Fuel Pump Amperage

Dears,

I did a current ramp test on 3 cars. All showing nice and even bumps of waveform but the amperage is around 600mah while Idling. I snapped the throttled but no amp increased.

Is this normal? Does fuel pump amp increase under load? what if it doesn't?
Does the waveform only show mechanical of commutator?
How can I know if a fuel pump doesn't have good psi using waveform?




Any answer is highly appreciated.

karim wrote: I did a current ramp test on 3 cars. All showing nice and even bumps of waveform but the amperage is around 600mah while Idling.

600 mAh? Did you mean six amps? 'Cause that's a pretty typical fuel pump current draw.

I snapped the throttled but no amp increased.

Is this normal? Does fuel pump amp increase under load? what if it doesn't?

That's not unusual at all! In the case of a mechanical returnless or return system, the fuel pump is running at full speed any time it's on. It's all down to the pressure regulator to make sure that fuel pressure keeps up with demand. In other words, the pump never knows if you're idling, cruising or WOT, it just keeps pumping as hard as it can. :lol: On these systems, the only time you'll see significant changes in pump current is during cranking, when battery voltage is low.

The variable here is electronic returnless systems, which WILL change pump current draw with changes in engine load. Though, on most systems I've seen, you only see big changes during cranking and very heavy load.

Does the waveform only show mechanical of commutator?

It mostly shows the electrical integrity of the pump, but there are a few mechanical issues it can pick up on. One would be worn pump bushings/bearings. Very high current draw could indicate a seized pump. Very low draw could indicate a high pressure leak inside the tank, or low fuel level.

How can I know if a fuel pump doesn't have good psi using waveform?

You can't. Not with any real accuracy, anyway. Unfortunately, it's entirely possible to have a pump that's drawing reasonable current, but not producing enough pressure or volume. There are extreme cases that you CAN make generalizations, like if a pump is drawing one amp. You don't need a gauge to know that pump isn't moving much fuel. :lol:

Thank you very much Tyler
God sent you to teach me. I do appreciate your effort of helping me. You are right right 600 mah means 6 AMP since I am on conversion low amp probe.

I really learned much from you. Now it is clear as a blue sky to me.

Have a great weekend

No problem!