Bullnose Enthusiasts Forum

Messing with Fuel Tank Sending units again

Classic

List

Threaded

39 messages Options

ArdWrknTrk

Re: Messing with Fuel Tank Sending units again

Administrator

If you're getting the pulsing around 5.5V it is just like stock, no matter what DC says.

The SWAD-J that Gary is using is cheap and dead stable.
All you need is a 9V battery clip, no need to reinvent the wheel.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ratdude747

Re: Messing with Fuel Tank Sending units again

It's a steady 5VDC (or whatever it was; matched up to what Gary set his adjustable unit to). No pulsing like the stock electromechanical units. I think the lack of pulsing is why the needles are slow to move... the pulsing helps break stiction in the gauge movement?

My comment on rolling my own would be to design a custom circuit board (PCB) that would be a drop-in replacement without any hacking. I've designed several custom PCBs in the past and these days they're wicked cheap (and low enough lead time) from China. A hobby of mine if you will.

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

ArdWrknTrk

Re: Messing with Fuel Tank Sending units again

Administrator

The gauges are like a reverse thermostat. The pulse isn't unsticking anything.
They are damped by design and there is a reason.
The fact these 6V gauges are from the 40's says all you need to know.

Hey, if you like puttering with circuit boards PCBWay, JLC pcb and many others are a great resource.
No more screwing around with acetate and nasty chemicals.
Just make a Gerber file , or Eagle, whatever... and click a button.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ratdude747

Re: Messing with Fuel Tank Sending units again

The last time I designed and ordered boards it was from AllPCB. Give them Gerbers and they do the rest.

(I use KiCAD for designing such... been using it since my days in EET school).

Anybody who visited my table at the truck show last year saw a bunch of my extra boards from the last several years on display.

----

That said, unless it becomes particularly bothersome, I'll probably keep the Dennis Carpenter unit. It works well *enough*, and is solid state at least.

It's also possible that crimping down the contacts on the connector to the sending unit had an effect and this is how it shows. I didn't retest it after crimping (I noticed the connector felt a bit loose when I doing final assembly and happened to have needle nose pliers under the truck already).

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

ratdude747

Re: Messing with Fuel Tank Sending units again

Had a full to empty to full cycle... took 14 gallons on a 19 gallon tank (needle almost touching the E mark, what was determined to be the lowest the gauge can read). Other than the occasional quick drop to 7/8, it's very linear... I'm calling it a win.

Up next: the ultimate test... Gary's Truck Show!

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

Gary Lewis

Re: Messing with Fuel Tank Sending units again

Administrator

Bring it on, and safe travels!

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

ratdude747

Re: Messing with Fuel Tank Sending units again

In reply to this post by ratdude747

10 month update:

Full no longer reads as full but as 3/4 tank. Been like that since the winter. But it would seem to unstick and read full not long after filling up and driving

While filling it up yesterday (on a long all-day drive home), I noticed something peculiar... the needle did read full during filling, but then dropped down to 3/4 by the time the pump clicked off. Yes I do leave accessory power on when filling. Due to not having an electric pump, I don't see it as enough of a hazard to have the sending unit power active during filling (and with as slow as the gauges are to warm up after power cycling, I don't like leaving it off if I want to ensure I actually got a good fill).

Seems the upper end of the sending unit has marginally high resistance. Not bad enough to warrant dropping the tank or lifting the bed, but I will note it as a quirk. Knock on wood, but the rest of the range is OK still.

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

Gary Lewis

Re: Messing with Fuel Tank Sending units again

Administrator

I've seen that and assumed like you that the top of the range has a problem. But, again like you, it wasn't bad enough to cause me to drop the tank. What I'm really interested in is the bottom end of the range, and if that works then I can use the trip odometer to see that it has only been a few miles since filling up and the gauge really should be reading full.

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: Messing with Fuel Tank Sending units again

Administrator

In reply to this post by ratdude747

https://www.ebay.com/itm/Gas-Tank-Sending-Unit-19-gallon-fuel-tank-1980-84-F100-350-Ford-Truck-NOS-/225642164958?_trksid=p2349526.m4383.l4275.c1#viTabs_0

Gary Lewis

Re: Messing with Fuel Tank Sending units again

Administrator

Good find, David! That's a nice price and fits 1980 to 84:

F100/350 - - 133" W/B
F150/350(Super Cab) - - 155”,168" W/B
F350(81) — (Regular Cab)
136.8", 160.8" W/B

Gary, AKA "Gary fellow": Profile

BigBrother-84

Re: Messing with Fuel Tank Sending units again

Gary, just curious why it is not also listed for Crew Cabs 19gal equipped trucks.

Is Big Brother's 19 tank different from a regular or extended cab?

Jeff / 1984 F350 Crew Cab 4x4/5.8L w351 4V/ T18/ D50 4.10 front/ 8' bed.
Restored 2019-2022.
Nicknamed «Big Brother 1984», due to its soooo-looong shape & nod to George Orwell's 1984 famous novel.

Gary Lewis

Re: Messing with Fuel Tank Sending units again

Administrator

Actually, it looks to me like the MPC has an error. The snippet below is from the 1986 F-Series brochure and you can see that the Crew Cab is the only one with a 168" wheelbase. So I think when the MPC said "F150/350(Super Cab) - - 155”,168" W/B" it was in error. The Super Cab had 155" wheelbase and the Crew Cab had 168, but they ran both together after "Super Cab".

Ralph?

Gary, AKA "Gary fellow": Profile

BigBrother-84

Re: Messing with Fuel Tank Sending units again

Just to precise I am talking about the standard midship 19gal tank (Big Bro doesn't have the optional rear tank).
I didn't realize that the optional rear one can also be 19gal capacity.

So my question could be read as of «Uh? All midship 19gal tanks aren't the same?»

Jeff / 1984 F350 Crew Cab 4x4/5.8L w351 4V/ T18/ D50 4.10 front/ 8' bed.
Restored 2019-2022.
Nicknamed «Big Brother 1984», due to its soooo-looong shape & nod to George Orwell's 1984 famous novel.

ArdWrknTrk

Re: Messing with Fuel Tank Sending units again

Administrator

In all cases the aft tank would be 19 gallons.
Except for Broncos that kept their spare tire on the swing--away tailgate carrier.
These came with a deeper rear tank and a skid plate for off road as can be seen here: https://www.garysgaragemahal.com/1985-on-f-series.html

Short bed trucks (117" wb) got a 16 gallon midship tank.
Pretty much all 133 and longer wheelbase trucks came with a 19 gallon midship tank.

Chassis cab trucks had straight frame rails behind the cab that were narrower to fit industry standard dump, utility or flat/rack beds.
Pickup tanks don't fit inside the CC trucks frame. They came with a 22 gallon tank.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Messing with Fuel Tank Sending units again

Administrator

Thanks, Jim. You said it better than I could.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Messing with Fuel Tank Sending units again

Administrator

To more directly address Jeff's question «Uh? All midship 19gal tanks aren't the same?»
(Sorry, I didn't catch this edit.

)

The tank bung size changed for '85, when electric in-tank pumps became available.
So wether you had an electric pump (4 pin connector) or a mechanical pump (2 pin. sender only) the '85 & on tanks came with a bigger hole on top.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

81-F150-Explorer

Re: Messing with Fuel Tank Sending units again

In reply to this post by Gary Lewis

I think the error is an omission of the words (Crew Cab) in the list. But since it states 168 wb it's not a horrible error, as that would cover the Crew Cab.

Since the Final MPC was updated from the earlier MPC's from 1980/ on up you get a lot of omissions like this. The Crew Cab was introduced in 1983 for example.

Truck: 1981 F-150 Explorer / Engine: 300-6 California MCU Feedback System / Trans: T-18 - 4 speed / 2.75 Ford Rear Axle Open Diff.

Gary Lewis

Re: Messing with Fuel Tank Sending units again

Administrator

Yes, that's exactly what I'm saying - since it shows 168" WB then it is a crew cab. Just doesn't say so.

Gary, AKA "Gary fellow": Profile

BigBrother-84

Re: Messing with Fuel Tank Sending units again

Thanks guys!

Jeff / 1984 F350 Crew Cab 4x4/5.8L w351 4V/ T18/ D50 4.10 front/ 8' bed.
Restored 2019-2022.
Nicknamed «Big Brother 1984», due to its soooo-looong shape & nod to George Orwell's 1984 famous novel.