Fuel pump questions: LRA / 3FE -> LS

[tmxmotorsports]

Ok I did some troubleshooting tonight. Installed a fuel pressure gauge. At idle it holds 50psi and the pump is silent. When I blip the throttle the intake manifold pressure drops, which lets the fuel regulator ramp up and my gauge pegs out to the mechanical limit and stays there - which is well above 80psi (where the gauge numbers stop).

I removed the return line at the tank and let that feed into a gas can to make sure there were no return restrictions… there aren’t.

I did a bit more than that, but the conclusion is that the stock regulator can’t drop enough pressure/flow for this pump. I think the fuel line pressure is too high causing back pressure on the pump which is causing the whine. It’s consistently dead quiet until I blip the throttle.

So at this point I’m thinking I’ll just get a 3FE pump and I’ll have to address the pump again when it’s time for the LS.

Or regulate it before the 62 regulator it may just be easier to just go with the 3fe fuel pump if your planning an ls swap and you will have the other pump on hand if you need to switch it out.

 

[toy_tek]

I’m done experimenting for now, not sure exactly how well two regulators would work.

Also… using the return line to drain the tank sure beats pulling the drain plug.

 

[tmxmotorsports]

I’m done experimenting for now, not sure exactly how well two regulators would work.

Also… using the return line to drain the tank sure beats pulling the drain plug.

I made a 2x4 wooden thingamabob for my jack to raise and lower the Lra tank has castor's so I can roll the tank around then roll the jack under that and lift it up. How was your mounting holes I've had to use a bur bit for the bolt holes.

 

[toy_tek]

I made a 2x4 wooden thingamabob for my jack to raise and lower the Lra tank has castor's so I can roll the tank around then roll the jack under that and lift it up. How was your mounting holes I've had to use a bur bit for the bolt holes.

No issue w the mounting holes, i used all the OEM bolts after I cleaned them up.

Someone gave me an older harbor freight ATV jack a number of years ago… I can’t kill that damn thing. Used it for transmission swap and it’s perfect for the LRA tank as well. Going to mod it and put swivel casters on the front instead of the uni-directional rollers.

 

[toy_tek]

New Delphi pump, old pump, Denso pump

Figured I'd post the final result here. Ordered a Delphi CFE 0486 which is a direct replacement for the factory 62 pump, $100 from Napa. It is indentical, however unfortunately the box label says "Made in China". I decided I'd test it before mounting it in the tank, and it worked fine pumping water out of a 5 gallon bucket.

Mounted it in the tank, installed the tank, jumped the test pins to check pressure, and got 50 psi. Started the truck, and as soon as I blipped the throttle, again the pressure shot to the mechanical extreme on the gauge and the new pump started squealing. So I realized the noise wasn't really a pump issue. I found an old regulator in my spares bin, popped that in, and then the gauge showed 40psi at idle. When I blipped the throttle, it would bump up around 45psi and then regulate back to 40. And no noise. Test drive confirmed, no pump noise, maintained correct pressure on the gauge.

So the noise was a regulator issue. However, I am not sure if the Denso pump may have damaged the original regulator or not. I didn't have a pressure test adaptor before I changed the pump to know what the original regulator did prior to the Denso pump - however the truck always ran fine. Last summer I had swapped those to regulators to check something else and they both performed the same. So ... I really don't know if the higher pressure pump caused this issue or not. The real test would be to re-install the Denso with the "newer" regulator, but that's a bit of unnessesarry work at this point and I suppose I run the risk of damaging the working regulator. And those aren't cheap anymore.

Anyway, at least I have the tank drop / fuel pump replacement procedure down pretty well. So I'll just install the Denso pump when it's needed. Thx for the feedback in the thread, always nice to have other opinions to consider.

Gauge installed with LCE adaptor 1093076 (link)
Final pressure at idle: