failed CO emission 6.2 na

[jerheff]

87 gmc failed emission test. black smoke during test. any suuggestions? new air filter, new fuel filter. just bought, previous owner claims 38000 on motor. plenty of power, but won,t do me much good if I can't get it smogged. new to diesels. thanks

[twaddle]

Hi there
The previous owner may have installed a rebuilt motor but did he also install reconditioned or new injectors and is the pump timing OK? Does the engine fire up from cold with any excess smoke or difficult to start issues?
Was the engine at working temperature when the smog test was carried out or had it been sitting idling before being tested, both of these things can cause poor emission readings.

If the engine performs and feels as though it is generally a good unit then start with the simple things, air and fuel filter followed by injectors which will need to be tested.

I'd also recommend changing all oils and filters, nothing to do with emissions just something I always do with a "new" second hand truck as you never know how the previous owner(s) have been at oil changes etc or if the levels are low.

Good luck and let us know how you get on and welcome to the world of GM diesels.

Jim Twaddle
Biggar, Scotland.

[jerheff]

it starts a liitle rough. generally 3-4 tries and then a noticable amount of black smoke. heavy diesel stain at end of tailpipes, both sides. new air and fuel filter. air cleaner system seems un obstructed. unable to get the guy to reply back regarding injectors. no noticeable black smoke at idle. moderate to heavy black smoke when pushing hard on accelerator pedal. what is the best approach to solving problem? new to diesel. thanks jim for the response.

[britannic]

I agree with Jim, start out by checking the timing is on, once you've done that, then work through the rest of his suggestions.

[moondoggie]

[font=times][size=+]Good Day!

It would be greatly helpful if you could describe the test protocol.

[i]

[Craig M]

Others have stated that testing with the tank full of waste vegitable oil rather than diesel helps on the tests.

[moondoggie]

Good Day!

"...testing with the tank full of waste vegitable oil rather than diesel..." For heavens sake, PLEASE don't consider doing this unless you really know what you're doing. WVO in diesels is a terrific idea, but it's a really complex subject - simply dumping some in your tank (without FULLY knowing what you're doing) to pass an emissions test is MUCH more likely to cause your truck to not run at all than to have the desired effect.

On the other hand, 20% biodiesel might not be a bad idea in your situation, but I would not even consider doing this MUCH SAFER thing unless & until I'd talked to lots of folks that actually know about biodiesel.

Blessings!

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