Would a fuel pressure regulator help the OEM LP?

[illflem]

Tom, the dampener you linked to is just the same as the one from Grainger on the previous page except not stainless. $17 vs. $47

 

[rweis]

The Grainger one also has an ability to adjust the air pressure within.



Bob Weis

 

[Un-Hemi]

Yeahbut.... (yes, however....)

The Grainger unit is primarily designed for domestic water supply hammer problems. It has a diaphram. It has 1/2" male pipe thread fitting on it, and it's inexpensive. (I'd position it on the supply side of the fuel filter to prevent contamination of the VP-44 if the diaphram disintegrates. ) It's not stainless. It will probably work.



The Matronics unit is designed as a high-reliability fuel pressure pulsation dampener for aviation use. It does not have a diaphram, and relies upon a head of air for its operation. It has an AN fitting and is relatively expensive, compared to the Watts (Grainger) unit. It's stainless. It will probably work.



There are significant differences in the construction and manufacturer's intended use of these two units.



If one chose to, one could solder up a hammer stack out of domestic copper water pipe and NPT fittings. It wouldn't rust. It will probably work.



Ideally, someone should research all three units and determine which works most satisfactorily for the longest period of time.



Cheers!



Tom

 

[Steve Campbell]

Carter 4601 .....

mounted back by the tank works just fine for me.



I started thinking about this same idea (having a pressure relief valve downstream of the lift pump) 2 1/2 years ago. I bought a fairly expensive valve from Summit and then did not use it. Instead, on my 99, there is a pre filter port on top of the fuel filter. I put a small adjustable valve (kind of like what illflem suggests to eliminate fuel pressure spikes to the pressure sender) and a line "teed" into the return. I have the valve opened enough to keep 10-12 lbs of pressure on the output (engine) side of the filter. With a clean filter, maybe I see a 2 lb drop in pressure between idle and WOT, yet my "spill back valve" in the lift pump never closes.



If a person had bigger injectors and box (DD1's and EZ for me) the pressure relief valve may be necessary to keep the pressure from dropping, but at least this system does not tax the internal valve in the lift pump. Approx 55,000mi on this go round.

 

[rweis]

Steve,



Sounds like a simple solution, AND it works, one of the KEY features.



I think the Mallory unit will do basically the same thing but self adjust is the only difference.



Have you had any problems with the line "T" into the return? I was a little concerned with overloading the return line with the bypass bleed off. I was going to T into the "burp" line at the tank, larger line but I have no idea of the volume of the bleed off. I figuered that if the VP can bleed off a 1/4 inch line (or so, not measured) the tank "burp" line should be fine.



Everything I read about the bypass was to be careful about puting too small a return line on it because it is taking off a pressure line and puting it into a unpressurized line.



Bob Weis

 

[Steve Campbell]

I had similar concerns....

and found a thread a couple of months after my project was completed. I emailed one of the "princilals" from that thread and he replied with a very knowledgable answer (Wish I could remember who it was to be able to give him credit). I was assured that what I was did was OK



If someone had 2 pumps (pusher and lift), you might be able to "overpressure" the stock return line... . but with only one regular output pump (like the 4601 HP)..... there should be no problem.

 

[illflem]

Bob, you only need to return the extra fuel from the relief valve right back to the pump inlet, shouldn't be more than a foot. I wouldn't be too concerned about the hose handling the flow.

 

[rweis]

Bill,



That would be a whole lot easier than trying to get into the "burp" line. I was wondering if it would cause any problems with the feeding the inlet to the pump since it would be under some pressure.



The second question I have is that I am going to put a RACOR 690 filter before the lp and would it cause any problems with the flow at low VP demand of trying to wash the filter backwards?



There is always a flow through, but at idle (worse case) is the bleed off the bypass more than the VP is demanding? What happens if the fuel just circulates? Would it cause the lp bypass to open?



I don't know the answers, what do you think?



Bob Weis

 

[illflem]

As long as your truck is running it's using fuel and sending some back via the return line from the injection pump and injectors. The relief will only be bypassing a portion of this so the fuel will never flow backwards though the intake line from the tank.

Even if you were to bump your lift pump on without starting the engine and 100% of the fuel wasn't being used it would basically just pump in a circle from the relief to the pump inlet, there would be no flow from the tank at all, forwards or backwards.

Some hydraulic and water pumps are set up exactly like this.

 

[rweis]

Mallory 4307M installed this weekend.



Mallory is set at 14 psi.



Pre OEM filter set at 14, gives 13 post filter.



WOT pre 12, post 10. Ran WOT (full go pedal) enough to give it time to stabilize the psi (0-75 mph).



Will tow this next weekend and will see how the pressures are then.



Pre filter

Idle = 14, 65 mph steady speed empty = 14, wot = 12

Post filter

Idle = 13, 65 mph steady speed empty = 13, wot = 10



Bob Weis

 

[merryman]

Steve;

Might you have pictures or diagrams?

Sometimes my lack of mechanical training or experience makes for a little difficulty in following.

If no phots, how about a little more detail in explaination.



Thanks



Vaughn

 

[rweis]

I want to tow this weekend first. I want to see it with much higher demands for hours.



Pleminary short run test was very good though. The pitch of the lp motor is a little lower now also which I translate to less effort on the lp. I do not have a conveinent way to measure the amperage draw of the lp.



Only LONG term mileage will really prove it out, but I am happy with it.



Bob Weis

 

[RustyJC]

This could be fun!



Split-style bearings (like main and rod bearings) are often called "sleeve bearings" (not bushings). Solid bearings (like cam bearings in a small-block Chevy) are often called "bushings", depending on their applications, but they're really just a solid sleeve bearing. Ball or roller-bearings often use the term "anti-friction bearings" or "rolling element bearings".



Oh, you say to-mah-to and I say to-may-to, you say po-tah-to and I say po-tay-to... ... ... .



Rusty

 

[rweis]

Ahhhhhhhhh, Rusty,



Might have gotten responses in the wrong thread?, lol



Good information though.



Bob Weis

 

[Steve Campbell]

Merryman.....

no pictures, but..... my stock system and yours are slightly different. I have the "old" style filter head where the "can" comes off of the bottom ot access filter changes. Two "test" ports in the top... . one pre-filter and one post-filter.



Anyway, my pressure sender is located in the post-port and the "bypass" is in the pre-port. I did this for two reasons, 1) pressure reading post-filter lets me know when to change filter and 2) bypass pre allows the "air" that is filtered out of the fuel to return to the tank. (OK,... . it is only MY hypothesis. )



Hope that helped some!!!!!

 

[rweis]

Not towed yet but,



Found 14 psi pre filter is a little high. The check valve ball in the lp was still opening (with this particular OEM pump) occassionally.



Reset pre filter psi to 13 and the check valve ball seems to stay closed all the time. Pre filter 13 gives me 12 post filter.



On normal aceleration it stays 13/12. On hard acceleration it is 12/11 until I back off to normal cruise pedal then back to 13/12. On WOT from a standing start it went to 12/10 until I backed off (75mph). Post filter psi has not gone below 10. Have not towed yet either.



Other observations:



Before the bypass I noticed when the engine speed decreased rapidly, like during a transmission shift, the VP bypass back to the filter would spike the psi sometimes from 14 to 18 - 20 psi for a second or two. The pre filter psi did not seem to spike. With the bypass this psi spiking has stopped. Maybe because it has an alternate route back to the tank? Not sure, but no more psi spikes. Very steady pressures. I tried a standing start wot to 75 mph then fully off the go pedal to idle (barked the turbo), no fp psi spikes either pre or post filter.



I also specifically listened to the lp before this modification, park, idle. In listening again, the pitch of the sound is noticeably lower. I take that to mean less head pressure (which is manually set at the bypass regulator). Seems to be running more freely.



Just reporting observations, more after towing this weekend.



Bob Weis

 

[Steve Campbell]

Bob Weis....

My experience was the same as yours.

 

[rweis]

Towing weekend... ... ... ... ... ... ... ... .....



Perfect respons from the lp. Loaded wot, boost to 32, egt to 1100, fp pre/post 12/10 stable as a rock.



Idle at a stoplight, 13/12. No way the lp bypass is actuating. Fp is rock stable. No fluxuation or wavering. No spiking.



I am pleased and think the RACOR 690 / Mallory 4307M / Stanadyne Performance Formula combination will solve all but the lp motor wearing out, and for that carry a spare. Should be good for 80 - 100k miles, but that will take time to prove.



I have 23k miles and will try to remember to bring this thread back up at 50k, 75k, 100k or when the lp fails.



I've got mine, good luck in searching what's right for you in "fixing" your OEM lp problems.



Bob Weis