4ZE1 - Electrical Issue

[adam101990]

Hi team,
First time poster long time reader (finally set up an accout)

I am having an issue where my TF Rodeo will start and stay running with the key in start position, 5 seconds after releasing the key it will die.
It is not the fuel pump relay however I can trick it into running by bridging it (all the reds stay on but does not charge)

I am guessing that my ECM relay may of died but dont want to spend money needlesly.

The only thing to change is my drivers side floor pan got a bit wet. (aussie so the on ECU side)
Didnt touch the ecu but the wiring that goes under the seat and out to the (pump?) got wet.

Any Ideas or am I going to have to stuff around finding it?

[adam101990]

I Just found this post on another page. This one says that if the alternator dies, it wont pump fuel?
Can any one confirm?

http://www.4x4wire.com/forums/ubbthreads.php/ubb/showflat/Number/511852/site_id/1#import

Here is an part from it

've stated it here years ago that the oil pressure switch was a safety that would cut the fuel pump if you loose oil pressure. In that time, I've come to realize that is *wrong*.

I'll have to check the wiring diagrams again when I get home, but from memory, the fuel pump is powered through the charge relay that the alternator kicks in. This does not flow through the switch. So, loosing the switch (or oil pressure) will not kill the motor. Loosing the alternator will though.

It was really confusing. I had a hard time figuring out the point of the circuit though the switch. It looked like it was only powered through the switch with the key in the 'start' position, then the charge relay took over powering the pump after the key moved back to 'run', but that didn't make sense. I'll have to check the diagrams again to refresh my memory.

The fuel pump gets juice through its own relay -- the wiring between the fuel pump and the switched legs of that relay is pretty simple. The complexity lies on the signal side of the fuel pump relay, because the fuel pump relay is fed power from either the battery or the alternator, depending on the state of the alternator charge relay.

IIRC1, the charge relay is a single-pole double-throw switch (SPDT), spring-defaulting normally to closed (NC) for ignition-switched 12V, with the other pole connected to the alternator output
IIRC2, the fuel pump relay is a normally closed (NC) single-pole single-throw (SPST) switch.

Let's try to simplify (over-simplify?) this to a handful of states...

STATE 1 -- key off
Before you insert the key, there is no charge from the alternator, so the charge relay is in its default spring-loaded position to the ignition-switched battery current. With the ignition OFF, the ignition-switched side of the charge relay is dead, so there's no juice flowing to the fuel pump relay. Result: the fuel pump does not run.

STATE 2 -- key run, engine off (not yet started)
When you insert the key and turn it to RUN (not all the way to START yet), there is still no charge from the alternator, so the charge relay is in its default spring-loaded position to the ignition-switched battery current. With the ignition keyed to RUN but not yet turned to START, the ignition-switched side of the charge relay is still dead, so there's no juice flowing to the fuel pump relay. Result: the fuel pump does not run.

STATE 3 -- key start (starter turns)
When you insert the key and turn it to START, there is still no charge from the alternator, so the charge relay remains in its default spring-loaded position to the ignition-switched battery current. With the ignition set to START, the ignition-switched side of the charge relay is live, so there's juice flowing from the battery through the ignition, through the charge relay, and to the fuel pump relay. Result: the fuel pump runs.

STATE 4 -- key run, engine running, alternator functions
With the engine running and the key turned to RUN, the alternator provides enough juice to energize the charge relay, keeping it switched away from its default spring-loaded position. Switching the charge relay out of default interrupts connects alternator output to the fuel pump relay. Result: the fuel pump runs as long as the alternator keeps charging.

STATE 5 -- key run, engine off (stalled)
With the engine NOT running and the key turned to RUN, the alternator does not provide juice to energize the charge relay, so it switches back to the default spring-loaded position. With the key in RUN and not START, the ignition-switched side of the charge relay is dead, so there's no juice flowing to the fuel pump relay. Result: the fuel pump does not run.

STATE 6 -- key run, engine on, alternator stops charging
With the engine running and the key turned to RUN, a fully failed alternator will not provide enough juice to keep the charge relay energized, so it switches back to the default spring-loaded position. With the key in RUN and not START, the ignition-switched side of the charge relay is dead, so there's no juice flowing to the fuel pump relay. Result: the fuel pump does not run. (Diagnostic -- the engine will start when the key is turned to START, but will not continue running after the key is turned back to RUN.)

Note that STATE 2, STATE 5, and STATE 6 are similar -- the difference being how the charge relay ended up in default.
* For STATE 2, the charge relay has yet to be energized.
* For STATE 5, the charge relay was energized while the motor was turning the alternator, but the motor stalled and the alternator stopped turning, so the charge relay ended up in default.
* For STATE 6, the charge relay was energized while the alternator was working, but the alternator stopped working, so the charge relay ended up in default.

This may be an over-simplification, because I think I recall something about a timer (or was it a pressure switch), and we have a supplemental question about the oil pressure switch... but this gets through the complexity of the alternator and charge relay.

How'd I do?

[geeves]

4ze1.jpg

If the alternator lights are on then this must be a clue. When you bridge the fuel pump contacts and the engine is running what is the voltage at the battery? My money is oon about 12 not 14 so a charging circuit problem must be considered. How did the carpet get wet. Could the alternator of got a dunking at the same time?
If its 14 then I would be having a closer look at the fuses and the relay

[adam101990]

Yeah I have the book and such (online) water got into the cab through a hole at the back of my sill panel which will only come out at an extreme angle... Onto my feet. I was on the beach the other weekend and was cleaning all the salt off and thought I would see what happen (not a smart idea)

I have definitely killed the alternator which was not charging at all. I have now replaced this and all running sweet.

I have driven it for a few days since I did a creek crossing (water lapping the windscreen, but air filter was none dry) and it might have just given up the ghost or just chucked a tanty because I decided to ride my bike Wednesday and wouldnt start Thursday morning.

All in all, worst designed motor that I have come across. All it took was for me to ask the right questions of Google and wallah (this was a premature post tbh and was racking my brain for the answer

[geeves]

All relays are voltage dependant to a degree if the alternator is not charging the battery will slowly go flat Once the voltage drops to a certain undefined voltage the relay will release