'89 240. No Power, Won'T Rev. Intermittent. I Think It'S The Intank Fp

Hi everyone,
First post. I normally stick to Turbobricks, but I learned that Three Fat Tigers had "moved" over to Volvospeed. His advice was always very good, so I'm posting here to pick his brain!

Anyways, thanks in advance, TFT!

I am going to shamelessly copy my posts from TB.

Last Night:

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So, all of a sudden, my '89 (B230F, LH 2.4) loses about 70% of its power. I can't accelerate up this hill, I've got it floored and it just loses speed. I pull over, and start fiddling around. There is a whistling noise from the rear of the car when I put load on the engine. In neutral, it won't rev over 3000.

1. I pull the fuel pump fuse, no change in idle, and it still revs to 3000. Fuse is cool.
2. I check the codes. 1-1-1, no problems
3. Get under the car with it running, fuel pump fuse in, fuel pump is cool, makes funky irregular noises (I think the noises are coming from the fuel pump). I whack it with a hammer thinking it might loosen up some brushes or something, but no improvement.

So it seems pretty obvious to me that it's the main fuel pump, but I've been wrong before, so I wanted to run it by TB. I do think it's odd it wasn't drawing a ton of current (I thought that was a typical indicator of a dying fuel pump), and odd that LH didn't throw any codes.
I am planning on checking for voltage at the pump with the car running before replacing the pump.

Any insight? Am I diagnosing this right?
Thanks!

Today:

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I did some more investigating today. Weird Stuff.

1. In-tank is not running. I jumpered the fuel pump relay, then disconnected the lead for the main fuel pump. No sound from the in-tank, and no difference when I unplug/ plug it.

2. The driveability problem went away. The car still wasn't driving/ running right when I first started working on it. Then after tinkering for a bit, it was running and driving normally, even though the intank wasn't running.
Things I did that might have changed it:
-Opened gas cap to listen to pump. Maybe the vacuum released, and now the main pump and handle pumping on it's own, without working against the vacuum.
- Wiggled some spark plug wires. They all seemed tight.

3. The main pump runs regardless of whether fuse #6 is in, or any fuse for that matter. I checked the wire hooked up to #6, and it does indeed look like the same wire for the fuel pump/ fuel pump relay. Weird!!! I hope the previous owner/ mechanics didn't do a ugly splice in somewhere.

So here are my currrent theories on the loss of power problem:
1. Dead Intank pump. Main pump can't compensate when vacuum builds.
2. Intermittently failing AMM.

It seems at the very least I need to replace the intank, regardless of whether it's the cause of this problem.
I might go for a longish drive sometime soon, try to build some vacuum and replicate the loss of power, then open the cap and see if it goes away.
I think I will get my parents to send me my spare AMM so I can try swapping it if/when the problem occurs again.

Thanks guys!

First I would work on getting the in-tank pump working. Remove the #4 fuse, jumper the left side of the #6 fuse holder to the right side of the #4 holder, you should hear the tank pump running. If not, go to the sending unit connector and confirm power is present, or apply power to that point directly, black would be the power for the pump, brown is for ground. To test the main pump, you can jumper the left side of the #6 fuse holder to the left side of the #4 holder, you should hear the main pump running.

On your car, the power source (upstream of the fuel pump relay) for the main pump comes from the blade fuse in the engine compartment, not from fuse #6 so no surprise it will run if it is removed.

If the pump still doesn't work, inspect the sending unit wiring for any breaks via the access panel in the floor above the tank, otherwise you need to pull the sending unit and replace the pump.

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