RPM are set with a tach while the dizzy vacuum advance is plugged, no vacuum gauge involved.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.