Engine Idle Issues (1 Viewer)

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Joined
Dec 24, 2013
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Location
Toronto, ONT
Basically ...it just does not idle. As long as I am pumping the gas pedal, its great; but as soon as I let go...its off!

I've checked the fuel cut-off solenoid cable, with key in ignition, I can hear a slight clicking noise if I discount / re-connect the cable. I've checked my fuses; they are all good.

2+ weeks ago had the same problem; the mechanic replaced the fuel filter and disassembled / cleaned the carburetor. So this time, the fuel filter is clean. I did not take it out to check the flow but looks clear with no visible dirt / debris inside.

I'm totally stumped...would appreciate some advise.
 
Could it be a piece of debris stuck in the idle circuit of the carb? If it was recently rebuilt you may not even need a new set of gaskets. Disassemble, run small wire through all circuits and reassemble. Good luck.
 
great time to learn how to inspect an engine without a computer.

1. Connect vacuum gauge directly to manifold vacuum barb. If less than 18inHg, find and repair vacuum leak.
2. If idle solenoid clicks strongly and reliably (slight click isn’t confidence-inducing for me) then move forward.
3. What changed beforehand to issue. Have you done any work at all? (This is very important to disclose all work done prior).
4. Does choking the engine resolve/improve idle?

Your issue usually is very indicative of a failed/intermittent solenoid and or a bad vacuum leak.
 
Start simple: check all your vacuum lines, are the connected? Cracked? Brittle? Several times I’ve had similar symptoms come down to vacuum leaks.
 
Will it run at higher rpm without pumping?
 
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great time to learn how to inspect an engine without a computer.

1. Connect vacuum gauge directly to manifold vacuum barb. If less than 18inHg, find and repair vacuum leak.
2. If idle solenoid clicks strongly and reliably (slight click isn’t confidence-inducing for me) then move forward.
3. What changed beforehand to issue. Have you done any work at all? (This is very important to disclose all work done prior).
4. Does choking the engine resolve/improve idle?

Your issue usually is very indicative of a failed/intermittent solenoid and or a bad vacuum leak.
Hi Nate

Thanks for your list of checks.
  1. As a solo mechanic can't keep the engine running to measure the vacuum in the current condition. Previously, when things were good, I was getting ~15 inHg. I recently changed the brake booster and installed a new vacuum hose.
  2. The clicking is very weak / faint. Decided to purchase a new solenoid valve (CCOT as it for $16); but it might take 2-3 weeks to get here.
  3. I have been doing a radiator flush the previous week. Completed 6 flushes and still going. Don't think this has any impact. But, just before the problem arose, we went into the desert and got stuck in the mud. Really had to apply alot of power to get out; was concerned maybe some dirt / debris got into the carburetor. Fuel filter (new) was clean. The air filter is clean too. Not sure about the state of the inside of the filter housing (the bit from the filter to the carburetor). Eventually; had to be pulled out. Drove back to the farm and hosed it down (from the outside only). That's when the problem first started. Drove home (~2hrs) including stop/go in traffic. Stopped along the way, and no issues. Next day, could not hold in idle.
  4. My choke cable is not connected. I cant figure out how to re-connect? As long as I pump the gas ...the engine is turning. The minute I'm in neutral the engine cuts out.
I took off the air filter today and applied a healthy dose of carburetor cleaner fluid. That seemed to do the trick and it was running fine. After a few hours, the problem was back. Tried the carburetor cleaner fluid again and no luck. I strongly suspect its the solenoid valve.

I am out of time, thinking I might as well bite the bullet and purchase a new carburetor.
 
Can't just spray carb cleaner into it and have it do anything, you need to remove the carb to completely disassemble to clean the parts

Or have a mechanic do it but just spraying won't do anything

I would also spray around the carb for vacuum leaks. Search around lots of info on this
 
Close the choke manually on the carb and attempt to start up. You can use the choke/throttle on the carb to keep it alive. If choking helps - it’s a vac leak, which if 15inHg is the vac you had before hand- that’s low and indicative of a manifold gasket leak or something missing/cracked off of intake manifold.
 
Close the choke manually on the carb and attempt to start up. You can use the choke/throttle on the carb to keep it alive. If choking helps - it’s a vac leak, which if 15inHg is the vac you had before hand- that’s low and indicative of a manifold gasket leak or something missing/cracked off of intake manifold.
Thanks @mattressking

I'm trying to understand what you are saying; please excuse my the basic questions...

From my understanding, I've got 3 vacuum lines :
1- From the PCV to the Inlet Manifold (connects below the carburetor directly on the manifold)
2- From top end of the engine block to the Carburetor intake
3- From brake booster to intake manifold. Recently installed a new hose; maybe the connector to the intake manifold is leaking?

Have I missed one?

IMG_3666.JPG



IMG_3708.JPG


This is what I don't understand..
1- If there is a leak on the PCV hose / the brake booster hose, then dirty air is being sucked directly into the engine. This is not good, but it should not effect the carburetor. Right?
2- If there is a leak on the engine block hose, ok, then dirt gets directly into the carburetor. Understood ...not good either.
3- If the vacuum is roughly 15 inHg; and you mentioned that's low, which points to a potential gasket leak. This would effect the performance of the engine overall, but not the carburetor?

Both times this has happened after I applied alot of force / torque; the first when I was stuck in the mud while the second I was stopped on a slope and did not want to roll back (the car behind me was at my bumper). Im not sure if that related or just coincidence.

I am buying a new OEM carburetor. Bought new PCV and replacement hoses. Will also change the engine block hose and attach proper o-rings.

Hoping that would solve the problem. Will have to live with the gasket problem for now.

Appreciate your guidance / help.
 
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Why by a new carb when it costs you less than $ 50 for a rebuild kit?--you get to learn the carb circuit and how it functions--Invaluable later on)Follow Pinhead's video--
Vacuum is a great t'shooting tool---
 

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Thanks @mattressking

I'm trying to understand what you are saying; please excuse my the basic questions...

From my understanding, I've got 3 vacuum lines :
1- From the PCV to the Inlet Manifold (connects below the carburetor directly on the manifold) Yes
2- From top end of the engine block to the Carburetor intake. What is this exactly, do you mean intake manifold gasket? If so yes, also the carb insulator is another.
3- From brake booster to intake manifold. Recently installed a new hose; maybe the connector to the intake manifold is leaking? - Maybe but if its tight, its a very small leak.

Nope, but if you have 15inHg you have a big leak from intake manifold gasket (likely). Every truck usually drops to 15inHg when the manifold gasket leaks, so you need to R+R the manifold and check for flatness then reassemble with OEM or a good quality gasket. There's a few tricks here to avoid machining I can go into as well.
Have I missed one?

This is what I don't understand..
1- If there is a leak on the PCV hose / the brake booster hose, then dirty air is being sucked directly into the engine. This is not good, but it should not effect the carburetor. Right?
2- If there is a leak on the engine block hose, ok, then dirt gets directly into the carburetor. Understood ...not good either.
3- If the vacuum is roughly 15 inHg; and you mentioned that's low, which points to a potential gasket leak. This would effect the performance of the engine overall, but not the carburetor?

Both times this has happened after I applied alot of force / torque; the first when I was stuck in the mud while the second I was stopped on a slope and did not want to roll back (the car behind me was at my bumper). Im not sure if that related or just coincidence.

I am buying a new OEM carburetor. Bought new PCV and replacement hoses. Will also change the engine block hose and attach proper o-rings.

Hoping that would solve the problem. Will have to live with the gasket problem for now.

Appreciate your guidance / help.

1. Dirty air....if you mean the quality of the air, that does not matter. Air leaking is the issue, it causes the air/fuel mixture to become unbalanced and cause running issues (in this case overly lean because of excess air). With a carbureted vehicle there isn't a computer to adjust for more air, therefore you must fix the leak and retune the carb/timing once the leaks are gone. At sea level you want 18-22inHg but closer to 20-22 is where you want to be. At 15inHg when you tune the carb you are attempting to add more fuel and reduce air however what you are actually doing is choking the engine in attempt to mask the air leak by adding fuel. The other way (lazy and hack mechanic method) is to add timing, so make sure you are between 7 and a max or 10deg at idle (MAX 950rpms).
2. See 1.
3. This directly relates to poor function of the carb because your carburetor controls the mixture of air and fuel into the cylinders. It uses engine vacuum to force air and fuel through the circuits to control mixture. So it is a requirement to fix the leaks else you are masking your issues with an improperly tuned carburetor and poor timing.

I won't stop you from getting a new OEM carburetor as the H3662 (Fuji replica) is an OK carb however I recommend going through them, I've seen dropped emulsifier tubes, failed/failing fuel cut solenoid o-rings and floats that absorb the water in fuel.
 
Why by a new carb when it costs you less than $ 50 for a rebuild kit?--you get to learn the carb circuit and how it functions--Invaluable later on)Follow Pinhead's video--
Vacuum is a great t'shooting tool---

@sggoat - I'm short of time, packing up and headed back to Toronto. I was able to get an OEM carburetor, parts are readily available here. I've kept the old carburetor and ordered a kit from CCOT Also ordered a separate solenoid valve, but it came with two points. I will play with it when I have time back in Toronto.

Thanks for the vacuum list; great reference.


Nope, but if you have 15inHg you have a big leak from intake manifold gasket (likely). Every truck usually drops to 15inHg when the manifold gasket leaks, so you need to R+R the manifold and check for flatness then reassemble with OEM or a good quality gasket. There's a few tricks here to avoid machining I can go into as well.


1. Dirty air....if you mean the quality of the air, that does not matter. Air leaking is the issue, it causes the air/fuel mixture to become unbalanced and cause running issues (in this case overly lean because of excess air). With a carbureted vehicle there isn't a computer to adjust for more air, therefore you must fix the leak and retune the carb/timing once the leaks are gone. At sea level you want 18-22inHg but closer to 20-22 is where you want to be. At 15inHg when you tune the carb you are attempting to add more fuel and reduce air however what you are actually doing is choking the engine in attempt to mask the air leak by adding fuel. The other way (lazy and hack mechanic method) is to add timing, so make sure you are between 7 and a max or 10deg at idle (MAX 950rpms).
2. See 1.
3. This directly relates to poor function of the carb because your carburetor controls the mixture of air and fuel into the cylinders. It uses engine vacuum to force air and fuel through the circuits to control mixture. So it is a requirement to fix the leaks else you are masking your issues with an improperly tuned carburetor and poor timing.

I won't stop you from getting a new OEM carburetor as the H3662 (Fuji replica) is an OK carb however I recommend going through them, I've seen dropped emulsifier tubes, failed/failing fuel cut solenoid o-rings and floats that absorb the water in fuel.

@mattressking - thanks for all the detail / explanation. Got it....vacuum leak means the air-fuel mixture is not correct / balanced.

I got a Mitsutech carburetor. Managed to do the switch and everything is ok. Got the mechanic to do the be final adjustment. Need to learn this art.
 

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