Fuel Gage Problem

[oldnavy]

I've had the old fuel sending unit out and cleaned it, but gage is still not reading correctly. The low fuel light comes on for the system check at start, and the gage will not go all the way to full mark when tank is filled. It also seems to go to the last bottom mark too quick then stop dropping before it ever has a low fuel light come on. I have run it down to about 3 gal with no low fuel light on and the gage not moving for at least 100 miles or more before I add fuel.

Any idea's any from the pro's welcome, but I'm not crazy about paying big bucks for new sending unit.

[bubbazook2]

Hi ol'Nav I've got similar problem on my Benz, I cleaned sender but didn't gain much. My gauge reads from approx. 9 o'clock to 5/8 when full. Warning lite comes on around 9 or 10, also when starting. But does yours dance between 9 and 5/8 with key off?? Mine does, have to disconnect neg. battery cable to stop. Any suggestions ( and all ) appreciated, thanks guys, great forum Bill (Bubba)

[oldnavy]

Originally Posted by bubbazook2

Hi ol'Nav I've got similar problem on my Benz, I cleaned sender but didn't gain much. My gauge reads from approx. 9 o'clock to 5/8 when full. Warning lite comes on around 9 or 10, also when starting. But does yours dance between 9 and 5/8 with key off?? Mine does, have to disconnect neg. battery cable to stop. Any suggestions ( and all ) appreciated, thanks guys, great forum Bill (Bubba)

Yes mine stops just below the last line, but before the warning light. I have never had the warning light to come on, except when starting the car. When full it gets just barely above 3/4 line. I've had the sender completely apart, and even cleaned the wires and turminals, the only thing I can think of wrong is the pointer needs to be pulled off and rotated a little to the right. I'm not sure if this can be done, but will find out after the holidays.

As for your problem sounds like a ground short in gage, but may sender, I would doubt it's in the wires, but you never know. I would check your connectors (male & female) first, then sending unit and last the gage then wiring. Thats the easiest to check first to hardest last. My bet is on a faulty gage. Do you have a miltimeter? You will need one to check this out, if not get a $10 cheapo at Wally World as it will serve the purpose.

sound like you may have sludge in fuel tank from water in fuel tank that lets "bugs" grow in tank. Try adding some anti fungal additive to see if it works...common problem in jet fuel on aircraft..trust me I know. We treat tanks on jets every 6 months..use a product called biobore (biocide)(spelling may not be correct).If you do make sure you change the filters shortly afterwards otherwise they may clog. Good luck.

[oldnavy]

I don't have bio critters as I use biocide regular every fill (I run 49 cetane, B2 fuel) and I've cleaned (new lower screen and fitted hose) and recheck sending unit twice. I have disassembled the sending unit to clean, reassembled the sending unit. I've never run it low enough I guess to have the fuel light come on, the most I've ever put in the tank is 16.3 gallons. I guess I'll start carrying a fuel can as it gets close to next fill time, and drive the thing till fuel light comes on or I run out or whichever occures first.

Originally Posted by oldnavy

I don't have bio critters as I use biocide regular every fill (I run 49 cetane, B2 fuel) and I've cleaned (new lower screen and fitted hose) and recheck sending unit twice. I have disassembled the sending unit to clean, reassembled the sending unit. I've never run it low enough I guess to have the fuel light come on, the most I've ever put in the tank is 16.3 gallons. I guess I'll start carrying a fuel can as it gets close to next fill time, and drive the thing till fuel light comes on or I run out or whichever occures first.

Make sure your primer is in good working order and that you perhaps bring a wrench to bleed the lines

I am about to do the same with the 300SD becuase I have NEVER put more than 17gal in a supposedly 23gal tank?

My light works btw...as it should...needed a clean...I have no new advice for ya..
sorry

[bubbazook2]

Hi ol'Navy thanks for info, I've got elcheapo multimeter so will check wires. Like you said it's like need to rotate needle on gauge, when it's off you can hear it tapping on the stop,ha,ha. sometimes going down the road the fuel gauge and temp gauge start dancing wildly together then all at once they stop. most of time it does it when seat belt lite comes on but not always. I unhooked warning box on drivers kick panel, got rid of belt lite thats about it. I suspect I probabley need rebuilt inst. panel. any recom. appreciated, thanks again. really enjoy reading the forum everyday and getting hot scoop on a lot of maintenance problems. Bubba

[oldnavy]

Yup I have the new style of hand primer, and 5 gallon polly jerry can. I may however wait till spring and better weather for standing around outside a car.

Sounds like you may be better off just swapping out the dash unit Bubba.

[bubbazook2]

I tjhink your right ol Navy, I forgot to mention last week I ran about quart or so of PS diesel clean thru IP and engine, then replaced prefilter and main filter, didn't see any black specs. I remember trouble we had with JP-5 and micro orggies on the F8D,E crusaders fuel cells. were always replacing fuel p robes That was 40 yrs ago here in Beaufort and later on USS Oriskany. Bubba

[oldnavy]

I'm still getting the black spec's in my prefilter as the B2 cleans the whole fuel system, tank & lines. Sometime's I think it might have been worth taking the car in someplace and having it done.

[oldnavy]

Originally Posted by mespe

try the hand pump while at home. Mine was a bear to loosen the first time. It won't hurt to manually pump the thingt a few times. And yes it will remove all the air fronm thelines

I don't have the old clear plastic hand primer that you had to turn to loosen and was prone to leaking, I have the new model primer that works far better and has much more suction.