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fuel injection question


hotrod8645's Avatar
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03-23-04, 06:57 PM   #1  
fuel injection question

Hey guys!
I have a problem with a 92 Lumina Sedan 3.1 multi port fuel injected when you try to start this car it just cranks if I floor it I can get it started then it backfires and black smoke poors out I saw that the throttle body was dumping out gas.
I assume it might be a leaking injector I took it to a garage and they had it two days but say they cant find anything ( I have no confidence in any of the garages around here) I took it to the garage because I dont have a way to check the injectors any advice?

 
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davo's Avatar
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03-23-04, 07:47 PM   #2  
If it's dumping that much fuel remove the upper plenum and pull the fuel rail.Disconnect the electrical connection and crank the engine.Any injector that sprays,squirts or drips fuel is bad.You can do this in less than 1/2 hour if you take your time at it.Then let us know the outcome.

 
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03-23-04, 08:14 PM   #3  
if I pull the fuel rail and crank the engine wont the injectors pop out? how would I see if one was leaking?

 
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03-23-04, 08:22 PM   #4  
Do a leak down test.

Put a fuel pressure gauge on. Turn the key on and pressurize the system. Turn off the key and clamp off the pressure line along with the return line. Wait and if the needle drops there is a leaking injector.

 
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03-24-04, 03:47 AM   #5  
Davo is telling you the only way to determine WHICH ONE is leaking. When you pull the fuel rail, the injectors stay with the rail. If they are unplugged, they won't open electrically and if any squirt, they are leaking.
Before doing that, try checking the vacuum line on the regulator for fuel in it and do the rest pressure leakdown test that Warn spoke of. Just remember, it can also leak down back to the tank through the fuel pump so you may have to pinch off both hoses after pressurizing them to be sure it's the injectors leaking.

 
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03-24-04, 04:17 AM   #6  
uh...

...it HAS to be something leaking at the engine...an injector stuck open or a bad pressure regulator...otherwise he wouldn't have black smoke. fuel coming out of the throttle body sound like a pressure regulator to me...after getting that upper plenum off...slip the vacuum line off of it and turn the key on to see if fuel shoots out of the regulator vacuum nipple...if so, you need one

 
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03-24-04, 05:24 AM   #7  
Re: uh...

Originally posted by carguyinva
...it HAS to be something leaking at the engine...an injector stuck open or a bad pressure regulator...otherwise he wouldn't have black smoke. fuel coming out of the throttle body
I agree, but the only way to confirm it is to see the leak down and restricting the feed and return is the only way to confirm it has "engine" leakdown. There could be other ways to flood an engine during cranking although I admit it's not real likely with that much fuel.

 
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03-24-04, 05:32 AM   #8  
a matter of semantics perhaps...

...but i'd be surprised if you could get enough pressure with that gross leak and get clamps on the lines fast enough...fuel is going to go where it goes as soon as the pump runs. if fuel is running out of the throttle body...it's getting into the upper plenum area...the injectors are way down stream of that.

your test procedure is correct tho for isolating leaking injectors...i just believe it's going to be VERY obvious

 
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03-24-04, 12:18 PM   #9  
Your probably right but I don't know how this thing even runs after it gets started.

 
hotrod8645's Avatar
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03-24-04, 07:14 PM   #10  
you guys have been a big help thanks
I have fuel leaking from the pressure regulator so I going to replace it.
In reply to "I dont even know hows it runs after its started"
this car runs so good even the garage commented on it.
keep in mind it only floods after it has been shut off for 15 min. or more.

 
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03-25-04, 04:13 AM   #11  
you never told us that...

keep in mind it only floods after it has been shut off for 15 min. or more.

glad you found the problem...

 
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03-26-04, 08:26 PM   #12  
Thanks all
it was the pressure regulator the car runs and starts perfect now!

 
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