Injectors not firing

[andreic]

Hello all,

I have just finished putting together a 1.8L engine that I've rebuilt over the winter. I am trying to get it started. The engine is built with an L-Jet fuel delivery system. A few months ago I had tested the L-Jet on a different engine, and it worked well.

With the new engine installation, the injectors are not firing at all. I have checked and there is spark, there is fuel pressure in the FI rails, and the injectors themselves are good (I pulled one out, and hooking a 9V battery to the terminals I got a solid squirt of gasoline). But when I crank the engine (with the injector out) nothing happens.

I have checked all the electrical connections and they seem good. I also checked that the ECU gets power (at pin 10 12V+ and at pin 17 ground).

What would the next step in debugging the system be? Everything else that I thought to check seemed to be OK: for example I tested that by slightly opening the "door" in the AFM the fuel pump starts working, as it should. In fact I managed to get the engine to fire a couple of times by manually getting the cold start valve to squirt (again, with the 9V battery). But of course that is no substitute for the injectors firing.

Any help would be appreciated.

Thanks, Andrei.

[Dave at Pelican Parts]

First: check the wiring. In particular, the L-jet cars have a white wire that plugs into the coil (-) terminal that carries the points signal to the injection, telling the injectors when to open.

Next: Check that the injectors are getting power. They should get power when the key is on, I believe. The power goes through the resistor pack that hangs off the battery. The ECU provides the ground in order to get them to open. The power to the injectors is provided by the other half of the dual relay.

--DD

[andreic]

Thanks Dave.

I figured out what was wrong. The harness plug going to the specific injector I had pulled out was bad. One other injector was stuck from sitting, so the engine was getting fuel only from 2 injectors. The one injector that was stuck I managed to get unstuck. I also did a temporary fix on the plug that was broken. After fixing these issues the motor now runs well (ignoring some issues, see below), and I managed to break it in (25 minutes at 2500 RPM, new cam).

Two questions:

a) Fixing the plug that was broken was only a temporary fix (using a soldering iron). Where can I buy the little crimp-on metal connectors that go inside the injector plug part of the harness?

b) The only thing that is still not working is the idle. The engine will die at idle, whether it be cold or warm. I tried using the idle adjustment screw on the throttle body, and the highest I can get the idle to is about 500 RPM with the screw all out.

From what I read the problems could be a vacuum leak (I'll check for that tomorrow or Monday), or the fact that I use Jake Raby's 9550 cam (non-stock). Are there other reasons it would not idle? If it's the cam that's the problem, can the throttle be modified to let in slightly more air at idle?

[Dave at Pelican Parts]

It's possible your cam is causing the vane in the air flow meter to flutter, dumping excess fuel at idle. Or it could be a vacuum leak, making for a lean mixture.

The crimp-on connectors are probably available from electronics specialty places; 3mm female spade connectors with retaining barbs. You might ping Jeff Bowlsby (contact him through The Classic Porsche 914) and see if he has a source.

--DD