Lift a plug wire from the coil and create a gap Have a helper crank engine and look for spark. If no spark check for 12 volts (with test light or volt meter) on the green wire plugged into the coil or a fuel injector while cranking the starter. There is no power if the engine is not turning. These green wires are powered by the ASD relay. It is turned on by the engine computer and a signal the computer receives from the crank position sensor. I have had bad connections in between the crank position sensor and computer.
The fuel pump is just one of many components that could cause poor starting if not at peak efficiency. You don't say whether the engine is petrol or diesel powered but in both cases a good cranking speed is essential to cold starting and again in both cases sufficient fuel must be delivered into the combustion chambers in the right form; bad spray patterns due to worn or dirty injectors can cause bad starting, though most commonly in the case of petrol engines it is a poor spark or worn spark plugs and in the case of diesel engines tired or defective heater plugs that cause poor starting.
There is quite a bit to think about and quite a bit to check...
Answers & Comments
Lift a plug wire from the coil and create a gap Have a helper crank engine and look for spark. If no spark check for 12 volts (with test light or volt meter) on the green wire plugged into the coil or a fuel injector while cranking the starter. There is no power if the engine is not turning. These green wires are powered by the ASD relay. It is turned on by the engine computer and a signal the computer receives from the crank position sensor. I have had bad connections in between the crank position sensor and computer.
The fuel pump is just one of many components that could cause poor starting if not at peak efficiency. You don't say whether the engine is petrol or diesel powered but in both cases a good cranking speed is essential to cold starting and again in both cases sufficient fuel must be delivered into the combustion chambers in the right form; bad spray patterns due to worn or dirty injectors can cause bad starting, though most commonly in the case of petrol engines it is a poor spark or worn spark plugs and in the case of diesel engines tired or defective heater plugs that cause poor starting.
There is quite a bit to think about and quite a bit to check...