Help!!!!
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Freshman User
Joined: Mar 2004
Posts: 44
Likes: 0
From: PARIS, TN
Help!!!!
Hello all! This is my first posting here. Yesterday I finally bought the EXACT truck I have wanted since 1988. I bought a 1988 F-150
4X4 longbed, reg. cab. 300ci. 6cyl, 5 speed, rubber floor mat, no air from factory, RSW with 94,xxx miles on it. Paint is rough but the body is near perfect.
Now, this is going to be a near all-out restoratoin with a 4" lift kit and 35-13.50-15 tires on black rock crawler rims.
Here is one of many little problems, but the one that bugs me the most: The truck has Dual fuel tanks, but the fuel gauge allways
reads maxed out on full, even when empty. I read through the last 10 pages of post's and found some Ideas, but no answers.
To those reading this with experiance of this in the past:
1) Was it/is it usually the sending unit(s)?
2) Where is the cheapest place to get them?
3) IF it is in the gauge, can I replace just the gauge, or do I have to replace the entire insturment cluster?
4) How hard is it to fix.
---------------------------------------------------------------------------
ANY help would be GREATLY appreciated!
4X4 longbed, reg. cab. 300ci. 6cyl, 5 speed, rubber floor mat, no air from factory, RSW with 94,xxx miles on it. Paint is rough but the body is near perfect.
Now, this is going to be a near all-out restoratoin with a 4" lift kit and 35-13.50-15 tires on black rock crawler rims.
Here is one of many little problems, but the one that bugs me the most: The truck has Dual fuel tanks, but the fuel gauge allways
reads maxed out on full, even when empty. I read through the last 10 pages of post's and found some Ideas, but no answers.
To those reading this with experiance of this in the past:
1) Was it/is it usually the sending unit(s)?
2) Where is the cheapest place to get them?
3) IF it is in the gauge, can I replace just the gauge, or do I have to replace the entire insturment cluster?
4) How hard is it to fix.
---------------------------------------------------------------------------
ANY help would be GREATLY appreciated!
Cargo Master
Joined: Sep 2003
Posts: 2,543
Likes: 2
From: Georgia
99.9% the problem is with the fuel sending unit.
To change them you will have to have clearance to get to the top of the fuel tank.
You can do this by removing the tanks or the bed.
I have been looking for sending units myself & the cheapest that I have found so far is at autozone.com. Just a little over a $100.00.
To change them you will have to have clearance to get to the top of the fuel tank.
You can do this by removing the tanks or the bed.
I have been looking for sending units myself & the cheapest that I have found so far is at autozone.com. Just a little over a $100.00.
Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
Re: Help!!!!
Congrats on finding your favorite truck. Always fun when that happens!
The problem could be the sending units, the gauge, the wiring behind the cluster, or the crossover valve/switch that changes which tank you are running off, based on the position of the switch in the dash.
If the truck runs, the problem is not the switch in the dash, so you can rule that out.
The next test is a bit tricky... take the trim off the dash, take the cluster out of the dash (be careful to properly release the speedo cable!) and put it aside somewhere safe.
Set your front/rear tank switch to front.
Start the truck.
Attach the black wire of your ohm meter to ground, and on the cluster connectors that are hanging in the dash, locate the yellow/white stripped wire, and push the red lead against that only.
You should have an indication of how much fuel you have, 15 ohms indicating empty, 90 ohms indicating half full, and 160 ohms indicating full. Give or take a few ohms.
With the truck running still, flip the switch to the rear tank, and again push the red lead against the contact on the connector that corresponds to the yellow/white wire. You should have a reading also between 15 and 160 ohms, as above.
Assuming you're fuel tanks do not have the exact amount of fuel in them, you should have different readings. If you do, then the problem is with the gauge or the cluster itself. If you are getting no resistance, meaning the ohm meter is off scale, then you have a wiring problem (break, actually) between the connector and the fuel sender units. Since you stated that both tanks give the same results, the problem will invariably be the common ground between the two, attaching to the frame. Means the wire ring on the end of the wire attached to the frame rotted off.
If you get zero ohms on both tanks, then the wiring harness between the connector and the crossover valve is shorted.
If you do have different readings, approximately matching the different amounts of gas you have in the two tanks, then you know its the cluster, or the gauge itself.
Since the cluster is an electromechanical thing, you can rule the cluster out just by looking at it. The greenish plastic membrane on the back with circuit traces (flexi circuits) is how the signals get from the connectors to the gauges inside, and if its burnt, melted, ripped, etc, obviously thats where your problem is. In this case I'd recommend just getting another cluster out of the junkyard, and swap your speedo over to it so your mileage is correct if that matters to you.
if the back of the cluster is okay, then the problem is with the gauge itself, and if you take apart the cluster, you'll see that the fuel gauge plate just pushes in. You can replace the cluster for about 20-40 dollars depending on the junkyard, or buy just the gauge. Me, being lazy, I'd buy the whole cluster and put it in with the four torx screws and call it a day, and use whichever cluster lens is nicer.
Hope that helps....
1) Was it/is it usually the sending unit(s)?
2) Where is the cheapest place to get them?
3) IF it is in the gauge, can I replace just the gauge, or do I have to replace the entire insturment cluster?
4) How hard is it to fix.
---------------------------------------------------------------------------
ANY help would be GREATLY appreciated! [/B][/QUOTE]
The problem could be the sending units, the gauge, the wiring behind the cluster, or the crossover valve/switch that changes which tank you are running off, based on the position of the switch in the dash.
If the truck runs, the problem is not the switch in the dash, so you can rule that out.
The next test is a bit tricky... take the trim off the dash, take the cluster out of the dash (be careful to properly release the speedo cable!) and put it aside somewhere safe.
Set your front/rear tank switch to front.
Start the truck.
Attach the black wire of your ohm meter to ground, and on the cluster connectors that are hanging in the dash, locate the yellow/white stripped wire, and push the red lead against that only.
You should have an indication of how much fuel you have, 15 ohms indicating empty, 90 ohms indicating half full, and 160 ohms indicating full. Give or take a few ohms.
With the truck running still, flip the switch to the rear tank, and again push the red lead against the contact on the connector that corresponds to the yellow/white wire. You should have a reading also between 15 and 160 ohms, as above.
Assuming you're fuel tanks do not have the exact amount of fuel in them, you should have different readings. If you do, then the problem is with the gauge or the cluster itself. If you are getting no resistance, meaning the ohm meter is off scale, then you have a wiring problem (break, actually) between the connector and the fuel sender units. Since you stated that both tanks give the same results, the problem will invariably be the common ground between the two, attaching to the frame. Means the wire ring on the end of the wire attached to the frame rotted off.
If you get zero ohms on both tanks, then the wiring harness between the connector and the crossover valve is shorted.
If you do have different readings, approximately matching the different amounts of gas you have in the two tanks, then you know its the cluster, or the gauge itself.
Since the cluster is an electromechanical thing, you can rule the cluster out just by looking at it. The greenish plastic membrane on the back with circuit traces (flexi circuits) is how the signals get from the connectors to the gauges inside, and if its burnt, melted, ripped, etc, obviously thats where your problem is. In this case I'd recommend just getting another cluster out of the junkyard, and swap your speedo over to it so your mileage is correct if that matters to you.
if the back of the cluster is okay, then the problem is with the gauge itself, and if you take apart the cluster, you'll see that the fuel gauge plate just pushes in. You can replace the cluster for about 20-40 dollars depending on the junkyard, or buy just the gauge. Me, being lazy, I'd buy the whole cluster and put it in with the four torx screws and call it a day, and use whichever cluster lens is nicer.
Hope that helps....
1) Was it/is it usually the sending unit(s)?
2) Where is the cheapest place to get them?
3) IF it is in the gauge, can I replace just the gauge, or do I have to replace the entire insturment cluster?
4) How hard is it to fix.
---------------------------------------------------------------------------
ANY help would be GREATLY appreciated! [/B][/QUOTE]
