Fuel pump and sending unit

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Re: Fuel pump and sending unit

Postby gt350fme » Mon Mar 22, 2021 11:38 am

I recently rebuilt my fuel pump unit mostly because the fuel level cable contact was intermittently failing at the bulkhead, the rubber bulkhead was also cracked leaking.
My internet searches found a cheap fix for the bulkhead connection and seal in the following pics.
Replacement wire and connectors should be soldered and shrink wrapped.
Also of note for carbureted engines is the fuel pump pressure variance of the many stock in tank fuel pumps out there, some are lower pressure some higher, for a stock engine pressure is not an issue, but if a larger performance engine is used 5-7 psi is a minimum, racing applications need even more pressure and flow.
Hope this helps.
John
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1964 Chevy K20 Panel
1973 GT Vega Hatchback
1984 944 porsche
1992 Lexus SC 400
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Re: Fuel pump and sending unit

Postby TTait » Mon Mar 22, 2021 8:03 pm

I've got to stick with the 4.3 liter engine for the foreseeable future, so no problem there. Upgrading the fuel pump some day to put in a stroker is the least of my worries - how to pay for all that would be a higher concern.

My connections at the top of the tank seem solid - I can just solder new wires on to the underside - but I like what you did there. What kind of rubber is the grommet? Is it fuel rated? Did you use any special wire inside the tank?

Can anyone describe how the sock/ filter screen is supposed to connect up to the pump assembly, is it somehow related to clamp B above?
On my third H Body - 1975 Monza 2+2 4.3L Orange/Black (Current State: Running great - needs the AC finished before summer hits hard)
76 Monza 2+2 L4 (1982-1987)
77 Starfire V6 (1987-1987)
82 Delorean - Universal Raffle Car (2005-2013)
81 Delorean 2009 - Present
17 Chevy Bolt 2017-Present
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Re: Fuel pump and sending unit

Postby gt350fme » Mon Mar 22, 2021 10:05 pm

I would think that you could carefully quickly solder a new wire to the underside pin before damage to rubber bulkhead.

Pics are copied from internet and the grommet is not fuel rated that I know of and may leak later we will see not leaking now don’t try at home, I may have to go with plan B later GOOD POINT!
I do have a fuel rated bulk head purchased from Amazon that has 3 holes for wires and nut that tightens from inside like $40 but needs a larger hole, will cross that bridge if first try leaks

Rubber piece B holds and insulates the pump to the end bracket and also secures over the filter, piece B that I needed is different than the one shown, mine has 2 ears and fits into said bracket, the one shown would not fit my bracket.

I will post a pic of my finished unit later for reference.
Last edited by gt350fme on Mon Mar 22, 2021 10:39 pm, edited 1 time in total.
1964 Chevy K20 Panel
1973 GT Vega Hatchback
1984 944 porsche
1992 Lexus SC 400
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Re: Fuel pump and sending unit

Postby gt350fme » Mon Mar 22, 2021 10:37 pm

A bit modified, I used a stewart warner fuel sender but the rest is stock,
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1992 Lexus SC 400
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1973 Chevrolet Vega GT

Re: Fuel pump and sending unit

Postby TTait » Tue Mar 23, 2021 1:17 pm

That helps a lot, thank you. It reminds me that if the shop is going to paint my tank for me, I should probably paint the top of the sender assembly too.

I'm hoping to stop by there today at the end of the day and plug in my rebuilt sender to see if the gas gauge suddenly springs to life - it should, it was getting 0 ohms before but one can never be sure. Either way I have an alternate sender and the new fuel pump arriving later this week.

On yours, I suspect the grommets will hold up ok if you don't keep the tank topped off too often. I think a leak is less of an issue than a spark. I'm not sure I ever believed the official story on TWA800, but I wouldn't want a spark in the fuel tank either way.

As I have to replace the positive lead going to my new fuel pump, I think my plan is going to be to go buy a foot or so of small diameter rubber/teflon fuel line at the auto parts store, and run the new wire inside that, cable tied to the main frame of the sending unit so nothing can move or come loose. That way if the wire insulation on any of this ever does degrade there is no chance for contact or a spark. I'm not prone to paranoia usually, but an extra dose of security might not hurt this time.
On my third H Body - 1975 Monza 2+2 4.3L Orange/Black (Current State: Running great - needs the AC finished before summer hits hard)
76 Monza 2+2 L4 (1982-1987)
77 Starfire V6 (1987-1987)
82 Delorean - Universal Raffle Car (2005-2013)
81 Delorean 2009 - Present
17 Chevy Bolt 2017-Present
TTait
 
Posts: 58
Joined: Sat Feb 20, 2021 1:47 pm

Re: Fuel pump and sending unit

Postby monzaaddict » Tue Mar 23, 2021 3:39 pm

carefully open the part where the rheostat is . it may just need to be cleaned. or even just spray electrical cleaner through an opening if there is one
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Re: Fuel pump and sending unit

Postby TTait » Wed Mar 24, 2021 6:29 pm

The tabs holding it together were shot, the "wire" band coming down to it had an intermittant connection, it needed to be cleaned and the small spring loaded contact was half broken and needed to be soldered back together on one side.

Its now all cleaned up and repaired and I soldered the case back together - tested it out yesterday and it works like new. Once the new fuel pump comes in I'll take a few photos and add them here.

Thanks guys.

Tom
On my third H Body - 1975 Monza 2+2 4.3L Orange/Black (Current State: Running great - needs the AC finished before summer hits hard)
76 Monza 2+2 L4 (1982-1987)
77 Starfire V6 (1987-1987)
82 Delorean - Universal Raffle Car (2005-2013)
81 Delorean 2009 - Present
17 Chevy Bolt 2017-Present
TTait
 
Posts: 58
Joined: Sat Feb 20, 2021 1:47 pm

Re: Fuel pump and sending unit

Postby monzaz » Mon Jun 14, 2021 4:38 pm

I know old post...BUT good for reference.
I have a sending unit that read correct with ignition on BUT the minute you start the motor and vibration happens the gauge jumps all over the place.
Anyone with any ideas?
This tank had VERY VERY old fuel I just want to see if anyone else had this issue and fixed it first before tearing into it blind. :)
Thanks, Jim
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Richfield, Oh
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