Fuel pump LPH: how high is too high?

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wa-chiss
Posts: 2569
Joined: Mon Feb 20, 2006 10:23 pm
Car: 1990 Nissan S13 H/C KA24E
2005 Toyota Sequoia
1976 Honda CB750F Super Sport
Location: San Angelo, TX

Post

Short story:

My fuel pump quit working. I didn't have time to wait for a walbro 255 lph pump and the factory one is like 125 lph or something. As a Toyota tech, I've installed superchargers on Tundras that are Flex Fuel. They say the pump in the fit kit isn't required as it's the same as the one in the tank already. It's a denso pump that puts out 320 lph (from what I've read). I have one and I'm about to install it, but I just thought about if it'll be ok.

Is that too much for the stock regulator? I have 10.6:1 CR, stage 2 cams yada yada yada. No Adjustable FPR, no gauge, stock injectors, stock rail. I just don't know if the regulator can flow enough that the pressures don't climb to dangerous levels.


amc49
Posts: 1183
Joined: Mon Jun 19, 2017 7:24 pm
Car: '11 Nissan Versa
'17 Nissan Altima

Post

Pump fuel flow ratings are usually done using an open ended tube, not under regulation..........meaning under regulation you have no numbers of any worth at all. The regulator bodies will generally flow enough, it's the flow ability of your bypass setup that needs to be worried about. Your restriction there is the injectors.

wa-chiss
Posts: 2569
Joined: Mon Feb 20, 2006 10:23 pm
Car: 1990 Nissan S13 H/C KA24E
2005 Toyota Sequoia
1976 Honda CB750F Super Sport
Location: San Angelo, TX

Post

I put the Denso 320LPH pump in and she started. However, it ran rough. REALLY rough. I got the idle to stabilize enough to check which cylinder(s) were misfiring. Got to #2 plug wire, no change in idle when I removed it. Managed to get the car to work the next day (2 mile drive). I swapped the pump for a factory pump just to eliminate that possibility, still no change. Checked the spark plug, fouled. Cleaned the plug and retried, still misfire on 2. Change the plug, still a misfire. Take the injector out and supply power and ground, no click. Check another injector, audible click. The injectors have over 200,000mi on them so I decided to swap all 4 with new units. The engine actually runs GREAT now.

I'm debating on swapping the 320LPH pump back in.


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