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i havent been able to revive my fuel gauge yet, i connected a loose wire near back tank back to the frame, added a frame to batt ground, replaced engine to firewall grnd and replaced all burnt fuses.
SO its starting to look like either the sending unit or gauge cluster
ALSO living in canada i have a MPH speedo which works but eventually im gonna estimate wrong and get a photoradar ticket.
So assuming some wire isnt diconnected behind the cluster, what do guys usually do when gauges go bad or need replacing? replace gauge by gauge or just do the whole cluster?
I would like a tach if any cluster came with them?
The following assumes the oil & temp gauges are working. If the other gauges work, the cluster voltage regulator is good.
Ground the wire that connects to the tank sending unit. Turn the key on. The fuel gauge should go full scale. If it does go full scale, your sender is bad.
If it doesn't go full scale, check the sender wire for breaks running forward along the frame.
If no breaks & wire shows continuity, remove the cluster. Connect wires to the studs on the fuel gauge, power wires with a 1.5V battery. Gauge should go to about 1/4 scale. If gauge doesn't move, gauge is bad, replace it.
You can swap to an 85MPH speedo head, they also have KPH on them. No other changes need to be made, just swap the head.
The 73-79 trucks never had an in cluster tach option.
The following assumes the oil & temp gauges are working. If the other gauges work, the cluster voltage regulator is good.
Ground the wire that connects to the tank sending unit. Turn the key on. The fuel gauge should go full scale. If it does go full scale, your sender is bad.
If it doesn't go full scale, check the sender wire for breaks running forward along the frame.
If no breaks & wire shows continuity, remove the cluster. Connect wires to the studs on the fuel gauge, power wires with a 1.5V battery. Gauge should go to about 1/4 scale. If gauge doesn't move, gauge is bad, replace it.
You can swap to an 85MPH speedo head, they also have KPH on them. No other changes need to be made, just swap the head.
The 73-79 trucks never had an in cluster tach option.
thanks for the good diagnostic info.
I also just ordered a borescope camera too, to diagnose which tank is in better shape internally and use/save that one. maybe the main tank gauge /sender works, right now the other main tank was disconnected either by previous owner cuz it didnt work/rusty or thieves syphoning gas
yup the speedo, temp/oil press ga all work.
So what do you mean 85 mph speedo head, as in just remove that mph speedo and 85 with both mph/kmh will drop in?
Theres a big empty rectangle on left side of cluster so maybe i can french in a tach into that space instad of clamped to the column?
The following assumes the oil & temp gauges are working. If the other gauges work, the cluster voltage regulator is good.
Ground the wire that connects to the tank sending unit. Turn the key on. The fuel gauge should go full scale. If it does go full scale, your sender is bad.
If it doesn't go full scale, check the sender wire for breaks running forward along the frame.
If no breaks & wire shows continuity, remove the cluster. Connect wires to the studs on the fuel gauge, power wires with a 1.5V battery. Gauge should go to about 1/4 scale. If gauge doesn't move, gauge is bad, replace it.
You can swap to an 85MPH speedo head, they also have KPH on them. No other changes need to be made, just swap the head.
The 73-79 trucks never had an in cluster tach option.
Hey ScottScott
Very nice will be useful for future readers.
Unless I miss read the 2 nd line I think it might need corrected. BAD should be changed to good.
Alex
Hey ScottScott SORRY,,, As usual, I did miss read the grounding. I read it in a hurry and did NOT pay enough attention.
After reading more slowly, made perfecr sense..Again Great job writing it up.
Alex
Last edited by Old Guy F-250; Aug 11, 2024 at 08:14 PM.
Reason: Add bad to good make correction to previous statement..
"So what do you mean 85 mph speedo head, as in just remove that mph speedo and 85 with both mph/kmh will drop in?"
Yes, the 78-79 85 MPH & KPM speedo head will drop right in place of your current 100 MPH speedo head. You have to remove the cluster, remove 5 screws to remover the face, two screws on the back of the speedo head & pop it out. No other changes have to be made, these speedos all read the same, 60 MPH at 1000 RPM input. Here's a pic of the 85 MPH speedo head.
Ok so the borescope camera was kind of a bust.
i could ONLY get it in the rear tank and by time its in there , there are so many twists and kinks its hardly maneuverable but i did see some rust at the fuel line 1/2 wayish up.
I also see captain hooks hook or something shaped just like it.
i couldnt tell if that was the beginning of the sender coming in from the top or the pickup end.
if it was the pickup end it must not even have any sock/filter on it.
also seen on same unit some whitish cylinder that looked more like a fuel pump then a float for gas gauge
then some steel mount type stuff at the other end.
i may have to pull off the fill hoses at the tank to see better.
now i guess i suit up and lay underneath in 30C heat see about diagnosing gauges
For all that camera $ and work you could of just dropped the rear tank. Sending unit test and tank drop: https://www.ford-trucks.com/forums/1...l#post14696841
Old school gas tank float is a brass float, repop sending unit white plastic float. Pick up tube NO sock filter ='s bad. If you are going to pull the main fill hose from the tank, easier to drop the complete tank.
For all that camera $ and work you could of just dropped the rear tank. Sending unit test and tank drop: https://www.ford-trucks.com/forums/1...l#post14696841
Old school gas tank float is a brass float, repop sending unit white plastic float. Pick up tube NO sock filter ='s bad. If you are going to pull the main fill hose from the tank, easier to drop the complete tank.
i would agree back when i lived 3 miles from my moms place witha attached and detached garages and most my tools and all my stepdads tools.
but now i sold my house and live 90 miles away in different city and only have a min of tools in this condo
SO 1 trip back n forth to moms garage to retrieve tools costs 60 bucks in my camaro probly 120 in my truck, assuming it makes it there.
plus a new tank is 400 cdn so 50 cdn on a camera i may be able to use elsewhere isnt so bad.
and im not a Youtuber so i cant or have no use for buyying a new set of $100 harborfrieght tools on every truck revival, lol
i havent been able to revive my fuel gauge yet, i connected a loose wire near back tank back to the frame, added a frame to batt ground, replaced engine to firewall grnd and replaced all burnt fuses.
SO its starting to look like either the sending unit or gauge cluster
ALSO living in canada i have a MPH speedo which works but eventually im gonna estimate wrong and get a photoradar ticket.
So assuming some wire isnt diconnected behind the cluster, what do guys usually do when gauges go bad or need replacing? replace gauge by gauge or just do the whole cluster?
I would like a tach if any cluster came with them?
Never yet had a gauge "go bad" ... and the one time I thought I did in 1992, it was actually correct, I just didn't believe it.
The 1977 speedometer only reads to 85 MPH and 135+ KPH ... BUT it has KPH too. You could post a sticky note with correct speeds MPH vs KPH.
i confirmed the fuel gauge is good, with a 1.5 v battery it slowly went up to around a 1/4 tank
SO ive ordered a new tank and sending unit
then i said eff it and ordered a new carb too
Might as well start tracking down a replacement rubber fill neck. And did you get a EEC or none EEC tank? What type of tank do you have now?
"There are two differences between the tanks. Tanks with EEC have a hole in the top center of the tank. A rubber grommet and check valve are pressed into the hole. A line goes from the check valve along the inside of the passenger side frame rail to the engine compartment where it hooks up to a charcoal canister.
Non-EEC tanks don't have this hole. The other difference is the nipple for the breather line that is located right next to the nipple for the filler hose is located 180 degrees opposite. If you are going from an EEC tankto a non-EEC tankyou must also change the fuelcap to a vented style. The EEC tanks are vented through the EEC system and use a sealed fuelcap. Non-EEC tanks vent through the fuelfiller cap. If you run a non-EEC tankand a sealed cap you can and probably have fuelstarvation problems."
You could post a sticky note with correct speeds MPH vs KPH.