Too much fuel pressure?

[6.5TD Burb]

For a DS4 equipped engine, is it possible have too much fuel pressure going to the injection pump? I'm revamping the lift pump/filter manager setup and was trying to figure out if I need to throw a regulator on the pump or not. Unregulated it should put out 15 PSI.

 

[Paveltolz]

I understand that Stanadyne recommends pressures stay around 9psi. I haven't seen a TSB on it but that's the word I got.

 

[THEFERMANATOR]

i wouldnt go more than 12.

 

[JMJNet]

There is efficiency factor along the way due to the distance from the tank to the FFM to the IP plus how good the tank sock conditions.

So 15 psi may become 4-6 psi at IP or even less.

 

[Dunedain15]

There is efficiency factor along the way due to the distance from the tank to the FFM to the IP plus how good the tank sock conditions.

So 15 psi may become 4-6 psi at IP or even less.

I think this is why it's recommended to put your fuel pressure sender after the FFM.

 

[6.5TD Burb]

Plumbing in a regulator it is then.

Here's what I got so far:

The tank will be dropped for a new sending unit and the factory fuel manager will be removed after plumbing in the new system. Honestly I don't care for how much farther back it is than the factory lift pump but the torsion bar crossmember kinda ruled that space. Could have put it on the passenger frame rail I guess, to get it closer to the injection pump but I really did not want to run fuel lines all over the underside.

 

[Burning oil]

Are those the same filters pre and post LP? The pump may not Flow on Fail??? Did you use a relay to power LP?

 

[6.5TD Burb]

No, the rear filter is a 30 micron and the foremost filter is a 5 micron. Actually thinking about adding a 2 micron in the engine bay later on. Maybe overkill but good peace of mind.
You know that's a good question. Don't see it on their site: http://www.summitracing.com/parts/sum-g3136-2
Haven't hooked it up yet as far as power is concerned. With having the factory lift pump on a toggle switch this one will be as well; there was a break in the circuit that I never traced down that kept the old lift pump from being powered with the key.

 

[bison]

No, the rear filter is a 30 micron and the foremost filter is a 5 micron. Actually thinking about adding a 2 micron in the engine bay later on. Maybe overkill but good peace of mind.
You know that's a good question. Don't see it on their site: http://www.summitracing.com/parts/sum-g3136-2
Haven't hooked it up yet as far as power is concerned. With having the factory lift pump on a toggle switch this one will be as well; there was a break in the circuit that I never traced down that kept the old lift pump from being powered with the key.

94 modeIs were never powered by the key to start with.

IP housing pressure is factory not to exceed 15-16 PSI or it wiII interfere with the advance mechanism.

 

[6.5TD Burb]

Interesting bit of information; either way it never got power.

 

[6.5TD Burb]

In case anyone was wondering, I did finish the install and right now with the regulator untouched it holds a steady 6psi. Pressure difference between the gauge at the manifold and in cab gauge is 1psi. (http://www.supermotors.net/registry/20000/83768 Pictures of the project.) Even with my foot on the floor it holds a steady 6psi; if it does drop it's only by a fraction.

 

[great white]

To the original question of too much pressure: pretty much nope.

Ds4 has run on 25 psi in mine with no issues (was having trouble with raptor pump when an internal seal went). I know of at least one other that has run one on 25 psi for a period without issue.

Mine runs at 13 psi every day. It likes it there. Runs smooth and quiet. Raptor keeps it steady at 13 psi, even at wot. If you're really "on it", you might see a transient "12" flash on the digital display. But don't blink: you'll miss it.

Lift pump pressure doesn't effect timing in a ds4 like it can in a db2. Timing is controlled by the fuel solenoid via the fsd and the PCM. Worst thing that can happen is you might get a little more pintle stroke when the pressure is ramped up by the plungers.

 

[6.5TD Burb]

Probably the final update to this revision. Bumped the pressure up to 9 PSI and it seemed to like it just fine there. Good idle and power delivery felt smoother. With the fuel pump the needle barely moves even with my foot buried deep in the carpet. In the day time I can't see anything out of the tailpipe, at night I can see a haze. Only down side is this pump is extremely loud. I can hear it over the engine at idle and easily hear it inside the cabin...Don't care. She runs great.

 

[greenmeanh1]

I have my fuel pressure sender right above the IP within 3 inches of the input. I have an air bleeder there as well. I float my pressure manualy from the dash using a PWM controlled Raptor 150 30psi pump which also has a manual internal output PSI set feature... Over the last 5kmiles i have expiremented with different pressures while driving in various conditions.
Some findings.
Fuel pressure will drop a few PSI in higher altitudes. I have found increasing the fuel pressure to compensate seems to help quite a bit.
At higher RPMs lower fuel pressure seems to work better and provide lower overall temps for some reason. I set to around 3psi when im above 80mph. Around town i run 7-9psi.
In the cold winter higher pressure helps pump the jelly LOL. Last year in Ottawa at a -25 start i needed 16psi to get fuel moving. Once warmed a bit i back it off to about 9psi.
At first install i set the Raptor internaly to 16 psi and would PWM down from that to 7-9 average. Through the RPM range/load the pressure would not budge. I have since set the Raptor to full 30 psi and run the PWM very low. The pump motor is barely turning but still maintains a steady 9psi @ idle to about 8psi @ 1800rpm. Above that the pressure will start to drop or float with the load. At 3100rpm 85mph i will be seeing 3-4 psi. I get at least 1mpg better this way and no shrotage of power and less fiddling with the pressure knob while driving.

 

[WarWagon]

There is a point where you blow the driveshaft seal out of the IP IIRC it is 30PSI. This is the only concern other than what your hoses can take.

I ran a unregulated 15 PSI Mallory for years. It sucks when the brushes/relay/WTF ever fails as the engine stops in about 2 seconds after the LP that isn't flow on fail.

 

[Will L.]

Interesting about the difference in pressures, but it all makes sense.

If you want to run a pump that is not flow on fail, you just have to add a little plumbing to get around it as a bypass line. Put 2 "t" fittings before and after the lift pump, running 1 line through the pump as normal. Now connect the 2 "t" fittings together with a 1 way check valve to not let fuel flow from the high pressure side back to the low pressure side. The bypass line will do nothing as long as the LP is working. When the LP stops running and the IP sucks fuel it will pull fuel through the 1 way check valve and get you home.