Fuel Pump diagnosis

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Sep 11, 2016
Los Angeles, CA
Hello fellow mudders. I had a crank but no start issue out of nowhere yesterday. First thought was F***!, the immobilizer issue has struck me! But no, I quickly ruled that out, when I shot some starting fluid into the throtttle body and it started right up....and then died. Not getting fuel. I just want to make sure I am not missing anything here. After that I checked the fuses. All good. Went to the back and uncovered the fuel pump, key on, no pump noises. Checked the power going to the pump. 12 v going in. Starter definitely no worky. Anything else I should be checking before I go pick up a new pump?
I'd straight power it up from that connection at the top of the cover or by the rear drivers side door opening. There's a connection there.
I'd check for flow that way without opening the rail. There's a fair amount of good info in the FSM if you can get it. The pump does run for a really small amount of time before starter engagement. After that only with the starter turning.

That is all what I have read, I've no positive proof. For sure you can take it out and test in a five gallon bucket for flow rate. I'd suspect a fuse, I'd at least go through a that before I took the pump out.
If you have 12v and ground at the pump and it doesn't run, just check the connector pins, if good then order a new pump.
I figured my diagnosis was pretty solid. Ordered pump and screen (OEM) tonight.

I'm interested to know if the Denso pump kit (950-0107) is as well made, or identical to, the OEM pump (23221-66040). There's a huge price difference and the screen is extra with the OEM. Parts numbers are for my '98 LC BTW...
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I'm interested to know if the Denso pump kit (280-0233) is as well made, or identical to, the OEM pump (23221-66040). There's a huge price difference and the screen is extra with the OEM. Parts numbers are for my '98 LC BTW...
I am showing a rebuilt starter for (280-0233). As for the fuel pump and screen (filter), depending on who you ask the OEM pump parts are either Denso or Delphi. I have seen pics of boxes coming straight from the dealer parts counter with either Delphi (USA made) or Denso (Japan) inside the box. I called the local dealership in Culver City and I was told that if I ordered from them I could get either one. They would not promise either one. Although the lady said that most would be Denso (initially she did dot want to give me any info, but I called three times and she wanted me to leave her alone). So I just ordered these:

Denso Pump

Delphi Strainer/Filter

Together I only spent about $150. Dealer would have been nearly $400. I will examine the parts closely and take note of any differences in quality or appearance for you.
I am showing a rebuilt starter for (280-0233).

My mistake, I copied the wrong part number from my 'wish list.' The correct Denso pump & strainer kit I was referring to is P/N 950-0107. (Edited previous post to avoid future confusion.)

Thanks for the manufacturer info! Sounds like the Denso pump & strainer kit is 'as good as' OEM, then.
Meanwhile I got these today ( both appear to be high quality):


I will have these installed tonight for sure. I have a lot of practice with fuel pumps from tuning my 335i (N54), with a fair amount of custom installation. This should be a breeze.
All done! Started up first try. About a 120 minute round trip. At first I thought the new pump was non operational because it was so quiet. Not that the original was noisy, but the new one was not even slightly audible.

The OEM pump felt a little lighter than the replacement. Also the metal casting for the case on the original appeared goldish in color like brass? And you may have noticed in the pic that the replacement had a taller plastic end cap and slightly shorter overall pump portion vs the original, even though the overall length was the same.

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