SMFire History Posted December 28, 2013 Share Posted December 28, 2013 (edited) I've been going through the wiring harness and identifying loose wires, switches, etc in an effort to figure everything out and clean things up. I ran across what's called the "Fuel Gauge Switch" in the wiring diagram. Anyone know what this is for? It looks like a pull knob attached to an electric switch rather than a pull cable. It does not pull out with reasonable force and I don't want to break it. The knob turns but it isn't threaded and doesn't have a set screw like the light switch knob.Looks like this... Edited December 28, 2013 by SMFire History Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/ Share on other sites More sharing options...
fxfymn Posted December 28, 2013 Share Posted December 28, 2013 I'm guessing here: Was there a fuel gauge on the pump panel as well as the dash? Might be the switch to change the gauge the sending unit is connected to. Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223447 Share on other sites More sharing options...
rickykarenpr Posted December 28, 2013 Share Posted December 28, 2013 in what truck you have the fuel gauge?? Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223448 Share on other sites More sharing options...
bulldogboy Posted December 28, 2013 Share Posted December 28, 2013 It's been a long time for me but I seem to remember that you had to pull the switch out to activate the fuel gauge. Why it was set up this way, I haven't a clue. bulldogboy Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223465 Share on other sites More sharing options...
rickykarenpr Posted December 28, 2013 Share Posted December 28, 2013 original switch Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223466 Share on other sites More sharing options...
SMFire History Posted December 28, 2013 Author Share Posted December 28, 2013 in what truck you have the fuel gauge??1952 LS125 EngineNo fuel gauge on the panel.Switch design is consistent with the other OEM switches. Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223473 Share on other sites More sharing options...
fxfymn Posted December 29, 2013 Share Posted December 29, 2013 Dual tanks??What is connected to the back of the switch? Wires or cables? Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223639 Share on other sites More sharing options...
609albert Posted December 30, 2013 Share Posted December 30, 2013 the LS 125 is that the hall-scott engine? 1000 or 1250 gpm pump ? at this point I can't even guess what the switch does,but I would like to know also. Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223791 Share on other sites More sharing options...
SMFire History Posted December 30, 2013 Author Share Posted December 30, 2013 (edited) Not dual tanks, and I don't believe its a Hall Scott. 1250 gpm pump. My buddies in Oceanside said they have a secondary electric fuel pump near the tank that is activated by the fuel knob. Part of the redundant system. I do not see another pump on ours so maybe it was removed some time ago. They say its an electric pull switch. I'll check it out next time I'm there. Edited December 30, 2013 by SMFire History Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223806 Share on other sites More sharing options...
Solution Charlie Hatfield Posted December 30, 2013 Solution Share Posted December 30, 2013 The switch basically turns on the fuel gauge. why its like that was always a mystery to me, as every "L" had one. If your fuel tank is at the back of the vehicle, an electric pump is located on the left inner frame rail near the diff. If the tank is behind the cab, then it will be located on the frame near it. Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223847 Share on other sites More sharing options...
609albert Posted December 31, 2013 Share Posted December 31, 2013 I would bet that with the 1250 pump, you'll have a hall-scott engine ,and with that engine the hood is 11''longer that a'L' with the 707 c.i. mack , I'll measure my hood tomorrow. my fuel tank is at the rear of the truck under the frame and has a the standard mechanical pump on the engine. Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-223995 Share on other sites More sharing options...
SMFire History Posted December 31, 2013 Author Share Posted December 31, 2013 (edited) Thanks all for the input. I'll try to get the switch loosened up to see if our fuel gauge will work with it pulled. We have the 707cu in motor so not the Hall-Scott and the pump is rated at 1250 GPM. The switch is hard to get to but I snapped a pic from beneath the dash. It looks like a weird lever type switch???Oops... Forgot to mention no electric fuel pump anywhere from the tank to the mechanical location on the side of the block. We're using a low pressure fuel pump in place of the mechanical until it is rebuilt as it had grenaded inside. Edited December 31, 2013 by SMFire History Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-224110 Share on other sites More sharing options...
j hancock Posted December 31, 2013 Share Posted December 31, 2013 That style of switch is original. The pull action of the rod makes the contacts rotate in the housing.I have an ignition switch that is the same style out of an E model fire truck. Also, I think A, E, and L headlight switches were all that same style. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-224116 Share on other sites More sharing options...
SMFire History Posted December 31, 2013 Author Share Posted December 31, 2013 That style of switch is original. The pull action of the rod makes the contacts rotate in the housing.I have an ignition switch that is the same style out of an E model fire truck. Also, I think A, E, and L headlight switches were all that same style.Any problem with spraying break free or another synthetic based cleaners in there to loosen it up? Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-224117 Share on other sites More sharing options...
j hancock Posted December 31, 2013 Share Posted December 31, 2013 Not sure on the synthetic. Might be OK. The steel rod may be rusted at the mounting ferrule where it passes through the dash.Use sparingly and see if it gains you anything. The switch housing and knob are an early plastic or Bakelite. No need to melt it. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-224127 Share on other sites More sharing options...
farmer52 Posted December 31, 2013 Share Posted December 31, 2013 Can you remove the knob (likely threaded) and remove the switch easily? Might be easier to see and work on. Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-224160 Share on other sites More sharing options...
609albert Posted January 1, 2014 Share Posted January 1, 2014 I know I got off track with the Hall -Scott engine ,but the hood on an LS85 is 46'' long in the center and pumper with the H-S are about 11''longer. Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-224241 Share on other sites More sharing options...
SMFire History Posted May 11, 2019 Author Share Posted May 11, 2019 Just trying to follow up on some loose ends from previous posts. Never got this fuel switch off or loosened up. Today I was able to get the 2 wires off and bypass the switch so 12v is getting to the fuel gauge. Still reading empty. Quote Link to comment https://www.bigmacktrucks.com/topic/34038-fuel-gauge-switch/#findComment-422450 Share on other sites More sharing options...
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