Something went wrong - Fuel issue / Carb? (1 Viewer)

Joined
Jun 2, 2010
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60
Location
Parker Colorado
Please feed me some ideas, here is the synopsys:


76-40, 2F, Aisan carb.

1. Vehicle was running durably, no major running concerns.

2. Then a problem started: Carb started flooding - (fuel bowl filled to max right up the sight glass and over the top, then she was dumping raw fuel under pressure into throttle body- resulting in a wet flood stall. would not idle and would not restart till she dried out a bit , and then within a moment the same thing would happen Assumed stuck float or bad needle valve - also decided it was a good time to do a full carb clean and rebuild.

3 rebuilt carb fully. - used all appropriate parts from carb kit

4. reinstalled carb.

5. She started right up, perfect fuel level in the bowl now. Nice shiny carb.

6. Gave a "tune-up" By setting the following items:
Set mixture ( lean idle drop method )
Set Idle
Set high Idle
Set timing (Set to BB near bottom of window)
then reset them all a second time for good measure
Fresh plugs and points were put in 3 months ago

7. Now running really nice in the shop, she was idling super smooth, Vacuum was at 16in ( I am at 6500 feet)

8. Headed out for a test drive, running fantastic, lots of power, no missing, Checked for engine knock as I wanted to make sure having the BB that advanced was not too far. To do this I drove at 20mph and mashed the gas - no knocking or pinging Just solid torque and no lugging. I drove 25 miles at different speeds and conditions all gears - Running great.

9 NOW THE PROBLEM STARTS

10. I was at a stop sign, and I decided I would "launch" fairly hard, I had done similar just moments before with no issues.

11. it was not an abusive start, but after hitting second, I did go to full gas pedal - On pedal application into 2nd gear, She started going totally flat like it was either flooding out or starving out - and all power was lost. So I clutched, braked and lifted my foot off the gas. came to a stop and she was idiling perfectly.

12. Tried to go again and immedialy on gas she stumbled and stalled. - quick restart, idles perfectly.

13. tried simple gas pedal wlile stopped - she would barly run on any minor push of the throttle, and if you held the pedal there, she would try to rev for an instant, and then would stall - a hard throttle push would get the RPMs up and she would stay running, but it was hard to get past the "dead zone" and even when you did, you could kinda tell something was not right. and if you dropped into the dead zone she would stall - unless you released the pedal and let her go back to idle.

14. Left her idilng, and got out to inspect things, every thing looked fine, fuel level on the mark in the window was spot on. I Hand applied throttle, same symptoms and stalling, The carb seemed noisier than I recall ( air flow & fuel noise - the wooshing sound) It really seems that there is too much fuel dumping in, I can see it and it looks like a lot

15. for some strange reason I flipped the choke closed and instead of stalling as she normally would ( when warm) she kept idling -although much rougher. I hand actuated the throttle, and although she acted "choked", it did not stall.

16. Back in the cab - with the choke still set. I found that I could drive now - although not smooth, and basically to a max speed of 25 Mph in 4th ( i did not want to push her hard) Any time I pushed in the choke - she would die (or try to).

17. I got her slowly home - about 12 miles.

Summary

She was running fine one moment, and then poof something?? happened. I am not sure where to start, and I dont want go all psycho on it.

  • I will recheck vacuum level, have not done it yet.
  • I will check for vacuum leaks with propane and or water spray bottle.
  • I will check the timing
  • Is it possible that something is wrong internal to the carb?? like a spring failed or a BB got stuck ??
  • How do I tell?
  • My gut is telling me that its too much fuel being drawn in, and possibly with the choke set it drops the airflow down enough that it is drawing (sucking) less gas. kinda convoluted as usually the choke makes things richer, but in this case I am wondering if it is actually leaning it out enough to run.
All thoughts are appreciated.
 
Joined
Aug 4, 2009
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Sounds like your float was set/installed incorrectly or is sticking. Your needle valve could also be the culprit. I would take the top horn off and reinspect the float/needle valve installation.
 
Joined
Jun 2, 2010
Messages
60
Location
Parker Colorado
yes, it was originally that problem till I rebuilt the carb... but now the fuel level "looks" to be perfect. Its right at the bottom of the dot on the sight glass. and steady right there.

is it possible that some kind of pressure is building in the bowl?

I have not tried to drive it again today, my first step is going to see if the problem went away - But I doubt it has,
 
Joined
Jun 2, 2010
Messages
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Parker Colorado
I did grab the dizzy after i tightened the clamp - i also re-pointed my strobe light at the timing window after tightening to make sure it dodnt move......

BUT Stranger things have happened- I will re-check it as part of my solution efforts.
 
Joined
May 3, 2009
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I think you've got a bit of debris from the gas tank or the rebuild efforts lodged in a fuel passage. Do a redneck rebuild. Here's my recent experience:

The vehicle was running great. I was pushing things a bit. Fast starts at every stop sign (well, fast for a 40 anyway) and really opening her up on a stretch of highway that I ended up on. Once I got to town it was all 20 mph speed limits so I put-put-putted into a parking space in front of the shop I was going into. Two minutes later I back out. The truck seems to be running a bit odd, I assume a little carbon - whatever. So I basically just idle around the corner to where there was a 35 mph street so I can open her up again. I hit the gas an BOOOOG...cough...sputter...etc. As soon as I took my foot off the gas the truck idled fine. Pulling the choke allowed me to limp home at 10-15 mph (it was raining pretty hard). In the shop everything seemed fine. Idle speed, timing, idle vacuum, no loose hoses or anything. With no load on the engine I could slowly get the rpm up to 2000 or so. Pulling the choke gave me another 500. So I did as good a redneck rebuild as I could under the circumstances. About ten attempts later I was able to de-choke and rev the engine repeatedly. A quick drive showed that all the symptoms were gone. The 40 is still running great.:steer:
 

John Smith

In the garage
SILVER Star
Joined
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Does your fuel cut solenoid on the carb click when you turn the key to the On position?
 
Joined
Feb 6, 2002
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Location
OC, CA
 
 
 
 
I think you've got a bit of debris from the gas tank....
X2

You have to wonder why the float stuck open in the first place and dirt from the tank is at the top of the list. It ran fine for a while, indicating that there isn't anything fundamentally wrong with the carb. Take it for a drive and mash the pedal. When it starts to bog and stumble, put the tranny in N, turn off the key and coast to a stop and check the fuel level in the window. I bet it is low because the tank or filter is clogged and it isn't getting enough fuel.
 
Joined
Jun 2, 2010
Messages
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Location
Parker Colorado
I agree that it could be a fuel-mung caused problem - but its not due to the fuel level dropping in the bowl - I can stand and look at the fuel level and hand actuate the throttle and it bogs and dies as described. all the while the level is at the center of the dot on the window

I really think it is drawing WAY to much fuel, its like a tornado of fuel in there. I can see the perfect little thin stream above the top of the venturi when I lunge the throttle - AND I see the cloud of fuel being drawn from the venturi --- its noisy and she smells like I am sucking on a hooka attached to the tail pipe. ( very rich ) But it is different from when I had a stuck needle valve, then it was just pouring in the fuel as a liquid - now it does look like its vaporized somewhat

All I had time to do today was start it to see if it still was showing the problem. Started from a stone cold start, and the problem persists. fired right up though, and idles like silk

It might be a few days till I can get back out to work on it.

I know I gotta pull the carb off - I just dont know what the heck I am looking for... Especially if it is a "too much fuel issue" never had that before --- its always has been a too little issue. AND I am really not sure I am right on the "too much fuel" assumption.
 
Joined
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Check your fuel line going into your fuel filter. Put a see through fuel filter on and see if you get a bunch of metal flakes. Sounds like filter is clogged and once you hit the gas it starves for fuel.

I had this same exact issue last summer drained remaining fuel from tank and flushed tank and and installed new fuel filter...problem solved
 
Joined
Feb 6, 2002
Messages
15,139
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It isn't likely to be running rich. If it was rich, it wouldn't be the problem you describe. It can run really rich and still run fine at high speed. It will just make a lot of carbon monoxide. If it misfires, bucks and spits back through the carb, it is a lean misfire. Maybe the dirt got into the bowl and is clogging the main jets.

Check for crap in the tank. Take the line off at the filter, blow back into the tank and then let it run into a clear jar to look for pieces of junk.
 
Joined
Jun 2, 2010
Messages
60
Location
Parker Colorado
UPDATE

You-all were mostly right - I was way wrong.

And "Numby" was spot on.

I had a piece of debris perfectly and solidly lodged in the primary jet.

With the carb still on the buggy, I pulled the top off the carb, and then the primary bowl drain (jet access bolt) and then reached through and removed the primary jet and its washer. It was plugged, a little blow of pressure from my lips and the debris popped out. For good measure, I hit all the passages with some pressurized carb cleaner - and reassembled

The fuel filter was new from when I did the carb overhaul, but I changed it out again anyway in case it had a tear? - I am sure my tank is poor, but my filters are not that bad when I change them, I have seen much worse.

I also flushed the fuel line and pump (Downside of the filter), by extending it with some flex tube to a gas can on the floor. kept the buggy running for a moment or two off of fuel in the bowl and some that I sprayed in with a spray bottle... dangerous right? sigh!

I did get some big flakes out of it - obviously the pump does not get an opportunity to flow unobstructed and this allowed the stuff to flow/pump out.

Thanks all! BACK ON THE TRAIL !
 

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