That too. Looking at the parts reference Rock Auto has for the fuel pump module, I think the 19420859 module for the (later / FFS) left tank is compatible from 2003-2006 but they have no GM part #s for the sending unit. So my gut tells me the 19421094 sender kit might fit neither of yours NealinAZ.

But you might take a peek behind the heat shields and see if the access panel for the tanks are visible in front of the rear wheels, because some parts references show 2003 having early and late fuel systems. So perhaps this is something GM changed mid-model year, or only used with certain option packages - i.e. 'EXCLUDES FFS OPTIONS' from the description you posted previously.

 

If your 2003 VIN is after 35114929, you have the new system.

 

Woohoo (I think), my VIN is earlier! Thank you Sir!!!

 

Oh, bummer! That sux!

 

I've never seen it before, but she reads over the full mark now! =D

In all wasn't bad. Left the front tires on the ground and lifted the rear up until the tires were about 2" off the ground. Then blocked up under the frame jack points and left some weight on the jack under the diff carrier. I lost no fuel from the right side, and about a gallon from the left with the gauge pointing to the second red mark to the left - the dic was complaining about low fuel. Was a bit messy doing it with the front lower than the rear because the fuel wanted to run down the inside of the metal shield and dump out on top of my stack of wood under the jacking point.

Not sure if I missed it mentioned somewhere, but the float arm on the right sending unit is of a different design than the left. I just swapped it into the new sending unit. Original right arm on top.



Full res here

Now swapped, notice how the float on the right side arm is pointing outward.



Full res here

The left side was a bit of a challenge - couldn't manage to get it in the tank with the sending unit attached. Also highly recommend replacing the inlet sock - look how nasty mine was.



Ful res here

About 3 hours start to finish.

I noticed both of my old sending units were of the same design as oelarse posted here, so these "junk" senders were still being used in 2001. When I swept the right one from empty to full I could feel it "catching" and the DMM jumped to infinite briefly between what I would estimate was 3/4 and 7/8.

I'm actually somewhat curious what a newer design sending unit looks like, and might actually drop some coin on one for a 2008 or newer just to compare size and shape. If they're essentially identical and all that needs to be done to make them work is swapping the float arms, I'd do that just for "fun".

To everyone who's not installed this newer fuel sender, I'd say to not waste money on Techron as there's nothing it's going to do to resolve a mechanical problem with the contact segments.

 

Back in 06 mine read 5/8 to 3/4 at a full tank. Used Sea Foam from the parts store, never had problems again and used Texaco back in the day. Now periodic Sea Foam treatment and all is well. 120 k on my 98 coupe.

 

NealinAZ - to address your question about fuel line tools, my 2001 had toolless quick disconnects. The kind you release by squeezing the clips together with your fingers. I hope yours is similar - I'm sure this saved me a ton of time.

If yours ends up being one equipped with the FFS fuel system and you do indeed end up replacing the senders, I'd greatly appreciate it if you'd post pics of the senders. It looks like the newer C5s and C6s all call for GM 19420828, but switched to GM 19420830 from 2007-2013. They look to have the same mount and housing and the float arms look identical as well, so I'm curious what the difference is considering the newer part is $30 less. Looking at the best pics I can find of them it looks like the way they attach to the pump housing is different from the older style, so transplanting one into a pre-FFS car seems a no-go, but I still might buy one just to experiment with.

Here's what a couple of the segment contacts look like from one of my old senders under magnification.



Full res here

What's causing these to give false readings is the contact material (presumably silver) is getting smeared by the bead of the wiper, creating an electrical bridge between the segments. Each segment has a fixed resistor value connected by the traces on the PCB, with "full" being about 230 ohms, and empty being about 40 ohms. When a bunch of them become bridged the realized resistance is reduced.

I'm not big on additives, but evidently they do help. My guess as to why is because they're adding detergent type agents that help carry the metal bridging away. That said, if you add up what's spent on additives over 6-7 years I'd rather use that $ to put a new part in. Especially if that new part will be problem-free longer. I think the whole idea of this being caused by sulfur contamination was a smoke and mirrors campaign by GM to avoid paying a bunch of warranty claims.

I'm of the mind that GM eventually perfected the construction and composition of the contact surfaces, because I'm responsible for numerous 2006-2013 GM vehicles that have never had fuel gauge issues and have never been fed a drop of any kind of additive. Most have been filled almost exclusively with 87 or 89 octane mid-tier swill.

 

I am replacing a right fuel sender on a 1998 C5 and the original was a 3 wire and the one you are speaking of is a 2 wire, i just bought one part # 19421094, what did you do or your original was a 2 wire?

 

All ours were 2 wire sending units. You might post a pic of what you have.

 

@bkorecky looking forward to seeing those comparison pics.

I should be doing my '99 next Sunday. Not sure if I'll run into a similar scenario (three wire vs. 2). I'm just waiting on new gaskets from Racetronix. I've seen many have been able to use the original gaskets and bolts without issue. However forum member @tabbruzz found his gasket rotted and cracked into two pieces when he pulled his sending unit. I'm not taking any chances. So waiting on the gaskets.

 

Curious how you guys are reducing the fire risk? That's the only thing that's worrying me.

 

This is my original right side sender stripped. On the left you will notice the three connector pads. My new one is in the car, it came with the 3rd pad but no resistor, sorry can't compare but also notice on my old sender there is a resistor under the #3409. Green thing. It is 240 ohms. I am going to add an inline 240 ohm resister to the 3rd wire, Searching this forum for days i found one line stating that the 3rd wire talks to the other sending unit so the resistor has to be there for gage accuracy. My gage works now but it is on reserve with the needle just below the top red line. I did have to take the float off the new RockAuto unit and use the original and just re soldered the old harness to the new unit. I would like to make a small extension harness with the resistor in it rather than splitting the wires apart but that will be based on finding original connectors. As far as fire prevention i just got as much fuel out by driving as i could.

 

Whenever I work around gasoline, I do two things at my shop: 1) shut the main breaker off to the shop and 2) lock all the doors into the shop from outside. No sparks and no one can come in with something burning. In addition I have halon extinguisher next to me, ready to go.

 

That third contact pad does throw a bit of a monkey wrench into the works. That's annoying.

 

I don't have a FSM for anything older than my '01, but it's entirely possible it's not connected to anything on the PCM side. Just speculating.

Even if it is (connected to something), it's evidently a simple fixed resistance value. But I'd love to know how bkorecky's setup would work as-is without adding an in-line 240 ohm resistor.

 

I did start the car briefly to see whats up without the resistor. Gas gage cycled fine and read correctly but tanks are pretty much empty. No codes. As a kid i tried to redesign GM many many times over different issues and all i learned was don't assume and hang parts and i am not smarter than GM. Before i started this repair i verified fuel transfer and will still cary a few gallons for the first couple tanks after complete. Connectors are very expensive so just going to splice the resistor in line. The hardest part was peeling back the tape and the wire is the bottom pin on the connector when connected..... dark with a white stripe. I ordered resistors a few hours ago from ebay for $4.06 and got 80 of them so if in need ---- let me know! I'm thinking mid to late next week for testing weather dependent.

 

Looking forward to your debrief. Good luck!

 

Has anyone ever tried the reprogram the PCM #02-06-04-010A (06/27/2003) for erratic fuel gauge reading. Didn’t know if this would be a waste of money at a dealership or not. My gauge only ever goes to 3/4 at fill up than drops until you reset it again. Don’t know if the jet pump is even transferring fuel, so I fill up every 200 miles

 

That's probably not going to fix it but it might indicate closer to 7/8ths. I certainly wouldn't trust the clowns at the dealership to lookup and flash a 20 year old TSB.

You need a new sender, maybe both.

Edit: Sorry if I missed it, what year is yours?

 

Thanks it’s a 2000 M6