Hey, guys, I'm a new guy on the block. I have a 1984 F150 Stepside with more than a few issues I need to fix, the most annoying of which is a bad fuel level sending unit. It's the 16 gal. side mount tank. The gauge will fluctuate +/- a quarter of a tank from where you actually are, plus when you fill up completely the gauge only reads a half-tank. The damn thing's left me stranded four times already. After the second time I started carrying a 2 gal. jerry can in the bed. I've already got a new sending unit on the way, & I'm planning a road trip to Ohio this summer. I'd really like to get this fixed before I head out. If you guys have any tips on replacing the sending unit, i.e. which way's the easiest, I would greatly appreciate it. Thanks a million in advance.

 

If the question is "So I have the right sending unit on the way?" I'll post part of the parts catalog and let you pick from the myriad of options. But, if the question is "How best to swap it out?" then I'll suggest lowering the tank via the all-thread bolts that hold the ends of the straps together. I've been able to get the sending units out of the tanks that way on several trucks w/o taking the tank completely out.

After you get the tank low enough you should blow off the top of the tank with compressed air to make sure nothing will fall into the tank. You should be able to just about sit up under the truck to see the top of the tank. Use a brass drift to drive the lock ring off, and then pull the sender out.

EDIT: And welcome to FTE!

 

I definitely regret not trying your method Gary haha. I changed mine out on Saturday also after being left stranded when the gauge marking incorrectly. This time my gauge showed a little less than a quarter full so I went ahead and dropped it completely. Turned out to be over half full and wasn't fun to put back in the truck. Well worth the work tho

 

Glad you got it fixed.

 

Until one can find a replacement sending unit and install it, use this method... fill the tank completely and drive as you normally do for 100 miles [assuming the odometer works!] and refill, completely. Check your gas mileage; most likely, you will not run out of gas in 100 miles. After this initial gas mileage check, you can estimate how far you can safely drive before needing more fuel. For your 16 gallon tank, using your calculated gas mileage, multiply that by 13 and that will estimate how far you can drive with 3 gallons remaining in the tank.


Welcome to the forum family, JohnnyAce!

 

Thanks for the advice, guys. I still haven't replaced it yet, but I did get a new unit. My biggest concern is getting the strap bolts loose without breaking them. I'm told that the bolts are a special type that's not easy to find.

 

They look like all-thread to me. And if they aren't, they could be.

Anyway, soak them in PB Blaster several times and they'll probably come loose just fine.

 

They're just flange head bolts. 13mm head and 15mm nut. Use a wire brush on them real good and some Kroil. Once you break them free just a tad, turn them a little at a time and brush them all the way around the bolt since you can only get one side at a time. Even doing that you may have to back them off until they start to seize and run them back up to keep cleaning the threads out. The nuts are also prevailing torque type locking nuts which are "squished" so they're a pain coming off and going back on.

 

And make sure you have a buddy help or run the tank close to dry, which from reading your post isn't to hard to do Sorry had to knock on ya

 

Ha ha, yeah same here. Dad's gauge was doing the same thing as the OP's so he decided to take the cluster out and the needle promptly fell off and disappeared. So, he started just filling up every 100 miles which worked OK until the EEC system took a **** and it started running out in 80.

 

If the truck is new to you I suggest dropping the tank completely so you can look inside for gunk. A new tank is only $120 or so, and may be worth it if the old one is full of rust. I put two ratchet straps loosely under the tank, and dropped it into them. Then you can drop it all the way or just roll it in the straps.

 

I had the same problem with my 83 F100. Replaced the fuel sending unit and problem was still there. Ended up being a bad Instrument Cluster Voltage regulator.

 

Well, I got the sending unit replaced. Unfortunately, that didn't fix the problem. So the next thing I replaced was the instrument voltage stabilizer. That kinda fixed the problem, but not really. Now my oil pressure gauge kinda works when it wants to, and my fuel level gauge sorta works when it feels like. Mostly it stays pegged below empty, but occasionally it'll swing madly between where the fuel level actually is & empty.
I'm thinking it may be the printed circuit board. At any rate, I'll be doing a cab swap with an '86 XLT Lariat parts truck I just picked up, , so maybe I'll just swipe the instrument cluster out of it.

 

The ICVR does control the power to the three gauges you mentioned. Was the replacement ICVR new? Unfortunately, with today's supply of replacement parts, new does not necessarily equate to good.

 

I took my tank out the first time. After the first one was junk the free replacement was installed without even touching the gas tank strap bolts. No problem.