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DS4 pump mods

buddy said:
So are you saying youve only done it on a DB2, or on older DS4 pumps?
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I have played with a DS pumps and DB pumps since they came out back in the 80's, I went to GM school to learn how to rebuild the early db pumps with the governor ring that came apart and clogged the pumps. I have also played around with the DS pumps and have been running a DS pump with the regulator in the inlet (Allen screw) turned up, an optic bump with the pump turned back after setting the timing and TDC offset then the learn and a whole lot more combination's of things that are not supposed to work. I think the most knowledgeable individual I ever spoke to on these pumps was GMCTD, he knows his stuff.

When this thread started I was going to say something but figured I didn;t need the strife. I have a few mods for the DS pump that have been in the works,

In retrospect I wanted to tell 6.2 that his pumps seized from Hydraulic lock nothing else, You can only push so much fluid though a fixed orifice in a specific amount of time. That is about all I willing to say until there is more long term study of a few modifications. I will say that the spill chamber on the DS pump is an interesting item.

I am not an expert just someone that has been around the Stanadyne distributor pumps for a long time.
 
schiker said:
I'll bite. I have had so many hooks in my mouth snatched out and some swallowed it don't bother me much anymore I just like the intellectual stimulation.

The spill/fill chamber is sorta seperate from housing pressure is what 6.2 turbo is saying I believe. But fill/spill chamber "vents" or flows to the housing chamber and out the return fitting in a few paths. One through the advance piston path and the other through the head from spill I think. Also, maybe some high pressure leakage from plungers "blowby" due to clearances I imagine. Which might be appreciable at high rpm high line pressure???

I can see appreciably higher transfer pump pressure elevating housing pressure if it wants to exceed expected output mechanism flow/pressure and the return fitting is restricting flow. Its looks like a realitively small output hole (at least smaller than input hole) and I imagine Stanadyne designed the pump to recirculate most fuel and just return enough to flush a little bit and allow some pressure bleed off. But change internal flowrates and pressure could rise easy enough. The GM DB -DS IP's were suppose to live in the V-8 valley and be designed to like warmer fuel than traditional IP's of its generational birth. Might have been a design feature to return less fuel to the tank than traditional. Note guessing about maybe the longer GM fuel filter maintenance schedule /smaller size compared to others???.
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You are correct the sides are not completely isolated from each other. Where does the spill chamber empty into?
Charge pressure if you will, does increase case pressure as rpm increases and with a fixed orifice (return) you can only move so much fluid through it in a specific amount of time.

I truly wanted to stay out of this, but what is the goal of a DS pump modification?
 
buddy said:
I can get your DS4 to pump more fuel than you imagined, without even touching it ;)
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I already know that, :D This mod is because I can, not because I need to. Just my way of relaxing. Isn't this why we do the things we do? If it doesn't work nobody is out anything but me.
 
My pumps that seized were at idle, one from waste oil,and one from the pump being cocked from two much line tension after adjusting the timing,and only tightening two nuts. The broken cam pins were probably from extreme hydraulic pressure ,but they are very small compared to the DS4 cam pins.
 
6.2 turbo said:
My pumps that seized were at idle, one from waste oil,and one from the pump being cocked from two much line tension after adjusting the timing,and only tightening two nuts. The broken cam pins were probably from extreme hydraulic pressure ,but they are very small compared to the DS4 cam pins.
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This is all great information, how did the waste oil run and for how long?? was it filtered through progressive filters?
 
I ran 50 % to 100% waste motor oil in warm weather . I pumped it through an engine oil filter first,and the truck has a Napa fuel water seperator,this worked fine for a year or more,untill one morning it was a little cold and the head and rotor seized from not getting lubed properly. If waste motor oil wouldn't carbon the injector nozzles so bad I would be tempted to try it again. Used atf worked better.
 
6.2 turbo said:
I ran 50 % to 100% waste motor oil in warm weather . I pumped it through an engine oil filter first,and the truck has a Napa fuel water seperator,this worked fine for a year or more,untill one morning it was a little cold and the head and rotor seized from not getting lubed properly. If waste motor oil wouldn't carbon the injector nozzles so bad I would be tempted to try it again. Used atf worked better.
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How did it run on ATF? Did it smoke a lot how was power? Engine oil get dirty fast?
 
using a lot of either is something that wouldnt work on the DS4, because the OS needs the fuel to be quite clear.

So the motor oil wasnt lubricating it? It lost all its lubrication ability?
 
It is to thick when cold, and won't lube the rotor,unless the head and rotor are on the loose side , lubricity is not the problem. Now that I think about it , I had a tight fit on that head and rotor,because of chasing a hot start issue,turned out to be the plungers were too loose instead .
 
I run 50/50 mix mostly used atf from our shops trans flush machine and an occasional real low mileage engine oil change never a prob unless I go and get greedy then it starts rough and ses light comes on until it warms up a little. I have a friend that has been doing this for years with a db2 no prob.when he revs it up the exhaust doesnt even smell like a diesel!! Hope my ds4 hold up to it as well. I did notice when passing a prius the other day that a properly aimed tailpipe can make a sooty mess for someone with an open window!!!! I just had to do it!!
 
If you can get it to smoke while at passing speed already then your turbo aint doing well or the DS4, injectors, valves and everything else aint liking it.
 
I need to make a video,before I take the 6.2 heads off,maybe a burnout or just a drive by,and cold start.
 
Not to sidetrack the thoughts of how to modify our pumps but didn't someone already talk to Penninsula Diesel about pumps and they said they could build a DS4 that could flow more fuel than we could ever use. Like the pump they use on their 400hp marine motor but modified a little to be more street friendly. The only question for me would be proof and price. And if they can prove it without a doubt I'd probably pay the price.

Either way you guys got me ropped in, I think I am gonna pull apart the bad pump I have and see what I can do with it.
 
IIRC that was a DB4 mechanical, DS4 gives plenty of fuel depending how far you want to go with it, like 158 at Bonneville :) that said the electronics on a DS4 can be a PITA, but a remoted FSD cures a lot of that.
 
1:44 This is my 6.2 with the 4 plunger pump. The governor is close to stock,which is limiting the smoke somewhat.
 
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