Diesel Fuel Gauge

[Homer Shannon]

I have a Tempo TP18T, 18 gallon fuel tank in my boat. It is equipped with the Tempo 280050 fuel level sending unit and the Tempo 280140 fuel gauge. The gauge fluctuates wildly when the boat is in motion and it is not accurate – even at rest. When the tank is full, the gauge reads just under ¾ full. When it reads ¼ full I still have half a tank (8 gallons) of fuel.

A friend of mine recommended installing a fuel gauge sender for a truck saddle tank. These, like this one, https://www.amazon.com/KUS-USA-Water...57644088&psc=1, operate with a sliding mechanism, not the lever arm of the Tempo unit. My friend says it is more stable and more accurate. All sending units seem to be able to use the same gauge. The bolt pattern for installation of the two units looks at least close – I’m not aware if there is a standard for this.

Before I go and install one of these truck senders, is there any way to calm down the stock lever-arm sender and a way to make it more accurate (bending the arm, perhaps). I do have an ohm meter and suppose I could take readings with the arm at differing angles.

[kaisardog]

2 things come to mind: 1/ What is your tank depth? The old miserable faryman diesel i had in my rhodes 30 some 30 years ago had the same inaccurate read problem. No matter how i bent the mechanical float arm , the gauge never read full when tank was full. ( The old gauge and ssending units were heavy things of beauty so much to spouses dismay i saved them, wrongly thinking i d reuse them .) i reengined that boat with a new yanmar 2 gm 20 f and put in a new aluminum 18 g tank . i had to carefully match sender unit to depth of tank not its capacity in gallons . Then i got accurate readings. Maybe yr sender arm length is a mismatch to yr tank depth in which case it would be worth $30 to replace it. Moeller, of vacuum pump fame, makes really good systems. They could help you select new parts. 2/ the fact that yr gauge readings fluctuate so wildly tells me something may be causing inaccurate current to be sent to the gauge. Most likely cause of that is deteriorated ground wire or sensor wire as when the wrire deteriorates the resistance can be much higher. Give yourself new sensor wires and ground and bend the float arm and see if that fixes the gremlins. Or spend $$, at least it is not a BOAT unit. ( ‘break out another thousand,,’ )

[BigAl.NZ]

I have been through this recently. Resistive senders are a bit better than the arm unit you have, but they may only have 6 or 8 data points (a series of reed switches up the length of the tube).

I am now looking at a Oceanic Systems N2K native sender which can be calibrated to any tank shape and programmed for various levels of dampening. Good to within a few litres of whats left.

[GordMay]

Tempo’s sending unit uses wire-wound resistors, compatible with 35-240 Ohm gauges

Often a problem occurs when the sending unit’s floating arm becomes saturated. On older units the floats may be made of cork. Over time these floats can lose buoyancy, and give inaccurate [low] readings.

See also ➥ https://www.cruisersforum.com/forums....html#post2597

[ranger58sb]

We converted from an earlier swing-arm sender to WEMA/KUS straight-shaft fuel level senders... and the new units seemed to be very stable.

One problem, with any sender, might be about how high the sensor float can actually get to, inside the tank. If it can't really get to the top of the unit for whatever reason, might be the resistance level doesn't ever get to 33 Ohms (for example)... so the gauge might indicate a lower level than what's really in the tank.

We also converted from original analog Faria fuel gauges to CruzPro digital gauges... which will work with several standard resistance-type senders (pick from a menu), including the KUS models. One of their fuel gauges will actually "learn" your tank level even if your tank shape isn't a standard cube of some sort. Given a relatively small 18-gallon fuel tank, going through the set-up routine would be very easy... and you'd essentially be telling your gauge what exact amount to display at various specific resistance levels the sender encounters.

-Chris

[Homer Shannon]

Thank you for your comments. My gauge is "new", at least as new as the tank and sender and inaccuracy and fluctuations have been there since day one. I think the float arm is just flopping around a lot.

I happened upon this forum post, https://www.cruisersforum.com/forums...ow-251862.html, which coveres a similar topic - I use the time-run method to more accuately know my fuel level. The post mentions non-contact level sensors, which I looked into a bit last night. One of these would be fabulous for use as a holding-tank-full alarm. When the boat gets home this fall, I'll dig in and see if I can sort out knowing the status of several critical tanks.

[marcjsmith]

how about a tank tender setup. Ive got it on my fuel tank and my fresh water tanks.
not cheap though....http://tanktender.com/


I also have a sight glass on my fuel tank.

[Bycrick]

The Tank Tender is a convenient, but very expensive, packaging of very cheap, and readily available, pneumatic fittings. I built the equivalent for 8 tanks for about $300 using pneumatic parts from Parker-Hannifin.

[marcjsmith]

Originally Posted by Bycrick

The Tank Tender is a convenient, but very expensive, packaging of very cheap, and readily available, pneumatic fittings. I built the equivalent for 8 tanks for about $300 using pneumatic parts from Parker-Hannifin.

mine came with the boat uninstalled. Figured no point in not installing it.


maybe post a "how to" for the OP

[Bycrick]

How to tend my tanks on the cheap. In the 80s, I had found some small pneumatic valves that were about the same size as the normal Class A circuit breaker. I paid about $0.75 each. They looked like oversized toggle switches. I think they were Parker Hannefin. In 2000, with new boat and more tanks, I went to expand the system. The valves are ganged together with the standard two-port hose connections. All hose is standard 1/8” pneumatic hose. The pump is a standard pneumatic cylinder with two check valves, one in and one out. The measuring tubes were made from a 1/4” brass pipe plug, threaded into the top of the tank. I glued a piece of 1/4” fiberglass tubing into the bottom of the plug and drilled and tapped the top of the plug #10x32 to accept the standard hose fitting. The pressure is read on a low-pressure gauge from a pneumatic supplier, about $18. That’s the whole thing.

The new valves were under $20/each. I don’t remember what the cylinder cost. But the total for 8 tanks was under $300, although I did reuse a couple of the old valves.