Fuel sending unit

[jmeti000]

I refuse to put airtex anything in my jeep and just need the sending unit. Was told by the dealer they dont make the sending units for my jeep anymore :bawl:. Anyone know of a decent aftermarket fuel sender or where I can find an OEM one for an 87 4.0?

Thanks,

Me

 

[Rush Power Systems]

Sending units don’t really go south that much, when they do usually it is an easy fix. If you float is bad you can replace that or repair it. Broken wires in the leads from the resistor board can be replaced with new ones, and if the resistor board is not making contact you can clean it with light steel wool same with the contact terminal, so I would pull it and look at what you have to work with.

 

[kastein]

I think rockauto carries one. If not, any 87-90 4.0 donor at the yard works - 2.5s will work iirc but you have to put your fuel pump on it.

Rush, up here in the rust belt they actually go bad pretty often, every 10-15 years they rot out bad enough that they leak or the pressure line starts blasting everywhere from a pinhole rust spot.

 

[jmeti000]

Its not rust, its a reading issue. My gauge will read almost empty but when I go fill it up it will only take 10-12 gallons and its a 20 gallon tank. I thought perhaps it might be the float, but I just swapped out the float a few months ago because it had a pinhole leak. I figure either the float has a leak again or the resistance readings on the reostat are all out of wack...either way im tired of messin with it and would rather just put a new unit in and be done with it (if I can find one).

 

[Rush Power Systems]

@ kastein - So your sending unit is in the gas tank, if you are getting rust on it you have much larger problems than a bad sending unit, sounds like a bad O-ring, unless you are talking about the entire fuel system. Here in Utah we have an abundance of salt (Great Salt Lake), sometimes in the winter the streets are white with salt, but never a problem in the tank.

@jmeti000 - It is a disposable world, you may need to hit a junk yard, rebuild a used one and graft in a quality pump.

 

[kastein]

The sending unit is the entire bracket, formed tubing, etc that the pump and gauge potentiometer are mounted to. I have never seen it called anything else. You are talking about the gauge pot or the fuel pump.

 

[Rush Power Systems]

right, and it is in the tank, so if you have rust on it you are getting water in the tank.

 

[kastein]

... please go look at your tank. The part that rusts is the part that shows, I.e. is the problem is circled by the fuel sender assembly locking ring and the rubber hose(s) to/from the filter and fuel rail connect to it.

 

[Rush Power Systems]

pull your head out of your :moon:

OP: "I refuse to put airtex anything in my jeep and just need the sending unit", we are talking about the SENDING UNIT, aaannnddd it is IN the tank, not on the outside.

I have pulled too many tanks to count and have never seen one on the outside of the tank. yes the top rusts, when we do a FP we paint the flange to help stop rust, but again if the wires from the resistor plate are bad you run new wires. fuel gauge has nothing to do with fuel leaks or rusted tubes.

reading is the best path to understanding! :explosion

 

[kastein]

The sending unit is the entire bracket, formed tubing, etc that the pump and gauge potentiometer are mounted to. I have never seen it called anything else. You are talking about the gauge pot or the fuel pump.

right, and it is in the tank, so if you have rust on it you are getting water in the tank.

pull your head out of your :moon:

OP: "I refuse to put airtex anything in my jeep and just need the sending unit", we are talking about the SENDING UNIT, aaannnddd it is IN the tank, not on the outside.

I have pulled too many tanks to count and have never seen one on the outside of the tank. yes the top rusts, when we do a FP we paint the flange to help stop rust, but again if the wires from the resistor plate are bad you run new wires. fuel gauge has nothing to do with fuel leaks or rusted tubes.

reading is the best path to understanding! :explosion

Highlights in bold.

Agreed, reading is the best path to understanding. The sending unit is what I said it is, and rusts from the outside. What you are talking about, and what the OP wants, is the potentiometer or wiring itself, which clearly is not exposed to the outside environment. Some companies and OEMs apply the terms differently, so I can see how you could get confused - better terms would be hangar, sending unit/potentiometer, pump, and harness, but jeep calls it the sending unit and pump. You can get the wiring harness individually (p/n 5600 1859) but the rest is all called the sender:

To clear things up here, please turn to figure 14-4100 in your 87-90 jeep official parts catalog. See item #22, titled "SENDING UNIT, Fuel - w/Fuel Injected Eng. ***"

The diagram clearly shows that this includes the bracket/steel lines, etc as well as the pot and other parts. That is what Jeep said the sending unit is, that's what I say it is.

The part number needed here is either 8350 4488 or 8350 4487 depending on whether it has a 13.5 or a 20.2 gallon tank, respectively. I've never seen just the pot for sale - Jeep never sold em individually, nor has any aftermarket company I am aware of.

I found one on jeep4x4center but the picture shows it as a late model sender and they want over three hundred for it! :shocked: you could try ebay or others. Occasionally they sell on there for around 50 shipped.

As for the hangar/sending unit bracket/whatever else we want to call it not rusting, I wish I lived where you do. Here I am pretty sure they found a way to make plastic rust.

 

[Rush Power Systems]

Ah I see how you are confused, we don’t give up when OEMs say it is not serviceable, we rebuild many rare, hard to find, and obsolete parts that the OEMs say are not serviceable.

Yes the sending unit is a full assembly consisting of a float, a potentiometer, and wring, the float can be repaired or easily replaced since they are reproduced and many different vehicles use the same design float.

There are 3 parts to a potentiometer, they are the moveable contact, the resistor board, and housing, although some sending units potentiometer do not have housing, the assumption is the fuel will keep the components clean. If it has a housing you remove it, if the contact is varnished you clean it, if the resistor board contact are dirty you clean them, in each case you use steel wool. If the wire out to the gauge is broken or has high resistance you replace it

So to clarify, I am talking about rebuilding not replacing.

 

[Pelican]

I think you have hit on the problem here: Kastein didn't know that there are 3 parts to a pot....! Another example of an EE with a lack of practical knowledge!

 

[kastein]

Cool story bro, I've been doing EE stuff for over a decade and build custom wiring harnesses and embedded systems for fun. I spent more time with a soldering iron and a scope by the time I left college than many "EEs" do in a lifetime... probably the ones you're comparing me to. Just put a 94 xj 4.0 into an 87 yj with a cj7 dash and made all the electronics work together and look 100% original, a chrysler v6 into a toyota pickup using a factory toyota transmission is next - again with all factory gauges and equipment working. This isn't my first rodeo. I'm reverse engineering the obd2 XJ AW4 TCU for fun, too.

As for your "3 parts to a pot" comment, I don't even know what to say to that. First, the renix sender element is a 2 terminal pot IIRC (same as a 3 terminal but lacking a connection to one end of the resistance strip) and second, where the hell did I say anything about how many parts a pot has? I said what parts are in what jeep calls a fuel sender.

Anyways - actual on topic productive input -

I am not saying they aren't rebuildable - just that I've never found a place to buy a brand new resistance board (or nichrome winding in the case of a renix sender) alone. Iirc there's a single 1/4" selftapper holding the pot down and a few .187" or smaller flag terminals for the electrical wiring. If you want to clean one up, that depends so heavily on the problem it has (corroded, varnished, broken wire, wiper needs retensioning, etc) that more investigation is needed before fixing it.

I would suggest getting an early (91-95, 96 is even more different) HO sender and simply bolting it in but the resistance curve goes the other direction, so full and empty get swapped and the gauge is nowhere near linear. Everyone gets the idea of switching the wires to the pot but clearly that won't work. I've heard of people swapping an HO gauge into the gauge cluster to go with an HO sender, and vice versa, IIRC there is one wire you have to handle specially to make the low fuel warning light work but that's about it. Hopefully you can find that by searching if it is useful info to you.

 

[Rush Power Systems]

Yawn, since 85’ I have been paid to, install vortec (first and second gen) in everything you could think of including 86 conquest with 400 trans (my own), modifying turbo cars from the day when that was a trip to the fish store to modern ECUs. Grafted OBD-1 Q45, into OBD-2 Q45 with active suspension and traction control, so not really impressed with the AW4 TCU stuff, but good for you.

I build custom regulators and high tech alternators for US and other military around the world, custom built industrial charging systems for industrial equipment not available in the US and designed and built high amp alternators for the Japanese police. Designed, built and installed thousands of dual, triple, and up to 12 alternators on one vehicle, in all types of vehicles. Designed and build obsolete rectifiers that the original manufacturer (Motorola) could not build.

Only company in the world with 4 alternators in a Grand Cherokee, only company on the world to fit 3 alternators in the 4.0 XJ W/O removing AC. Currently building harness for 99’ Grand Cherokee 4.0 engine and trans / transfer into 97 Wrangler with 4 cly, had a hold up on hardware development with Novak since has never been done before – yup BCM to non BCM and just to make it fun remove SKIM and factory gauges, I know cake walk. Oh and Mega-squirt a snow blower, just to see if it could be done.

Not that we are having a pissing match, but i can write my screen name in the snow and well.....

Sorry on the “3 parts to pot” trying to dumb it down, did not realize I was talking to an expert. But can you blame me? OP is in need of a sending unit and does not want crap, I suggest a rebuild and you start talking about rust??? Sorry I got lost in your wisdom.

Never said anything about resistor board replacement, said clean it, if you can’t clean it is junk, that better? But now you are finally getting around helping in the guy, see what I am saying? “I have a bad sensor”, “oh you have rusted tubes”, OK thanks for the help. Guy could have said blah, blah, blah, and you could have said banana and it would have been just as helpful.

Your final paragraph, great advice, but it is still cheap aftermarket or super expensive OEM, NOS or reproduction, and we are right back to square one.

So sorry for trying to help the guy, Jmeti000 install new fuel lines, problem solved.

 

[kastein]

Honestly, what I'd have to suggest (if the pot can't be cleaned up or otherwise rebuilt) is to get one that isn't FUBAR and clean it up, swap it in and call it a day. I'm surprised there aren't any in the local junkyards, around here I'm lucky to see one RENIX in a month go through the you-pull but I'd heard that they were still a lot more common down in TX/the rest of the south/southwest. Fairly easy to test at the junkyard before buying, put your ohm-meter (preferably analog for this, it's easier to see a needle twitch than a slow-updating DMM screen...) on 200 ohm scale, sweep the float arm from one end to the other slowly, make sure the needle moves smoothly and doesn't twitch around. IIRC, a RENIX sender should read 0 ohms at empty, 44 ohms at half tank, and 88 ohms at full tank, though I can't find a reference for this in my 88 FSM.

Rush - Look man, he asked for guidance on getting a decent aftermarket or OEM fuel sending unit without saying what was wrong with his, I recommended some possible vendors for what the freakin' OEM and everyone else call a fuel sending unit and mentioned offhand the common failure modes I've seen in my area - wasn't implying his problem was the same, just what I see the most of. Things jumped the shark and you started telling me I had no idea what I was talking about / I returned the favor / we got in an argument because we were calling different subcomponents/assemblies the same thing, it seems. If I'd known WHY he needed a new one right off, this would have played out very differently, all I knew was he needed one somehow.

I could care less if I impress you (no offense, it's doubtful I would anyways), my point is that I'm not an idiot when it comes to electronics or as Pelican put it "have a lack of practical knowledge" ('scuse me, we're talking about a variable resistor here, this is first year crap, it aint rocket science unless everyone's using different terms to start out with!), nothing more.

BCM to non BCM fun... doesn't the 99 WJ use PCI bus as well, rather than CCD? That plus a 97 TJ instrument cluster would get interesting, I've worked with CCD but haven't dug into PCI yet, haven't needed to.

 

[magimerlin]

Just a ? For the OP. How do you know it is a 20 gallon tank? Both tanks, the 13 and 20 gallon are both identical in outside dimensions. It's the inside tube that limits dome to 13 gallons. And befor anyone ?'s me I changed out both my 89's from 13 gallon tanks to the 20 gallon ones so I'm not speculating here.

But back to my question for the OP. Did you replace the tank to the 20 gallon, and or did it use to take 18-20 gallons to fill and just recently started taking less to fill according to the gauge saying it's empty.?

 

[Rush Power Systems]

“Honestly, what I'd have to suggest (if the pot can't be cleaned up or otherwise rebuilt) is to get one that isn't FUBAR and clean it up, swap it in and call it a day. I'm surprised there aren't any in the local junkyards, around here I'm lucky to see one RENIX in a month go through the you-pull but I'd heard that they were still a lot more common down in TX/the rest of the south/southwest. Fairly easy to test at the junkyard before buying, put your ohm-meter (preferably analog for this, it's easier to see a needle twitch than a slow-updating DMM screen...) on 200 ohm scale, sweep the float arm from one end to the other slowly, make sure the needle moves smoothly and doesn't twitch around. IIRC, a RENIX sender should read 0 ohms at empty, 44 ohms at half tank, and 88 ohms at full tank, though I can't find a reference for this in my 88 FSM.”

So then, what I was saying in the first place.

“Things jumped the shark and you started telling me I had no idea what I was talking about”

No that happened when you started offering non-relevant advice.

See this is why we keep our EE’s on a very short leash, here is the thing, most EE’s, speaking from experiences, are more interested in showing you what they know than solving the problem. For instance, the Steves, Wozniak knows his sh*t, but without Jobs he is just a guy in his garage b*tching about Microsoft steeling his ideas. Ironic since problem solvers around the world have built a OS that is much better than both A & M in every way with the exception of the fact that they are a square peg, in a round Microsoft holed world.

The reason my office is so far away from engineering dept., is that techno nerds get on my nerves, we are developing computer controls for a Fisker style bike with 4 alternators, every day I need to say “yes that is a great idea but the customer needs the proto-type finished first.

Bottom line - OP wanted a problem solved and not info on your experience on rusted tubes. just saying.

 

[Rush Power Systems]

Just a ? For the OP. How do you know it is a 20 gallon tank? Both tanks, the 13 and 20 gallon are both identical in outside dimensions. It's the inside tube that limits dome to 13 gallons. And befor anyone ?'s me I changed out both my 89's from 13 gallon tanks to the 20 gallon ones so I'm not speculating here.

But back to my question for the OP. Did you replace the tank to the 20 gallon, and or did it use to take 18-20 gallons to fill and just recently started taking less to fill according to the gauge saying it's empty.?

:rof: too busy with the pissing match to think of that, good question.

 

[Pelican]

"God, I love the smell of napalm in the morning."

Kastein, I'm assuming that you perceived the irony in my post. Thought I would try to sort of get the dust bunnies out of the closet.

 

[Rush Power Systems]

"God, I love the smell of napalm in the morning."

Kastein, I'm assuming that you perceived the irony in my post. Thought I would try to sort of get the dust bunnies out of the closet.

Oh how dramatic, what are you guys dating? “stop picking on my BFF!”