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Discussion Starter · #1 ·
Has anybody had this happen?

Started the car, it ran a little rough, threw a code. Pulled the code - P0300 random misfire.

Had the hood up, smelled gas, saw what looked like liquid leaking out of the joint between the exhaust manifold (stock) and exhaust pipe on passenger side.

I shut down the car, pulled the dipstick and it smells like gas, with what looks like thinner than expected oil. (But not overfilled on dipstick.) Removed the oil cap, inside of head looks clean as a pin with thin oil film - again smells like gas.

I'll pull the plug and drain and change the oil, but before firing everything up again, I need to figure out if I've really got fuel getting into the crankcase and exactly how.

Engine is a stock 77K mile LT1.

What all could cause this? If a cylinder isn't firing, but getting a normal amount of fuel injected, I would have guessed that the raw gas would just blow out with the normal exhaust cycle which could explain what I saw & smelled leaking out of the exhaust. I wouldn't suspect there would be enough to leak past the rings on what has always appeared to be a healthy running engine. It runs strong and doesn't use any oil, so I don't suspect any ring / compression problems.

All advise will be appreciated!
 

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most likely an injector stuck open (dirt on injector seat prolly)...''pees'' while the engine is stopped...an injector electrical wire from the injector to the ecm that is frayed and shorting to ground (ecm grounds the injectors to open them, power is suppled to the injectors full time) will also ''wash'' the cylinder .

put a fuel pressure gauge on it, watch pressure decay when key is turned ''off'', should be very slow drop, hold 10 psi after 12 hour sit (ideal would be full 40+ psi after sitting, but ''never happens'' )

don't ignore this little problem, it will eat the rings out of the ''sick'' hole in VERY short miles.

MUST change the oil asap.
 

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Discussion Starter · #3 ·
Man, I think you're right on target here. I just checked the fuel pressure and when you turn on the key, it runs right to 42 and the pump shuts off just like it should. Then the pressure instantly falls to 0. I tried that a couple of times with the same result. I wondered if it could be the fuel pressure regulator instantly bleeding the gas back to the tank, but the peeing injector makes more sense in this case.

What's the easiest way to figure out which injector is the problem? Take the fuel rail off and pull them all? Will the leaker(s) stand out from the others?
 

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Another thing to look for is a complete failure of the fuel pressure regulator. I'd put my money on this ahead of failed injector(s). But either is possible. As a quick check, see if there's any evidence of fuel or fuel smell in it's vacuum line.
 

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Discussion Starter · #5 ·
I pulled the vacuum line off and found no evidence of fuel there. But if the FPR totally crashed, wouldn't the fuel either return to the tank or bleed out through the vacuum line and into the intake?

I've got the injectors out. Is there a way to test them at home to see if one or more is leaking fuel? If I rigged up my air compressor to blow air through an injector, would a good one not let anything through and one that's stuck open allow air through?

I'll probably take them to someone on Monday and get them professionally cleaned / serviced, but until then I would be nice to figure out if one or more is letting fuel through all the time.
 

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There are simple checks you can do to check for a ruptured diaphragm in the FPR. There are also procedures to determine if the injector(s) are causing such a problem. But they are performed with the injectors still installed. Once they're out, only a specialist with the proper equipment can determine their condition beyond a simple ohm check. Consult your factory service manual. Either the FPR or injector(s) could flood your intake system with fuel. And either way, such excessive flooding will find it's way into the crankcase, past the rings.
 

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Have you pulled the spark plugs and found the Misfire? I would think that spark plug would look black "RICH" on the cylinder with the bad injector if that is the problem.
 

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Discussion Starter · #8 ·
I've pulled the plugs out of the passenger side bank (problem side) and think I've found the problem injector. The #2 plug is a lot cleaner that the other three plugs.

I also tried shooting air through the injectors and the #2 injector will let some air through where as the other seven will not.

I'm changing oil now and will take the injectors in Monday to have them serviced.

I haven't checked compression yet to see if I've got any bigger problems. I don't really think this has been going on long enough to cause a problem (0 miles driven, I shut it down after probably less than 2 minutes of run time.) But I can see how that continuing to flood a cylinder with gas would wash out all lubrication pretty quickly.

I'm thinking about shooting some WD 40 down the #2 hole and letting it sit for a while before putting everything back together and firing it up. Thought procss being that it will coat and lubricate the cylinder wall.

Is this a good plan? Any suggestions?
 

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Discussion Starter · #9 ·
Changed the oil and there was a lot of gas in the crankcase.

With the passenger side plugs out, I thought I would crank the engine to blow out any remaining fuel. Bad idea - it wouldn't turn over. Pulled the driver side plugs and two cylinders were full of gas - that's why it wouldn't crank. After purging all of that, engine turns over fine. But this makes me wonder again where the problem is. After looking at the plugs on the passenger side (where I originally had raw gas in the exhaust) I thought I knew where the problem was - one leaking injector. But now that I've pulled gas out of three cylinders on both banks, it makes me wonder about the FPR. I pulled the vacuum line off that, but didn't find evidence of fuel there.

Anyway, I cleaned the plugs and reinstalled. I'm thinking now that I'll replace the FPR and get the injectors serviced and that should fix it.

New question - When I was buying oil & pricing a FPR & injectors at a local parts store, I was told that the process of 'servicing' an injector was a complete waste of time & money - that they couldn't really be cleaned and the best choice was to buy new ones. Is this true? Eight new injectors at about $100 a pop sounds really steep to me.
 

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New question - When I was buying oil & pricing a FPR & injectors at a local parts store, I was told that the process of 'servicing' an injector was a complete waste of time & money - that they couldn't really be cleaned and the best choice was to buy new ones. Is this true? Eight new injectors at about $100 a pop sounds really steep to me.
The only evidence I can provide is anecdotal, but here you go.

I have a friend that is building a restorod using a '93 LT1. He was testing the engine on a stand, and observed wildly different spark plug readings (based on the way the engine operated). Several were lean, several were rich, and a couple were normal. He elected to send his injectors out for ultrasonic cleaning to

http://www.witchhunter.com/index.php4

When the injectors came back, the issues with engine operation went away, and the variations in spark plug readings disappeared. No other changes were made to the engine.

Now, your case may be different - but for $17 an injector compared to $100 each for new ones, I'd probably try the cleaning route first. At the very least, they should be able to tell you which injector(s) are faulty, and you won't have to replace all of them.

Good luck!

Steven
 

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The only evidence I can provide is anecdotal, but here you go.

I have a friend that is building a restorod using a '93 LT1. He was testing the engine on a stand, and observed wildly different spark plug readings (based on the way the engine operated). Several were lean, several were rich, and a couple were normal. He elected to send his injectors out for ultrasonic cleaning to

http://www.witchhunter.com/index.php4

When the injectors came back, the issues with engine operation went away, and the variations in spark plug readings disappeared. No other changes were made to the engine.

Now, your case may be different - but for $17 an injector compared to $100 each for new ones, I'd probably try the cleaning route first. At the very least, they should be able to tell you which injector(s) are faulty, and you won't have to replace all of them.

Good luck!

Steven
Had my injectors on the '86 done by www.tpis.com. Total price with shipping was $128 (a little cheaper). They sent a paper with all the readings pre and post cleaning in the packaging. Even if that doesn't solve the problem, it's worth the $$ since there's 77k on the clock.
 

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Changed the oil and there was a lot of gas in the crankcase.

With the passenger side plugs out, I thought I would crank the engine to blow out any remaining fuel. Bad idea - it wouldn't turn over. Pulled the driver side plugs and two cylinders were full of gas - that's why it wouldn't crank. After purging all of that, engine turns over fine. But this makes me wonder again where the problem is. After looking at the plugs on the passenger side (where I originally had raw gas in the exhaust) I thought I knew where the problem was - one leaking injector. But now that I've pulled gas out of three cylinders on both banks, it makes me wonder about the FPR. I pulled the vacuum line off that, but didn't find evidence of fuel there.

Anyway, I cleaned the plugs and reinstalled. I'm thinking now that I'll replace the FPR and get the injectors serviced and that should fix it.

New question - When I was buying oil & pricing a FPR & injectors at a local parts store, I was told that the process of 'servicing' an injector was a complete waste of time & money - that they couldn't really be cleaned and the best choice was to buy new ones. Is this true? Eight new injectors at about $100 a pop sounds really steep to me.
Good catch. I think you may be onto something from what you described and the way you checked that injector. Even if you have to buy a whole set, don't pay $100 a piece for them You can buy Ford Motorsports 24# injectors online for around $300 a set. Don't be alarmed! :surprised They're made by Bosch and are a drop-in replacement. I have 30# FMS injectors in my modified LT1. Oh, and your parts store is out to lunch on the subject of having injectors serviced. They're either lying to sell you their over-priced crap or simply talking out their asses.
Just curious, what are these robbers asking for a stock FPR replacement? You can buy a top quality Aeromotive adjustable FPR for about $150. And unlike the stock LT1 units, it has a replaceable diaphragm. It comes pre-set to factory specs (but check it anyway) and is adjustable if ever required for future modifications.
I'll be curious to see what is found when you send the injectors off and here's why. It's not impossible that even if you did indeed have only one cylinder flooding, it could have dumped such an excess of fuel that it could have blown back through the intake and wetted other cylinders as well. I've also seen this with severe coolant leaks into one cylinder and a piston disintegrating and passing debris into other holes. Good luck and let us know. :thumbsup:
 

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Discussion Starter · #13 ·
Finally got the time to finish this. Tried another simple test on the car - with the fuel rail un-bolted from the intake and the injectors in place in the rail, set 8 cups under the injectors and put the fuse back in the fuel pump just to see for sure where the gas was going. Turned out that nothing came out of the FPR, but the #2 injector was the guilty party. As soon as pressure came up approaching 40 psi, it started bleeding till pressure dropped to zero.

I don't know if this is a recommended test procedure, with the cups in place I didn't have gas blowing everywhere, but it did quickly identify where the stuff was coming from.

I'm still surprised that enough gas flowed from #2 across the intake into #3 & #5 to prevent the motor from turning over, but it happened.:huh:

Anyway, I did replace the single injector and the car is back among the running!!

Thanks for the advise on this.
 

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Great info:thumbsup: Glad your back up and running again:cheers:
 
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