Unknown underhood fuel leak

[thatoneguygeoff]

I have a 97 4Runner with a supercharged 5vz-fe. Whenever I get on the gas there is an overwhelming smell of gas that fills the cab. It only seems to happen when the supercharger is making boost. There are no visible signs of a fuel leak anywhere under the hood and the smell is that of more than just a little drop and more of a spray. Does anyone have any experience with this?

 

[SpidermanGeek]

I have no experience, but my first thought is leaky injectors.

 

[jeremyc74]

The fuel path is pretty straightforward. You have the pump feeding one end of the fuel rail, and the regulator bypassing from the other end, back to the tank to maintain the right pressure. I'd get a good look at the regulator, and where the lines are connected to it, and go from there.

You want to be very careful with this. Atomized fuel under the hood will light off VERY quickly, and there are plenty of ignition sources under there. A fuel leak that's spraying instead of dripping is a dangerous thing. :boom:

 

[thatoneguygeoff]

It's like the leak only occurs when the fuel pressure spikes when the boost comes on

 

[jeremyc74]

It's like the leak only occurs when the fuel pressure spikes when the boost comes on

That could be due to the engine rocking, and pulling on a connection somewhere.

I'm not all that familiar with the supercharger installation on these trucks, but do you have to alter the fuel pressure when the boost come on? It could have something to do with that too.

 

[thatoneguygeoff]

I have tried revving it in my driveway and it won't do it. Only when there is a load on the engine while driving. The fuel pressure is automatically adjusted with the AFM and the fuel pressure regulator. Looking at a diagram I just found it looks like there is a seal on the regulator. I will check that out after work today.

 

[HiLife]

I hope when you are running your truck that you have a fire extinguisher or two near by just in case.
Stay safe.

 

[thatoneguygeoff]

Yea I keep one next to my seat

 

[azcat90]

Seals

Change the FI O rings top and bottom - use dab of WD40 to lubricate rings before re-seating into engine and fuel rail.

 

[gamefreakgc]

There's nothing fancy about the supercharger, it doesn't change the fuel system at all. You've got a leaking seal most likely, at boost the fuel pressure is at maximum so it's seeping out somewhere. Injectors and hoses are the best places to start.

Is there a way to jump the fuel pump at the diagnostic port? It was easy to do on OBD-I systems but never tried on an OBD-II.

 

[GSPRunner]

Having this EXACT issue on my supercharged rig. I was thinking leaking injector but haven't had time to look at it yet.

 

[jeremyc74]

A leaking injector O-Ring makes good sense. On a N/A truck you'd likely never notice it because the intake is always under a slight vacuum. Once you're under boost it could be pushing the mixture back out past the injector seals.

 

[ajonesnv]

So, can I throw in that the charcoal canister could be a possibility, however the likeliness of it smelling only on acceleration is low.

 

[azcat90]

Make sure you have a 17 mm box wrench for the fuel rail and careful not to drop the 4 aluminum gaskets - magnets won't pick them up.

 

[thatoneguygeoff]

All of my injector seals (upper and lower) are dry and not leaking. Next step is to check the banjo fittings and fuel pressure regulator

 

[azcat90]

Dry?

All of my injector seals (upper and lower) are dry and not leaking. Next step is to check the banjo fittings and fuel pressure regulator

Did you pull the injectors out to inspect the seals?

 

[thatoneguygeoff]

Ok so I just checked all of the connections on the fuel lines under the hood( supply, fuel rail cross over, and return) and the leak looks like it is one of the hose to banjo/elbow crimp connections near the drivers side rear of the fuel rail

There is a lot of dried fuel residue that has accumulated just below the lines onto the lower intake plenum. I have removed all of the residue with brake cleaner and degreaser and will check it again in a day or so to see if it reappears.

 

[thatoneguygeoff]

It is underneath the supercharger so it will have to come off to verify my findings.

 

[rideexileex]

Any updates?

 

[thatoneguygeoff]

I'm going to look at it after work today. I didn't do much driving after my last post but my drive to work this morning I was driving fast and up in the boost and the fuel smell was pretty strong. Thee should be some new evidence there now.