94/95 LT1 leaking raw gas from manifolds -- what could be the diagnosis? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-08-2011, 07:56 PM
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94/95 LT1 leaking raw gas from manifolds -- what could be the diagnosis?

Hi guys,

Engine is a 93 Camaro upgraded to a 94/95 configuration.

I've been doing a conversion project for a while -- had to drop the exhaust to access a stripped bolt elsewhere. I hadn't fired the car yet -- when i decided to give it a test fire, i smelled raw gas coming from somewhere.

upon inspection, i noticed that there was gas literally DRIPPING from the exhaust manifolds on both sides. I don't think a sticky injector could dump that much gas, but it is possible -- the car has been sitting for about 5 months so maybe one got gummed up.

i turned off the engine -- i didn't notice that it was running that rough. after about 20 seconds of running it (with lots of smoke from the gas) it seemed like it ran a bit better. when i turned it back on, there was the dripping gas again on start up.

What could it be? FI? Or fuel pressure regulator? i don't know if gas has gotten in the oil (which is a fresh change) so i'm not sure if i should change it right away. It's been sitting about a week since i've last cranked it.

What should I do? do you think the oil should be changed (has about 50 seconds on the oil...just worried about the gas tainting it)

any ideas?

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Old 04-08-2011, 08:37 PM
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fire it up with fresh oil for a few sec.
if you have to ask if the oil is ok your better off changing it(i had a jetta the added a gallon to the crankcase once)

i would start then with pulling the plugs you will see if all or a few cyl are getting wet

if there all wet probably something in the fuel sys. high pressure is unlikely in a return fuel system but i wouldn't rule it out easy to check.


if one or 2 are wet look deeper into the ign system.
the ign might be tricky on that one if its a lt1 i hvnt worked on any but i know its not traditional sbc stuff.
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Old 04-08-2011, 09:07 PM
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fuel

first off, if you have fuel dripping out of the exhaust, don't start it up till you find out what the heck and fix the problem, then dry out the exhaust in a well vented area, like outside. otherwise you might start up more than you bargained for, like a fire. it isn't all that great for the o2 sensors or catalytic converts either.
it sounds like you have a badly leaking injector. start by pulling the park plugs and see which ones are wet. then check the corresponding injectors, or just have them all ultrasonically cleaned and then they will all be balanced as far as spray pattern and amount of injection. the other way to tell is by letting it sit overnight, so the injectors would all be dry at the tip, then cycle the ign key on and off several times (each time the fuel pump should run for 2 secs and pressure up the system, don't actually start the engine) and then remove the injectors to find which ones are wet on the injector tip. they should be dry if the engine wasn't started.
if there is raw fuel dripping out the exhaust you will want to be carefull about starting because if, per chance, it happens to dump a bunch of fuel into a cylinder and the engine trys to compress it, like when the engine is crankning over, you can bend a connecting rod. fuel doesn't compress like air does, so the rod takes the brunt of the ordeal. also, if there is that much fuel in the pipes your oil will definatley be contaminated. be carefull because you can cause a small exlosion inside the engine upon start up and your oil pan and valve covers don't take too kindly to that. or your eardrums for that matter.
good luck, keep us posted,
dsraven
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Old 04-09-2011, 01:16 PM
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thanks for the warning dsraven. I happen to have a spare set of injectors so if i do have a badly leaking one i can swap it out. I will try the test you suggested and see if that solves the problem. I hope i havent caused any damage to the engine -- its ran for a total of maybe 1 minute since i put it in, but i know in engine years that might as well mean 50 hours if there is a problem afoot.

barring this test, and the fuel pressure regulator, could it be anything else? The injectors have a max flow rate of 24lbs right? they are stock injectors -- im just wondering if the tune that was programmed onto the PCM is causing the injectors to dump too much fuel.
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Old 04-10-2011, 03:34 PM
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fuel

well, the only place the engine can get fuel on an injected engine is from the injectors, or if there is a hole in the diaphagm of the pressure regulator i guess it could suck fuel up past that. have you done a fuel pressure test on the rail?. otherwise, if it is overfuelling, you must either have some badly leaking injectors or a tune that is grossly wrong for your engine. i would think it is the injectors though. was the tune programmed with your injectors in mind?
do the previous test and see what you find, when you pull the plugs, see if all the cylinders are wet or just a few. since the injectors are set close to the end of the intake runners, the wet cylinders would be the culprits. I can't remember on those injestors if they are retained to the rail with a clip, or if the rail actually holds the injectors down when the rail is bolted own. if the injectors have a retainer clip on them, then you would be able to remove the rail with the injectors attached, and the fuel lines attached, and then turn on the key for the fuel pump to run (don't try to start it or there will be fuel spraying everywhere-bad bad), then you would be able to see exactly what is going on at the tip of each injector. they should be dry because they are made to hold the system presure unless energized. the pump should run for 2 secs when the key is turnes on, then it shuts off, so you may have to turn the key on a few times to get a good reading.
good luck and keep us posted
dsraven
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Old 04-10-2011, 03:45 PM
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raw fuel

have you had any of the injectors out of the engine,had this happen on a s10 a few weeks ago the oring got jacked up and it dumped raw fuel out of the exahust
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Old 04-10-2011, 07:46 PM
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I think I know at least part of the problem (if not the whole problem) I haven't been out to the shop to confirm but when there was fuel dumping out, i realized that the O2 sensors were hooked up, but the exhaust system was.

since the exhaust was dropped, the o2 sensors were reading pure air and started dumping a bunch of fuel to lean it out. I don't know if this is the WHOLE problem (could still be a faulty injector, i'll find out next weekend), but I think it has a big something to do with it.

As for the tune, I'm just doing a stock tune, with the fan temps turned down and CAGS/CARS and VATS disabled. Everything else is stock (or so the .bin file said...) so I think that's okay.

i hope i haven't caused any real damage -- the engine has been run for a grand total of 60 seconds or so, probably less. But who knows :-(

I'll change the oil, check for leaking injectors and a busted diaphragm in the fuel pressure regulator. When i rehook the exhaust back up, i'll fire it again, and see if there is still a gassy smell coming from the exhaust. If i shoot flames, i know I'll have to keep looking :-p
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