NEW 74 620 PICS carb issues help please

[mobbin620]

whats up guys just registered to the site i had bought this truck a few months ago the problem has been i havent been able to register the vehicle because it wont pass emissions!!! its driving me crazy!

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im convinced its the vacuum lines?? the truck runs good doesnt smoke, but it does seem like it drinks quiet a bit a fuel for what it is. also the truck wants to diesel after i shut off the motor i usually have to just dump the clutch to get it to shut off a sign of being to rich??? which also would cause it to fail emissions? any help would be appreciated.

 

 

 

 

 

[jon521]

http://community.ratsun.net/topic/691-how-to-post-pictures-and-keep-online-photo-albums/

 

welcome!

[mobbin620]

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[motavated]

HE HE! In arizona they require smog tests on a 74? I thought cali was bad!

[motavated]

http://olddatsuns.com/

All your answers will be found here.

[Wide14u]

how old do you have to be to be exempt

[mobbin620]

i think its 68.

[jon521]

what are those buckseats from?

[herculesinwyoming]

they are chevy cavalier seats from about 2000 model

[Tucson620]

Hey mobbin - Think I'm in the same canoe as you, prepping my rescued '76 620 for emissions, looking around for parts. I've got a Weber (and my truck ain't fancy looking as yours) Haven't gone yet, but am pretty concerned about passing.

 

How many times have you tried passing? Post up some of your numbers and I bet you get helpful suggestions. You up in the Center of the Universe?

 

Also, I'd love to hear about the test - did they put you on the rollers or just an idle test? How close did they poke around under the hood?

 

For vacuum issues (I'm getting familiar with this) did you do the carb cleaner spray test? Pretty accurate. I've learned leaks aren't always there at idle, but can be a big problem just off idle. I've chased ignition and Weber jetting stuff, then circled back and learned VACUUM LEAKS (!) are the typical issue, especially for old Arizona vacuum lines.

[mobbin620]

i have gone through emissions 4 times now (paid twice) you get a retest for free..

 

 

hydrocarbons load test - 672 should be no more than 400,

hydrocarbons idle test - 1579 should be no more than 400.

carbon monoxide load test 10.73 should be no more than 4.20.

and i passed the carbon monoxide idle test 2.02

 

tucson, what is a carb clean spray test?? i had the carb rebuilt already but did not solve the issue...

as far as the emissions test its self they to an idle test and a loaded test on the rollers. as far as looking under the hood, its just a glance.

 

any help is appriciated.

 

[Tucson620]

i have gone through emissions 4 times now (paid twice) you get a retest for free..

 

 

hydrocarbons load test - 672 should be no more than 400,

hydrocarbons idle test - 1579 should be no more than 400.

carbon monoxide load test 10.73 should be no more than 4.20.

and i passed the carbon monoxide idle test 2.02

 

tucson, what is a carb clean spray test?? i had the carb rebuilt already but did not solve the issue...

as far as the emissions test its self they to an idle test and a loaded test on the rollers. as far as looking under the hood, its just a glance.

 

any help is appriciated.

 

 

Well... Sounds like you're in the middle of overall tuning, so there's a lot of possibilities. Not the greatest tuning expert, maybe others can help. The engine run OK - smooth/rough at idle and through the rev range?

 

Carb spray test is a quick way to identify vacuum leaks - basically carefully spray carb cleaner (mostly ether - even brake fluid cleaner works) around the various vacuum fittings and carb. base. If the engine idle changes, it indicates a leak, sucking air around/outside the carb. Also, eliminate possible leak sources from all hoses, and there's a bunch with stock emissions stuff. Weber's site has a recommended procedure here: Weber Trouble Shooting Guide.pdf

 

High hydrocarbons is unburnt fuel or oil - could hint at your ignition system or vacuum leak. . You gone through the spark stuff, new plugs, check timing and advance stuff, etc. Points distributor?

 

High carbon monoxide is usually incomplete combustion - carb adjustments, all working, try to lean it out further.

 

I've been tuning for an idle test - wasn't sure if they'd put me on a roller for a load test (dammit).

[herculesinwyoming]

put a cat converter on it

[mobbin620]

the truck runs great! every time the truck with start right up, and it will idle comp. fine, runs great no issues at any speed. other than trying to get up too speed! lol it being a 4cyl. the truck does smoke a little if im idling n rev it up in neutral. im almost positve that it is going to be somthing with the vacuum lines.

 

when i got the truck the guy told me that he did have an aftermarket carb on it. but had taken it off b4 he had sold it n none of the vacuum lines were hooked up just plugged off. so when i ran it through emissions the way it was it failed. the 2nd time through worse than the 1st. shows what happens taking it to 2 mechanics to try n fix it.

 

ill take a few better pics of what all is actually hooked up n whats going where.

 

n just putting a cat on my truck isnt going to fix the problem, but thanks anyways.

[datzenmike]

the truck does smoke a little if im idling n rev it up in neutral.

 

Smoke:

 

If it's black then running rich. Choke not shutting off fully, float level too high: carb over filling and flooding, wrong jet size, air filter plugged or dirty. Plugs will be dry but powdery black.

 

If blue, you are burning oil. Rings worn out, valve guide seals worn, over filled with oil. Plugs will be shiny black and oily.

 

White smoke is usually steam from coolant getting into the combustion chamber from warped head and or blown or nearly blown head gasket. Exhaust will have a sweet smell from the antifreeze. Often the cylinders affected will have abnormally clean plugs compared to the others.

 

 

Not much you can do about burning oil. The oil will be a source of high CO (incomplete combustion) and hydrocarbon emissions.

 

As for vacuum leaks, they can cause idle problems. Too much air means it will run lean and not rich... at least at low speeds. A vacuum leak had less effect as the engine revs up. The most important vacuum line is the one going to the vacuum advance on the distributor.