Grasping at straws:

The fuel pump should be receiving much more than just 12 volts. Seems insignificant but there's less than 1 volt difference between a fully charged battery (12.6v) and one that's nearly dead (11.6v). A battery at 12v is below 50% charged and that's when measured without load. It will register lower under load. And there's a voltage drop in the long, possibly corroded wiring between the battery and fuel pump.

We're well over 50 posts in this thread and I'm not sure what you've tried. (1) Have you tried jump starting the car tied to another running vehicle? This should eliminate any low battery voltage issues. (2) Have you tried testing the fuel pump in situ directly from your existing battery with a length of quality wire? This will highlight or eliminate the internal wiring as the problem. A heavy extension cord is cheap.

-- Chuck

 

Thanks for your responses guys. I havent had much time to figure this problem out and have been just dealing with it for the past few months. My fuel pump is hooked up directly to the battery using the SOS rewire kit. I do believe it may just be a battery issue. I'm on an agm battery and its approx 3-4yrs old. @Chuck S Good idea, I'll try hooking up my battery to another car via jumper and see if that solves the problem, that would be an easy test to see if the problem is indeed the battery. The last time I took everything back out, everything checked out. Voltage was flowing through all the connectors and all the crimps were still in in-tact with no damage/corrosion. It's gotta be the battery, I'll report back in a year when i get around to testing it LOL.

 

With my issue, the crimped/re pinned wires from SOS kit to the factory blue plug on top of fuel basket was the issue. It looks fine on inspection, but obviously not, as it was getting intermittent connectivity either through the ground or power, so after months of problems I deduced that best option is to just bypass the plug altogether and drill two holes down the top of the basket to run direct power and ground to the fuel pump and then epoxy around the holes/wires so I don't get any fuel vapor exposure. Its worked ever since. If your trying to eek out every bit of voltage to pump this is likely going to be the best performing as well.

 

Thanks for putting this thread together, Junky!

I just wanted to pop in and say that I had the same symptoms pop up a couple of weeks ago.
This was a rather deceptive issue to diagnose without knowing exactly what to measure. Looking back, I guess it would maybe be continuity (ohms)?
Thankfully I got the issue resolved last weekend without drilling through the housing. In my case, it was caused by my shoddy wire crimping (from 2018) and a loose ground terminal in the fuel pump to housing connection.

I installed an AEM 340lph fuel pump and the SOS Wiring Kit in 2017 or 2018. It was one of my first big wiring projects and my first time crimping on terminals. So..... yeahh. Went about as well as you would expect. I'll try and add some pics from last weekend here in a minute.

The tricky part about this is that when you test the wiring connections down to the fuel pump for voltage, you're likely moving those wires around a bit and reconnecting the connector to the top of the housing. So in my case, I think that movement was enough to wiggle that ground terminal back into place to get it to show voltage and be able to prime the pump. So when I put it back together, it magically started and I was confused. I thought it might've been a battery issue since I had a fresh battery hooked up.

Then a few days later it did the same thing with the fuel pump not priming. So I got fed up and took action. I removed the fuel pump yet again, de-pinned every connector from the pump to the relay, and that's when I found my shoddy crimping work. I ended up snipping off and replacing all of the terminals. It sucked. A lot. Even though I got lucky and had a bunch of spare terminals and wire grommets from various projects. This also gave me the chance to do a bit of wire organizing and consolidating with heat shrink which helped make the wires a lot easier to manage and group together.

 

Here are those pics!



I had to leave my S in my friend's neighborhood overnight with no top on it. Made me slightly nervous, but nothing happened thankfully.

No top = easy access. I'm actually pretty lucky that this happened while I have my Robbins top out to re-glue the rear window.

Fuel pump out the first time. Nothing seemed out of the ordinary. Tested voltage and it was getting 12.7V during key-on.

All the connections seemed to be fine although I didn't tug on the wires. I put it back and hooked up a battery to help it get full power and the S started up, so I drove it straight home.

Second time pulling out the fuel pump housing.

The Black ground wire came out of the connector when I gave it a nudge. It was loose in there. I ended up taking that off and re-crimping a new terminal on to help the two wires fit in the connector housing better.

I took a look at the fuel pump housing connector as well.

Everything looks normal here. I decided I was going to depin all the connectors though

Tada! It just popped right out whenever I got the cover off. That seems like a big problem. I'm really glad it didn't start moving around and sparking.

This is why it is important to learn how to properly use wiring tools and install terminals securely. I have since improved my crimp game. You know what they say, crimpin' ain't easy. lol

 

Classic! I remember this problem still all to vividly and it sucked, getting stranded multiple times and the confusion that I went through to finally figure it out. I option to just bypass the whole thing and run direct to 100% eliminate further issue down the road. Glad my thread helped you some and you got it worked out. And yeah, you got lucky with the timing of not having a top to work around!

 

Great photos and captions. I am glad that you got it working again.