LMC EFI Tank Sender problem

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tadslc

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I recently purchased a LMC EFI Tank kit, #32-5984.

Install went well until it came to the fuel gauge reading.

When I fill up its only showing 1/4 tank and this goes to 0 quickly.

Checked gauge and it works as it should. Disconnected pink wire from sender, needle goes to 3 o'clock position, ground pink wire it goes to 0.

Purchased a new sender from LMC. Checked ohms, correct. Hooked the sender to the pink wire and ground outside the tank and the gauge works as it should. FYI - These come with the "floatless" style sender.

Dropped the tank, installed the replacement sender, reinstalled everything. Nothing...

Does the exact same thing as the other sender.

What am I missing???


Thanks!
 

RustyPile

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Make certain the sender has a good frame ground strap. Grounding the sender lead is not all conclusive. Check the resistor on the back of the gauge.. Should be ~ 85 ohms.. Resistor must be removed from gauge to get a proper reading.
 
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tadslc

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Make certain the sender has a good frame ground strap. Grounding the sender lead is not all conclusive. Check the resistor on the back of the gauge.. Should be ~ 85 ohms.. Resistor must be removed from gauge to get a proper reading.
Thanks

Good ground and gauge works fine. The gauge is a replacement with the internal resister.
 

tadslc

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I just tested the original sender in a bucket of water hooked up to an ohm meter and it worked fine. 0 empty and 82 full.
 

RustyPile

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I just tested the original sender in a bucket of water hooked up to an ohm meter and it worked fine. 0 empty and 82 full.
No need to use a bucket of water or a bucket of anything.. Simple connect the sender to a multimeter and swing the arm through its range of travel.. Do this test to both senders and compare the 2 responses.. Then using jumpers to ground, connect the senders (one at a time) to the sender wire. Again, swing the float arm through its range of travel, making note of the gauge needle movement from both senders.. I'm betting you'll find that new gauge is defective or incompatible..

[EDIT] Something else to consider. Make sure the float isn't hanging up at the 1/4 mark...
 

tadslc

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No need to use a bucket of water or a bucket of anything.. Simple connect the sender to a multimeter and swing the arm through its range of travel.. Do this test to both senders and compare the 2 responses.. Then using jumpers to ground, connect the senders (one at a time) to the sender wire. Again, swing the float arm through its range of travel, making note of the gauge needle movement from both senders.. I'm betting you'll find that new gauge is defective or incompatible..

[EDIT] Something else to consider. Make sure the float isn't hanging up at the 1/4 mark...

There is no arm on these "floatless" senders.

As stated previously, I have already checked both senders with an ohm meter. Both are fine.

I also have checked the replacement sender and replacement gauge and they work as they should when connect to the pink wire and ground. Empty to Full.
 

RustyPile

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There is no arm on these "floatless" senders.

As stated previously, I have already checked both senders with an ohm meter. Both are fine.

I also have checked the replacement sender and replacement gauge and they work as they should when connect to the pink wire and ground. Empty to Full.
I realize there's no "arm", but you can't figure out how to make the rheostat "wiper" change the resistance???? You've argued and debated every suggestion made here.. I have over 30 years working as a professional. Specialized in A/C and electrical the last 20 of those years.. Yet I don't know what I'm talking about??? You have a good day, sir....
 

tadslc

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I realize there's no "arm", but you can't figure out how to make the rheostat "wiper" change the resistance???? You've argued and debated every suggestion made here.. I have over 30 years working as a professional. Specialized in A/C and electrical the last 20 of those years.. Yet I don't know what I'm talking about??? You have a good day, sir....

There must be some disconnect in the way I am explaining myself. Apologies if you've taken offense.

I have repeatedly said I have checked resistance using a ohm meter and both senders check out fine. Easy to do on these. I also checked in a bucket of water (hooked to an ohm meter) to make sure the float travels freely like it's vertically mounted in the tank and it does.

Bottom line is that every check you can do on the sender - gauge combo has been done and everything checks out good. It's only when the sender is actually mounted in the tank (which is a bitch to replace) does it not work.

I'm almost thinking there is something wrong with the tank and it's not allowing fuel to get to the sender. I know that sounds crazy but that's where I'm at. I will once again pull the sender out and this time check with an endoscope to see how the tank is constructed.
 

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First let me say -- The problem I have with working with you is, you do don't read and comprehend my words or you do not follow instructions. Tad, I've been doing this since before these square bodies were even on the drawing boards. I got started doing this before the Viet Nam war was raging. Cars still had generators and 6 volt electrical systems. Some cars had positive post grounding systems.

OK, I'll try one more time. . Go back and read each and every one of my posts.. Do the tests like I instructed NOT like you think they should be done. Totally disregard any testing you have done on your own, start over.. DO NOT assume just because a part is new it has to be good. Conduct a proper test and PROVE it to be good. Follow instructions..

OEM fuel gauges have a serviceable resistor. When it goes bad, it can be replaced. If the gauge is an aftermarket unit that has that resistor "built-in" and it goes bad, the gauge has to be replaced..

Grounding the sending unit wire is NOT an all conclusive test for the gauge operation.. It definitely determines that there is continuity.. But a bad gauge resistor will often give the same test results as having a good resistor.. Using jumpers, connect the sending unit outside the tank. Forget the bucket of water, you don't need it. Maneuver the "level indicator", whether it be an arm with a float on the end of it, or, as you say, "floatless".. Check the gauge response.. As you move the "level indicator" through its range of travel, empty to full, you should see a likewise response from the gauge.. Check both sending units in this manner. If you get dissimilar responses from each, then the unit that doesn't give a proper response is bad.. If you get bad responses from BOTH senders, your gauge is probably bad.... If you get good responses from both sender units, then you probably have something going on inside the tank.. Something is hindering full travel of the "level indicator"...

If you deviate even the slightest from any of my instructions, be advised --- I'm done.
 

tadslc

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You are quite the bully RP

I have done everything you have suggested, several times over. May not have described the tests to your satisfaction but I'm not loosing any sleep over it.

Found the issue and the problem is now fixed.

I'm no rookie myself, having started wrenching about 50 years ago. American cars were never my thing but for some reason I love my C10.
 

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You are quite the bully RP

I have done everything you have suggested, several times over. May not have described the tests to your satisfaction but I'm not loosing any sleep over it.

Found the issue and the problem is now fixed.

I'm no rookie myself, having started wrenching about 50 years ago. American cars were never my thing but for some reason I love my C10.
So after all the drama and head scratching....what was the issue? It's ok if it was user oversight, that's how we all learn. Let's hear it. :popcorn:
 

tadslc

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So after all the drama and head scratching....what was the issue? It's ok if it was user oversight, that's how we all learn. Let's hear it. :popcorn:
So you really want to embarrass me?

It turned out to be the gauge.

And... the reason why I wasn't getting a reading from the senders after replacing the gauge...

Not enough gas in tank, but that's another story...:33:
 

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NOT trying to embarrass you, but go back and read post #5... I hope the lesson you have learned is more read, read, read, with less type, type, type.....
 

tadslc

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NOT trying to embarrass you, but go back and read post #5... I hope the lesson you have learned is more read, read, read, with less type, type, type.....

You didn't embarrass me in the least RP, you just ticked me off. I was referring to the post from SquareRoot in jest.

I did everything you suggested before you suggested, read my response to your post #5 with my post #6.
 

RustyPile

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You're still doing it --- type, type, type, before reading what I said... The last sentence in the 1st paragraph of post #5, I said "I'm betting you'll find that new gauge is defective or incompatible.."

In post #9, I also told you that if you get good readings when testing the sending units externally from the tank, you might have something hindering full travel of the "level indicator".. Explain to me how a properly operating gauge system can indicate more fuel than what's actually in the tank???

Tad, I've argued my points with you way more than I normally do, so there's no need for this discussion to go any further.. I'm placing you on my ignore list.
 

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