New float/sending unit probs (Page 1/2)
gregr75 JAN 20, 08:05 PM
New fuel pump doesn't turn on when ignition turned on, or 12V applied directly to the harness. Dropped the fuel tank, and found out it was not the fuel pump, but a bad negative wire feeding the fuel pump, on the float/sending unit, one end soldered to the body and the other end going to the fuel pump connector. I purchased this sending unit new about 6 months ago.

I'm going to ask the supplier of the sending unit for a refund, I think this should be reason enough to ask for a return. I'm hoping I don't get pushback because it was put into gasoline… Etc.

In the event this happens, Can I just get normal stranded wire and solder it myself and redo the connector. Is there a fuel safe wire or solder that should be used?

[This message has been edited by gregr75 (edited 01-20-2024).]

theogre JAN 20, 11:18 PM
Wire(s) in the tank...

Solder doesn't matter. 60/40 Lead solder melts lower then most lead free types.

Many Wire insulation won't like gas to start w/ & often hates Ethanol gas now.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

gregr75 JAN 22, 07:18 PM
Thanks. TFS is sending out a replacement unit to me.
OldGuyinaGT JAN 23, 04:06 PM
Sounds like you have the problem addressed, but for what it's worth, wire with cross-linked polyethylene (XCPE) insulation and GXL rating is gasoline-resistant. Teflon insulated wire (NEMA HP3-Type EE) would also be suitable (probably greater chemical resistance) but may be a bit stiffer. The Type EE stuff is the real deal; my company uses it because it's required for safety-related equipment in nuclear power plants, because of its low outgassing and high temperature ratings, as well as chemical resistance.
MERATIME JAN 26, 01:59 AM
Same situation, TFS sent me replacement because I had that issue with the new defective sending unit I recently purchased. Rep said they had over 100 returns/exchanges with these sending units recently. Replacement installed today. Hopefully this one doesn’t fail !

[This message has been edited by MERATIME (edited 01-26-2024).]

gregr75 JAN 26, 02:46 PM
yeah its annoying having to drop the tank multiple times. this ones getting bench tested thouroughly before it goes in.
theogre JAN 26, 03:48 PM
⚠️ Warning: Whatever bench test Must Not allow the Pump to run dry!

Loop the out to return lines on the sender kit then fill container enough gas so pump has flow to cool & lube it.
If test is in the tank, 2-3 Gallons should be enough when tank is level.
fierogt28 JAN 27, 05:37 PM
When you get the new sender, before testing the float arm for perfect accuracy, use a multimeter and on OHMS check the resistance value on the wiring.
It needs to be 1 on empty (right at bottom position)
And the middle range is at 45 Ohms.
And finally at 90ohms at full with the float arm maxed out at top.
If those ranges are accurate, you’re good.
I bought Rodney’s fuel sending unit assembly and this was checked on mine. It was perfect.
Another issue that members that bought TFS sender is the float will interfere with the baffle in the tank.
I don’t know if TFS corrected this issue because in another thread, it was mentioned why the gauge was incorrect or wrong to the actual gas in the tank.
I understood it was at under 1/2 tank condition because the float was not fully dropping due to contact on the baffle.
Rodney’s reproduction tank has a different baffle design than stock. So, this issue won’t happen.
Rodney’s fuel senders are really nice, as I bought 2 of them. There very well priced.

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

Patrick JAN 27, 05:56 PM

quote
Originally posted by theogre:

⚠️ Warning: Whatever bench test Must Not allow the Pump to run dry!

Loop the out to return lines on the sender kit then fill container enough gas so pump has flow to cool & lube it.
If test is in the tank, 2-3 Gallons should be enough when tank is level.



IMO, it's a whole lot safer to be using something other than gasoline if bench-testing a fuel pump in an open container (ie large bucket). I've used varsol.
theogre JAN 28, 07:05 PM

quote
Originally posted by fierogt28:
When you get the new sender, before testing the float arm for perfect accuracy, use a multimeter and on OHMS check the resistance value on the wiring.
It needs to be 1 on empty (right at bottom position)
And the middle range is at 45 Ohms.
And finally at 90ohms at full with the float arm maxed out at top.
If those ranges are accurate, you’re good.

Sender Should 0Ω @ "Empty" w/ float @ bottom of travel.
Problem is Many meters have problems w/ probe used &/or in them &/or don't have/use Rel feature & don't read below ~ 2 - 4 Ω right.

1 to 3 Ω Error is a Big Deal for sender operate in 0 to 90 Ω.
See Fuel, Engine Temp or Oil Pressure gauges have problems? https://www.fiero.nl/forum/Forum2/HTML/146784.html