I was browsing the forums this morning and saw a discussion on a secondary fuel system, and noticed u have one installed. My first question, why?
What exactly is the benefit? and why not just install a higher pressure electric fuel pump and ditch the whole mechanical lift pump?

 

I installed the electric pump because I was able to drag the piston pump down to 5 psi. I was concerned that this was causing the truck to lose timing advance at full power. The electric system with the bypass regulator after the filter gives me no less than 15 psi under all conditions.

"Secondary" is kind of a misnomer. When the electric pump is on, fuel pressure at the piston pump outlet is around 25 psi, so the piston pump is not delivering any fuel at all. If the eccentric on the cam went flat fuel pressure would not change a bit.

Why not ditch the mechanical pump? Because it was just as easy to keep it. This way the truck is not dependent on an electric pump to run. I like the fact that if I gut the shutoff solenoid the truck can be driven with no electrical system whatsoever. I did not want to change that - which is why I resisted installing an electric pump for so long. Once I figured out how to do it without losing the mechanical pump, I couldn't wait to try it.

I want to make it clear that I no longer recommend buying the piston pump. For about $50 more than Cummins wants for the pump and the pieces to install it, you can have a fuel system that will give you 15 psi under all conditions.

One thing I'd like to test in the future is a 2nd gen pressure spring in the piston pump now that I have the bypass regulator installed. With 30 psi on tap it might be able to push enough fuel through the filter to maintain 15 psi at the injection pump...

 

Hey dave, what years have the KDP, i read somewhere that a 98.5 had one, but i had never seen that before... If thats possible, i htink you might need to look or tell me where to look to kill it...

Mike

 

That's quite the hijack there, Mike.

 

im good at that...im unhijacking the thread..

shoot me a PM...

Mike

 

Ok I got ya. Soooo if I were to do a fuel system to feed my up and coming mods an electric pump would be the way to go and ditch the whole mechanical lift pump. I have already done this on my 92 ford IDI diesel so im just trying to understand why on the dodge.
Now what r the fuel requirements (PSI requirements) to feed 400 HP?
I saw on the tech site its like 20-30 PSI on a stock 93. what would happen if one were to put 40 or more PSI through the VE? basicaly just find out what seals need replacing?

 

There's no need to ditch the stock fuel pump, I would (and did) keep it as backup. The stock pickup is a big restriction so you have to run a new feed line anyway. Might as well leave it operational "just in case".

I wouldn't want to see more than 18 psi going into the VE. You will pop the front shaft seal first and fill the crankcase with fuel. I also worry about the long term effect of high input pressure on the vane pump. There have been problems with VP44's (similar design) due to this. Keep the pressure around 15 psi at all times and you will have plenty of fuel available.

The internal pressure is over 100 PSI with the KSB engaged. High input pressure wouldn't make much difference.

 

OK, I got ya! Another question for you now, in a 400HP setup like what im looking for, "Towing Twins" what is the optimal bottom turbo? Im not too good at reading what a 1.34 AR means on a turbo. Im looking at one in Quakertown PA and I'll have the dough to purchase tomarrow. Im itching for my next power mod its been awhile. This is the listing, is it sufficient enough for my needs?
http://cgi.ebay.com/ebaymotors/DETRO...QQcmdZViewItem
Thanks again Dave!

 

Save your money. You ain't got enough cubes to sling that turbo.

 

I dont know what displacement hs to do with power potential. I know a lot of guys with newer (12 & 24V) trucks use an HT3B as a bottom. That IS a big turbo. There are a few guys running twins in a 1st Gen, and do just fine in terms of driveability and MPGs.

I would try a single with a hybrid kit (like a Stage 4 HTT kit, maybe) and see what kind of boost and EGT you run. I will say for towing, you cant get too much air, though.

Daniel