Leadfoot

I don't know if this is a good thing of not but here it goes. The original pump on my 1990 non-ic started leaking so I went and bought another pump after I broke the first pump trying to work on it. Any how the second pump was from an IC motor from a 1992, all along I was told the pumps are the same from 89-93. Later I found out the pumps are the same, the only thing different is the wiring from the computer energizes the KSB at differnt times. On a non-IC motor the KSB blocks off the fuel bypass and increases internal pump pressure from 100 psi to 160 psi. Since my truck was non-IC the KSB on the IC pump was pressurized all the time and made a noticable horsepower increase.

The pump shop told me all this after the second pump started leaking at the distributor head the same as the first pump. The second pump was sitting for about six years and ran in my truck for about 4 months before it started leaking. The pump shop told me not to hook up the KSB because they belived the leak may have been caused by the increase in internal pump pressure.

This may be a mod for some and I am not an expert on these pumps by no means. If someone has some real data to validate or refute this statement please speak up. Good luck.

Ace

Ever heard the old saying "you can't put 10 pounds of (expletive deleted) in a 5 pound bag?" I believe that since the vane pump in the VE is primarily responsible for providing the fuel flow downstream to the injectors (5# bag), as long as there remains any positive pressure upstream on the lift pump side(anything more than 5 pounds of *expletive,* Fuel in this case), you cannot influence power production in terms of fuel delivery to the VE. This is just a belief I have based my understanding of the principles involved. That could of course be entirely wrong, wouldn't be the 1st time I misunderstood the principles involved. Anyone please elaborate to confirm or deny this.

wannadiesel

That's the way I approached it too. What changed my mind about the piston pump was when Stomp posted that he was having trouble maintaining case pressure with low inlet pressure to the VE. When you lose case pressure, you lose timing advance. The real problem is that the vane pump is too small, so it needs to be force fed as a band-aid.

Underpsi

The vane can only pump as fast as the IP is turning correct? So that means case pressure should vary with rpm? Which obviously means you would need more inlet pressure as the rpm's rise

Ace

That makes sense. But I'm curious how Stomp knew he had low case pressure, and what value we have estimated to be the max inlet pressure the VE needs or can live well with. I recall seeing somewhere that max inlet pressure should not exceed 15 psi for some reason I can't recall. Is there a thread where Stomp talked about this in any detail?

wannadiesel

He had tapped the pump cover for a gauge.

Supposedly when you get over 20 psi the front seal wants to pop out. KTA Cummins made himself a seal retainer and is running well over that.

There's a thread but I don't have time to look for it right now.

Underpsi

The max inlet pressure should not exceed a certain amount I forget the exact amount but its because the you can blow the seals out of the ip. Stomp had a gauge hooked right into his pump to monitor the pressure

Ace

What, no time to do my searches for me!! That's outrageous!!! Well, I got a piston pump, so I guess I'll just put it on one of these days if I notice any issues with the fuel pressure and go from there.

Tks...

Begle1

So he doesn't loose case pressure as long as he is maintaing pressure to the vane pump. What kind of PSI are we talking; 20?

Would there be an advantage to be had if the case pressure was to go higher than stock? Would the timing advance even more, or is there a limit of the timing advance?

gman07

I think the timing piston hits the case; there's a thread somewhere on here about modifying the piston or cover. This would allow greater advance as case pressures increase.

Begle1

So, how do you get case pressures that high? Do you need to put an auxiallary hi-pressure pump through the fuel solenoid, or can you get that kind of pressure just my romping it up in the RPM's?

Is that much advance even beneficial? Isn't there a point where it just couldn't advance no more?

I think I've heard somebody talk about shaving pistons; I guess that's so they can slide farther under higher pressure without hitting the case.

NeedMoPower

Brian did. It was actually 485 according to his dyno graphs on diesel central.

gman07

You'll have to wait for a guru to answer that one; I have no idea.

I have no idea about how a certain case pressure corresponds to timing advance in degrees. I'd love to do the research, but money's too tight for that.

Sled pullers run LOTS of timing, so I'd assume there are benefits to be had. Plus with the dynamic advance of the VE, we can have the torque of retarded timing down low with the power of advanced timing in the upper range.

wannadiesel

The vane pump supplies the pressure, but pressure is controlled by the pressure regulator valve that the KSB uses, along with the overflow valve at the back of the pump where the return line connects.

The fuel takes a certain amount of time to burn. The faster you spin the engine, the sooner you have to start the fire going in order to have peak pressure at the best piston position. Too much timing can be bad, but that's not the issue here. What we're talking about is losing the timing advance we would normally get from the VE. Lose case pressure and you lose timing, simple as that.

JDGnut

The pumps I've seen just have an orfice in the return bango.. no over flow valve Like a P-pump..