January 1, 2005

How To Check For Leaking Fuel Injector

Leaking Fuel Injector

It’s possible that one of the fuel injectors is leaking. Normally, pressure is maintained in the fuel system after engine shutdown. Because of this pressure, a leaking injector would discharge fuel to its cylinder until the pressure was near zero. Burning off that excess fuel would lead to the black smoke on startup. Also, because the pressure in the fuel system is down to zero or near zero, a number of cranks on startup would be required to rebuild the pressure sufficiently for the engine to start.

MVS member sting asks:

1996 850
When I first start my 850 a puff of black smoke will be emitted from exhaust. After the car starts it vanishes. I recently had my annual emissions check and have noe issues. it passed with flying colors. I have no CEL light, all maintenace completed including new battery, plugs, C&R, MAF and fuel filter. I have cleaned the TB and IAC as well. Car runs great with the exception of intermittant start problems where the engine takes 6-7 cranks to turn over, other times it starts no problem. But I am curious bout the black smoke at start up for a couple of seconds. Any ideas?

MVS member TAfinley replied with:

Black smoke is an indicator of very rich mixture. You say the engine cranks a bit before starting, and that’s a significant clue.

It’s possible that one of the fuel injectors is leaking. Normally, pressure is maintained in the fuel system after engine shutdown. Because of this pressure, a leaking injector would discharge fuel to its cylinder until the pressure was near zero. Burning off that excess fuel would lead to the black smoke on startup. Also, because the pressure in the fuel system is down to zero or near zero, a number of cranks on startup would be required to rebuild the pressure sufficiently for the engine to start.

How To Check For Leaking Fuel Injector

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One response to “How To Check For Leaking Fuel Injector”

  1. Cal Sherman says:

    My 960 is running very rich, hard starting, missing, engine idle is erratic. The engine is the 2.9 inline 6 cyl. No check engine lights, have not checked codes yet.

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