Gas in intake manifold.
Thread Starter
Instructor
Joined: Apr 2011
Posts: 208
Likes: 0
From: Trophy Club Texas
Gas in intake manifold.
I am in the process of removing the plenum to replace the EGR valve, and fuel injectors. I noticed though that when I removed the Throttle Body there was a pool of gas just behind it in the intake.
That's not normal is it? I knew I had been smelling gas, but didn't know where it was. Now I know.
What would cause it to pool up like that?
That's not normal is it? I knew I had been smelling gas, but didn't know where it was. Now I know.
What would cause it to pool up like that?
Thread Starter
Instructor
Joined: Apr 2011
Posts: 208
Likes: 0
From: Trophy Club Texas
I am in the process of removing the plenum to replace the EGR valve, and fuel injectors. I noticed though that when I removed the Throttle Body there was a pool of gas just behind it in the intake.
That's not normal is it? I knew I had been smelling gas, but didn't know where it was. Now I know.
What would cause it to pool up like that?
That's not normal is it? I knew I had been smelling gas, but didn't know where it was. Now I know.
What would cause it to pool up like that?
Sounds like my Fuel Regulator has gone bad, and the fuel is now being pulled through the vacume line into the intake.
This would also explain why It's hard to start and idle after the car has been run for a while. It would also explain the rich/unburnt fuel smell coming out of the exhaust. Also, it would explain why some of that unburnt fuel makes it's way all the way back to the cats on deceleration causing light backfiring.
Instructor
Joined: Aug 2010
Posts: 238
Likes: 0
From: Asheboro North Carolina
Fuel flows into the intake manifold through the injectors. If one or more of the injectors is bad it may cause a constant leak and the gas has to go someplace. There is no other source of fuel flow into the manifold other than through the injectors, so your plan to replace them is probably the correct course of action. Are they the original Mutec injectors? After replacing them, you should inspect the plugs and possibly replace them as well. If any are sooty black they will indicate a very rich condition and further explain the other symptoms you mentioned.
Melting Slicks
Joined: Nov 2005
Posts: 2,736
Likes: 0
From: WAY UPSTATE NY
I think I've figured it out myself... Let me know if you agree..
Sounds like my Fuel Regulator has gone bad, and the fuel is now being pulled through the vacume line into the intake.
This would also explain why It's hard to start and idle after the car has been run for a while. It would also explain the rich/unburnt fuel smell coming out of the exhaust. Also, it would explain why some of that unburnt fuel makes it's way all the way back to the cats on deceleration causing light backfiring.
Sounds like my Fuel Regulator has gone bad, and the fuel is now being pulled through the vacume line into the intake.
This would also explain why It's hard to start and idle after the car has been run for a while. It would also explain the rich/unburnt fuel smell coming out of the exhaust. Also, it would explain why some of that unburnt fuel makes it's way all the way back to the cats on deceleration causing light backfiring.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
As noted ; faulty diaphragm in fuel reg is usual cause of fuel in the plenum
Thread Starter
Instructor
Joined: Apr 2011
Posts: 208
Likes: 0
From: Trophy Club Texas
I WILL be replacing the injectors too because they are the original multec injectors, and that was one of the original reasons. along with my EGR Valve, that I was removing the plenum anyway.
I just had been smelling gas for a while and didn't know where it was coming from... until now. (Thought maybe one of the injectors was leaking a bit)
Better to have found it this way rather than wait until the diaphram completely ruptured and would be standing along side the road with my vette in flames...
Instructor
Joined: Aug 2010
Posts: 238
Likes: 0
From: Asheboro North Carolina
By the way, all opinions I've expressed are based on what I observe on my 95 with LT1, and leaky injectors I've seen demonstrated online several years ago.
Ahh! Just dawned on me why I'm probably wrong and you're right. I didn't consider that regulator is a sealed unit and the vacuum line would suck fuel into the intake if there was a diaphragm leak.
Last edited by hogsnvettes; Jan 19, 2012 at 07:35 AM. Reason: Add comment
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
On a TPI engine the OP has, the TB is a lot further away from the injectors than on a LT1
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Aug 2011
Posts: 2,844
Likes: 176
don't know if this is lt1 or tpi, but tpis is selling some of there nos parts pretty good deal...
http://www.ebay.com/itm/L98-TPI-Fuel...#ht_500wt_1073
http://www.ebay.com/itm/L98-TPI-Fuel...#ht_500wt_1073
Racer
Joined: Nov 2006
Posts: 420
Likes: 0
From: Sierra Madre California
I had the exact same issue with my '88. I determined, after a little research, that it is not an uncommon problem and is almost always the fuel pressure regulator diaphram. You can replace the diaphram without removing the regulator, just by removing the plenum. Simply remove the screws on the regulator, put on the new diaphram, and put the top back on. Just make sure that you tighten the screws carefully to avoid wrinkling the diaphram.
Not very expensive and relatively easy; a casual evening's work, and not much more than a hour if you're experienced. Because it's cheap and easy, I would do this before you start fooling with injectors.
Not very expensive and relatively easy; a casual evening's work, and not much more than a hour if you're experienced. Because it's cheap and easy, I would do this before you start fooling with injectors.
Last edited by jesredvette; Jan 25, 2012 at 02:49 AM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
My car caught on fire after the vacuum hose blew off the regulator and sprayed fuel all over the engine. Fire extinguisher saved the car. Don't wait to fix this.
This is what my fuel pressure regulator diaphragm looked like (note the large hole):
This is what my fuel pressure regulator diaphragm looked like (note the large hole):
Racer
Joined: Nov 2006
Posts: 420
Likes: 0
From: Sierra Madre California
Cliff is right. Pooling gas is never good. Replace the diaphram now.
In addition to avoiding a potential nightmare (fire) you will see mileage start to improve and the car will run so much better without raw gas in the plenum.
In addition to avoiding a potential nightmare (fire) you will see mileage start to improve and the car will run so much better without raw gas in the plenum.
Burning Brakes
Joined: Jun 2008
Posts: 892
Likes: 1
From: New Smyrna Beach Florida
I had the exact same issue with my '88. I determined, after a little research, that it is not an uncommon problem and is almost always the fuel pressure regulator diaphram. You can replace the diaphram without removing the regulator, just by removing the plenum. Simply remove the screws on the regulator, put on the new diaphram, and put the top back on. Just make sure that you tighten the screws carefully to avoid wrinkling the diaphram.
Not very expensive and relatively easy; a casual evening's work, and not much more than a hour if you're experienced. Because it's cheap and easy, I would do this before you start fooling with injectors.
Not very expensive and relatively easy; a casual evening's work, and not much more than a hour if you're experienced. Because it's cheap and easy, I would do this before you start fooling with injectors.
Just remember before you start the job, you will need a TAMPER RESISTANT T10 torx driver. Ask me how I know...
