Fuel gauge fluctuations

[Towrigdually]

so I usually never let my fuel gauge get below 1/4 tank and during my last drive I did just ever so slightly. 

When I took a sharp turn into the gas station my fuel gauge dropped right to 0 and stayed. 

 

I immediately shut the truck off and then bumped the starter to listen for the fass to run, which it did. So I let it run but it came up normally but the needle then vibrates quickly as it climbs to 17-18 psi. If I let it sit for a few seconds it settles out no problem. 

 

Now everytime i get slightly above a 1/4 tank it starts to fluctuate between 18 down to 7-8 whenever I stop or make a turn. 

 

Side note, this is an autometer 0-15psi gauge and I've been overpressuring it for over 2 years. Could the gauge have went bad finally? Or maybe a different issue? The truck has no power loss and starts right up no matter how long it been sitting wheather it be over night or just enough to fill up. The fass 95 pump has been on for about a year now. 

 

Has anyone ever had a similar issue?

Edited July 14, 2018 by Towrigdually

[greed]

It could be the gauge is going bad after seeing too high of pressure for that length of time. I had a Nordskog digital (electrical) gauge that would start to fluctuate. The sending unit caused it. Sometimes the fluctuation was the factory lift pump getting ready to tale a dump. I solved the gauge problem by going with an Isspro mechanical plumbed directly into the cab.

[JAG1]

That's what I did as well after having the same experience with electrical F/P gauge.

[Dieselfuture]

Probably guage, how is your fuel system set up. Do you use draw straw or basket, maybe something came lose on a turn 

[Towrigdually]

1 hour ago, greed said:

It could be the gauge is going bad after seeing too high of pressure for that length of time. I had a Nordskog digital (electrical) gauge that would start to fluctuate. The sending unit caused it. Sometimes the fluctuation was the factory lift pump getting ready to tale a dump. I solved the gauge problem by going with an Isspro mechanical plumbed directly into the cab.

 

Its already a mechanical gauge but I agree, I might have put to much pressure on it finally

40 minutes ago, Dieselfuture said:

Probably guage, how is your fuel system set up. Do you use draw straw or basket, maybe something came lose on a turn 

 

Systems goes from tank, sump, fass, fuel gauge T, then injection pump. I plan to check all fittings tommorow morning.

[JAG1]

When my tank is low I can see my mechanical gauge fluctuate and at the same moment hear the lift pump sucking some air. It's usually on hills, inclines or take offs with a low tank.

 

What we really need is a tank sump that has the draw straw going down in there.

[dripley]

I think the fuel basket works great. Worked fine stock and now that mine is modified for the AD I installed it still works flawlessly. On at least 2 occasions I have put just pinch over 35 gallons in my tank. Once in stock trim and once in the modified trim.

[Towrigdually]

Checked all fittings this morning and all tight. Spray some soapy water on all fittings and areas where air could be introduced to the system, even fuel lines, and don't see any bubbles from being sucked into the system at all. 

 

So i think I need a gauge and maybe a new snubber

[tylertrebilcock]

On 7/13/2018 at 6:34 PM, Towrigdually said:

so I usually never let my fuel gauge get below 1/4 tank and during my last drive I did just ever so slightly. 

When I took a sharp turn into the gas station my fuel gauge dropped right to 0 and stayed. 

 

I immediately shut the truck off and then bumped the starter to listen for the fass to run, which it did. So I let it run but it came up normally but the needle then vibrates quickly as it climbs to 17-18 psi. If I let it sit for a few seconds it settles out no problem. 

 

Now everytime i get slightly above a 1/4 tank it starts to fluctuate between 18 down to 7-8 whenever I stop or make a turn. 

 

Side note, this is an autometer 0-15psi gauge and I've been overpressuring it for over 2 years. Could the gauge have went bad finally? Or maybe a different issue? The truck has no power loss and starts right up no matter how long it been sitting wheather it be over night or just enough to fill up. The fass 95 pump has been on for about a year now. 

 

Has anyone ever had a similar issue?

You probably just sucked air through the fass. 1/4 tank on my truck is actually an 1/8 and I found this out the hard way when I ran out of diesel just as the needle hit the 1/8 mark. When this happened my gauge jumped to 20psi and then dropped straight to zero. I usually refill just below half now and my gauge hasn’t fluctuated at all. Fill ups are about 20 gallons typically, which doesn’t make sense if it’s just below half considering the tank is only 32 G iirc

[01cummins4ever]

I get the same symptoms around a 1/4 tank, I just passed it off as low fuel sloshing around in tank and sucking air,The last time I let it go just below 1/4 tank the fuel psi. was was bouncing around like crazy, and ended up putting 28 gallons in a 33 gallon tank, I believe the fuel level sending units tend to be inaccurate especially when you top it off and have to drive 100 miles just to move off the full mark, once mine hits a half it goes down quick

[015point9]

My old gauge exactly the same.  Got new gauge just because had to drop tank, so why not?  Now all I get is low fuel sign  in dash.  Irritating 

[IBMobile]

12 minutes ago, 01cummins4ever said:

I believe the fuel level sending units tend to be inaccurate especially when you top it off and have to drive 100 miles just to move off the full mark, once mine hits a half it goes down quick

Mine does the same thing.  I adjusted my thinking.  It was easier than fooling with the sender unit. 

[dripley]

2 hours ago, IBMobile said:

Mine does the same thing.  I adjusted my thinking.  It was easier than fooling with the sender unit. 

Mine is the same way, I get about 440 out of the first half wish I could repeat that on the second half.

 Funny thing is it was opposite of that when new. Once I got the in tank it went the other way. 

[Mopar1973Man]

4 hours ago, dripley said:

I get about 440 out of the first half wish I could repeat that on the second half.

 

Man don't I wish. 300 to 350 miles on the first half. 

 

[dripley]

1 minute ago, Mopar1973Man said:

 

Man don't I wish. 300 to 350 miles on the first half

 I guess what I was trying to say is the gauge says 1/2 but the fuel used is more like 2/3 of tank. I got pretty excited after having that in tank pump installed because I thought improved the fuel mileage. Wrong!!!!

 

When she was new and the needle hit empty I could drive for near 100 miles. She is the exact opposite today.

[Towrigdually]

6 hours ago, 01cummins4ever said:

I get the same symptoms around a 1/4 tank, I just passed it off as low fuel sloshing around in tank and sucking air,The last time I let it go just below 1/4 tank the fuel psi. was was bouncing around like crazy, and ended up putting 28 gallons in a 33 gallon tank, I believe the fuel level sending units tend to be inaccurate especially when you top it off and have to drive 100 miles just to move off the full mark, once mine hits a half it goes down quick

Hmmmm I guess next time I fill up I'll need to pay attention to how much I put in. That might be the issue entirely 

[Mopar1973Man]

In my past rigs I was really fussy about making sure the float arm just about touch the bottom of the tank. I wanted to know where EMPTY exactly was. I'm currently not happy with the current float setup. Fill it up and it sits on full for at least 100 miles and the starts to fall. Now my Quadzilla shows my consumed fuel in gallons and really close to being right on most of the time. By the time I hit Ontario on my return trip I'm normally close to 15 to 18 gallons used. I typically hit the half mark at about 17.5 to 18 gallons which is about right for 35 gallon fuel tank. (35 / 2 = 17.5 Gallons). When the fuel light comes on at the 1/8 of a tank I typically have 10-11 gallons left. So the span between 1/2 and 1/8 mark falls ball of lead chucked out in the lake. 

 

Personally, the 2nd gen cluster sucks for accuracy. Volt gauge once it hits 11.99 volts the gauge drops to 8 and chimes. It will not rise back up till there is 12.01 Volts again.

 

Oil pressure gauge that changes to coolant temperatures. 

 

Coolant is pretty close to right. 

[Towrigdually]

10 minutes ago, Mopar1973Man said:

 

Man don't I wish. 300 to 350 miles on the first half. 

 

 

Seeing your mileage makes me semi-regret getting larger tires...

1 minute ago, Mopar1973Man said:

In my past rigs I was really fussy about making sure the float arm just about touch the bottom of the tank. I wanted to know where EMPTY exactly was. I'm currently not happy with the current float setup. Fill it up and it sits on full for at least 100 miles and the starts to fall. Now my Quadzilla shows my consumed fuel in gallons and really close to being right on most of the time. By the time I hit Ontario on my return trip I'm normally close to 15 to 18 gallons used. I typically hit the half mark at about 17.5 to 18 gallons which is about right for 35 gallon fuel tank. (35 / 2 = 17.5 Gallons). When the fuel light comes on at the 1/8 of a tank I typically have 10-11 gallons left. So the span between 1/2 and 1/8 mark falls ball of lead chucked out in the lake. 

 

Personally, the 2nd gen cluster sucks for accuracy. Volt gauge once it hits 11.99 volts the gauge drops to 8 and chimes. It will not rise back up till there is 12.01 Volts again.

 

Oil pressure gauge that changes to coolant temperatures. 

 

Coolant is pretty close to right. 

Right now I usually go between 76-90 miles before it comes off full. That's if I don't fill the fuel neck. 

So maybe I do have a cluster or sending unit issue, it wouldn't surprise me. I'll have to investigate further into it 

 

[dripley]

When it comes to the fuel you just have get used to what it reads. I know when I hit a half tank on the gauge it is really 2/3 rds. No big deal. When the light comes on I have about 3.5 gallons left. It is just what it is. All my vehicles have been like that. I just learned to live with it. I never had the need to know that I burnt or had 4.25 gallons left or burnt. Not that anal I guess.

When it comes to the fuel you just have get used to what it reads. I know when I hit a half tank on the gauge it is really 2/3 rds. No big deal. When the light comes on I have about 3.5 gallons left. It is just what it is. All my vehicles have been like that. I just learned to live with it. I never had the need to know that I burnt or had 4.25 gallons left or burnt. Not that anal I guess.

[Mopar1973Man]

1 minute ago, Towrigdually said:

Seeing your mileage makes me semi-regret getting larger tires...

 

 

Larger the tire size, the lower the final ratio, and more engine load and lower fuel mileage. This is why I've been studying the 245's now. Dropping from 31" tires to 30" tires. I'm still debating in my mind of a 215/85 R16 (8.5") or 245/75 R16 (9.6") both are 30" tall. Where the 235/85 R16 (9.3") and 265/75 R16 (10.4") are 31" tall. 

 

All comes down to rotational mass and final gear ratio. Bigger tires do look cool but looking cool comes with a price tag.

 

 

 

4 minutes ago, dripley said:

I never had the need to know that I burnt or had 4.25 gallons left or burnt. Not that anal I guess.

 

I've got to. Being the next diesel fuel station might be a very long ways away. Living on the east side of the island population density it much higher. Out here towns don't have to have a fuel station and some may or may not have fuel that day. It does happen. So being able to understand you remaining range you have left in gallons and miles is very helpful to know what your next step is being fuel might be another 100 miles to reach. 

16 minutes ago, Towrigdually said:

Right now I usually go between 76-90 miles before it comes off full. That's if I don't fill the fuel neck. 

So maybe I do have a cluster or sending unit issue, it wouldn't surprise me. I'll have to investigate further into it 

 

 

Might be. I can tell you as the senders wear they typically hit empty higher on the gauge. So when mine failed I was hitting empty at 3/8 of a tank.