Hey Guys,

Over the last year, I have noticed from time to time the smell of fuel in the engine compartment.
I could never find any visible signs of fuel and the smell was very brief. However, my concern and curiosity got the best of me and I decided to dig deeper.
Since I believed that the fuel injectors were original on this 17 year old car, I decided to be proactive and purchased a rebuild kit for the injectors. Once received, I pulled all the injectors out of the car to rebuild and discovered that every single plastic injector body was cracked. Some worse than others but all were affected - so much for rebuilding.

Because these are a standard Denso fuel injector and I was rather short on cash at that moment, I elected to buy a complete set of rebuilt and refurbished original Denso units off ebay. Units arrived, looked brand new and I installed them with success. No leaks anywhere and the car fired right up. It wasn't too long before I noticed a change in the car when starting it and it only affects the car when I have been driving. Cold starts are absolutely perfect but if I leave the car for 15 minutes or so after driving, the car kinda stumbles when I start it. My starts were always very consistent and the starter would turn the engine about 4-5 times before it fired up - all very normal. Now, with these new injectors, the car may fire after only a turn or two of the starter and the engine stumbles when this happens. And it can be different throughout the course of the day.

Since there are no external leaks and the engine performance seems perfect when the car is running, I have a theory that maybe a couple of injectors may be dribbling raw fuel into the cylinders after the car is shut off? Maybe the piston inside the injector isn't sealing well?
This is based on the theory that after the car sits, any dribbles of fuel into the cylinder(s) evaporates and hence I get a predictable cold start but if left only for about 15 minutes, it is not enough time for that fuel to evaporate in the cylinder and I get a fire on cylinders prematurely causing the engine to stumble. I should also add that if I shut the engine off and start it within about 5 or so minutes, the car again starts normally. I think that is because not enough time has passed to have enough dribbled fuel into the cylinders to cause the aforementioned condition. Does anyone have experience with a similar condition? I want to contact the seller about it but would rather be more certain on the possibility first.

 

The usual problematic area for our 4.2L engines are those dreaded fuel dampers on the rail. They are known to leak, sometimes, unless they are not, or maybe they are. Maybe they leak a bit, and cause the fuel pressure to drop a bit and let fuel evaporate in the rail, causing hard start. Some folks activate the fuel pump with the key a couple of times before activating the starter to build pressure back. See if that helps. There are posts about this, mostly about the difficulty to work a repair. They seem available from Jaguar ($$), but are reputedly hard to press back in place and not leak. I would think there would be at least a hint of a smell in this scenario.

Other thought would be that you are experiencing the early sign of an aging fuel pump. You might want to replace the fuel filter just because, and throw in one of the better fuel injector cleaners (Techron?) to see if it helps. These pumps are $$$ unfortunately, with no immediately known after market part.

Other thought is a leaking fuel pressure sensor. Known to leak externally (smell) and even internally through the vacuum line and push leaked fuel into the throttle body.

Fuel pressure is available over OBDII, so even a cheap ELM327 can read it. Should be 55psi under pretty much all circumstances.

Best of luck, keep us posted.

 

With fire extinguisher at the ready, I fired it up and looked very closely for any sign of fuel. Didn't notice any and there is no fuel smell anywhere.
If I assume that the install of the rebuilt injectors is done correctly, I have to place the blame on the last set of parts - the injectors themselves.
It's not that it is hard starting and I have fuel pressure right in the 55 range so thats also good.
Its that it starts differently every time
As I said - when cold - exactly the same
When restarted from hot after several minutes - the same
When starting after about 10-15 minutes - a stumble and oftentimes the car starts, albeit roughly - after only a couple of turns of the starter.

I think I am going to have to set to pull the rails out, let the pump build pressure with the injectors exposed and see if any fuel starts dribbling out.
Without some sort of fuel injector test setup, that's the only way I can provide enough pressure to the injectors to witness it.
I will keep the forum posted.

It just occurred to me that if I keep the computer hooked up after I shut the engine off, I can see how quickly the rail pressure drops (I think? )
This will give me some indication of a internal leak anyway. Popping the rails to witness any dribbling will positively ID the problem though

 

Would removing the metal plate in front of the plastic intake (by the thermostat) help with this analysis? Would there be a strong smell of fuel if there was a leak? Seems way easier on the face of it.

Remember the "rubber" section of hose between the 2 fuel rail sections is really hard plastic covered in rubber and is not available as a separate part AFAIK. Be super cautious with it.