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This pic was taken key on, engine off, after adding back the 2-3 gallons I'd drained. As you can see, it seems to be working. Gas station next, weather permitting......
OK, SUCCESS......I think. I went to the gas station, left key on, and when filling the gauge moved nice and smooth, until 1/2 full. It stopped at 1/2 full for maybe 6-8 seconds as I kept filling. Then it started moving nice and smooth from 1/2 to full. HOORAY!! I attribute the brief stoppage@1/2 full to the fact that the right side was empty, and the jet pump/equalizer tube had to do its "thing" before the gauge could move again. However, at no time was the needle erratic. When I had the wrong float arm in, it would only go to 5/8-3/4 full, then after 20 miles of driving it finally went to full, and stayed there. Real test will be when I drive it 100-150 miles, but all seems well. I'd love to clean up the mistakes I made, edit some posts, and have a sticky made. But realistically, I think we now need to see what can be done to help the '97-'99, or whatever years need that resistor. Then the sticky would be ready. One thing I did prove is you can't use the left side float arm on the right side sender on a 2000 model! You were correct in thinking you didn't like the way it looks, and you were right. Thanks so much for all your help @spfautsch
Thanks, Mr. Black. You helped a lot, too. If I had any additional advice to give, it would be do one side at a time, and think things through CAREFULLY. I thought I did that, but still got mixed up somehow......
Yes, Rock had just one, so the other came from GM Parts Direct. They are identical part numbers. I used both of my old floats. I got the old ones out last night for pics. Today I got the meter out, set it to ohms, and connected alligator leads to the meter leads and cgecked both the old senders. They seem to work fine, with ohms/resistance changing in a fairly linear pattern on each sender. For the Hell of it, I reversed polarity on each sender. Made no difference in readings. Now, how the PCM sees things, IDK. If one side is reversed, and the other isn't, does that make a difference? IDK that, either. The shop manual doesnt address my stupidity/confusion/hypothetical situations!! I got about 43 ohms at "empty," and 198 at full. Interestingly, that 198 ohm reading was actually at about 3/4-7/8 travel. Going higher with the travel resulted in the ohms going to an entirely different reading, like maybe .26? It didn't change from there until the float ran out of travel (brim full tank). I attribute this as the reason why the gauge reads full in most any car for 80-100 miles, then the gauge will start dropping quicker in the next 100 miles. Meaning what we all know, that when your cars gauge reads 3/4 or 1/2 tank, it's really a bit lower than that, because the gauge won't move for the first 100 miles or so. Hope this all makes sense. If you read my earlier post, I mentioned I "cheated" a bit, because the left/fuel pump side was giving me trouble. So I just changed the sender on that side, and reinstalled the unit. The sender seemed to move freely, though, in both sides. Hope this all makes sense....
The reason it switched from 198 to .26 is because you were using an auto-ranging DVOM. (Digital Volt Ohm Meter) It will display the reading using the lowest scale and will automatically change up to the next scale when the meter limits are reached. Your meter has scales for 200, 2,000, 200,000, and 2,000,000 ohms. Once it exceeded the 200 ohm scale, it switched to the 2,000 scale and displayed 260 ohms as .26k ohms. You probably did not notice the small "k" next to the reading. (.26 x 1,000 = 260) Just like money, the k means multiply by 1,000, and M means multiply by 1,000,000.
If it exceeds 2 million ohms resistance, it will display OL, OFL, or I on the far left of the display. This means the resistance is more than the meter can display, so it is Over Limit, Over Function Limit, or Infinity, depending on the meter brand. They all mean the same thing. (This is the exact opposite of a 0 zero reading, which means there is NO resistance and there is continuity.)
The meter should also display the OL, OFL, or I when you first put the meter in the Ohms function. This is an open circuit reading. If you touch the leads together, it should display 0.0 or maybe a couple tenths of an ohm such as .3. Anything more than that and there is a problem with the leads or possibly a low battery in the meter.
Always happy to help anyone willing to help themselves!
Keep us posted. Now that I know you have a lift I'm going to make it my mission to badger you until you buy some kind of scan tool. :-) These 20+ year old cars are more computer than machine.
I think the 97-99 folks would be best served by splicing in a 240 ohm resistor outside the bulkhead connector. I know something like that would be frowned upon by originality purists, but I'm not very confident any old resistor would survive submerged in fuel, especially ethanol blended fuel.
Always happy to help anyone willing to help themselves!
Keep us posted. Now that I know you have a lift I'm going to make it my mission to badger you until you buy some kind of scan tool. :-) These 20+ year old cars are more computer than machine.
I think the 97-99 folks would be best served by splicing in a 240 ohm resistor outside the bulkhead connector. I know something like that would be frowned upon by originality purists, but I'm not very confident any old resistor would survive submerged in fuel, especially ethanol blended fuel.
I agree about submerging "any old resistor" in fuel for a long time!!
The reason it switched from 198 to .26 is because you were using an auto-ranging DVOM. (Digital Volt Ohm Meter) It will display the reading using the lowest scale and will automatically change up to the next scale when the meter limits are reached. Your meter has scales for 200, 2,000, 200,000, and 2,000,000 ohms. Once it exceeded the 200 ohm scale, it switched to the 2,000 scale and displayed 260 ohms as .26k ohms. You probably did not notice the small "k" next to the reading. (.26 x 1,000 = 260) Just like money, the k means multiply by 1,000, and M means multiply by 1,000,000.
If it exceeds 2 million ohms resistance, it will display OL, OFL, or I on the far left of the display. This means the resistance is more than the meter can display, so it is Over Limit, Over Function Limit, or Infinity, depending on the meter brand. They all mean the same thing. (This is the exact opposite of a 0 zero reading, which means there is NO resistance and there is continuity.)
The meter should also display the OL, OFL, or I when you first put the meter in the Ohms function. This is an open circuit reading. If you touch the leads together, it should display 0.0 or maybe a couple tenths of an ohm such as .3. Anything more than that and there is a problem with the leads or possibly a low battery in the meter.
I am now showing slightly under the 3/4 mark. So all seems well. Won't know more for awhile, due to Vararam install, and relocating an oil cooler.......
I'm going through similar sender checks. The info I found and how I interpret the fuel system is as follows:
-From empty then filling, the DS tank will fill first.
-Once DS tank is full, fuel passes through crossover tube into PS tank.
-Once PS tank is full, pressure backs up and clicks the pump off.
-Unless the car is running, there is no fuel transfer or siphoning done by PS tank. PS tank is only siphoning into DS tank when car is running due to DS pump supplying fuel to PS siphon jet.
-0-1/2 on gauge is DS tank being full. 1/2-full on gauge is from the PS tank. When both senders are at max resistance = tanks full. When DS is "full" and PS is "empty" then gauge reads 1/2.
-By normal operation, DS tank must always read full regardless of PS tank level. If DS tank reads less than full AND PS tank shows anything above "empty" then CEL should come on. This means the PS is not siphoning fuel correctly or a sender issue. PS tank must read full down to empty BEFORE the DS tank can begin to read full down to empty.
-Pins B/C on the yellow bulkhead connector is the sensor wires to read resistance (dark blue and light blue on DS/PS respectively) Normal range 40-250 Ohms
I'm going through similar sender checks. The info I found and how I interpret the fuel system is as follows:
-From empty then filling, the DS tank will fill first.
-Once DS tank is full, fuel passes through crossover tube into PS tank.
-Once PS tank is full, pressure backs up and clicks the pump off.
-Unless the car is running, there is no fuel transfer or siphoning done by PS tank. PS tank is only siphoning into DS tank when car is running due to DS pump supplying fuel to PS siphon jet.
-0-1/2 on gauge is DS tank being full. 1/2-full on gauge is from the PS tank. When both senders are at max resistance = tanks full. When DS is "full" and PS is "empty" then gauge reads 1/2.
-By normal operation, DS tank must always read full regardless of PS tank level. If DS tank reads less than full AND PS tank shows anything above "empty" then CEL should come on. This means the PS is not siphoning fuel correctly or a sender issue. PS tank must read full down to empty BEFORE the DS tank can begin to read full down to empty.
-Pins B/C on the yellow bulkhead connector is the sensor wires to read resistance (dark blue and light blue on DS/PS respectively) Normal range 40-250 Ohms
When I did mine a couple weeks ago, when I drained the tanks, each side had about 1-1/2 gallons, totalling 3. There was a bit more in drivers (left side) side. Maybe 2 gallons to 1 on right side. Of course, it had sat overnight. So I'm thinking as the car sits for several hours the tanks equalize. As I mentioned to @Mr Black , this runs contrary to what I've always been told, and heard about C5 storage protocol. That would be to never store the C5 long term with less than 1/2 tank of fuel. But if they equalize, as it appears they seem to do, it wouldn't be as critical as everyone says. However, I've always stored vehicles with a full tank and gas preservative/Star-Tron/Stabil, etc., mainly because empty fuel tanks promote condensation. Just a good rule of thumb. My .02.....
Hi guys!
I´ve been following this thread because I have the same issue. The meter works fine from half tank and down but not from full to half.
Ordered this fella GM Genuine Parts 19421094 but i lacks the Ohm resistor ´cause I have a -98.
So my question is. I get it´s a 250 ohm I must have but what is the voltage of it?
Someone soldered it to the yellow cable outside the tank. Anyone got any pictures or instruktions on that?
Resistors aren't necessarily rated for voltage, but rather how much power (in watts) they can safely dissipate. I think 1/2 watt would be sufficient but would defer to user bkorecky as he seems to be the only one here that's done this. Also, I believe he used a 240 ohm resistor.
As far as hookup, it simply needs to go between the blue and yellow wires. There's no polarity to worry about so that's really it.
i have a 2006 zo6 and i need to change both fuel sending units....
is there a part number for both left and right fuel sending units that are for a 2006... everyone i find says 2007-2013
im wondering if i can just change the plastic piece off new arms with the wipers and use my old sensor or maybe cleaning the sensors would work...
Doesn't seem common that BOTH sending units go bad. IMO I would confirm 100% that they are in fact bad by back probing the signal wires before taking anything apart.
Doesn't seem common that BOTH sending units go bad. IMO I would confirm 100% that they are in fact bad by back probing the signal wires before taking anything apart.
i got codes for both tanks… i’m doing a clutch soon
so i wanna change both sending units while tanks are accessible
I got about 43 ohms at "empty," and 198 at full. Interestingly, that 198 ohm reading was actually at about 3/4-7/8 travel. Going higher with the travel resulted in the ohms going to an entirely different reading, like maybe .26? It didn't change from there until the float ran out of travel (brim full tank). I attribute this as the reason why the gauge reads full in most any car for 80-100 miles, then the gauge will start dropping quicker in the next 100 miles. Meaning what we all know, that when your cars gauge reads 3/4 or 1/2 tank, it's really a bit lower than that, because the gauge won't move for the first 100 miles or so. Hope this all makes sense. If you read my earlier post, I mentioned I "cheated" a bit, because the left/fuel pump side was giving me trouble. So I just changed the sender on that side, and reinstalled the unit. The sender seemed to move freely, though, in both sides. Hope this all makes sense....
