710K failed emissions

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mm58
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710K failed emissions

Post by mm58 »

I normally pass emissions without too much fuss, but this time
it failed due to high hydrocarbons. Carbon monoxide was fine.

Wondering where I should focus my attention to make any adjustments.

Thanks...


Mike
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rmel
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Re: 710K failed emissions

Post by rmel »

Hydrocarbons in the exhaust implies unburnt gas. Likely running too rich,
or misfiring on a cylinder. What do your plugs look like? Does the report
indicate what the AFR was and at what RPM did it fail? I presume running
speed. AFR under 12 is rich.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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mm58
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Re: 710K failed emissions

Post by mm58 »

The numbers were in ppm. I failed both at idle and at speed on the rollers.

Idle standard is 350 and I read 1384.
Running standard is 300 and I read 521.

Mike

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rmel
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Re: 710K failed emissions

Post by rmel »

OK, well wrt AFR I was referring to Air Fuel Ratio.
But the exhaust sniffer guys probably deal more with
contamination levels e.g. PPM.

Is there any indication of running rough in idle or hesitation
when you goose the engine? Might be an indication that one
of the carbs is at play, hopefully the plugs will give you a clue.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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mm58
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Re: 710K failed emissions

Post by mm58 »

I have been noticing white/grey exhaust smoke at random times at idle. Varies. Most of the time no smoke at all, then for some reason at a stop it starts smoking. Otherwise it seems to be running fine with good acceleration and no funny noises.

I'll be pulling the plugs and having a look this weekend.

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mm58
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Re: 710K failed emissions

Post by mm58 »

Update:

Looked at all four sparkplugs and they all appear equally the same with
no significant 'wetness' or oil. IMO they looked pretty normal. (but then I could be wrong)

But I did discover the #1, or forward most shutoff solenoid to be bad/broken.
I hoping that will be the reason for my troubles because that would be an easy
fix.


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mm58
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Re: 710K failed emissions

Post by mm58 »

Heres a pic of one of the plugs. All four were virtually identical.


MikeImage

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rmel
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Re: 710K failed emissions

Post by rmel »

Looks like a clean ignition -- if anything, possibly running lean not rich.
Not what you'd expect with the HC readings you had esp. at idle.

Although on the other side of the combustion chart, if you run excessively
lean, you can fail to combust. Following that hypothesis, a vacuum leak
that could effect all four cylinders. Might be worth checking the brake
vacuum boost line and the vacuum balance line that connects both carbs
which is under the shroud.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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mm58
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Re: 710K failed emissions

Post by mm58 »

Ok roger that. Sounds like an interesting idea. Now on to inspect the vacuum lines...

Thanks!


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mm58
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Re: 710K failed emissions

Post by mm58 »

Inspected the vacuum lines/connections and they appear good (at least what I could get to)

I put a guage on it and I am pulling about 20 inches HG at idle.

Under the tins, the carb balance hose looks to be intact and tight.

My 710 is not set up for the "automatic hot air regulation". There is no thermostat or control element on the air intake system. I suppose that's okay though. The vacuum port that would support a control element is capped off.

I also checked the ignition timing, and I am running at TDC. If I adjust either side of TDC, smoke increases, so I'm just leaving it there.


Mike

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rmel
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Re: 710K failed emissions

Post by rmel »

Hmmm, smokes? And worse with advanced or retarded timing.
Does it continue to smoke after she's completely warmed up?

I'm grasping at straws at this point. But with your results 4X
higher HC's at idle you should smell it in the exhaust.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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mm58
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Re: 710K failed emissions

Post by mm58 »

Also... I am seeing raw fuel being spit out the exhaust pipe. Just enough to
see little spots hit the pavement. It's intermittent though.


What I am noticing is that when I disconnect the plug wires one at a time while running,
there is a noticeable drop in rpm on each cylinder as expected, EXCEPT for cyl #1.
When I disconnect that plug wire, there's no change. So I thought maybe that cyl 1 wasn't firing.
I rechecked the plug on cyl #1 again and this time it looked wet, but there is a good spark
on that plug.

Wondering if not having that fuel cutoff valve on cyl #1 is causing issues (??)

What is the plug gap supposed to be?



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rmel
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Re: 710K failed emissions

Post by rmel »

Hmmm, I do know one thing from my own experience, if fuel can bypass
the acceleration jets or emulsion tube then raw gas goes into the intake
and raw gas will not ignite. Earlier this year both my acc jets got plugged
and raw fuel was leaking right at the base of the jets, I was nearly running
on 2 cylinders as a result.

The fuel cut-off solenoids are supposed to open only when there is 24V
present, closed and no fuel otherwise. But it seems yours on #1 is bad,
maybe stuck open in a bad way? That seems like the first obvious thing
to address. And it must be running rough on 3 cylinders.

Funny, I just bought one solenoid as a spare just in case.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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mm58
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Location: Tucson, AZ

Re: 710K failed emissions

Post by mm58 »

I've since pulled the failed cutoff solenoid out.
The brass end with the actual valve was totally broken off the end.
So I've just sealed the hole with an M8x1.0 bolt.

Hmmm, now that's got me thinking. I wonder if that broken off end is lodged down inside there(??)
Time to get out the borescope.

I'll pull the cover off the carbs and see if anything's amiss. I'll take a look at the acceleration jets.


Mike

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Re: 710K failed emissions

Post by ChickenPinz »

Have you done a compression check?
710K
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