Lift Pump volume and suction

[JTodd]

I am troubleshooting a fuel starvation issue and pulled my LP to test it, as well as to blow some air back into the tank to see if I could clean the sock out a bit.

Note: This LP is only a couple months old.

With a bucket about a third full of diesel, I attached a clear hose to the intake side of the LP and hit it with 12v. With the LP no more than a couple inches (2 or 3) from the level of the fuel, it would not suck it up. If I filled the hose, priming the pump and started it, it would run and pump. I used a two stage battery charger for current. If using 10a, it would barely do anything. If I used 50a it would pump, but less than the 35gph spec.

A couple questions regarding this.
1. does this sound right in general?
2. Is the LP typically able to self prime?
3. What amperage should be at the pump during normal operation?

Thank you for your help.

[Kennedy]

A battery charger is not necessarily a good source of power. Having a battery or regulated DC power supply would be best.

I've seen very poor results from aftermarket lift pumps which is why we only promote the AC Delco unit. The Kennedy llift pump also works VERY well, but some with problematic fuel supply systems could have trouble with this one.

[JTodd]

A battery charger is not necessarily a good source of power. Having a battery or regulated DC power supply would be best.

I've seen very poor results from aftermarket lift pumps which is why we only promote the AC Delco unit. The Kennedy llift pump also works VERY well, but some with problematic fuel supply systems could have trouble with this one.

Trying to troubleshoot a increasingly problematic system, I think I have narrowed it to the LP. Since the pump was off, I attached a length of pipe to the feed side line and sucked on it to see if I could start fuel flow. I really did not have much problem drawing fuel, so I think it is the LP is not able to either draw fuel from the tank, or is not strong enough to push fuel up to the fuel manager.

Do my symptoms sound like failing LP?

Just curious, why is a charger not a good 12v source? I recognize it is not filtered through the battery, but it is still 12v, and works well for testing that something is functioning. I did just find a 12v transformer from an electronic device that I am going to modify to work on things like this, except it will be really low amps.

[mrwilecoyote]

Try it off the battery. Agreed the batt charged is not a good idea.
I solved my LP problems with a Raptor...lol
Way too much money for a 6.5 though. I had it laying around from a Cummins.

[JTodd]

Try it off the battery. Agreed the batt charged is not a good idea.


Why? It is 12v.

[DmaxMaverick]

Why? It is 12v.

It's not quite that simple.
Almost every battery charger outputs modified DC, not clean DC. And, depending on the current draw, 12V isn't 12V. The current is still AC, only that every other cycle is missing. The voltage and amperage will vary, depending on the capacity state of the battery it's charging (as it's supposed to do). Using one can often destroy many electrical devices, and most electronics dependent on clean DC power. If you want a good AC powered DC power source, get one (they cost a lot more than a charger or new battery). Otherwise, use a fully charged battery.

[JohnC]

I agree that the battery charger is not a good source of power for testing accessories. Also, the lift pump should be able to lift (suck) fuel at least the depth of the tank, otherwise it can't work. If it doesn't suck fuel but pumps when primed it probably has a bad check valve.