No power to Injectors and Fuel pump

[Drift99]

Hello everyone,
I have a 92 ls400 1UZ in my 89 240sx. Im having trouble figuring out why its not getting power to the injectors or fuel pump. It has run great for the most part last drift season (i believe it might have had this same issue twice before but kinda went away on its own).

The engine cranks and cranks with spark but no fuel. The engine did finally start twice in a row after hours of cranking attempts but wouldnt start up again (the time it did start, i had the pump relay bridged).
I have tried my other ecu i have with no luck.

I know the pump relay was wired to the ecu by the guy that did my harness. I feel like something is telling the ecu to disable the pump and injectors.
The pump relay isnt getting power to trigger the switch when cranking.

I dont have my radiator hooked up at the moment but I dont think that would have an effect.

I would greatly appreciate any ideas/suggestions!

 

[Zuffen]

I read your Post a few days ago and forgot to have a look for you at my diagrams.

If both ECU's have the same problem I would point a finger at the fuel system itself.

Why not check if the injectors are pulsing?

I'd unplug an injector (any injector will do) and see if you have 12volts on the black/orange pin when the ignition is on. If you don't have power there it indicates there is a problem in the wiring from relay feeding the fuel system. From memory it also feeds the ignition so if you have spark you should have power at the injectors.

The real culprit (I believe) is the fuel pump relay.

Try hot wiring the fuel pump and ensure it is running all the time (for testing only).

Once you have the pump running try starting it.

If it starts and runs, you know where the problem is. If you can't find the problem with the circuit an easy permanent fix is run a tachometric relay in the fuel system. This will ensure the pump stops if the engine stalls, or stops running.

Have a play and let us know how it goes.

 

[Drift99]

Thank you Zuffen,
I determined that the main injectors have power but are not pulsing. If I spray some quick start into the intake it fires up instantly and the injectors start working normally. Im thinking the cold start injector is responsible to get the engine fired up and then the main injectors take over...? Maybe the cold start isnt working? I read about people deleting the cold start altogether with no issues though so that also has me thinking otherwise. Any ideas?

 

[Zuffen]

The injectors still should pulse when cranking as the cold start isn't designed to run the engine, rather assist the engine in very cold (probably 0degrees C temps) conditions to start.

Lack of cold start could be one of a few issues.

The cold start injector relies on the cold start thermo-switch in the front water-bridge. Check it's a) plugged in and also check it for continuity and earth.

Also check the injector pulses by applying power to the end of appropriate wires with the ECU disconnected. This is easier than taking off the manifold to get at it.

If it's faulty then the manifold must come off.

 

[Drift99]

Thanks Zuffen, I will give that a try.

 

[Bushwhacker]

Do you have 12v at the STA wire when cranking the engine?