Cylinder not firing, please help.

billfred1 · Last edited by billfred1 on Mon Feb 16, 2015 7:30 pm; edited 2 times in total

I've been racking my brain on this. Single port stock 1300 with 1600 p/c kit, 1300 heads. New coil, wires, fuel tank, filter, etc. Carb is a 30 Pict 1. Choke set up properly. One small washer under float valve.

It starts and idles good, runs pretty good in the cold. Off idle, at low RPM, I get a little stutter (even when warm). No back firing.

My mechanical fuel pump is putting out 2 PSI (according to my 0-15psi gage).

I've dialed in my fuel/air mix screw per standard.

I've got a 122.5 main jet, 55 pilot jet.

Any thoughts? Should I consider different jetting? Do I need more fuel pressure? It's not a problem that makes it un-driveable, but I know its not right.
_________________
Bill
1966 Beetle

billfred1 · Posted: Mon Jan 26, 2015 4:29 am Post subject:

I found a 125 main jet in an old carb I had. I might try that and see how it goes. From what research I've done, that might be the correct size for this set up anyway.
_________________
Bill
1966 Beetle

madmike · Posted: Mon Jan 26, 2015 5:44 am Post subject:

Hope the plug wires arn't the fancy colored ones Crying or Very sad

pure junk!!!! and drove me nuts too Laughing

what happens when u stomp the throttle? OK? then it's not fuel related Wink

_________________
'Black Ice'Drag Buggy 'Turbo'
Rail Buggy 1915 turbo
76 Drag/Street bug 2180cc 'Turbo' 11:85 @113 mph"If I go any faster I'll burn up the Hamster" ,gets 28 mpg. also 10/09/22 11.90 @115 mph
"If I'm ever on Life Support,UNPLUG Me, Then Plug me back In see if that Works"

billfred1 · Posted: Mon Jan 26, 2015 5:51 am Post subject:

No colored wires. Newer napa ones. Seems ok when I stomp accelerator. Accel pump is working.
_________________
Bill
1966 Beetle

billfred1 · Posted: Mon Jan 26, 2015 8:24 am Post subject:

I guess it could be electrical, but I just can’t figure out what.

Points are good, checked with dwell meter. Distributor is stock and a fresh rebuilt one from “Tasb” (dizzy guy here on Samba). Timing and valves have been set.
_________________
Bill
1966 Beetle

bugguy076 · Posted: Mon Jan 26, 2015 9:30 am Post subject:

Is the fuel level set too high in carb? May be sloching out of bowl on incline.
_________________
Grubby Fingers Racing
1976 Drag Bug
1967 Street Bug

billfred1 · Posted: Tue Jan 27, 2015 5:49 am Post subject:

OK, now I am thinking it might be a spark issue. The 125 main jet didn’t help. I’m confident the carb is correct. It feels good under acceleration, good under steady fast RPM, idles pretty good.

Drove it to work this morning. It really seems like it stumbles the worst off idle. Like after low RPM then getting on the gas. It misses. Now I’m starting to wonder if it’s running rich and maybe fouling out plugs. Under fast RPM it can burn off the fuel, after I’ve sat at a light and then get on it, the plugs are missing because they are soaked with fuel?? Make sense? I guess I’ll pull the plugs tonight and see what they look like.
_________________
Bill
1966 Beetle

HRVW · Posted: Tue Jan 27, 2015 11:15 am Post subject:

I see 1300 heads (small valves) with a correct 30-1 Carb but larger 85.5 p & c that are starving....am I WRONG in my thinking?

Compression also comes under question.

billfred1 · Posted: Tue Jan 27, 2015 11:36 am Post subject:

jhoefer · Samba Member Joined: May 19, 2011 Posts: 987

Is the vacuum advance on your distributor working?

billfred1 · Posted: Tue Jan 27, 2015 11:54 am Post subject:

glutamodo · Posted: Tue Jan 27, 2015 2:12 pm Post subject:

The main jet won't make much/any difference at idle and transition. (Is this a 1300 carb without the power fuel jet, or at 1500 carb with it? You should base your choice on main jet as to whether or not you have that additional high speed enrichment available. )

I'd be looking at how loose the throttle shaft bushings are, how well the accelerator pump sprays and how it is aimed, (sounds like you see issues there already) and how well the distributor is advancing. Is this a correct 113905205K vacuum-only distributor, or something else?

-Andy

billfred1 · Posted: Tue Jan 27, 2015 2:34 pm Post subject:

Thanks Andy,
It's a 1300 carb with no power fuel jet, there's no flange markings. It has a 125 main jet, 125 AC jet.

I have the accle pump jet aimed just at the edge of the throttle plate and carb wall. However, it's function seems sporadic. testing without the engine running, sometimes I get a good stream, sometimes a trickle/mist.

My dizzy is the 113 905 205 K. Recently purchased from Tim Baranay (tasb). Advance seems to be working OK.

I also plan on checking for any air leaks (doubtful, since it idles great). The heat risers are clear, left side doesn't get super hot.
_________________
Bill
1966 Beetle

glutamodo · Posted: Tue Jan 27, 2015 3:18 pm Post subject:

I'd pull the accelerator pump dump tube and backflush it with some carb/choke cleaner and run some of that through the rest of the system too if possible. I remember one road trip where I had to stop on two different occasions and remove gunk that had somehow mucked up my accel pump outlet.

Here's an old thread where I showed how warm a really good heat riser gets up to:

http://www.thesamba.com/vw/forum/viewtopic.php?t=150145&start=27

FYI - there probably is a modification state number on the carb, up to mid 66 it was on the bowl.

Image may have been reduced in size. Click image to view fullscreen.

mark tucker · Posted: Tue Jan 27, 2015 3:50 pm Post subject:

look down the carb with it running to see if it is dripping,use a mirrior so you dont catch you head on fire if it burps. you can also try some platinum sparking bolts. clean the idle circut good with crab cleaner. it sounds lke a idle circut issue.or crabs pissing down thise own throats.

billfred1 · Posted: Tue Jan 27, 2015 3:59 pm Post subject:

Well, a warm engine is much better.

It had been sitting out in the cold all day (25F). It was tough going when I took off. It was missing and sputtering a ton for the first 10 minutes. Had some frost under the carb on the manifold. After about 20 minutes of the engine running, it started running good. Responded well under hard accel.

Got home, the heat risers were warm.

I also checked for intake leaks with the carb cleaner. All good except, I do have a leak around the throttle shaft. It does idle good though.
_________________
Bill
1966 Beetle

billfred1 · Posted: Tue Jan 27, 2015 6:26 pm Post subject:

It is the 47-1 carb.

Also, I pulled the plugs. 3 of the 4 looked kind of lean. However, plug #4 was noticeably darker than the other 3. Is that normal?

_________________
Bill
1966 Beetle

HRVW · Posted: Wed Jan 28, 2015 4:48 am Post subject:

Okay for whatever floats.

As a former engine builder (now retired) the 1300 heads had SMALL valves for the 77mm pistons along with the 30-1 Carb as a combo.

Now you have the 85,5 pistons that need MORE fuel with only SMALL valves (see my drift?)

In addition the carb has a Vacuum leak at the shaft that will suck in air and starve the cyls ...thus the inconsistent idle.

The nozzle that sprays should be replaced if it DRIBBLES or cleaned out with Carb cleaner and blown out with compressed air. There needs to be a strong spray from the nozzle.

Normally the 85.5 would need a 127.5 main jet but here again you have a engine combo that needs working over as a MILEAGE engine that I did DECADES ago with an assortment of jets etc to work with.

My compression statement was in reference to your combustion chamber that determines proper air/fuel ratio needed......here again the heads/cyls/carb combo.

Wish you luck.

billfred1 · Posted: Wed Jan 28, 2015 8:18 am Post subject:

OK thanks. Maybe I'll work on a larger jet.
If I went with a 127.5 main, would I also need to change other jets (I've got 125 air correction and 55 idle)?

I'll also work on the throttle shaft leak.

Maybe I should just pony up for a new carb. Any recommendations on type for my set up?
_________________
Bill
1966 Beetle

glutamodo · Posted: Wed Jan 28, 2015 8:58 am Post subject:

The main jetting for high speeds is one thing to think about, but it won't affect the low speeds at all. You can put the carb top from a 28PICT-1 or a later 30PICT-1 and get a power fuel system outlet for that high speed enrichment.

One thing with the smaller valves and single port heads is you end up high velocity flow though them even at low engine speeds. This should make your engine run actually better at low speeds. But will be restrictive at the high end.

Most carbs will show some leakage at the throttle shaft. But how much play can you feel or see? (engine off, grab the throttle lever and check for play both at the closed position and partway open.)


Hello! Log in or Register \| Help \| Donate \| Buy Shirts	See all banner ads \| Advertise on TheSamba.com

Forum Index -> Performance/Engines/Transmissions		Share:
		Print View

	Forum Index -> Performance/Engines/Transmissions	All times are Mountain Standard Time/Pacific Daylight Savings Time Page: 1, 2, 3 Next
Page 1 of 3