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Detroit Diesel (DD671N) Questions
Wayne,
1st: on a 671... no smoke usually means compression is fine. If compression was bad, you would get smoke on startup until they warm. if it warms and they still smoke badly... you need a rebuild fast... If it runs after fuel is shut off or it runs away then you needed a rebuild last year. 2nd: Do you have Racors? Is the fuel level in the tank ABOVE or BELOW the injectors? If the answer is YES and BELOW then go buy a Racor rebuild kit or at least buy the washer that sits over the metal ball. That washer will disfigure over time causing the ball to not seat and the fuel will drain back into the tank. Also make sure all other seals, especially the top seals are in good shape (A rebuild kit comes with all new seals) 3rd: Is the engine turning over the normal speed? If not, batteries may be low. A slow turnover will cause an engine to slow start. 4th: DO your exhaust ports have the heat sheilds over them? If not, you can use a temp gun to find a bad cylinder. If not, you can play with the fuel rack with the cover off to find a bad cylinder. (Not recommended unless you know what you are doing or have 6 fingers on your right hand) BUT AGAIN... no smoke means you probably have 6 good cylinders. 5th- Spend 90% of your time playing with the inbound fuel system. A few hints: While the engine is running.. everything PAST the lift pump (The first pump after the racor) is under PRESSURE. Check this area first for leaks while the engine is running-higher speed the better. Everything BEFOre the lift pump is under SUCTION. This is harder to find because there will be no visible fuel most of the time. (See #2) You can put some semi-viscous liquid around the seals and see if it is sucked in but that can be difficult to see. (Spit, clean oil, etc) Don's waste your money on a compression check ($500 +++) until you have tried most everything else Have fun... I am in a similar situation with one of our boats but we have smoke and 1 bad cylinder.... kind of a smoking gun... Ed ed at Estrobel dot com Wayne.B wrote: On Tue, 24 Jan 2006 20:34:46 -0500, Larry wrote: No valves. Intake ports and exhaust ports open as the piston passes over them near BDC when the blower recharges the air and blows out the dead gases. That's what I thought but everyone else says there are exhaust valves in the head. |
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