Need Diagnostic Help

[GERMS]

I realized my L20B is running rough, it has a cannon side draft intake with one 40 Weber. So I took number one spark plug off and nothing happens, engine does not rev down. Number two is the same way. Number three and four show the proper signs of them working fine, engine revs down. I get spark at number one and two spark plugs. Did a compression check and has around 150 PSI on each cylinder.

 

Took it to a mechanic and said he would need to re do a compression check, if that shows good, a valve adjustment might be needed. If that is okay then he would have to check the block and head for cracks.

 

Anyone who dealt with something like this know what could be the problem? A friend told me it could also be the weber carb, maybe its not squirting fuel properly on that side.

 

Any advice would be much appreciated, thanks! :cool:

[Pumpkn210]

If the intake is seperated then it very well could be the carb! I would check that out before paying a mechanic to look for all that other crap. I had fuel prollems in one of my carbs and it acted like you state!

[hang_510]

leak down test!

 

spark seen where? on the removed plug?

 

 

adjust the valves anyway

 

 

the carb isnt likey to fail on 1 side, maybe if a jet were clogged, check that too

[datzenmike]

I realized my L20B is running rough, it has a cannon side draft intake with one 40 Weber. So I took number one spark plug off and nothing happens, engine does not rev down. Number two is the same way. Number three and four show the proper signs of them working fine, engine revs down. I get spark at number one and two spark plugs. Did a compression check and has around 150 PSI on each cylinder.

 

Took it to a mechanic and said he would need to re do a compression check, if that shows good, a valve adjustment might be needed. If that is okay then he would have to check the block and head for cracks.

 

Anyone who dealt with something like this know what could be the problem? A friend told me it could also be the weber carb, maybe its not squirting fuel properly on that side.

 

Any advice would be much appreciated, thanks! :cool:

 

If you got 150 compression then the valves are fine. Tell your mechanic there's no need. You can do a bad compression check but it can only be low. You can't do one and get high numbers. Check the 1 & 2 plugs are they white?

[DISLEXICDIME]

sounds like plugs or wires

[datzenmike]

I'm thinking if the porcelain on the electrodes is white, it's running lean and the carb on those two cylinders is bad.

[I'm BLUE]

BRAND of plugs ? (NGK :D ) and what gap ?

[GERMS]

BRAND of plugs ? (NGK :D ) and what gap ?

 

I think I have them as .040, and yes they are NGK :cool: All new plugs and wires.

[GERMS]

If the intake is seperated then it very well could be the carb! I would check that out before paying a mechanic to look for all that other crap. I had fuel prollems in one of my carbs and it acted like you state!

 

Not sure what you mean by separated, but I will tell you this...I can see a few drops of fuel falling from the redline air filter on my weber. :blink:

[GERMS]

leak down test!

 

spark seen where? on the removed plug?

 

 

adjust the valves anyway

 

 

the carb isnt likey to fail on 1 side, maybe if a jet were clogged, check that too

 

Yes the plugs have spark.

[GERMS]

I'm thinking if the porcelain on the electrodes is white, it's running lean and the carb on those two cylinders is bad.

 

I'll check that out tonight, if it is the carb, will I have to get a specialist on webers? Or can I look into this myself? I'm pretty good with attention to detail if someone let's me know what to do. :D

[datzenmike]

Not sure what you mean by separated, but I will tell you this...I can see a few drops of fuel falling from the redline air filter on my weber. :blink:

 

This could be from two things.

 

The filter could be getting wet from standoff. This happens when the motor has a cam with late closing intake or short intake runners. At low speeds the piston is rising up the bore while the intake valve is still open causing some of the fuel/air to be pushed back out the intake valve. This pressure wave will reverse the air flow at the carb opening and fuel will wet the filter. You can sometimes see this as a fog of fuel droplets just above the carb throat. A damaged valve could also cause this but your compression is 150 so I doubt that.

 

The float is sticking or set wrong and the carb fuel bowl is over filled.

[ggzilla]

Remembers the weber feeds 1&2 from on barrel, and 3&4 from another. So it's quite likely the carb is not feeding the front two cylinders correctly. Or that you have a massive air leak on that side.

[banzai510(hainz)]

open top of sidedraft carb and there could be a jet block emulsion tube set up on that side.

Make sure they are screrwed IN all the way . My Mikunis would unscrew themselves out soemtimes givn a cut out or run out of gas feeling.

 

adjust valves anyways. to be certain bu like mik said you got 150 which is about right.

[GERMS]

Okay, I finally had the chance to check things out on my day off. Spark plug electrodes are almost all white, just a tiny smudge of light brown. Lean?

 

Opened the top of the weber, nothing seemed to be unscrewed or blocked as far as I can tell.

 

What's the next step? Should I take the carb off and rebuild it (clean it throughly)? Any way to inspect it and see if its working properly before buying a rebuild kit and taking it apart? See if it squirts as it should?

[banzai510(hainz)]

ck the jets if plugged

[banzai510(hainz)]

ck the jet block as I assume that side feeds #1&2 cylinders if a not crossover Lynx manifold.

 

Now you say thet 1 & 2 plugs are very clean. Swap them with 3&4 and see if they end up getting clean(white)

 

what can happen is a small head gasket leak can suck water in cleaning the plugs. or if you run a water passage tyep head it can suck water thru the intack manifold gasket. maybe but a new intake exhaust gasket. If you have loose bolts youll know if this could be it.

 

as for the compression if it reads 150 I think the valve lash is good. But I would ck the valve lash in the first place. Ive never done a compression ck myself. I go right for the valve lash if I loose a spark(bang)on a cylinder.

[GERMS]

ck the jet block as I assume that side feeds #1&2 cylinders if a not crossover Lynx manifold.

 

Now you say thet 1 & 2 plugs are very clean. Swap them with 3&4 and see if they end up getting clean(white)

 

what can happen is a small head gasket leak can suck water in cleaning the plugs. or if you run a water passage tyep head it can suck water thru the intack manifold gasket. maybe but a new intake exhaust gasket. If you have loose bolts youll know if this could be it.

 

as for the compression if it reads 150 I think the valve lash is good. But I would ck the valve lash in the first place. Ive never done a compression ck myself. I go right for the valve lash if I loose a spark(bang)on a cylinder.

 

banzai thanks for your help, but, I just don't know what I'm looking for, I took the cover off where the butterfly nut is, unscrewed the "things" that are on there to check them out but not sure if that's what I'm looking for, anyway you can give me exactly what I have to look for, I don't even know what the jet block is. I'm getting very close to taking it to a mechanic and get ripped off like always haha.

 

A picture would be nice with what to look for circled in red or something. Just an idea. :blink:

[banzai510(hainz)]

sorry I cant post photos anymore on ratsun . I need a new broswer.

 

I dont know Weber buy Mikunies. you see a brass jet and it will have a screw driver slot. If dont right you can take the whole assembly out. there is like 3 pieces to it.

 

also before you do this put your finger in the side of the carb and make sure that aire funnel(venturi thing is not wiggleing around. this will cut off the air at higher speed.

[GERMS]

Hey guys, well I had to get help from a mechanic, turned out to be the previous head gasket was placed without cleaning from the older gasket. So he surfaced it, adjusted valves, fixed exhaust leaks, and now it runs good.

 

But I have a new problem that I'm probably going to complain about to the mechanic because it didn't do this before.

 

Even with all cylinders burning, it still seems weak when going up hills and on the freeway when I try to give it more gas; it bogs and backfires. The only way it won't bog and backfire is by keeping my foot ont he gas very light...but that's a problem when going up a hill because it rides up like a turtle.

 

Is this a jet size issue? Mechanic said it was timed and tuned correctly, and it sure sounds like it idles very nice.

 

On a 40 weber sidedraft, what should be the correct jet sizes for a 2.0 lt l20B?

 

Thanks.

[banzai510(hainz)]

this is just me

Ever L motor person should have a spare L series intake and a weber 32/36 ready to bolt on. So 1 can trouble shoot.

 

I hate those single sidedraft carb setups. If you got a Lynx manifold that is better.

 

as for the head gasket issue . You never said it was overheating or anythhing or loosing water So WE assumed it was good. Compression is compression. So I cant see how that made a difference and you could have adjusted the valves yourself.

 

OK it idles fine.

what is the timming? Look closely and see if the distributor is cranked all the way to one side of the timming plate to get it to time. If it is then maybe the tooth is off and when you gas it it advances out of time.

Other option is the carb just isnt set right.

[datzenmike]

as for the head gasket issue . You never said it was overheating or anythhing or loosing water So WE assumed it was good. Compression is compression. So I cant see how that made a difference and you could have adjusted the valves yourself.

 

 

Other option is the carb just isnt set right.

 

Even with all cylinders burning, it still seems weak when going up hills and on the freeway when I try to give it more gas; it bogs and backfires. The only way it won't bog and backfire is by keeping my foot ont he gas very light...but that's a problem when going up a hill because it rides up like a turtle.

 

 

Your compression was 150 across you said so how would a new h/g help? And how is it running any better?

 

Check the plugs and read them. White is lean, black is super rich. Light tan is close.

[GERMS]

this is just me

Ever L motor person should have a spare L series intake and a weber 32/36 ready to bolt on. So 1 can trouble shoot.

 

I hate those single sidedraft carb setups. If you got a Lynx manifold that is better.

 

as for the head gasket issue . You never said it was overheating or anythhing or loosing water So WE assumed it was good. Compression is compression. So I cant see how that made a difference and you could have adjusted the valves yourself.

 

OK it idles fine.

what is the timming? Look closely and see if the distributor is cranked all the way to one side of the timming plate to get it to time. If it is then maybe the tooth is off and when you gas it it advances out of time.

Other option is the carb just isnt set right.

 

Well, the man said the person who put a new head gasket didn't scrape the previous gasket off too well, so in between piston one and two it wasn't set on flat. Which is why it was giving me good compression while doing one at a time.

 

I don't really have any experience with these things, I've spent so much time on my 68 dodge dart.

 

I'm getting tired of that side draft Weber, its a hog, it doesn't accelerate quick enough, and I have no clue why! Someone please come help haha

 

I checked the distributor and it was set to the right almost all the way with just a bit left to go. I disconnected the dist. choke thing and plugged the ends to see if that did anything and nothing.

 

I'm thinking it's the carburator but I'm no expert.

 

I almost want to just buy a Weber 32/36 and a stock intake.

 

Which Weber 32/36 do I need to get from the ones on ebay? Or should I get a used one? How reliable are these?

 

Thanks

[banzai510(hainz)]

DGV 5A is a basic manual choke version and is the cheapest.

 

PS on your 1 sidedraft set up. make sure you run the vacuum adv form the carb not the carb manifold. THATS if you have one. alot of sidedrafts wont have a vacuum adv port. Some do soem dont.

 

My 44mm DO NOT have a port. My 40s one of them do.

 

PS if you think the motor is slower now. I would put it to TDC keepn the chain tight and dial it up and look what the cam sprocket is reading. Is if the cam is timmed up right.

[GERMS]

DGV 5A is a basic manual choke version and is the cheapest.

 

PS on your 1 sidedraft set up. make sure you run the vacuum adv form the carb not the carb manifold. THATS if you have one. alot of sidedrafts wont have a vacuum adv port. Some do soem dont.

 

My 44mm DO NOT have a port. My 40s one of them do.

 

PS if you think the motor is slower now. I would put it to TDC keepn the chain tight and dial it up and look what the cam sprocket is reading. Is if the cam is timmed up right.

 

Hmmm, I think that's the problem, I have the vacuum advance from the manifold onto the dist, because I didn't find anywhere on the carb like you said. The mechanic should of known it wasn't supposed to go that way. He timed and tuned it with the dist adv. on the manifold. So what should I do? Plug the carb manifold thing and plug the dist adv? The the engine should be timed again with those things plugged up right? Hope that's all I need to do. I'll give it a shot before giving up and buying a 32/36. Thanks for your help!