Outer Limits 4x4 Board

About 6 months ago my NJ 3.0lt petrol was surging. I worked out that it was surging when turning and it turns out that it only occurred when the indicators were on. After much time spent chasing the problem i ended removing the immobilizer side of the alarm as they had split into the main ignition source to the barrel so it was stepping down from 6mm wire to about 2mm. This fixed the issue until recently it has started again. I have worked out that the surging is due to the fuel pump dropping about 0.5 to 0.75v when the indicators are on. You can also hear the pump "surging" when the indicators are on. (Hazards have no effect on the pump by the way) The wire i have used to bypass the imobiliser is good so i don't think this is the issue. I'm thinking that maybe there has been some wear to the control relay contacts or a bad earth somewhere. Any thoughts on this would be great.

Gabe

1 Maybe you have a short circuit somewhere in your indicator circuit? Possibly the indicator can. If you do, then this will load the whole electrics and cause a volts drop. Have you checked the voltage at the battery with the turn signals on and off? You should have very little volts drop with just turn signals.

2 If the fuel pump is dropping 0.5 to 0.75 volts, the whole injector control system will be similarly dropping and this may cause problems. How good is your alternator?

3 You say that the wire steps down from 6 mm to 2 mm at the ign barrel. How good is the splice into the original wiring?

date wrote:1 Maybe you have a short circuit somewhere in your indicator circuit? Possibly the indicator can. If you do, then this will load the whole electrics and cause a volts drop. Have you checked the voltage at the battery with the turn signals on and off? You should have very little volts drop with just turn signals.

2 If the fuel pump is dropping 0.5 to 0.75 volts, the whole injector control system will be similarly dropping and this may cause problems. How good is your alternator?

3 You say that the wire steps down from 6 mm to 2 mm at the ign barrel. How good is the splice into the original wiring?

The voltage drop is at the supply wire to the ign barrell only. There is no voltage drop at the battery or any other circuits. I have checked the drop at the fusable link near the battery for the ign supply and it would be lucky to be 0.02 of a volt. I am thinking maybe the indicator switch / combo switch may have poor contacts. Whatever it is, it is deffinately loading up that ign circuit. The splice to the original wires seem good, with plenty of solder. I might just re-do this connection just to rule it out.

If you are getting low voltage in a circuit, it can be 2 things - a high resistance somewhere between the measuring point and the supply; or it can be a high current draw because of a short circuit or high loading somewhere else - in the circuit you are measuring or elsewhere in the system. You seem to have checked the resistance aspect, so it is more likely to be a short somewhere dragging the voltage down (but not enough to blow the fuse so you could identify the troubled circuit).

Not sure of your exact setup, but it may not be the indicators which are dragging the voltage down. It probably is a high current draw in the indicator circuits which is giving you the problem. You may have a high resistance somewhere upstream from the switch, causing the volts to drop when the indicators are on. A high resistance joint downstream from the tapping point will not cause low voltage in the tapped circuit.

You may have a short somehwere else on other circuits from the ignition switch. Things such as the wipers etc are fed from the Aux circuit, so they can probably be ruled out. Check your W'shop manual wiring diagram and see what is fed only from the ign switch. Then check those circuits for shorts (use an Ohm meter between them and earth). Obviously you will have some circuits which show a loading but things such as the Ventilation fan should dhow open circuit (infinity resistance).

something is wrong with your fuel rail pressure regulator. Injectors operate at choked flow conditions so small pressure fluctuations don't affect injector flow. Also pressure reg helps keep pressure very high and at choked flow. I reckon your pressure reg is jammed open.