Injector Flooding???

[mearssr]

Long time reader, first time poster. Some of you guys really know fuel systems, so I figured this question would be best asked here. Hopefully this doesn't get too lengthy

I picked up a 90 z32 about a month ago. It had injector problems, and the previous to the previous owner had torn it all down and sold it. The guy I bought it from was clueless, but went ahead and bought an intake manifold and loaded fuel rail, used, off ebay, which he included when I bought the car.

Go figure the injectors he bought were the oval-connector style (later model), but I was lucky enough he'd bought the lower intake, fuel rails, and wiring pigtails to go with it all. I ohm an click tested the injectors, which all tested okay. (sure enough, 4 of the old injectors wouldn't even click when power applied). So I replaced the injector base seals, and put the rest of the top end together with new oem gaskets, and soldered the new wiring connectors to the old harness.

Well I got it together, and had no crank no start. Turns out when I cycled the key to get new fuel up the system, it'd flooded cyl #1 and hydrolocked against the starter. I pulled #1 spark plug, and it would crank, but even after fuel was drained from #1, every compression and exhaust stroke shot tons of fuel across the shop from the spark plug hole. Put back together, it still floods that cyl to hydrolock, whether I'm cranking or not.

So I figured either bad lower o-ring, or catastrophic injector failure. I tore the plenum and fuel rail off to do some testing. I pressurize the rail, and there was no leakage. I then turned the CAS, and each injector fires perfectly.

SOOOO, before I put this back together, does anybody have any idea how an injector could DUMP fuel into a cylinder, but behave properly and totally sealed when tested uninstalled? Thanks!

[mearssr]

Okay, writing it out and thinking about it for a couple hours may have led me to an answer.

The injector/pigtail assembly of the newer oval injectors sits higher than the older rectangular ones. I know I had to connect the harness to #1 before I could put the intake plenum down, since there's a bracket that sits right above it. If that bracket was pushing down on the injector, it could cock it at an angle and cause the o-ring to not seal within the plenum? I suppose this would also account for it sealing fine when the intake and rail is removed?

Does this make sense to anyone, or has anyone heard of this problem occurring? Sucks I have to wait until Saturday to further look into it!

[ceniack]

Those injectors are side feed and the way the fuel rail works on those is that if they don't leak with them in the fuel rail out of the manifold they won't leak in the manifold either.

also, you said that 4 of the injectors wouldn't click when you tested them? or did you get that fixed? if they are not clicking one or more of them could be stuck open (or when you apply current to them they may not be pulsing correctly and just staying open which could mean you have an issue with the wiring, the ecu, the injector, or a combination.

also, if the engine isn't even trying to start you are probably not getting spark. which could be a bad distributor, bad plugs, bad wires, or a combination of those things, or nothing at all.

I would first test to see if i am even getting spark first. if you are getting spark but still flooding the engine I would send the injectors off to Deatschwerks and have them cleaned and flow tested (they are good guys I used to work for them) to rule out the injectors.

[mearssr]

Thanks for the reply and the ideas! I finally got around to tearing into it, so I thought I'd post an update.

Turned out my suspicions were correct. With the newer style vg injectors installed, the connectors sit much higher than the older style. Injector #1 is directly below a bracket on the manifold that holds the center throttle cable cams. When the manifold was installed and torqued to spec, it pushed on the corner of the injector plug just enough cock the injector at a bit of angle and let fuel leak past the o-rings.

The 94+ vg30 plenums must be different. I trimmed a 1/4" notch in this bracket, and the problem's solved!