doesn't work,shows empty and it only takes 10 gal to fill up 1986 b2 has a 23 gal tank I think.how do I fix this?? sending unit?

 

Yep.You have to drop the tank to fix it.whil you got it down I would put in a new low pressure fuel pump since you already got the tank down.JMO

 

If Temp Gauge works fine, then voltage regulator in the instruent cluster is OK and problem will be in the Fuel Gauge circuit. An open circuit between the gauge and the sender, will make the gauge pointer drop to its low, or "Empty" indication. If that circuit happened to be shorted to ground, the gauge would go all the way high (Full). The resistance range on the sending unit side for both Temp and Fuel gauges is 10 ohms for the high end, and 73 ohms for the low end of the full scale.

If your Fuel Gauge is reading all the way low, like it does when the engine is off, there may be a break or bad connection in the wiring going from the gauge to the sending unit. I've seen sending units have a dead spot, where the gauge will drop to "E" when the fuel level reaches that certain level. Then when the fuel level drops past that dead spot, the gauge will register the correct fuel level again, at that lower amount. Not to say that it can never happen, I've not yet seen one fail completely. Personally, I'd suspect either an open in the wiring to the sending unit, or a bad gauge.

The wiring leads from the instrument cluster connectors, within the large harness passing through the firewall between the brake booster and the driver's side fender, branches out and down along the inside of the left frame rail to the fuel tank. If you're so inclined to troubleshoot that circuit, the Haynes manual states that the wire going to the sending unit will be yellow with a white stripe. It'll be housed in a snake-like (split) flexible conduit, accessible from under the vehicle, driver's side.

Be careful, there are plastic fuel lines running side-by-side with that wiring, too. If that plastic hose is punctured, it will have to be replaced with an OEM part, probably only from Ford.

 

WOW!!!!!!! Hooked you got that tech stuff down real good A-1 Job!!! But most of the people that post here are just your average fokes and are not into that much tech stuff,.The Ford BII sending units are know to be a POS and itf you replace it the fuel guage will work .
Again thanks for the great INFO we do need it here when the simple stuff dors not work.I have found your advice very helpful and iI do admiere your knowlage.So dont take this as a dis, its not!! just use the K.I.S. princeable first then go from there.
Jeff

 

I've been waiting for someone to say what you said. Being an ex-electronics tech, I DO tend to get too technical. My foremost intention isn't to impress anyone, it's just "me". I guess I can't help it. My mind wants to cover all the possibilities. And at the same time, I don't want to underestimate the technical potential of the individual(s) who may be wanting to know what to do and look for.

I'm also inhibited by an inner conflict as well; wanting to offer helpful advice, while not gobbling up this forum's data storage capacity. It's hard to find that "happy medium".

Thanks for your suggestion(s), however. I'll always keep what you said in mind in the future.

 

It goes from about 3/4 to empty,I'll wait and see if it gives an accurate reading before it runs out,I'll keep ya posted thanks for the info,btw does an 86 b2 have a low fuel light??

 

I know that earlier year models had a set of warning (LED) indicators in an optional center console module. Whether or not Ford continued that option through 1986, I'm not sure.

If they did, and it functioned in the same way as the earlier versions, that indicator works off the same sending unit as the fuel gauge; the one that is suspected bad in your case. So, unfortunately it couldn't be trusted as a "backup system" in the event the standard fuel level monitoring system malfunctioned.

 

Hooked,you were absolutely right about the gauge,it went from 3/4 to all the way down below empty and stayed there but I put a can of gas in the truck and waited...and sure enough,today while I was driving the gauge started to go up!!! it stopped at a little over 1/4 so I still don't know if its right but it looks that way...I'll see how many more miles I can get before it runs out..that way I'll know how much to expect from a full tank..usin the odometer instead of the gauge LOL

 

Yep! Your sending unit has a bad spot in its range of travel. If you're not familiar with how they work, there's an arm pivoting on a pin, with a small float attached to the long end. That float holds that end of the arm at the top of the fuel level. The float drops along with the fuel level, just like the float valve in the reservoir of the common toilet. The short end of the arm, opposite the pivot pin from the float, then actuates a wiper arm on a rheostat, or wire-wound type variable resistor, that varies the current passing through the Fuel Gauge, thereby allowing it to imitate the rise and fall of the fuel level.

In your case, either the wiper arm has lost the normal spring tension enough so contact against coils of the wound resistor wire between 3/4 and somewhere between 1/2 & 1/4 full has been lost, or the sending unit has gotten dirty. From this point forward. it could do just about anything; It might get better, worse or not change at all.

If it never gets better, or if it gets worse, replacement is the only way to fix it. Unfortunately, the only (widely) available replacement sending unit must be purchased with the submerged in-tank fuel pump. A person can get an idea of what the part looks like and costs at PartsAmerica.com, using their online replacement parts to vehicle matching utility. The unit isn't cheap. costing over $100, and replacing it can be a real pain in the *** for the shadetree mechanic.

I've wondered if one could successfully remove the needed components intact from the much less expensive sending unit for a carburated engine ('84-'85) Bronco-II/Ranger, and use them to "rebuild" the EFI engine model sending unit which has failed in this way, but in my case the problem isn't quite as bad as yours, and not worth that much trouble (and risk of failure).

If I were you, I'd closely monitor its behavour as long as you can stand it, and see if it gets better or worse. I know how un-nerving thinking you've suddenly lost all your fuel! I had to get a locking cap, so I have to suspect that someone was stealing my fuel. After living with it for more than 10 months now, it's not as shocking as it was in the beginning. Now, I can say my Bronco-II has begun developing its own unique personality, and I better understand why some folks refer to their "machines" as "she".

 

I will keep a close eye on it thank you sir!!