JEEP falls on its face on acceleration

This past weekend while running my JEEP I figured I need to open her up so I went for a quick rip down the road. Note: my JEEP is not on the road yet. When I accelerated I noticed upon hard acceleration it seemed as it was falling flat on it face. When I let off the throttle a small bit it cleared up. What does this mean? do I need to clean and rebuild the carb? or what.
Thanks for any help.

-Jim

1971 CJ5 :v6: w/HEI
1994 Tucker Sno-Cat T1000
2005 GMC 2500HD duramax diesel

" conserver water drink more beer." -Unknown

 

That is a common symptom of a bad accelerator pump. A high quality rebuild kit is what you need.

Well of course it could be an ignition thing too.

 

i bought my last carb rebuild kit from these guys and will definitely use them again http://www.carburetor.ca/

 

As mentioned, If it's not a dead spot right when you hit the gas...Then I am leaning toward a clogged filter or failing fuel pump.

 

I had an issue with a bad spring on my points. When the engine reved up the points would 'float' and I would get horrible acceleration and sputtering.

 

Good call, Ive experienced that myself.

 

I had a bad stumble last year but it was after a carb rebuild. I worked on it quite a bit but couldn't figure it out. Finally it cured itself and works fine now - never did figure out what the problem was.

 

A "stumble" is normally caused by a lean spot when you goose it. If the accelerator pump is not working or not working well enough to cover up that lean condition...then it will have a hesitation...until the air through the carb gets up enough speed to pull out fuel and make the mixture correct again. So, if it healed itself...it was most likely an accelerator pump issue (clogged or something). Incorrect timing will also make it fall down and hesitate...But normally that won't go away all by itself.

 

They were brand new points too, it left me scratching my head for a LONG time till I gave up and had a mechanic hook up a dwell meter to the thing.

They were the cheapest points NAPA sold for that distributor. I was stupid and should have just gotten the ones the guy at the counter suggested. It's cheaper to get a better part in the first place.

 

The JEEP falls when at higher rpm. Right off the bat is good. If you rev her a bit it runs like a grape ape. The plugs are light brown like they are supposed tobe. Any thoughts?

1971 CJ5 :v6: HEI
1994 Tucker Sno-Cat T1000
2005 GMC 2500HD duramamx diesel

"conserve water drink more beer." -unknown

 

Sorry no points.....HEI ignition. no points but very good point.

1971 CJ5 :v6: w HEI
1994 Tucker Sno-Cat T1000
2005 GMC 2500HD duramax diesel

"conserve water drink more beer." -unknown

 

No problem, just throwing ideas out there.

 

I'm still thinking fuel problem...If it conks out at high RPM...it's most likely running out of fuel...But...You say it goes away if you rev it. So, are you saying that when you rev it a few times...then it will hit high rpm just fine?

 

"falls when at higher rpm"

It could be running out of fuel so check things like fuel pump (good flow at pressure), in-line fuel filter, in carb fuel strainer, float level?, needle valve in carb, jets, pinched fuel line, fuel pickup in tank, etc.

How about timing? Is it good at high rpm?

A weak spark could limit high rpm power - plug gap, plug wires, coil.

I'm just throwing things out to get you looking.

 

Here is what I know:
-Plug wires are new (summer)
- fuel pump is new (September)
- Battery and altenator new (October)
- Falls on its face during hard acceleration.
- Let off a slight bit and it is normal
- If I rev her to high rpm and hold it there it runs fine. (Note: I do this slowly)
- In line filter #1 was changed in May of this year.
- Inline filter #2 will be changed this weekend.
- Haven't checked the screen on the carb yet.
- Still have a rochester 2G
- Sometimes dies while stopped and idleing.
- Just thought of something.....maybe my tank vent line is plugged. I remember someone talking about this in another post.
- I did run out of gas in my barnyard last weekend and when I went to check it out the cap area was sucking in air like a vacuum cleaner. And when I took off the cap it made the thhhhuuuuump sound. I will check this and change the hose if need be.
- Have not checked the internals in the carb yet.
- Checked the color of plugs but not the gap..... I will check this tomorrow.
- could have a bad coil but wouldn't it not run at all?
- Fuel pick up......I will check this too.
Thanks for all the help so far.

-Jim

1971 CJ5 :v6: w/HEI
1994 Tucker Sno-Cat T1000
2005 GMC 2500HD duramax diesel

"Conserve water drink more beer." -unknown

 

If you ran it dry of gas...You may of had some crud in the bottom of your tank...which was now sucked up into the filter or screen.

 

May as well check your mechanical and vacuum adv also.

 

So here is an update....Well I did not get much done with the jeep this weekend. I was messing around with wheel studs on a trailer. Bye the way they were buggers :evil:. I did start her up and ran her around before finishing putting away the haying equipment for the season. After doing this I loaded up the chainsaw and before I left I thought of checking what would happen if I took off the gas cap. Well this prooved the vent was not plugged. no change in fuel delivery. Loaded up the JEEP and headed up the mountain to clear back the fallen trees before the snow falls. got all of this done and then headed back down. I forgot th check the filters for some reason once I was done . Oh well I will check them on turkey day. (no work R)) Other than that I have not accomplished anything I said I was going too. Oh well...slow and steady wins the race.

-Jim

1971 CJ5 :v6: w/hei
1994 Tucker Sno-Cat T1000
2005 GMC 2500HD duramax diesel

"conserve water drink more beer." -unknown