Shinobi'sZ

When my car gets warm I notice at idle that I will occasionally see smoke white/grey, it smells like gas. I confirmed it's not coolant or oil...it smells like gas an leaves a black soot on the tail pipes. It reminds me of when my diesel injectors started sticking open at idle.

The car starts normally, and it doesn't miss, hesitate or stumble. I have an Aeromotive APR, coming off a -8 return line from the diaphragm in the middle of the stock 01' FPR...that returns back to the tank, I use a 97/98 fuel filter. 60lb mototron injectors (7 years old).

I put a fuel pressure tester on the end of the rail at the schrader valve, the running fuel pressure is 69psi. When the BAP kicks in it goes up to 74psi.

However if I just prime the system without starting the fuel pressure goes to 39/40....then when I turn the key off it rapidly drops down to under 10psi. It doesn't hold any pressure at all.

With a return system...similiar to a 97/98 rail (just larger return line), should my fuel pressure drop from 40-10 psi the second I turn the key off after priming?

I suspect injectors but want to make sure I'm testing them correctly.

0Anthony @ LGMotorsports

Depends on the return, and how everything is plumbed and where you are checking it. If you can isolate the rail, no the pressure should not drop much once it is turned off.

On the OEM setup there is a check valve to keep the fuel from back flowing to the tank so it should remain pretty close and just have a slow bleed off.

Shinobi'sZ

Thanks for the tip and I should have thought about that. I will find a
-8 AN cap to place over the check valve/diaphragm on the center of the rail that leads to my Aeromotive AFPR return. That way the rail will stay pressurized and I can see if the pressure bleeds down fast or it is 1-2 psi over a longer period of time.

That should tell me if the injectors are leaking, I guess they could also be bad and pulsing when the cylinder isn't firing too...hopefully they will leak and I can confirm that they are what's bad and simply replace.

LoneStarFRC

Another way to check for leaking injectors is to pop the fuel rail up with the injectors still attached, and place some clean towels/rags under each one. Turn the key on for a few seconds.

1BADAZ50TH

Thats how I checked mine.

0Anthony @ LGMotorsports

You can do that as well....but can be a bit dangerous given the size of the injectors he is running if one is stuck on. Also you have to make sure the clips are in that hold the injectors to the rails, on some of the aftermarket rails they do not use these and you can blow the injector out of the rail....causing another issue.

Shinobi'sZ

Yes but I have to plug the return first to cover what Anthony stated. I think that would work on a returnless type fuel system where the fuel filter is controlling the fuel pressure (like on an 99-04' stock fuel system). If you look at what Anthony stated the return line could be bleeding off the pressure. So I have to eliminate that first.

However once I remove the return and cap it, I could then follow the recommendations you guys made and is what I will do.

I want to check the ability for the system to hold pressure first with the injectors in. If it bleeds down, I will pull the rail with the injectors left in and flip upside down and turn the key on to prime the system and look for the injectors to leak....that will be a good way to spot the culprit if it is just one.

Shinobi'sZ

OK well I disconnected my return line and took off the fuel rail and turned the key to on and listened to the pump prime, my fuel pressure gauge that I had hooked up to the end of the fuel rail went to 80 psi (LPE 255 lph pump) and slowly bled back down after I turned the key off...but none of the fuel injectors leaked a drop of fuel anywhere!

I am beginning to wonder if the smoke I'm seeing is being caused by a bad o2 sensor...maybe it is causing it to run rich at idle?

I only see the smoke at idle...never under boost or part throttle. It is after the car heats up and I come to a stop that the white/grey exhaust appears @ idle and doesn't linger to long...smells heavily like gas and leaves black soot on my tail pipes.

If not the o2 sensors could the injectors being betting stuck after they are hot??

3boystoys

Get it on a scanner to see what the O2's are doing. Maybe your pressure at idle is too high or your pulse width of the injector is too wide leaving the injector open too long.
I would think the fuel trims would be WAY out of whack and should give a too rich condition away.

This is a good discussion of fuel trims:
http://www.motor.com/article.asp?article_ID=1075

RedZMonte

Rich Idle in the tune? what size injectors? You have an adjustable FPR and 74-80psi, might need to lower the pressure and retune. high fuel pressure can cause the injectors to push fuel past causing a rich condition.

Injectors have a Rating of Flow vs pressure.. exceed the pressure and you result in higher flow. white smoke indicates water.. condensation build up from a rich fuel condition at idle? Do you have Cats on the car or is it Catless? Pull the oil dipstick and smell it, if it smells like fuel then you most likely need to make a few adjustments, fuel will wash down the cyl wall and bleed into the oil.

Injectors tipically will either stick or not.. don't usually change with temp. if everything checks out have the injectors tested/cleaned..
this will help explain what you will see with a dirty injector.
http://sacramento.backpage.com/AutoS...ervice/4386193


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