Jeffrey Fontaine

OK, I feel like I'm chasing my tail. Trying to track down a rich condition, which intermittently sets the rich code, 45 IIRC.

Based on the threads below, I checked FP, which showed it was dropping off. Clamped the return line and still dropped, so the service manual says leaky injector. OK, so I buy new injectors and start to pull everything today. I pull the injectors out of the manifold but leave them connected to the rail. Ignition on puts pressure at 42psi. 30 mins later its at 26psi (with the return clamped), but not a drop came out of the injectors!!! WTF??? I'm not sure they are even the problem anymore. I don't understand how this can be happening, unless I guess my Actron fuel pressure tester from Advance is bad? I'm stumped, unless it should drop off that much, that fast.

Anyway, you can see here for what I've done so far:
https://www.thirdgen.org/forums/tpi/...ml#post3401698

I have a post in the general engine tech section as well:
https://www.thirdgen.org/forums/tech...rich-will.html

PLEASE HELP !!!

Jeffrey Fontaine

TTT. Anyone???

KrisW

iTrader: (5)

What regulator do you have? Stock?

Maybe the diaphragm is leaking backward with the fuel pump off????

That's the only thing I can think of. I have always done the "injector out" test like you did and found one or two leaky injectors...

mnorton

I think that's a normal condition, and that the fuel just leaks back through the fuel pump into the gas tank.

The system won't hold fuel pressure forever....

Jeffrey Fontaine

Well, the service manual says "does it hold pressure", but doesn't list a time frame. I thought while reading through past posts during a search that seemed like a big drop.

KrisW, the regulator is stock. The service manual says that if it doesn't hold when the return line is clamped (it is/was), then its the injectors. Maybe its going back through the pressure line, I could try clamping that too... But that wouldn't be the reason for my crappy (rich) idle...

KrisW

iTrader: (5)

You still have a crappy/rich idle with the new injectors or have you run them yet? Are your new injectors the same size as the old? Did you do your "injector out" test with your old injectors?

Did you replace or seriously clean your plugs after that?

Jeffrey Fontaine

I have yet to run the car after the injector swap. Hopefully I can tomorrow.

-I got injectors from someone on Ebay off a low mile TPI 305 Camaro.
-I did the "injector out" test w/ the old ones. I have ohm'd the new ones and plan to leak test them as well.
-I have not cleaned the plugs, and I doubt I will. I just swapped them less than 500 miles ago when I started diagnosing this issue.

DZcode

The fuel pump has a one way check valve that holds the pressure in the fuel line between the pump and the regulator. If you've clamped the return and the fuel pressure drops off quickly (and your injectors are not leaking) then it's the check valve in the fuel pump.

mnorton has a point, I don't think the pressure will stay put forever. On mine, the pressure at key turn is 42#. if I leave the pressure gauge on, it leaks down to 32# overnight.

If you get 42# at key-on, you should be okay. With the engine running disconnect the vacuume line from the FPR, the pressure should go back up to 42#. Reconnect the vacuume line and the pressure should go down (check the manual for how much - about 5 to 7 # I think). If it does not go down, you have a bad FPR resulting in a rich mixture. My 94 camaro was running rich and dumping gas in the oil. I put a vacuum pump on my FPR and it didn't change the pressure at all. I needed a new FPR.

Jeffrey Fontaine

I guess this would be diagnosing in the opposite direction, but a bad check valve would give hard starting, not the rich idle I am experiencing.

As you say, you drop to 32# overnight, I drop to 26# in 30 mins. After about 90 mins its -0-.

I'll test like that when i get it running again. FYI, the manual doesn't say how much, but in another post from a magazine article says 1psi for 2"hg. I think SOMEHOW the threads on the fuel line inlet are stripped, just great.