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No, it doesn't Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 2 Feb 2005 05:54:25
In Reply to: fuel pump cut of switch, J_P_33, Tue, 1 Feb 2005 15:00:28 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There was an overboost cut-out switch on older cars, but not on your Trionic '94.
OK, from your previous posts, you aren't getting power to the pump or to the fuse (#14) - I assume either side. The next place to look is the fuel pump relay. You should see 12 volts on pin 1 (red wire) all the time - it comes from the battery. Pin 4 (green) should be 12 volts when the ignition key is ON or Start - off otherwise.
Pin 2 (grey/red) is the switched 12 volts that should be going to your pump. Pin 5 (yellow/white) is connected directly to the ECU pin 31. It should be ground (or close to) to make the pump run.
First, make sure you've got the 12 volts to the relay (switched and unswitched power). If so, jumper pin 1 to pin 2 - the switch contacts of the relay. You don't even need the car on. You should hear the pump run. If you don't, trace the wiring - you've essentially connected the battery, through fuse 14, to the pump. If the pump runs, make sure there is good continuity from the ECU to relay.
If the signal from the ECU isn't turning the pump relay on, then I'd suspect crank position sensor.
A word of 'warning' when measuring voltages - remember Ohm's law about voltage drops. If you have a bad connection, for example, a crudded-up set of relay contacts - you may see 12 volts switched just fine with no load; but connect a load up (like a fuel pump), and the voltage can drop to zero.
Try this trick - remove fuse 14, and put a meter on the source side of the fuse while you crank the engine. If you see 12 volts, but it goes away when you connect the fuse up, two things come to mind-
First, the contacts on the fuel pump relay are dirty. Replace relay (or open it up and carefully clean the contacts). The other would be a fuel pump that's shorted. Yes ,you'd expect the fuse to blow, but not always.
posted by 192.249....
, Wed, 2 Feb 2005 05:54:25 <-- Viewing This Message
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