[macmatt]

Hey eveyrone. I'm fairly new here and the bronco I have right now is my second. It's an 88 w/302 efi. Everything on it works great except for the gas gauge. The guy I bought it from said he usually gets about 260-280 miles to a tank and he gauges it of course by the trip odo. So I took him at his word. When I got gas the other night though I decided to take note of how much it took to fill up and how many miles I had driven so I could get an idea about mileage. It turns out it gets around 13mpg which is the factory rating I believe or close to it. Anyway when I was done I noticed that it had taken about 19 gallons to fill. Which I though was odd since at minimum I though this thing had about a 25gal tank. As I've been able to find out mine actually has either a 32 or 33 gal tank (please correct me if I'm wrong). If that is true then I should be getting around 416 miles to a tank. But the PO said 300 at most. So my questions are 1)How many gallons is my tank? 2)How many miles should I get out of one tank roughly? 3)What steps should I take to diagnose my fuel gauge issue? I appreciate any help you all can give me.

 

[j. r. Nice]

Welcome back to the land of gas guzzlers!
Probably a math error somehwere. Tank should be 32 gal and maybe a little over with the filler tube. You might get 13 if most of it is freeway driving. What the PO is saying is about right for in-town. 9-10.

I would plan on recalculating at the next fill-up. It won't be long.

 

[youngbuck007]

The 32 gallon tank became standard on Bronco's in 1985. Did the PO tell you he ran out of gas before? Or did he just say that 300 miles was the max he ever ran it without refueling? 13mpg is certainly a good average for mpg in Bronco's, but that can change as quick as your driving style. If the gauge isn't working I wouldn't push it to the perceived "max". One way to tell would be to throw a 5 gallon can of gas in the back once you hit 300 on the trip and see how far it goes from there... at the first sign of a sputter I would pull over and add fuel. If you get to 350 or so without running out then you have your answer.

 

[Bruno2]

The fuel gauge issue may be the sending unit. I would look at the lockring area where the sending unit goes in and at least make sure it is plugged in. The only way I know to check the sending unit is to pullit and ohm it. What the proper ohm spectrum is irrelevant . You just want to see the needle on the meter move as the float arm travels upwards. Take notice of what size the OD of the lockring is b/c this is essential in getting the right sending unit. My 87 has the 2" lr and nobody makes a sending unit for it. They only ran it for a yr or so. Just like those stupid flange style(top hat)manual locking hubs. My sending unit works , but , if it quits I suppose I will have get another tank and go that way.

Good Luck!!

 

[BroncoJoe19]

I found a link to this on miesk5's broncolinks.com site.

http://www.supermotors.net/registry/media/569487_1

 

[macmatt]

Thanks for all the suggestions guys.

On the math thing what I did was take the mileage since my last fill up which was 257 miles (and I know it was full because it came out of the filler when I tried to top it off. Stupid non-working auto shutoffs)and divide it by the amount I put in (which was 19 gallons). So 257÷19=13.53 miles per gallon right? My driving is mostly around town with very short trips down the highway, and usually not too far. I only live 5 mins from where I work. So for the sake of argument let's say that is the mileage I'm getting, then that would calculate to about 432 miles to a tank (unfortunately where I live @3.18 per gallon that also calculates to 101.76 for a fill up :banghead )

The PO didn't tell me he ran out of gas before he just told me the average between fillups was around 300. He did tell me though that a couple of times he pushed it and didn't get a sputter until 340. He also told me filling it up from empty would only cost around 75.00. Which at the gas prices around here would be at least 95.00. I've noticed that if you start pumping gas and you use the hold on the pump handle and just wait for it to stop automatically that sometimes it stops way before it's full. So I'm thinking he may not have been paying much attention when he would get gas.

I'm dreading the idea of the gauge problem being the sending unit. But hey at least on this I don't have to drop the rear axle out to get the tank out like I do on my firebird. I was told that there was a test I could do on the wiring at the tank to see if the gauge would go up. Something that entails unplugging the connector on the tank and grounding one of the wires with the key on to see if the gauge goes up but I'm not sure how to do this. There are four wires going to the tank but when I last pulled off the wires there was only 3 terminals on the tank itself if I remember right. I was also told to check all the grounds under the hood but I have no idea where they are. Definitely need some direction in tis area.

BroncoJoe19
That diagram doesn't look like what I have on mine. I'll check again as soon as I get the chance though. One thing I noticed is that there seems to be a second pump on my fuel system. Did these trucks come with one in the tank and one on the left side frame rail? I looked up the pump and hanger assembly at work and all they show is an intank setup.

Again thanks for all the help and advice. I'm mostly experienced with GM and only the occasional Ford so this is all still a bit unfamiliar.

 

[BroncoJoe19]

macmatt,
Yes the '87 has two pumps. They went to a single pump design in 1990.

 

[miesk5]

yo,
Ck Tank Dimensions;
78-79 25.5 Gallon, 31 7/8" x 22 1/4" x 12 3/4"; 33 Gallon, 31 7/8" x 22 1/4" x 15 3/4";
80-83 25.5 Gallon, 31 7/8" x 22 1/4" x 12 3/4";
80-89 33 Gallon w/2" Sending Unit Hole, 31 7/8" x 22 1/4" x 15 3/4";
90-96 33 Gallon w/3 5/8" Sending Unit Hole, 31 7/8" x 22 1/4" x 15 3/4";
Weight, 32 Gal. in 88-96, 31.0 lbs

In case you need to Inspect/R&R sending unit, instead of dropping it, consider; Floor Pan Cut-out - see my site for Links
@ http://www.broncolinks.com/index.php?index=616

Examples are:
Cut-out Panel Measurements for Fuel Pump/Level Sender Replacement in an 88
Source: by Jem270 at http://www.supermotors.net/registry/9036/59534

"Each about 8-10" front-to-back and just over 3 ridges wide (as shown), so they'll cover a hole less than 8" long & 3 ridges wide)..."
Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.org/clubs/superford/vehicles/registry/detail.php?id=2742&s=33276#content

Lessons Learned
Source: by digitalbill (Bill Crozier) at http://fullsizebronco.com/forum/showthread.php?t=152867

Patch Panel, 48in. x 16in. for 80-96 Bronco & F Series; $35.00 as of June 2011
Source: by Jeff's Bronco Graveyard @
http://broncograveyard.com/bronco/i-34094-rear-bed-patch-panel-48in-x-16in-.html

or go to a yard w/portable sawzall / grinder and remove a patch from any up to 96 Bronco or F series.


84-89 Overview & High Pressure Pump Depiction; "...Two electric pumps are used on fuel injected models; a low pressure boost pump mounted in the fuel tank and a high pressure pump mounted on the vehicle frame. The low pressure pump is used to provide pressurized fuel to the inlet of the high pressure pump and helps prevent noise and heating problems. The externally mounted high pressure pump is capable of supplying 15.9 gallons of fuel an hour. System pressure is controlled by a pressure regulator mounted on the engine. The pressure regulator reduces fuel pressure to 39-40 psi (269-276 kPa) under normal operating conditions. At idle or high manifold vacuum condition, fuel pressure is reduced to approximately 30 psi (207 kPa)..."
Source: by Chilton


Fuel Level & Sender Testing in 87-88 Bronco & F Series; When the fuel gauge needle is below the 1/2 to 1/4 tank range the needle will swing all the way above the full mark on the fuel gauge; An erratic fuel gauge needle when the fuel tank is 1/2 to 1/4 full may be caused by excessive wear of the resistive film on the fuel pump sender assembly. The wear occurs during transporting of the vehicles via rail or truck over long distances. The fuel gauge will indicate correctly from a full tank to about 1/2 or 1/4 tank of fuel. When the fuel gauge needle is below the 1/2 to 1/4 tank range the needle will swing all the way above the full mark on the fuel gauge. To correct this, install a new fuel pump sender assembly.
Miesk5 Note, Pre-87 fuel level senders are TOTALLY different from 87-up. Not only do they work over a different range; they work in the opposite direction
Source: by Ford via Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/724794

Tech Tip Guide, General; "...Many times, the Ford fuel pump hanger/sender assemblies are frequently found with extensive corrosion on the cover and on the metal tubes. Over time, the terminals can loosen and cause intermittent loss of continuity. Erratic reading of the fuel sender level is one of the other problems that could occur..."
Source: by spectrapremium.com

Fuel Level & Sender Wiring Diagram in an 89

Source: by SeattleFSB (Seattle FSB) at SuperMotors.net

 

[macmatt]

Wow! Now that was informative. Thanks a bunch. My fuel gauge is currently sitting below empty where it has been since I bought it. The PO claims that the guy he bought the vehicle from told him that he blew a wheel cylinder one day and doused brake fluid all over the sending unit thus shorting it out. Now again I'm no Bronco or Ford expert by any means but when I looked at the tank and checked the connections for corrosion (I can reach them without removing the tank) I saw nothing. They were quite clean. I also can't see how it is at all possible that a blown wheel cylinder could possibly cause this problem. For that to happen the stream of fluid would have to go around the frame and then up onto the tank. That being said I was trying to figure out how to test the gauge without using the sending unit or removing it. I was told there is a way to remove the wires from the sending unit and turn the key on with one of the wires grounded to see if the fuel gauge goes up to full. Is this possible? If so which wire am I going for? The sending unit only has 3 terminals but there are 4 wires. Any ideas? I would like to verify the sending unit before I take the time to R&R it. Thanks for all the help so far. I really do appreciate it.

 

[youngbuck007]

What year is your firebird? I had an 87 TA and had to drop the tank a few times... never had to remove the rear just set jackstands under the frames to let the rear drop down. Then unbolt the back half of the exhaust and tank straps. It was a tight squeeze but it came thru...

 

[macmatt]

Yeah you can do it that way. But to be honest if I have to replace that pump I will be making an access hole in the trunk.

 

[miesk5]

yo,
Testing in 87-96; Fuel Gauge Moves from E to below E; "...Disconnect the connector at the fuel tank, ground the yellow with white tracer wire (make sure you have a good ground), turn the key on-if the gauge goes to empty, chances are, the fuel sender is the problem. If the gauge doesn't move, then recheck the grounding of the Y/W wire,if it is good then the problem is is forward of the sender (wiring/connectors/instrument cluster)..." Source: by 85bigbronco at FSB

 

[macmatt]

thanks! I'll try that asap

 

[macmatt]

Ok. Pulled the wires off the tank and grounded yellow/white wire and sure enough the gauge went to the empty mark from below empty. So I guess I need to get a sending unit. :cry Oh well. I'll just drive it the next couple of weeks to run some gas out then I'll have to get that done. Thanks for all the help everyone :thumbup