Simmonscoating
Full Access Member
Thanks Mel, Wisdom is key...
Well, I really don’t want to start an internet controversy but I think Mel maybe misunderstood my goal or what I was trying to accomplish with that particular mod. I really wish he had time to respond, but I disagree with just wiring the cold advance on all the time as being an equivalent to removing the ball from the fitting. When you energize the coil to move the ball which drops the housing pressure, the coil makes heat and will heat up the fuel. My goal with the mod is to have less restriction for fuel flow out of the housing so it can carry heat out of the pump, without using electronics which heats the fuel. If you want it to do the mod but be able to return it to stock then just pull the whole fitting out and replace it with a straight through barbed fitting. If you don’t like it, put the old fitting back in.I am running a 94 idi-t and thinking about doing the fitting mod while I have my truck in limbo for other repairs. I just don't want to damage anything, so Mel is saying its bad?
No I’m happy to help, if it was turned two flats you can go back two flats and be pretty close theoretically. The flats are referring to each side of an Allen, so two flats would be about 120*That's what I planned on anyways Wes , I think its a good idea and it makes sense. I spent 7 years of my life working on industrial valves used in paper mills, powerplants, etc.... we saw affects of heat through restriction when customers would "throttle" these giant valves and it wasn't good. Ill be replacing the whole fitting.
Not to continue to bug you but previous owner says he turned the pump up "two flats" is there any way to reference stock? Id like to turn it back to stock and go from there. Its the only "mod" that was done thus far.
Now for some mods, for these you will need an electric lift pump with an adjustable pressure regulator because you will need to be able to add fuel pressure to compensate for these changes. The pump housing has a fitting here:
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This fitting effectively has guts that act as a pressure relief valve to restrict the amount of fuel the pump returns to tank, as well as to hold a small amount of pressure in the housing. You can remove this fitting and replace it with a straight through barbed fitting, or you can knock out the guts with a punch and small hammer. This picked up 5ccs of fuel across the entire rpm range, but the biggest improvement is the amount of fuel that returns from the pump, with more fuel passing through the housing there is more fuel available to cool and lubricate the pump, prolonging the life of the pump, and helping to prevent heat soaking issues. Because there is less restriction, more fuel is required to supply the pump, hence the electric fuel pump and regulator being a requirement.
All in all, with my custom minimaxx locknut installed, I took a stock DB2 with 208k miles and severe hot starting issues, and made 107 ccs peak fueling. Im sure a fresh pump with new plungers would be capable of much more, but I wanted to test this on a "worst case scenario" pump.
TheWesPaul, what pressure did you need to make it work when you opened up the flow in the pump housing return fitting? Did you just turn your adjustable lift pump pressure up until the engine ran smooth? What was it like when the pressure wasn't dialed in correctly?
I run 5-6 psi, I’m testing a few other pump mods and I’m running a bit higher now, but 5-6 is what these pumps are calibrated for on a test bench so ideally that’s where you want to have them.