Bad Rings? Head Leak? Causes of erratic Air/Fuel ratio.
- Sluggo
- Wishin' I was Fishin'
- Location: Portland, Or.
- Contact:
- Status: Offline
Bad Rings? Head Leak? Causes of erratic Air/Fuel ratio.
So I got an Edelbrock Air/Fuel ratio meter. Almost wish I hadn't. I'm running very rich (12) most of the time but at idle it bounces back & forth rapidly between 15 (lean) and 12 (rich). If I jet it so that I run stoich while cruising and accelerating then it won't idle and goes way lean.
Most of the stuff I've read says that this is a sign of either improperly seated rings, head leak or low vacuum. I've always suspected that the rings did not seat properly. Being washed in fuel while my carbs were extremely over jetted and never having broken in rings before. I also have oil leaking from the bottom of where the #3 cylinder meets the head. I believe these are related.
Anyway, do you people think this is the cause of my problem. If I jet the carbs to run efficiently I can't idle because of all the blow by and head leak. If I jet them to idle smoothly (somewhat) I'm running very rich.
I plan on replacing the rings and doing a proper break in next week.
Most of the stuff I've read says that this is a sign of either improperly seated rings, head leak or low vacuum. I've always suspected that the rings did not seat properly. Being washed in fuel while my carbs were extremely over jetted and never having broken in rings before. I also have oil leaking from the bottom of where the #3 cylinder meets the head. I believe these are related.
Anyway, do you people think this is the cause of my problem. If I jet the carbs to run efficiently I can't idle because of all the blow by and head leak. If I jet them to idle smoothly (somewhat) I'm running very rich.
I plan on replacing the rings and doing a proper break in next week.
1977 Bus with Sunroof - "Lucky '77"
2000cc Type IV w/Dual Weber 36s,
Aircooled.net SVDA w/Compufire,
Redline Weber Fuel Pump,
Holley Regulator,
Half Ass Brush & Roller Rustoleum Paint Job,
Incomplete Custom Interior,
Dual Batteries,
Crunched Slider Door.
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- vwlover77
- IAC Addict!
- Location: North Canton, Ohio
- Status: Offline
Hmmmmm..... I would be hesitant to accuse the internals just yet.
Have you done a compression test? How about a leakdown test? Those are probably the best way to gauge what's going on in the cylinders.
My carb experience is limited to the simple, single 34PICT3 on upright engines, but can you adjust the idle circuit mixture independently of the main circuit??? Are there separate jets for the idle and main circuits?
Have you done a compression test? How about a leakdown test? Those are probably the best way to gauge what's going on in the cylinders.
My carb experience is limited to the simple, single 34PICT3 on upright engines, but can you adjust the idle circuit mixture independently of the main circuit??? Are there separate jets for the idle and main circuits?
Don
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78 Westy
71 Super Beetle Convertible Autostick
"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen
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78 Westy
71 Super Beetle Convertible Autostick
"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen
-
- IAC Addict!
- Status: Offline
If it idles erratically, pull one plug wire at a time while running. Don't worry about shock just keep your fingers clear off the end of the wire. Isolate the cylinder thats misfiring and fiddle with that carb. It took me a lot of years to figure out cause and effect on dual webers. I now tune them to a rock steady idle with nothing but my ear and the plug wire method. One plug at a time if a plug wire makes a big difference that cylinder is banging away happy. both plugs from the same bank make a big differenc and the plugs on the other bank don't make that big a difference the big difference side has the carb ahead of the other side. I gotta get one of those meter's I'm gonna have duals on my new bus engine as well as my buggy engine.
Bill
Bill
1/20/2013 end of an error
never owned a gun. have fired a few.
never owned a gun. have fired a few.
- bottomend
- Hardliest Working Man In Show Business
- Status: Offline
the engine purrs like a well fed sleeping kitten. Do the plug wire check and see if that shows you anything. I doubt it but hey, at this point anything is possible!
Sluggo keeps telling me taht he didn't really break in the rings like he should have. I'm wondering if thats the issues as well but if I rememeber correctly, his compression #'s are good all around. I know the guides are good cause I either did them myself of watched them being put in and fitted for the valves.
Sluggo keeps telling me taht he didn't really break in the rings like he should have. I'm wondering if thats the issues as well but if I rememeber correctly, his compression #'s are good all around. I know the guides are good cause I either did them myself of watched them being put in and fitted for the valves.
- RSorak 71Westy
- IAC Addict!
- Location: Memphis, TN
- Contact:
- Status: Offline
Is your exhaust system totally leak free? If not this will cause the readings your getting at idle.....Also if the engine burns any oil or has any vacuum leaks the readings will be wacky at idle like your seeing.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
- Sluggo
- Wishin' I was Fishin'
- Location: Portland, Or.
- Contact:
- Status: Offline
I wouldn't say that. This is from a previous thread and 7 months old.bottomend wrote:the engine purrs like a well fed sleeping kitten. Do the plug wire check and see if that shows you anything. I doubt it but hey, at this point anything is possible!
Sluggo keeps telling me taht he didn't really break in the rings like he should have. I'm wondering if thats the issues as well but if I rememeber correctly, his compression #'s are good all around. I know the guides are good cause I either did them myself of watched them being put in and fitted for the valves.
#1 - 100
#2 - 110
#3 - Just over 80 (same weak cylinder as before the rebuild)
#4 - 105
1977 Bus with Sunroof - "Lucky '77"
2000cc Type IV w/Dual Weber 36s,
Aircooled.net SVDA w/Compufire,
Redline Weber Fuel Pump,
Holley Regulator,
Half Ass Brush & Roller Rustoleum Paint Job,
Incomplete Custom Interior,
Dual Batteries,
Crunched Slider Door.
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- Sluggo
- Wishin' I was Fishin'
- Location: Portland, Or.
- Contact:
- Status: Offline
Did some tests.
Vac gauge bounces between 8.5 & 10 at idle.
(dry/oil)
#1 100/115
#2 110/125
#3 90/115
#4 95/120
Did the wire pull test too. All have an effect but #3 barely has an effect.
Plugs were gray.
Air/Fuel ratio monitor shows rich on all circuits but at idle blips back & forth form way lean to way rich. But it's mainly way lean.
I don't think I have a vac leak. Can rings also cause low vacuum?
Vac gauge bounces between 8.5 & 10 at idle.
(dry/oil)
#1 100/115
#2 110/125
#3 90/115
#4 95/120
Did the wire pull test too. All have an effect but #3 barely has an effect.
Plugs were gray.
Air/Fuel ratio monitor shows rich on all circuits but at idle blips back & forth form way lean to way rich. But it's mainly way lean.
I don't think I have a vac leak. Can rings also cause low vacuum?
1977 Bus with Sunroof - "Lucky '77"
2000cc Type IV w/Dual Weber 36s,
Aircooled.net SVDA w/Compufire,
Redline Weber Fuel Pump,
Holley Regulator,
Half Ass Brush & Roller Rustoleum Paint Job,
Incomplete Custom Interior,
Dual Batteries,
Crunched Slider Door.
------------------------------------------------------
- Sluggo
- Wishin' I was Fishin'
- Location: Portland, Or.
- Contact:
- Status: Offline
Not getting a response huh? Am I being shunned?
1977 Bus with Sunroof - "Lucky '77"
2000cc Type IV w/Dual Weber 36s,
Aircooled.net SVDA w/Compufire,
Redline Weber Fuel Pump,
Holley Regulator,
Half Ass Brush & Roller Rustoleum Paint Job,
Incomplete Custom Interior,
Dual Batteries,
Crunched Slider Door.
------------------------------------------------------
- fido
- Getting Hooked!
- Location: Norfolk, UK
- Status: Offline
posted by Twysted1 on shoptalk for a different Q...
I'd say running around 12 isnt too bad - better safe than sorry. I wouldnt want to run any leaner than 14 on an aircooler. Its all load dependant and weather dependant anyway with carbs.If your map values pop all over the place at low RPMs.
(With carbs that will probably happen at idle)
You can stick a new vw fuel filter (plastic, 2 bucks at any parts store) inline with the rubber hose. This helps dampen the oscillations to the map sensor.
Clayton
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73 Westy, 1700 auto, DRLA's, lots of guages...