AC Delco EP381 Fuel Pump Only Rotates Wrong Direction

[Cheap Heap]

I've been messing around with my fuel pump the last few days on my 93' C1500 350 TBI.

I wanted to upgrade to a higher pressure pump for an LS swap down the road.

I have a EP381 ACD pump but it will only rotate the wrong direction.

When I swap the polarity at the pump, it will not run at all.

What am I missing here?

 

[Jglew82]

Sounds like you got a bad one. I swapped an EP381 into mine with my 6.0 swap and had zero issues like that.

 

[Cheap Heap]

That's the only thing I can conclude as well.

I have way too much time invested in troubleshooting this simple DC motor, pretty frustrating...

 

[PlayingWithTBI]

Sounds like you got a bad one.

^^^X2 I put an EP381 in my 88 - no issues. If I had to venture a guess yours was assembled with diode(s) reversed, not allowing current to go in the correct direction. Send it back.

 

[Cheap Heap]

Thanks guys, just wanted to make sure I wasn't going crazy.

I ordered a replacement from RockAuto, it will be a few days before I can verify anything.

Good thing I don't need to drive this truck on a daily basis.

 

[Schurkey]

I have a EP381 ACD pump but it will only rotate the wrong direction.

When I swap the polarity at the pump, it will not run at all.

What am I missing here?

Sounds like you got a bad one.

I think the word you're looking for is "counterfeit". It's not a "bad" one, it's a Communist Chinese counterfeit.

When I got sold a batch of questionable AC spark plugs, I took pictures of them and sent 'em to AC-Delco (GM). They confirmed the plugs were "not authentic". They came from a dirtbag in Texas selling on Amazon.

 

[Jglew82]

Yep, I got a set of bogey injectors branded AC Delco before off rockauto. It’s very common with Motorcrap parts too.

 

[Cheap Heap]

That’s not exactly reassuring. I specially went with the EP381 for OEM quality. I’ve been reluctant to except something wrong with a brand new ACD pump, had this have been an aftermarket brand, I would have gave up troubleshooting a long time ago and assumed the pump was bad. I’ll need to take a closer look. I don’t see any specific markings on the pump itself.

The box looks like a legit ACD box and has a sticker that says ‘Made in Brazil’ nothing on the pump itself though.

 

[Schurkey]

My spark plugs said "Made in Japan".

And maybe they were. Who knows. The packaging and the ink-stamp printing on the porcelains looked first-rate. The lack of the "three dots" and the center electrode diameter (too large) were my first clues. What I didn't spot until after I'd marked-up the photos and send 'em to GM, was the different shape of the side electrode--original is gently rounded, counterfeit has a sharper bend.

As said previously, GM confirmed that these are "not authentic".

Three photos:
http://hbassociates.us/2020_Trailblazer_Spark_Plugs_LG_01.jpg
http://hbassociates.us/2020_Trailblazer_Spark_Plugs_LG_02.jpg
http://hbassociates.us/2020_Trailblazer_Spark_Plugs_LG_03.jpg

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[Cheap Heap]

I received a new pump yesterday from RockAuto. Plugged it in and it started right up in the proper direction. Running the same polarity as the original pump I removed two weeks ago. The new pump is much quieter as well. Installed the complete sending unit and the truck started right up. It’s crazy how much time I wasted troubleshooting bad pump #1, pretty frustrating. This should be a plug and play swap for anyone else swapping to a EP381 from a stock TBI pump.

The two pumps pretty much look identical. Pics below. Pump that works properly is on the right.

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