My fuel injected 1997 Suburban with the 454 blow out black smoke on startup. Smells like fuel and clears up after several seconds. Reminds me of the 70's when vehicles often ran over rich. What would cause that on a fuel injected engine? Are the fuel injectors leaking down when shut off? Runs good otherwise.
Black smoke on start up
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Injector leak down test needed. Perhaps they just need cleaning.
I wonder if it is a temp sensor that thinks it's substantially colder out than reality... just a thought.
First it should be checked for codes, then remedies applied...
A quality scanner will report such things as engine coolant temp, which as already suggested could be out of calibration and not necessarily set a fault code... If it's reporting say -10*C, and engine is warm, there's your problem... May not be the issue at all but unless it's having long crank times to clear a flooded engine, I doubt the injectors are leaking...
A quality scanner will report such things as engine coolant temp, which as already suggested could be out of calibration and not necessarily set a fault code... If it's reporting say -10*C, and engine is warm, there's your problem... May not be the issue at all but unless it's having long crank times to clear a flooded engine, I doubt the injectors are leaking...
Originally Posted By: cchase
I wonder if it is a temp sensor that thinks it's substantially colder out than reality... just a thought.
Meaning, manifold or 'ambient' temp not coolant temp, right?
I wonder if it is a temp sensor that thinks it's substantially colder out than reality... just a thought.
Meaning, manifold or 'ambient' temp not coolant temp, right?
Some of the 97-99 vehicles had an issue with the fuel filler pipe dissolving galvanizing compounds into the the fuel that finds it way into the injectors and clogging them.
These same compounds can stick an injector causing it to drip. I have seen this a few times with cheap Chinese replacement steel tanks also.
All the cleaner in the world wont help, if anything it may even drive the contaminates further into the pintle and seat, the units need to be cleaned and back flushed.
Pull the vacuum line off the regulator if any fuel is there the regulator is shot, also common.
Perform a pressure test with the vacuum line on/off.
These same compounds can stick an injector causing it to drip. I have seen this a few times with cheap Chinese replacement steel tanks also.
All the cleaner in the world wont help, if anything it may even drive the contaminates further into the pintle and seat, the units need to be cleaned and back flushed.
Pull the vacuum line off the regulator if any fuel is there the regulator is shot, also common.
Perform a pressure test with the vacuum line on/off.
Originally Posted By: ltslimjim
Originally Posted By: cchase
I wonder if it is a temp sensor that thinks it's substantially colder out than reality... just a thought.
Meaning, manifold or 'ambient' temp not coolant temp, right?
It depends on how the computer analyzes temperatures. Coolant temp sensors control fuel enrichment. On vehicles with an intake temp sensor and coolant temp sensor, they may be used in conjunction (I don't know).
Easy way to check operation is to find the sensor, then probe with a multimeter with the engine off and cold. Check the chart for what resistance should be present and compare with actual reading. Make sure you are probing the sensor used for the computer, not the one for the gauge (on some vehicles they are different).
Originally Posted By: cchase
I wonder if it is a temp sensor that thinks it's substantially colder out than reality... just a thought.
Meaning, manifold or 'ambient' temp not coolant temp, right?
It depends on how the computer analyzes temperatures. Coolant temp sensors control fuel enrichment. On vehicles with an intake temp sensor and coolant temp sensor, they may be used in conjunction (I don't know).
Easy way to check operation is to find the sensor, then probe with a multimeter with the engine off and cold. Check the chart for what resistance should be present and compare with actual reading. Make sure you are probing the sensor used for the computer, not the one for the gauge (on some vehicles they are different).
Try the simple fix first. Like the man suggested, use a 20 OZ bottle of Techron SYSTEM cleaner.
Most likely just an injector hanging open due to trash in the seat after shut off. The system should remain pressurized with the engine off. Find the outlet from the fuel filter under the driver side door (guessing based on most Chevy trucks). Turn the key on for about ten seconds and listen for the fuel pump prime, then turn the key off. Wait a about five minutes and then disconnect the fuel filter outlet line. If fuel just dribbles out without a "pffffssssttt" of pressure release first then an injector is most likely the problem.
^Would that also potentially condemn a fuel pressure regulator?
Originally Posted By: ltslimjim
^Would that also potentially condemn a fuel pressure regulator?
Yes, but there'd be additional issues that should show up with the regulator going bad. Most notably it would want to take much longer to get it to start if you waited a few seconds between key on and start (to let pump turn off) since it usually can't build pressure during starting with the regulator going out.
^Would that also potentially condemn a fuel pressure regulator?
Yes, but there'd be additional issues that should show up with the regulator going bad. Most notably it would want to take much longer to get it to start if you waited a few seconds between key on and start (to let pump turn off) since it usually can't build pressure during starting with the regulator going out.
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