SMOG results
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SMOG results
HI Guys,
what do these results say to you? The truck passed (barely) 6 months ago, completely stock. I changed the plugs, wires, cap, rotor, had the carb professionally rebuilt, ran a can of seaform through it and now it's failed the SMOG. It was.....warm when it tested, it did sit for maybe 15 minutes after I showed up waiting for the last guy to finish.
It seems like everything is pretty low but the CO....from what I've read sounds like it's running a little rich, but is the difference so small I can tune it out of the carb or retard the timing and get it under? It's a non-cat truck, but perhaps it'll be easier to stick a cheap cat on it to get the CO down a little instead of troubleshooting.
1986 f250 460
Thanks.
what do these results say to you? The truck passed (barely) 6 months ago, completely stock. I changed the plugs, wires, cap, rotor, had the carb professionally rebuilt, ran a can of seaform through it and now it's failed the SMOG. It was.....warm when it tested, it did sit for maybe 15 minutes after I showed up waiting for the last guy to finish.
It seems like everything is pretty low but the CO....from what I've read sounds like it's running a little rich, but is the difference so small I can tune it out of the carb or retard the timing and get it under? It's a non-cat truck, but perhaps it'll be easier to stick a cheap cat on it to get the CO down a little instead of troubleshooting.
1986 f250 460
Thanks.
Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
If all your fuel & ignition parts & engine are in good shape, then IMO the fastest & easiest thing to do is take it to a shop where they'll put it on an exhaust sniffer and tune the carb to make it pass.
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
That's rich.
My truck tests so low on CO that the test station is surprised.
Are your thermactor A.I.R. pumps functional?
Their purpose is to burn off CO in the exhaust ports and manifolds before it can escape the tailpipe.
My truck tests so low on CO that the test station is surprised.
Are your thermactor A.I.R. pumps functional?
Their purpose is to burn off CO in the exhaust ports and manifolds before it can escape the tailpipe.
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The gas is new, I've run a couple tanks through in the past couple weeks. How can I verify that the AIR pump is working? I should mention the exhaust burbles and pops on deceleration even around town, could be related to the rich condition?
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 39
From: EXTREME southwest CT
But you say the carb was rebuilt???
Try turning both idle mixture screws in while the engine is running.
Can you softly seat the screws and the engine doesn't die?
Sure sign of a bad PV, or it was rebuilt with the wrong gaskets behind the metering plates.
That's why I always say use the genuine Holley 3-1346 kit.
This is NOT a 4160, and a kit for one will leak.
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Fleet Mechanic
Joined: Jun 2010
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From: North Carolina
Remove the hose on the outlet of the pump - if air is blowing (positive pressure) from this outlet when the pump is running, then it is working.
I'm not sure what air control valves/bypass valves are downstream of the AIR pump on a '86 460, but they also play a role in how the outlet air is managed. The outlet air also passes through a check valve (or two) that regulate its passage into the exhaust header(s) and/or catalytic converter(s). All should function for the system to work.
Here is a general diagram that might help: https://www.ford-trucks.com/forums/1...l#post15682958
I'm not sure what air control valves/bypass valves are downstream of the AIR pump on a '86 460, but they also play a role in how the outlet air is managed. The outlet air also passes through a check valve (or two) that regulate its passage into the exhaust header(s) and/or catalytic converter(s). All should function for the system to work.
Here is a general diagram that might help: https://www.ford-trucks.com/forums/1...l#post15682958
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pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
There are two vacuum operated bypass valves.
One pump goes to a check valve back by the EGR valve and the check valve connects to a pipe across the back of the heads.
The other pump is plumbed to the stainless log manifold above each valve cover.
This one injects air directly into each runner of the exhaust manifolds.
Vacuum control is through a thermal switch, and possibly a delay valve.
One pump goes to a check valve back by the EGR valve and the check valve connects to a pipe across the back of the heads.
The other pump is plumbed to the stainless log manifold above each valve cover.
This one injects air directly into each runner of the exhaust manifolds.
Vacuum control is through a thermal switch, and possibly a delay valve.
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