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Thread: Warm start black smoke
12-08-2008, 12:07 AM #11
12-08-2008, 04:13 AM #12
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EGR/switch getting stuck on warm starts and functioning when in operating mode? Pindle stuck at start due to extreme carbon build up, but will not produce smoke when running. You have to hold the pedal
down to get it to start when warm? How do your spark plugs look? Just check the easiest one and see how black it is and lets see what you get here...
12-10-2008, 03:28 PM #13
One thing you might want to check is your coolant temperature sensor.
the coolant temp sensor signal acts as a choke on fuel injected engines, when it is cold it puts more gas in the engine (like pulling the choke on your lawnmore when you first start it) and as your coolant temp warms up, it tells the computer to lean out the gas mixture.
If the sensor is bad and is sending a cold coolant temp to computer, the computer would always be putting too much gas in. When you're starting from cold, that wouldn't be a problem, but when your engine is already warm, the air/fuel mixture would be too rich to start well and you'd need to open the throttle (pump the gas) to get more air in to allow it to start..the extra gas would come out as incomplete combustion and carbon deposits (black smoke)
New sensor is only $11.99 and can be checked with a ohmeter
Only thing is usually a bad CTS would cause a CEL code...but maybe it isn't bad enough to throw a code.
Last edited by Big6ft6; 12-12-2008 at 06:02 PM.
12-12-2008, 05:53 PM #14
black smoke is usually the by-product of your engine running rich, I would be checking the intake and TBI99 K1500 Suburban LT "THE BEAST"
Hypertech III, K&N, true dual
12-12-2008, 06:14 PM #15
My first thought is fuel pressure regulator. What happens is the diaphragm between the pressurized fuel and the vacuum line ruptures, allowing excess fuel into the intake. If the leak is slow enough, you don't see a problem while it's running, but, once you shut off the engine, the fuel system "depressurizes" through the FPR into the intake. Once you get enough in the intake, it will act "flooded" when you try to start it. If you wait long enough, the excess fuel in the intake will dissipate and you don't have a problem.
Easy enough to check: simply pull the vacuum line off of the FPR (As I understand it, your 7.4 FPR is easy enough to get to) after the engine's been running and see if there's any gasoline in the vacuum line. If yes, then replace FPR.
If no, I'd probably put a fuel pressure gauge on it and see if the fuel system holds pressure.'98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
'92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
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