Hesitation when accelerating, Carb, Coil or Ignition - Finally Fixed

[CharlestonG8R]

G'morning Sarge! I'm pretty sure it was closer to 700+ while I was adjusting last weekend - it was NOT less than 650. Bob at TPI asked same thing yesterday when I was placing an order for a dizzy tune up parts (cap, rotor, points, conds). Also, I had the vacuum line attached while setting lean low idle - and that might have given me an improper setup. Bob suggested removing it, re-setting timing first before setting low lean idle.

Hey brother, I've got a brand new Trollhole Dizzy sitting in the garage awaiting installation... Wanna install it and see if it improves anything for you? Just a thought.

 

[ErikinSC]

Thanks Jeremy, but unless there is something wrong INSIDE the carb - that I can't clean it or clear it.... I don't think it is a dizzy issue. Dizzy is a relatively NOS unit (non-USA vac adv) - but it will get a proper full tune up during this next week.

 

[ErikinSC]

Alright, round 7.... Tested the fuel pump per @Pin_Head, I got exactly 1 cup of fuel over 15 seconds of cranking (coil was disconnected).

I am pulling the carb (again) to install a heat shield :

I had to remove the insulator section due to the Weber A/M carb adapter plates. I found an insulator reference from @Weber Sarge - I might order that if this doesn't resolve my issues.

I have a replacement power valve :

And will install that while I have the carb off to install the heat shield. I will also try to clear the jet passages - again with carb cleaner, air and a stiff wire to make sure they are all clear.

here goes nothing...

 

[ErikinSC]

Observation: my float bowl level seems to stay / keep the fuel level just at this level above these inlets.

So any demand for additional fuel would appear to create a starvation effect thru those ports. Yes? No ?

 

[ErikinSC]

Heat shield installed. Check.

 

[Shep59]

I had the same problem in that the engine ran fine but when I would shift gears there would be a slight momentary lag when I engaged the next gear and consequently pressed the accelerator...My fix was the spring pressure adjustment on the accelerator pump lever...I chased this problem for the longest until one day I notice that spring and figured it had something to do with how much gas the pump would push..not sure if your linkage has this spring but it sure cured my issue...

 

[ErikinSC]

IDK Shep.

Disassembled and thoroughly cleaned the carb, AGAIN.

And reassembled.

It's midnight, and the witching hour. I'm taking a shower and going to bed before I turn into a pumpkin. I'll start her up and run her tomorrow.

 

[Weber Sarge]

Fuel level needs to be higher - as the vehicle moves forward the fuel will be forced against the inlets , but only to a point and probably not enough for demand in the wells for the main jets and emulsion tubes . Close up the float measurement by about 3mm , should fix it .
Sarge

 

[ErikinSC]

Sounds like a god idea @Weber Sarge warming it up now to reset lean low idle.

 

[ErikinSC]

New Developement. Got home, removed air cleaner, I saw smoke vapors and I can hear the fuel boiling inside the carb. Checking bowl level now.

 

[ErikinSC]

But, with my Aisin... I had the same problem - e.g. while driving along, fat, dumb and happy, I would reach a hill and 44 would stumble and try to die. If I pushed in the clutch and pumped the gas pedal, the engine would recover. As soon as I let the clutch out and tried to continue, the stumble and die.

When I called @FJ40Jim (from the side of I-15), he said, "It has to be either fuel starvation or bad coil. Since coils seldom fail, unless they dump their oil and you can't see any oil under your coil, my vote is fuel starvation". He suggested I recreate the problem and throw it into neutral, turn off the key and coast off the highway. Then check the sight-glass (which you don't have). He said, doing it in the listed order would 'leave everything exactly as it was when the problem occurred". He also said, "You can't recreate this without actually driving it under
load, it won't occur when it's sitting still because the secondary doesn't kick in and it's the secondary that demands the big gulp of fuel".

When I did that, it was obvious there was no fuel in my sight-glass... e.g. it was obvious the issue was fuel starvation.

Maybe doing what he suggested will help you diagnose the problem to fuel starvation... even without a sight-glass... I don't know...

Anyway, once I knew it was fuel starvation, I stared checking back upstream on the fuel feed line, from the carb and found that one of (I had two) my glass fuel filters (with replaceable filter elements) wasn't sealing properly (when screwed back together) and the fuel pump was sucking a ton of air, when the throttle demanded a lot of gas - e.g. under load.

So, your problem could be fuel starvation and the culprit could be a new fuel fuel filter (mine was brand new) - I would try a different fuel filter and see if it helps.

hth

Danny- I finally paid attention and did what you and @FJ40Jim suggested. when I pulled into the driveway, shut it down, jumped out, opend the hood, and pulled the air cleaner. saw misty smoke (gas boiling) and I could hear the gas bubbling inside the carb. Removed the top plate of the carb, and sure enough, fuel is at same level as in photo in #84, but it was very hot to touch....

So - I need to research the gas boiling in carb and order a non-metallic carb insulator that mounts on the intake manifold.... maybe...

 

[sggoat]

Headers cured the same prob on my 77------had a heat shield, but never had to install it after the headers went on

 

[Weber Sarge]

Carb boil is a pain on a Cruiser , hence why I wouldn't build setups for them - not to mention crappy kit parts that really don't work very well . If you go the insulator route , it would have to be at least 10mm thick - not the thinner 5mm one and I'd still use the oem heat shield . The stock exhaust manifold creates a pretty bad oven below the carb and that is why many models came with a carb fan - they really needed it .
Sarge

 

[Solace in Solitude]

Erik,

I don't recall whether you run headers or an exhaust manifold.

If headers, about a year ago, @Fast Eddy mentioned a ceramic heat shield (from sor.com, IIRC), to protect the intake manifold from the heat if the headers. Like Gary (@sggoat), I haven't needed the heat shield.

If exhaust manifold, I'm not sure whether the heat shield can be used between intake and exhaust manifolds. I haven't run the exhaust manifold.

You should be able to find a used OEM carb isolator/insulator, if you don't have one... It's about 3/8" thick IIRC., roughly 10mm. Try Georg (@orangefj45 ).

As @Weber Sarge,implies, if you aren't running a carb fan, perhaps you should... Either an oem setup or a homemade setup, like sggoat, or a combination of the two... Like me. I have an OEM fan that I was running,with a manual timer... But, I decided I wanted to be able to better control it in the extremes of Nevada, so I changed to a toggle switch. I can monitor temp and turn the fan on and off, as needed.

Hth

 

[ErikinSC]

Danny,

I'm stock exhaust, newly acquire OEM heat shield....but I cut out the insulator due to running the Weber carb.... Instead of modifying it. I've ordered a car insulator (1/2" thick) with hopes I can get away from the direct heat transfer thru the carb base adapter.

I have purchased a carb cooling fan also, but I understood it was designed to run AFTER the motor was turned off. I'm sure I could wire it up off the key - or like you off a switch.

Waiting for parts.... Beating my head against this wall.

If I only drive for a max of 15 mins.... You'd never know there was an issue. Too bad I like to drive more than that.

 

[joyRidaz]

I'm just catching up on this thread now. So pardon timing. About twenty posts back, we dismissed the vacuum leak... So not sure if the relevancy

Probably not the cure/cause, but I had a heat related vaccuum leak that only appeared after my rug was pretty hot. An old hose got looser as the heat amped up. Took me a while to chase down, cause it never appeared while idling in my driveway as I tinkered under the hood.

Two other things, for the gurus to set us straight on... I recall two heat related flaps... One on air intake, and another somewhere off the exhaust manifold maybe. I'd guess if they seized up it might make the heat situation worse.

I'd like to hear if anyone has found a way for the fan to kick in after hitting a specified temp.... Cause I agree with @ErikinSC that it turning on after the truck is off only helps for the next start.

Cheers

 

[Solace in Solitude]

i like driving more than 15 minutes too!!

My carb fan relay wiring has issues and I didn't want to mess with it. It's generally hot when it's hot in Nevada...

So I wired mine to a switch on the dash... I can turn it on for the duration of my drive, if it's hit out.

@GA Architect, IIRC, worked out a temp-based method for running the fan... In THIS THREAD, I think... Maybe GA can chime in... My 'borrowed' internet connection sucks this evening!

Erik, if you are boiling the gas out of your carb, I think the best first step is the heat shield and the carb insulator/isolator...

Can't you use it with the Weber? The full insulator/isolator is more than the block under the carb. It has a metal shield that covers much off the intake manifold.

Another thought is, how much heat is your carb getting from the head, under the air rail? I use an infrared thermometer to see what the temps are around my carb.

The cooling fan will help, but better to try to keep the heat down, using shields and isolators.

Also, make sure you have your fuel feed line in heat shield sleeves, as it comes around the front of the engine, and over the manifold. Your fuel could be almost boiling before it gets to your carb.

Hth

 

[ErikinSC]

i like driving more than 15 minutes too!!....

Erik, if you are boiling the gas out of your carb, I think the best first step is the heat shield and the carb insulator/isolator...

Can't you use it with the Weber? The full insulator/isolator is more than the block under the carb. It has a metal shield that covers much off the intake manifold.

Another thought is, how much heat is your carb getting from the head, under the air rail? I use an infrared thermometer to see what the temps are around my carb.

The cooling fan will help, but better to try to keep the heat down, using shields and isolators.

Also, make sure you have your fuel feed line in heat shield sleeves, as it comes around the front of the engine, and over the manifold. Your fuel could be almost boiling before it gets to your carb.

Hth

Danny, I did install the OEM heat shield, pics in post #85 & #87. The 'boiling fuel' was an misinterpretation of the symptom by me.... I was blinded with thinking I knew what the problem was, and kept creating proof.... trying to improve my skills. The education process has been frustrating.

That's generally why Weber installs get such a bad rap - the adapter kits for the Cruisers are a joke . Vac leaks also result in false lean best idle settings which takes all the good points of the Weber away in a hurry .
Throttle response should be very crisp and powerful if everything is right , including the timing and ignition systems .
Sarge

I failed to follow some simple steps, y'all. I ASSumed the ignition was fine, and ignored what our locoal LC Guru suggested I start with. I never actually checked the coil, or measured resistances, I just read that the coil would either work or it wouldn't. I could have simply checked the spark plug then... and saved some serious time.

So today, when i limped my frustrated, beaten self back over the bridge, slowly loosing power, until I could barely chug my rig through neighborhood streets at 15 mph, my favorite LC Guru drives up next to me - to call me out for driving so slowly.... Embarrassed and with no better option (because I would not listen to what I was told to do at the beginning) - i limped back to @lextechautomotive. I shamefully pulled into the parking lot and parked in disgrace behind the last bay, out side in the sun. I talked to Glenn... and recounted the symptoms, and he remembered asking me to check and replace the coil. I told him had not, because it would run fine until the motor warmed up.... and I uh, um, duh, err, eh....

Glenn leant his ear, and did what magical LC gurus do - he LISTENED to the motor, he held the carb, he pullled the throttle, and then he poured gas down her throat..... and proclaimed that it was not a fuel problem. He pullled a plug wwire, checked for spark...and nada (well, barely). So he grabbed a plug, plugged it into the wire, and still - nilch. not enough spark to notice. Glen checked the coil wire, and we were actually GOOD from the coil to the dizzy....

Glen told me to wait for it to cool off, drive home, replace the points and condensor... and all would be fine. Luckily, I had another set of points and a condensor in the glove box (sometimes I get lucky). I replaced the points and condensor, and found the contact on the movable side of the points was totally gone.... I rocked the truck in 4th gear to get the points ready to set, gappe dthe pints to .028..... and WALLA !!!!!! She runs again! I took her for a 40 miute ride around Charleston, and never missed a beat!

Thanks to all for the suggestions, ideas and explanations. I will say, that before this, i would not have thought i would be compfortable taking a carb apart..... for cleaning, rebuilding, probably not even to just dismantle one.... but Ive done it now enough times on this Weber 38.... I might be able to help someone else in the future and know what Im doing..... I also have a new found understanidngin of how points, condensors and spark contribute to the ignition process - and how hesitation is not necessarily a carb problem. Lesson Learned.

 

[Solace in Solitude]

Great news Erik! Glad it's finally resolved and you can drive longer than 15 minutes!!

 

[PabloCruise]

Danny, I did install the OEM heat shield, pics in post #85 & #87. The 'boiling fuel' was an misinterpretation of the symptom by me.... I was blinded with thinking I knew what the problem was, and kept creating proof.... trying to improve my skills. The education process has been frustrating.



I failed to follow some simple steps, y'all. I ASSumed the ignition was fine, and ignored what our locoal LC Guru suggested I start with. I never actually checked the coil, or measured resistances, I just read that the coil would either work or it wouldn't. I could have simply checked the spark plug then... and saved some serious time.

So today, when i limped my frustrated, beaten self back over the bridge, slowly loosing power, until I could barely chug my rig through neighborhood streets at 15 mph, my favorite LC Guru drives up next to me - to call me out for driving so slowly.... Embarrassed and with no better option (because I would not listen to what I was told to do at the beginning) - i limped back to @lextechautomotive. I shamefully pulled into the parking lot and parked in disgrace behind the last bay, out side in the sun. I talked to Glenn... and recounted the symptoms, and he remembered asking me to check and replace the coil. I told him had not, because it would run fine until the motor warmed up.... and I uh, um, duh, err, eh....

Glenn leant his ear, and did what magical LC gurus do - he LISTENED to the motor, he held the carb, he pullled the throttle, and then he poured gas down her throat..... and proclaimed that it was not a fuel problem. He pullled a plug wwire, checked for spark...and nada (well, barely). So he grabbed a plug, plugged it into the wire, and still - nilch. not enough spark to notice. Glen checked the coil wire, and we were actually GOOD from the coil to the dizzy....

Glen told me to wait for it to cool off, drive home, replace the points and condensor... and all would be fine. Luckily, I had another set of points and a condensor in the glove box (sometimes I get lucky). I replaced the points and condensor, and found the contact on the movable side of the points was totally gone.... I rocked the truck in 4th gear to get the points ready to set, gappe dthe pints to .028..... and WALLA !!!!!! She runs again! I took her for a 40 miute ride around Charleston, and never missed a beat!

Thanks to all for the suggestions, ideas and explanations. I will say, that before this, i would not have thought i would be compfortable taking a carb apart..... for cleaning, rebuilding, probably not even to just dismantle one.... but Ive done it now enough times on this Weber 38.... I might be able to help someone else in the future and know what Im doing..... I also have a new found understanidngin of how points, condensors and spark contribute to the ignition process - and how hesitation is not necessarily a carb problem. Lesson Learned.

So it was points, NOT coil, eh?