In the process of diagnosing various non functioning gauges I’m now at the fuel gauge. I’m pretty sure it’s the fuel sending until that needs replacing. I’m going to also tackle the pump as well since it’s there and I would rather not do it again later.

I was expecting fuel line quick connects and not hose clamps for the fuel lines per the pic. Are the clamps an acceptable replacement?

Also, the car is an 83 Z28, but the engine is a 93 LT1. Which year would I need to shop for the replacements? 83 or 93?

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None of that is supposed to be there. There is not supposed to be a hole in the trunk like that. That's a big mess and the tank should be dropped, the panel welded back in correctly and painted/undercoated and the entire sending unit replaced with one that hasn't been cut up.

GD

 

did someone clobber on that bolt on retainer ring,or did later tanks have that?-looks like a later sender for sure.

 

That would be the preferable method for sure but since it’s already there, why drop the tank? Is there more that I need to replace that isn’t accessible with the cut out?

I’m already planning to put a new sending unit/pump.

 

Structural integrity of the uni-body. That's one reason GM didn't put in an access panel. Rear end collision that results in the doors being jammed shut, and the fuel sender blasting out of the tank and soaking the interior...... perfect! It takes like 2-3 hours to pull the tank and put it back. Wouldn't you rather do it correctly than adulterate a new sending unit to fit that mess?

People should be slapped for $hit like that.

GD

 

I would much rather do it the correct way to begin with. I actually noticed the hatch while replacing the rear shocks.

However, doing the fuel pump stuff from the top is definitely faster. I can seal it up correctly post replacing. But if it comes to having to replace the fuel lines the tank is getting dropped either way.

 

I'm not positive, but that fuel sending unit may be correct for a 1983. I'm not convinced the hose clamps are wrong for a car that was originally carbureted. Either way they will work fine for a carbureted car, but if you have a high pressure in tank pump now those should be changed out.

Also, your fuel tank hatch access is not necessarily a problem. While there is a lot of general hatred toward the idea, nobody has ever come forward and provided any actual proof that is a real structural issue. Just lots of conjecture and opinion. Whoever did yours was sloppy and I would clean it up some personally, but that is your business and no need to turn this thread into another dumb war over fuel tank hatch doors. PM me if you want pics of one done right.

 

https://www.hawksmotorsports.com/82-...t-refurbished/

This link will clear up any notions of those hoses & clamps being factory.

There ARE access hatches done right, Tibo did the best job of one I've ever seen. Anything less than what Tibo did is more hazardous than having things uncut from a potential fuel leak perspective, no matter how many battles are fought in the "dumb war" over the subject.........

 

Definitely not carb’d now. I also haven’t had a problem with fuel delivery until this morning after I tried to start up after making some changes to my CAI. I didn’t hear the fuel pump when I turned the key and had a crank but no start. Since I don’t have a working gas gauge I figured now is as good a time as any to attempt fix both problems.

Instead of clamps, I need the plastic fuel line retainers?

From the top, without pulling it yet, the 93 sending units look like what is currently in there. Where would the differences show up? If I have the 93 compatible sending unit now, maybe that’s why the gas gauge isn’t functioning?

I can see why having a hatch cut out and taped back on isn’t ideal. I’ll look into the better ways to put it back together, post repair.

This is a 93 sending unit.

 

Looks like you have a plastic 4th gen tank and pickup (even easier to remove with it's flexible filler neck). Likely why your gauge doesn't work. Although I would be determining if that's a compatibility issue or a wiring problem because I doubt GM changed the sending unit specs significantly. Most of the time that's not the case and it's a wiring issue. You'll have to do more research and testing on that.

GD

 

It's impressive how people just rig stuff together with reckless abandon. They make hose clamps that are rated for EFI fuel pressure, but the clamps in OP's pics ain't them. Chances are pretty good the hose they used isn't rated for EFI pressure either. The sending unit lock ring that doesn't match or fit the sending unit is likewise questionable.

If it were me, I'd pull the tank completely, and replace it with an EFI tank with matching sending unit, and throw all the hacked up stuff in the trash where it belongs. That would also be the ideal opportunity to clean up the "access hole".

A bit of thought and a plan couldn't possibly result in a worse setup. What else did the previous owner hack up?

 

Definitely not a plastic 4th gen tank, you can see it's steel.

 

The sending unit and the lock ring are steel, but the tank I'm not so sure. Kinda looks plastic to me but for sure we need clarification. I just don't see that 4th gen sender fitting a 3rd gen tank and I haven't seen any 3rd gen setups that had a ring of studs and nuts.

GD

 

The plastic tank has a lock ring like the 3rd gen tank, I have 3 of them. The sending unit is also completely different. This definitely isn't a plastic 4th gen tank, it might be a 93-98 tank, I am not familiar with those

Did some quick digging on Rock Auto. It's probably a 93-98 tank. In the pictures of the sending units there is a lock ring like shown in the picture from the OP
https://www.rockauto.com/en/catalog/...assembly,10147

 

The connector as pictured below, has been spliced into the three wire sending unit.

Did 3rd gen cars have a 4 wire sending unit?

I have been finding all sorts of random crap on this car. It’s actually been a fun pandemic project.

I’m pulling the sending unit/pump this week. I’ll try to compare them to what’s out there and see if


it matches 93 sending units/pumps.

 

Went ahead and pulled it...

I’m not sure what I’m even looking at wiring wise. Seems pretty questionable.

It is a metal tank.

Also pretty sure it’s a 3rd gem pump.

 

Well there's no float unless you removed it so that's why the gauge doesn't work.

And the wiring is an absolute abortion. Rather than attempt to fix that, just put that in the fukcit bucket and start over.

GD

 

There was not a float. I don’t understand the wiring. Maybe the previous owner tried to replace the pump with one that did not match the sending unit?

Either way it’s all getting replaced. The question now is the what do I replace it with? A 93 sending unit/pump? It would seem pretty easy to match the existing connection on the car with a properly spliced harness.

 

Get the sending unit for a 93, it should have the correct ohm range for your gauge. Also get a pump for the same so it all works together. Wiring isn't that hard, but it looks like the connector on the 93 is different. You could make an intermediate harness to adapt from the body to the tank to make it plug and play. I might be able to make you one if I had a picture of the plug on the sender for the 93

looking at pictures of the sender, I don't think there will be a proper mating connector available. You're going to have to cut and splice the connector you need on the sender

 

Wow ... just ... wow. I am rendered speechless. Although after seeing what was outside the tank, I'm not all that surprised to see more of the same inside as well.

Generally, those are 3-wire. Sending unit, pump, ground.

You can get all the parts & pieces to make all the PED connectors at Mouser Electronics. The company name to search for is Aptiv this week I think. They're not cheeeeep by any means, but you can get EVERY bit of them: connector bodies, pins for the various size wire ranges, the silicone seals, etc. IMO well worth the price.

 

Guess I’m with GD and others on why someone would carve a hole in the car is pure laziness at the risk of safety. Would be hard driving that around knowing that is there

 

So the connector from the current sending unit is a 4 wire with three wires pinned , as pictured.

The connector under the tank requires the 4 pin connector. Can’t I just splice the old connector to the new three wire sending unit?

I will be patching the hatch with new sheet metal post fix. I’m paranoid now thanks to you guys, lol.


I’m also planning on running new rubber gas lines to the hard lines under the car.

 

Maybe. Gotta figure out what the 4 wires each do, and see if their functions are the same as the 3 on the other side. For instance, if there's 2 grounds.

 

Okay. Will the body wiring for the sending unit end up in the main wiring harness?

 

Eventually. It goes through the floorboard under the back seat and runs toward the front from there.

The info you need is all right there in the FSM for your car.

 

I actually just download the FSM. How does it compare to Haynes/Chilton?

 

Orders of magnitude better than Haynes or Chilton

 

The FSM is the most comprehensive manual made for these cars, and any other manuals don't compare. I wouldn't have been able to do half the work I've done on these cars without access to the FSM for my 88. All the information you need to right the previous owners wrongs (and unfortunately, it looks like theres many), is in there in the FSM.

 

I did some more digging today on my fuel pump/sender. The wiring appears to be spliced into the tail lights...is that even possible? I have a new pump/sender but this wiring thing is getting really confusing.

 

Any idiot can splice anything to anything. Whether it will function properly is another matter entirely.

Shake your head in wonder, get out your FSM, look up how it's supposed to be wired, and put it back right.

 

I am looking at replacement fuel line/connectors on Amazon. Is there an advantage to nylon lines vs. rubber?

 

The nylon ones are more long-term durable and less likely to fail, if installed under no stress trying to bend them or whatever. They can be shaped easily with one of those spring type tubing benders and a heat gun.

Another option you might want to consider is PTFE AN line. It may be possible to put that over whatever hose nipples you have to work with.

But in the end, there's nothing wrong with the rubber type either, as long as lengths are short and you use the right type.

 

* was not a thirdgen sending unit...

* Just re-pin the 3 wires on the new sending unit to match the body connector; better than cut/splice IMO.

Your car was originally a carburetor car,..... that means the original fuel tank sending unit only had 2 wires. A voltage wire for the fuel pump had to be added and there is no telling where the P/O might have pulled that voltage from. Most people would 'tap' into voltage @-or-near the fuse box for a relay and then run the relay "out" wire for pump wire thru the 'body' harness, then thru the body to the tank ( along with the original PINK sending unit wire )

The original wiring for the tank (gauge) in your ride = a PINK wire ( probably PURPLE wire at sending unit ) that would have run down the drivers side kick panel, thru the 'body' harness, then thru a hole in the body near the drivers side taillight, then under the car where it clips to the body/frame-rail and then connects to the factory sending unit harness at the corner of the tank. The ground (BLACK )would also pass thru the body in the same place and get screwed to the body inside the car (under rear drivers seat bottom IIRC, maybe on the back body panel,.... can be screwed anywhere and will be fine.) The fuel pump wire (relay-to-tank) is shown as the GREY wire in 4th gen schematics.


Factory wiring for Carburated car.....


Clamped rubber fuel lines are NEVER recommended for Fuel injection due to the 'high' pressure the fuel injected fuel pump produces. No big deal with 6-8 pounds of pressure MAX from a Carb fuel pump, but a different story when dealing with 45+ pounds of pressure from a Fuel injected fuel pump. (While not perfect, I'd use all metal lines and compression fitting before using clamped rubber for the 'main' fuel line.) Will a clamped rubber line work,... Yup; but I would not advise it and recommend that you carry a large fire extinguisher in the car at all times.