Fredbird

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?

Fredbird

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.

hogsnvettes

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.

nutz4c4

Likely the diaphram needs to be replaced..

rodj

Fuel from leaking injectors doesn't flow 10" uphill and against the airflow to the plenum
As noted ; faulty diaphragm in fuel reg is usual cause of fuel in the plenum

Fredbird

I would agree on this one... Since there is a vac. being pulled on the the regulator diaphram, if there is even a pinhole leak on that diaphram the gas will follow the draw of the vacume into the intake.

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...

hogsnvettes

Well I guess I'm confused by the OP's description of the problem. He says the fuel is pooling behind the TB. If the regulator has a faulty diaphragm wouldn't it be evident on the outside of the plenum? I'm also not sure how a bad regulator can cause unburnt fuel smell from the exhaust. If an injector begins to leak then fuel will continue to flow into the intake manifold until the pressure drops to a point where it stops. If the engine is not running, there is no airflow to prevent it from pooling in the intake.

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.

rodj

On a TPI engine the OP has, the TB is a lot further away from the injectors than on a LT1

Tunedport90

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

jesredvette

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.

Cliff Harris

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):

jesredvette

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.

Jimbo 89

Just remember before you start the job, you will need a TAMPER RESISTANT T10 torx driver. Ask me how I know...