Lift pump...If...and what if....

[Powered by Spearco]

I just went out and started the truck. It fires right up and then but not even 4sec. after running, it strts to make the noise. Is that because the pressure dif. between the inlet and the pump?

[Rabbit on Roids]

tee a pressure gauge into the inlet of the pump, if the noise comes and goes as pressure increases and decreases on the gauge, then that very well might be your problem.

[AudiVWguy]

Spearco,
Just unplug the pump it will still draw fuel through it. You can check to see if your problem goes away.

[Rabbit on Roids]

Spearco,
Just unplug the pump it will still draw fuel through it. You can check to see if your problem goes away.

that would be alot easier..

[Powered by Spearco]

Nope no different. But got some 1.9 AAZ injectors to install. Then we'll see.

[rabbitman]

I just went out and started the truck. It fires right up and then but not even 4sec. after running, it strts to make the noise. Is that because the pressure dif. between the inlet and the pump?

I believe that's due to the internal pressure taking a bit of time to build up.

[AudiVWguy]

Andrew,
when I experimented with adding the Facet pump to lift for the Giles pump, I felt like it advanced the timing. I got a 4 psi increase in pump pressure on the gauge. Driving it, it knocked more on acceleration than without it. So I quit using it.
What would happen to the timing if I were to enlarge the tiny hole on the return side a few thousands? Anybody played with this?
Cheers,
Jeff

[Rabbit on Roids]

andrew says it retards the timing tho. and i believe him. (not saying i dont believe you) but he gave an explanation as to why it retards it, and it very well might.

[burn_your_money]

Today we had a VE pump on the bench. It was for an AAZ making 20 PSI. We hadn`t really set anything up yet, just made sure that the max fueling was "close". I forget what RPM we were running, maybe 2000-3000 engine? With the pump being feed with 0 PSI the internal pump pressure was 75 PSI. We turned the feed pump pressure up to 20 PSI and the internal pump pressure rose to 95 psi. Therefore, positive pressure at the inlet of the pump will advance the timing.

I was expecting to see no change since pressure is being applied to both sides of the regulator but I was wrong.

[rabbitman]

So it looks like all that matters is the pressure difference on each side of the advance piston

Hey Burn, did you happen to see what the dynamic timing did?

[burn_your_money]

You know, I thought about looking at the piston before we started the experiment but once it was in action I totally forgot. Odds are the pump will still be on the bench when I get in in the morning. Maybe there will be time to check it out first thing.

[burn_your_money]

Just finished testing, there was no change in the advance.

[burn_your_money]

We cranked it up to around 45 psi when we were looking at the advance. I did see the gauge jump once though. I don't think it changed the actual advance, just jumped. I could be wrong though it was very quick

[burn_your_money]

We share the same thoughts Andrew. Not necessarily needing to have a regulator makes things a lot easier.

Next I want to hook a VE pump up to a flow gauge and see just how much fuel flow (GPH) is required under the most demanding situations. I don't know if I'll be able to do that though because I think it would require modifying one of the test benches

[wolf_walker]

GPH sounds like something one could test on the (work) bench pretty easily, messily, but easily.
Run it for ten minutes, do the match, etc.  I think.