Troubleshooting leaky injectors / Flooding problem
 

I'm trying to troubleshoot a flooding problem I'm having with my FD. It's a single turbo, running a Link G4+ Fury ECU. A little more background on my flooding issue is in this thread: https://www.rx7club.com/3rd-generati...loods-1148802/

I'm trying to confirm if my fuel injectors are leaking, as at this point I don't think it's a tuning issue - even with all the cold start enrichment mechanisms the Link ECU provided turned off/zeroed, the engine still floods while cranking. I've even played with reducing the fueling in the main fuel map for the cranking RPM/MAP range cells, without much success - It's trying to start, and will actually fire and get some combustion going, but quickly floods out - as evidenced by some fuel spewing past the exhaust mani gasket every time I crank it. While trying to start, I was logging data with PCLink, and based on the log data, it looks like the ECU is behaving correctly.

To test if the injectors are leaking, I hooked up a battery charger and then ran my fuel pump constantly for a full 20 minutes to keep the system pressurized at base pressure. The idea there is if any of the injectors were leaky, the garage would eventually stink of raw fuel, and I'd see a puddle when the fuel leaks past the exhaust mani gasket again. After 20 minutes of full fuel pressure, there was no fuel stink or puddles. To double check, I also pulled the spark plugs to see if there was any fuel getting into the combustion chambers - plugs came out dry.

So the question is, was that a conclusive test to rule out leaky injectors? I suppose it should be if the injector only leaks when it's supposed to be fully closed (off). Which brings up another thought - is it possible for injectors to behave in unpredictable ways during normal operation? (e.g., get non-linear or stick open longer relative to the pulse widths/duty cycles provided by the ECU, so in effect the ECU has no real control of fueling)

Before anyone tells me to check for compression & spark, done that and it's good on both fronts. Compression #'s (cold engine though) were 129psi on all faces, +/- 2 psi, normalized to 250 RPM & sea level per my RCT 5.2 rotary compression tester. Also pulled all the plugs and set up a quick test to observe for spark while cranking, all spark plugs fired properly while cranking and timing was spot on where it is supposed to be.

if i was going to see if they would leak id pull the injectors out of the manifold, but do somethign to keep them in the fuel rails bailing wire/ super strong rubber bands ect, then pressureize them and see if u can see drips. or just have them flow tested/cleaned anyway.

^Sending the injectors out for cleaning/flow testing is definitely the easy button...

But since the Link G4+ ECU has an injector test mode that allows you to run the injectors at whatever pulse widths you select, while logging your fuel pressure and voltage, I can do more than just test for leaks at home - I'd also be able to characterize static flow rates. Just need to fabricate a test jig to keep the injectors secured in the FFE fuel rails but outside of the engine bay and dumping into a measuring cup. I'm thinking some AL square tube stock, with holes drilled thru for the injectors to sit in would work - then just a couple of C-clamps to secure the square FFE fuel rails to that square "bottom" bar with the injectors sandwiched in between. A few feet of -6 hose & AN fittings to connect fuel pressure & return lines back to the car, and a wiring jumper for the injector clips.

I like the idea of fabricating an injector test rig, if you've got the ability to do that. It might be easier to disconnect the harness and use a noid light in place of the injectors to watch that they are pulsing briefly as opposed to turning on and staying on, but knowing the volume might be useful.