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Discussion Starter · #1 ·
Hello all, I've been having issues with my fuel guage. I haven't driven it much in the last year, about 1 or 2 times a month. I don't really need it anymore but it's nice to have when I do (Fred Sanford syndrome). Started a few months ago. Started it up and the gauges were all wonky, like the tach and oil pressure were on 0.

Beat on the dash and everything started working again. Later the gas needle dropped from 1/4 to sub 0 with low fuel light. I took the dash apart and checked the plugs and wires, disconnected and reconnected everything probably 10 times. The gauges as a whole acted up a couple of more times but at that time the gas guage stays at sub 0.

A few weeks ago I was messing around with it again (I have left the dash disasembled) and the gauge went to 100% full and stayed there. Then the other day I was trying again and got under it and jiggled the wires like from the hfcm up to under the hood, and under the hood guessing that loom contains the sending wires. The guage went from 100% f down to just over 1/2 and that is where it wants to stay. I know it's got about 1/8. I tried more jiggle but it stays there.
Any help please. Pin outs, wire diagrams, ideas, would be appreciated.

03 excursion 6.0
 

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I know of no wire diagrams for the dash, but it sounds like there is a solder joint issue. You could examine all the joints as see if you can tell a problem to reheat. Otherwise, Circuit Board Medics is a good deal.
 

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2005 F250 FX4 Lariat CCSB - ARP studs, EGR deleted, IPR coolant filter, PHP FICM tunes.
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OEM electronics don't always have great solder joints.

A few years ago I had an Explorer Eddie Bauer Edition. It has this neat display in the center console that displayed all kinds of cool stuff, including warning you of burned out bulbs.

It did this by routing lighting circuits through low value resistors and checking voltage drop across the resistors. No voltage drop across resistor means no current through bulb means probably burned out bulbs.

One day one of the headlights quit working. First attempt at a fix was running a jumper from the working headlight, which worked.

A replacement monitoring module, which lived in the center console, also made things work without the aforementioned jumper.

Examination of the guts of the old module revealed a cold solder joint. Reflowing solder on that joint returned that module to proper operation.
 

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Discussion Starter · #6 ·
So I spent spent some time on it yesterday. I found a pinout for a 02 f250, it seems to be simular. I ohmed out c220a #3 and 4. It read around 110-120. I believe the correct value to be 15-160 empty to full. When I would shake the truck the meter would go all erratic, quickly changing all over from 0-10k until it would settle back and hold steady in the lower 100s. Did a few times with the same result. I know it has 1/8.

On the wonky dash, it completely looses power but if I move the cluster around or give it a tap it restores. Wouldn't you think it would be the ground circuit or ign power circuit either internally or in the harness causing the intermittent drops in power? They would be c220c 15, 19, and maybe 20. If so at least I could try to narrow it down internally or maybe unplug the cluster and put the meter on the harness and see if I get a drop while moving the wires around.

I think I have 2 separate issues maybe related or unrelated they just started at the same time.

Blue Font Rectangle Screenshot Parallel
 

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I wouldn't count on a 7.3L wiring diagram being all that consistent with a 6.0L.
 

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Discussion Starter · #8 ·
I wouldn't count on a 7.3L wiring diagram being all that consistent with a 6.0L.
Thanks for the advice. The plugs and the wire colors match and I'm 100% I was on the fuel sender wires. I know it's got anti slosh but shouldn't it stay between the 15-160 ohms while I'm rocking the truck?
 

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Thanks for the advice. The plugs and the wire colors match and I'm 100% I was on the fuel sender wires. I know it's got anti slosh but shouldn't it stay between the 15-160 ohms while I'm rocking the truck?
Your sending unit SHOULD stay between 15-160, but rocking the tank and depending on where you're measuring from, not so sure if it WILL. I'd fill your fuel tank then check your fuel gauge. If it doesn't read full, disconnect the sending unit connector at the unit itself and measure resistance on the sending unit side. It should tell you if your problem is the unit or upstream (wiring or IC). Like you mentioned, a full tank should read ~160ohms at the unit.

Sounds like you have multiple issues - all related to the IC. I'd send it to CBM's to get rebuilt & resoldered.

-jokester
 
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Discussion Starter · #10 ·
Your sending unit SHOULD stay between 15-160, but rocking the tank and depending on where you're measuring from, not so sure if it WILL. I'd fill your fuel tank then check your fuel gauge. If it doesn't read full, disconnect the sending unit connector at the unit itself and measure resistance on the sending unit side. It should tell you if your problem is the unit or upstream (wiring or IC). Like you mentioned, a full tank should read ~160ohms at the unit.

Sounds like you have multiple issues - all related to the IC. I'd send it to CBM's to get rebuilt & resoldered.

-jokester
I just couldn't see the sending unit being the issue, especially with the dash going wonky but later after reading and looking at the parts online I'm thinking at the current 1/8 tank its been sitting at for months (could be 6) the sender itself is sitting high out of the lake of fuel so maybe that has something to do with it. It is original so maybe. Over the last few months gauge has sat pegged on f, e, and in the middle. I just crank it up and move it about 40ft each time.

I ain't filling it up right now, I'll have over $200 in diesel sitting and God help me when I finally decide to replace the sender(44 gallon tank).

There's no way I can get to the harness above the tank without dropping it. I was hoping there was another harness between the tank and dash I could check from but I don't know.

I am leaning towards the sender @ 400 bucks. It ohms out at 117 the guage says half tank. The reading bounces all around when rocking but returns to 117. And I can't really rock that hard or bounce on the hitch the suspension is so tight.
 

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If you know it's got ~1/8 of a tank, that should be ~33ohms. Test the sending unit at the connector to rule it out my connector was just forward of the tank.

-jokester
 
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Oops...I corrected my math above. 1/8 tank should be ~33ohms.

-jokester
 

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I had a ford car where the dash unit would read funny like you’re seeing. Common thing in that car and solution was to take it apart look for corrosion around the joints and clean it with rubbing alcohol. The corrosion was apparent as a white residue along the solder joints.
 

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Discussion Starter · #15 ·
I had a ford car where the dash unit would read funny like you’re seeing. Common thing in that car and solution was to take it apart look for corrosion around the joints and clean it with rubbing alcohol. The corrosion was apparent as a white residue along the solder joints.
Thanks. I was thinking I could use the pinout to help trace the exact circuit path for ground and power when disassembling the cluster. I got some of that 99% isopropyl.
 

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What's 117?
Goes from 15 to 160ohms, so 160-15=145. Divide 145 by 8 and you get 18 and some change. So, for every 1/8 of a tank, add ~18 (1/4 tank would be ~50, 1/2 tank would be ~100, 3/4 tank would be ~150, etc.). 117 puts you just shy of ~5/8 of a tank of fuel.

-jokester
 
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