The fuel gauge in my 66 recently started acting weird, basically drops too fast, and no....not due to my right foot. For example, a few weeks ago it showed 1/4 full when I filled the tank which then showed full on startup. Was surprised that it used a 1/4 tank on the 10 mile drive home. Drove it about 40 miles over the next couple weeks and again down to 1/4 tank. But when I filled the tank again it only took 4 gallons which is what I would have expected for that much driving, gauge now showing full again, then dropped another 1/4 on the same 10 mile drive home.
Does this sound more like a gauge or sender/float issue? Both sender and gauge are original.
Thanks,
Dave
Mine does the same thing. I got used to it and tend to ignore it as a result. Now I will be curious to see the solution.
First check the connections at the back of fuel gauge and at the fuel sender. Make sure the ground is good at sending unit. If OK, I would inspect the sender to see if the wiper contact is worn out. You can put an ohm meter on the wire connection and move the float arm while observing any erratic nonlinear readings on a sweep test. Usually, the wiper arm fails a visual inspection.
I think your fuel sender float has a hole and is filling with some amount of liquid. Easy fix. Happened to me as you describe.
Thanks for the replies.
Was wondering about a ground issue too so will check that first. Also thought about a float hole but the gauge only drops when driving, seems stable when parked. Would a hole react like that?
If grounds look good I'll pull the sender and check that and the float. Been meaning to install the new gas tank anyway....
Quote from: s2ms on March 08, 2023, 05:17:21 PM
Thanks for the replies.
Was wondering about a ground issue too so will check that first. Also thought about a float hole but the gauge only drops when driving, seems stable when parked. Would a hole react like that?
If grounds look good I'll pull the sender and check that and the float. Been meaning to install the new gas tank anyway....
I would think if the float had a hole in it , it would fill with fuel and always read empty , if you're going to replace the fuel tank then replace the sender with it .
Quote from: Lincoln tech on March 08, 2023, 05:41:29 PM
Quote from: s2ms on March 08, 2023, 05:17:21 PM
Thanks for the replies.
Was wondering about a ground issue too so will check that first. Also thought about a float hole but the gauge only drops when driving, seems stable when parked. Would a hole react like that?
If grounds look good I'll pull the sender and check that and the float. Been meaning to install the new gas tank anyway....
I would think if the float had a hole in it , it would fill with fuel and always read empty , if you're going to replace the fuel tank then replace the sender with it .
I have seen floats with a pin hole that have only been partially filled with fuel and make the gauge read goofy as they do not totally sink.
If you do end up pulling the sender out let us know your findings.
Number of years back I had the same problem. The float also had developed pin hole. Just ended up replacing the sending unit.
Quote from: trotrof1 on March 08, 2023, 06:51:05 PM
If you do end up pulling the sender out let us know your findings.
Will do.
The sender is original to the car so would like to have it rebuilt if possible. Any recommendations on someone who does that?
I was thinking the same thing. Maybe a replacement unit could be scavenged to renew the original. Has anyone out there been there done that?
Quote from: trotrof1 on March 08, 2023, 08:41:18 PM
I was thinking the same thing. Maybe a replacement unit could be scavenged to renew the original. Has anyone out there been there done that?
Of course only a original with a good face plate is worth any effort in saving. I have done a few using donor repro parts but I do not recommend that approach. There are people that rebuild the units for a nominal fee which is a better alternative IMO.
Quote from: Bob Gaines on March 08, 2023, 08:50:12 PM
Of course only a original with a good face plate is worth any effort in saving. I have done a few using donor repro parts but I do not recommend that approach. There are people that rebuild the units for a nominal fee which is a better alternative IMO.
Thanks Bob, any recommendations on who can rebuild these? My original looks in nice shape, externally anyway...
Hi Dave,
I will store your fuel in my gas tank? I will come down and help you. LOL
Cory
Quote from: s2ms on March 08, 2023, 11:50:08 PM
Quote from: Bob Gaines on March 08, 2023, 08:50:12 PM
Of course only a original with a good face plate is worth any effort in saving. I have done a few using donor repro parts but I do not recommend that approach. There are people that rebuild the units for a nominal fee which is a better alternative IMO.
Thanks Bob, any recommendations on who can rebuild these? My original looks in nice shape, externally anyway...
Try this guy. https://desertclassicparts.com/fuel-sending-unit-rebuilding-service/
COOL! Thanks Bob. I have a very good C4 core that I was going to sell! Now, I can get it restored. Yeah!
Steve
OOOPS! My bad! The one I have is a very good C6Z unit. The tube has some rust buildup in it but overall a restorable unit. Thanks again Bob for the contact.
Cheers,
Steve
Quote from: Bob Gaines on March 09, 2023, 12:06:00 AM
Try this guy. https://desertclassicparts.com/fuel-sending-unit-rebuilding-service/
Awesome, thanks Bob!
Quote from: 6s1640 on March 08, 2023, 11:51:23 PM
Hi Dave,
I will store your fuel in my gas tank? I will come down and help you. LOL
Cory
Sure thing Cory. I"ll be sure to fill-up with the 110 leaded at the Co-op first. ;)
This turned out to be an easier fix than expected, problem was the little constant voltage regulator that bolts on the instrument gauge cluster backside.
About 1.5 years ago I installed one of the new solid state regulators that apparently was not so.....solid. Never really considered this might be the issue because all the other gauges worked fine, but since the cluster was out to check connections decided to swap in an NOS regulator just in case and bingo, fuel gauge now works perfectly!
Thank you for the post repair report and give yourself a pat on the back.
Yes I remember those they send out a pulsing 6 volt signal.
Thanks for the information. That is one of the things that make this forum great.
Quote from: s2ms on March 15, 2023, 05:37:57 PM
This turned out to be an easier fix than expected, problem was the little constant voltage regulator that bolts on the instrument gauge cluster backside.
About 1.5 years ago I installed one of the new solid state regulators that apparently was not so.....solid. Never really considered this might be the issue because all the other gauges worked fine, but since the cluster was out to check connections decided to swap in an NOS regulator just in case and bingo, fuel gauge now works perfectly!
Hi Dave, That would have been my first recommendation, but having the other gauges working was keeping from making the recommendation. My experience, when the voltage regulator goes out, all the gauges seemed to swing. Any idea why the other gauges continued to work?
I guess you don't need me to store your 110 octane racing fuel in my gas tank. Dang.
Good job
Cory
Hi Cory,
I have no idea why only the fuel gauge was effected, maybe something specific to how it works? I thought all the gauges worked pretty much the same? Anyway, this one had me scratching my head.
I'm still planning to replace the gas tank so you might still have a chance to store some 110...
Dave
My alternator gauge jumps around! Could that be the constant voltage regulator [new solid state design] also??? Next, where can you find a NOS or used one to try???
Thanks,
Steve
Quote from: s2ms on March 15, 2023, 05:37:57 PM
This turned out to be an easier fix than expected, problem was the little constant voltage regulator that bolts on the instrument gauge cluster backside.
About 1.5 years ago I installed one of the new solid state regulators that apparently was not so.....solid. Never really considered this might be the issue because all the other gauges worked fine, but since the cluster was out to check connections decided to swap in an NOS regulator just in case and bingo, fuel gauge now works perfectly!
The originals are normally extremely dependable. I have yet to see a bad one despite dozens of 65 - 68 Mustangs and Cougars that I have owned or worked on.
Quote from: kingchief on March 16, 2023, 04:09:39 PM
My alternator gauge jumps around! Could that be the constant voltage regulator [new solid state design] also??? Next, where can you find a NOS or used one to try???
Thanks,
Steve
Steve,
Still pretty plentiful, do a search on ebay for B9MZ-10804-C, you will see several ranging in price from about $35 to >$100. Mostly Motorcraft but here's a FoMoCo: https://www.ebay.com/itm/314420424288
Dave
Quote from: kingchief on March 16, 2023, 04:09:39 PM
My alternator gauge jumps around! Could that be the constant voltage regulator [new solid state design] also??? Next, where can you find a NOS or used one to try???
Thanks,
Steve
The alternator gage is not in the circuit of the CVR so it is not involved.
Thank you for the info and I apologize for getting off topic.
Cheers,
Steve
Quote from: Rickmustang on March 08, 2023, 04:24:46 PM
I think your fuel sender float has a hole and is filling with some amount of liquid. Easy fix. Happened to me as you describe.
Agree same for me
I sent my fuel sending unit off to Desert Classic Parts. They did a wonderful job. Even sent it back with a new gasket and very well packaged and shipped. The texted pictures of it during the final testing of the unit. Very pleased and it looks marvelous!!!
Steve