Injector voltage problem [fixed]

[d3nso]

A local guy here has some problems with his AE86. He recently changed his headgasket. Now hes got problems getting his car back to run properly. With all injectors connected the injector voltage brakes down and the engine stalls after 5sec . But if he unpluggs one and let it run on 3 injectors it does not. Anyone expirienced a similar problems?

[Bean]

Bad earth? Is the ground cable on the intake runners connected properly?

[d3nso]

He said he checked all ground connections. Will have a look myself tomorrow and wanted to know if anybody has a idea where to start looking for the problem.

[Project D]

The ground on the intake runner would be the first thing I would look at.

[jondee86]

The injectors should be getting 12V straight from the keyswitch, and
the ECU switches the circuit to ground to pulse the injectors. So as
mentioned, the ECU ground wires to the bolt on top of the inlet manifold
runner need to be secured. That ground connection is well hidden and
is often missed when putting the engine harness back in place after
removing the head.

Otherwise...

Is the engine running low-Ohm injectors and a resistor pack ? If so,
check the resistance of both legs of the resistor pack. Also, when you
say the voltage breaks down, does this mean that the engine starts
to misfire and run roughly ?

Cheers... jondee86

[d3nso]

He is running stock low ohm injectors (grey color,he measured them at ~2ohms each). Where is the resistor pack located?
He said the car won't start with all injectors plugged in. If he tries to start the car with 3 plugged in it starts and runs but as soon he plugs in a fourth injector the car dies after a few seconds. No missfire or stuff like that.
I haven't seen the problem in person for now and the problem sounds very strange to me.

[jondee86]

Should look like one of these...



... and it will be on the intake side of the engine bay, most likely bolted
to the inner guard. I was thinking that there might be a problem there,
but now think it unlikely since the engine fails so quickly after connecting
the 4th injector.

As you say... unusual problem

Cheers... jondee86

[d3nso]

We have checked serveral things and have no idea what's ging on. One thing is the car dosen't have a resistor box (mine also didn't have one either?) and the injectors are definetly low impedance. All grounds are solid and the relays work. Any other ideas?

[jondee86]

Is the car running rich or lean ? What do the plugs look like ?

What happens if you try to rev the engine when it is running on three ?
Does it rev or does it choke and die ?

What I'm thinking is that this may be a fuel issue rather than an electrical
issue. Like a pump that is on its last legs and can't supply enough fuel for
four injectors without leaning out so much that the engine will no longer run.

Never actually known of this happening, but theoretically it is possible

Cheers... jondee86

[d3nso]

With three injectors you can rev the engine "normal". We installed a Skyline fuelpump just to be sure (4bar of fuel pressure now) and still the same problem. Also tried a aftermarket fpr with no luck. It seems like the injectors doesn't fully open or something like that.