88 305 TPI running pig rich when starting warm engine. I hadn't run the car for over a week when I tested F/P last night.

Turned ign. switch on and F/P went up to 45 psi and dropped 10 lbs in 13 minutes.

Repeated test a few times pinching pressure and return lines and then no lines again and pressure loss lessened to an average of 2 psi drop per 5 minutes per test.

How much pressure drop is acceptable in 5 or 10 minutes??


After pressure test I started the engine and saw the "Check engine light" go on for the first time. I checked the code and got a 15.

Could the coolant sensor be the problem or are the injectors leaking to much?

 

Mine does the EXACT same thing. Pig rich when starting warm or hot. My CTS is only 1 year old. Don't know what the hell the problem is...other than possible leaking injectors...

I don't get an SES light though.

Smoke through the exhaust when it happens...

 

Leaking injectors won't cause a bad CTS / CTS code. If you don';t have a scan tool to verify what your ECM is seeing from it, you can check the CTS manually with an ohmmeter. Do a search for something like CTS resistance, there's a chart of resistance @ temperature for GM IAT / CTS that's been posted a million times.


As for how much pressure drop is acceptable, depends where it's leaking. If ANYTHING is going through the injectors, i consider it unacceptable. Other than that, doesn't matter much at all as long as you don't have hot restart issues.

For example, ever since i put the Holley AFPR in, my pressure leaks down a lot worse than what you are describing, i'll be down to near nothing in 15 minutes. I've had my injectors out of the intake and verified they are not leaking at all. Since the ECM will reprime the fuel system after a couple minutes of being shut down anyway, it doesn't matter to me at all. It still has enough pressure to refire if i try to restart within a minute of shutdown, and that is all that matters.

Leaking injectors is horrible though, not just from a hard start perspective, but you're also contaminating your oil and washing down your cylinder walls as well.

 

Mine does the same. Pressure drops off rapidly.

A couple of years ago I thought it was a problem and went to the trouble of trying to find the cause.

Did the pinch the hose trick and discovered the leak-down was at the return end. Pulled the pump a few times (fortunately on a Vette it's super easy) from the tank but could never get the pressure to hold.

I even did the timing thing to log amount of pressure drop over a certain period of time. Posted all that info on the Vette forum asking for help.

I finally came to the conclusion that it's a non issue. Car starts and runs fine, no smoke or other indication of the "malfunction", so I just ignore it.

There'll always something else to worry about.

OF COURSE, if it's on the pressure side - injector(s), regulator- well, that has to be fixed because it'll end up hurting the engine, just as Ed said.

Jake

 

OK, so on a TPI engine, the Larger rubber line is the feed while the smaller rubber line is the return to the tank? Can someone verify this. I want to clamp off the return and watch the psi drop. I'm pretty sure my injectors are pissing away into my combustion chamber...

 

On my 88 IROC the flex lines are located on the drivers side near the power steering pump.

The pressure line is the larger of the two and is located above the return line.