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Addressing my RB25DET Fuel Pump & Alternator issues

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Two problems have come to my attention about my RB Z.


-First problem is the Alternator.

At least I believe. I have tested the alternator with a micro VAT. I have 42AMPs max output. I have some AC ripple that has concerned me, but I am un-sure the total allowable amount. If I remember correctly I have about 3 volts AC ripple in the system. That doesnt seem to be my issue however. Any time that a load is placed on electrical system it drastically affects the rest of the system. Turn signals for instance can be heard affecting the fuel pump pitch. That cant be correct. I have removed the 74 voltage regulator and connected the signal wire from the RB alternator to the battery with an inline resistor that keeps my max voltage below 13.8V. Without the resistor the voltage will spike 15.6V at times and Ive seen it get really close to 16V. I thought I may have had a ground issue but I bought a new battery ground cable and made several other ground straps for the engine. Why is my electrical system being loaded so heavily? Isnt the alternator suppose to regulate spikes and draws on the system?


-Second Problem Fuel.

As you can see by my other recent post with my Dyno results I have a fuel starvation issue. I have been through 90% of my fuel system. So Im at a loss for an explanation. So let me explain what Ive done.

I was using the original R33 pump for my car at first. I placed the pump in the tank with the pickup sock in the center of the tank. 1/4 tank left and any heavy accel/turning and the pickup would go dry. I still have this problem. However I dyno'd the car with a FULL tank. About 3-4 weeks ago I replaced the R33 pump with a used, but known good, Infiniti Q45 pump. These pumps have a tendency to go out and become loud (often referred to as "Angry Bees")and chances are if you pull one at a wrecking yard you will get a bad one. I pulled mine from a driving parts car I had a few years back. My logic was that the VH45DE is rated at 279ft/Lbs and about the same HP, the RB has a very similar rating so the pump should be a very qualified replacement part. Im using a brand new fuel filter for the R33.

Ive checked the FPR and the fuel rail for problems. My fuel lines have been checked as well and they are both flowing fine. I have a APEXi SAFC II installed and it isnt having much of an effect on the AFR at high load.

My guess is that the Q45 pump has gone bad while it sat on my self at home and that it may be time to upgrade the pump and tank. Id like to verify the problem before I go and spend money on new parts that may not fix my problem.


Anyone have input for testing the situation with-out an O-scope.

EDIT: Also I noted that the R33 Sending unit/fuel pump carrier as a very small orfice for the return line. approx 1/8" or so. Its really small. Ive been researching info about the fuel pump modulator and pin 104. Currently I am running a 5/16" return line.



Edited by rayaapp2
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