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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996.1 Fuel Pump & Sending Unit Polarity
Leading reported evidence
Use thin feeler gauge blade ground down
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Performed · outcome unconfirmed
I use a old thin feeler gauge blade ground down with a dremel..
Leading evidence: 'Use thin feeler gauge blade ground down' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace 20 year old original pump' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion · Original poster
I purchased an aftermarket Airtex fuel pump to replace the 20 year old original pump.
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4 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261026T191851Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I purchased an aftermarket Airtex fuel pump to replace the 20 year old original pump. While comparing the electrical, I observed the black and yellow terminals are the same on the pump itself, but on the fuel sender unit side, they're reversed. Does anyone have info about the sending unit polarity? This is the 2nd pump, from a different retailer, with the same "reversed" wires, so maybe I'm just being paranoid. (The first was from RockAuto, the second, which I received today is from an Amazon seller.)
The OEM pump does not have polarity markings, while the Airtex unit does (black is positive). Appreciate any advice. Thanks all, and Happy New Year!
fuel sending unit connector, Airtex left, VDO right
fuel sending unit connector, Airtex left, VDO right
Airtex fuel pump positive marking (black wire)
fuel pump, Airtex left, VDO right
I'd bench power them each with a battery.. Check the pump direction, Its entirely possible the pump unit fits other applications, and its fine or Airtex inverted the leads when they stuffed the connector.. (I've had this happen! on other vehicle replacements... )
They can be tested in a bucket of water just flush them with WD40 before install to clear any remaining water.. Dont suck water through the pickup screen its better to remove it for testing if you can without damage..
Thanks for the advice, PDX. Bench test results:
VDO (original pump)
positive:
black
wire
negative:
yellow
wire
Airtex (aftermarket)
positive:
black
wire
negative:
yellow
wire
Which leads to the conclusion, that the
sending unit connector side has the leads reversed
. I couldn't figure out how to remove the terminals from the plastic connector, so to remedy the problem, I cut and spliced a connector and added shrink wrap tubing. Although not for certain, I don't think a "full" tank of fuel will ever reach the spliced region. I'm near the end of a 3.4 to 3.8L rebuild and will be hopefully starting the car in the next few weeks.
Airtex (top) sending unit connector. Swap and splice so that black positive wire matches original VDO.
sending unit
Typically you slide a thin metal blade down the flat side of the connector to release a barb in side.. I use a old thin feeler gauge blade ground down with a dremel.. I'm sure someone sells a 100 dollar tool for the same purpose..
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