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* Back in 2010, I upgraded my fuel pump the to the Racetronix 255LPH with hotwire kit. Immediately after the change, the gauge was inaccurate when I took it for a test drive. It eventually became usable near empty but full was at 3/4.
* Then in 2015, I paid a dealer to diagnose why my fuel gauge was inaccurate and provided a spare NOS OEM float arm if needed. They only replaced the arm and didn't diagnose anything, so I no longer trusted them. No change in gauge behavior.
* Sometime in the past, the same dealer replaced a failed PCM. They loaded the latest GM calibration, I downloaded it, and uploaded the needed changes for the car to run. Comparing the fuel tank tables in the calibration, they are stock.
* October 2020, I found this thread (https://ls1tech.com/forums/fueling-i...get-ready.html) and I bought the 1998 kit (http://www.ws6project.com/user_stor/...oducts_id=6821) with the 255LPH pump to just to try the gauge fix. It sat in the shipping box for a year while I tried to find someone I trusted to install it.
* I dedicated a week of maintenance at a local shop that is very familiar with f-body's and part of the work involved was to install the above kit. After a $1000+ invoice (he has a high hourly rate and had to deal with some aftermarket suspension parts that made tank removal difficult) just for the kit install, the gauge behavior hasn't changed I left a message for WS6Store tech support but haven't received a callback yet.
I'm trying to do some research on what we can check/measure without dropping the tank again. I'm inferring that a '98 PCM is expecting a 0-90ohm output from the sender? I don't want to risk running out of fuel but I can get it close to E then measure the ohms, then fill it completely and re-measure. If the range is inaccurate at the purple & black connectors, then that would indicate a problem with the sender in the tank? If the range is accurate, then what? The shop is not looking forward to dropping the tank again nor am I ecstatic to pay a huge chunk of labor costs again; one shop question was the quality of the kit components (if they were ACDelco/Delphi vs some random crap). He claims he was careful installing the float arm. Since the problem began 11 years ago with the original swap, and continues with the new parts, I'm hoping it's something simple between the tank and the PCM.
I've got a crapped up fuel gauge and have read several threads over the years, and I think the 98's received the newer 40-240 ohm senders, although there's some debate on it. I ended up going w/ an ultragauge for fuel tracking until I decide to dig into mine.
I found a guy on the HPT forums that did this for his '02 about a decade ago. He still had his stock vs modified files to send me. Although not exactly the same, I think I've got the gist of it for the OEM fuel gage. I left the low fuel % and high AD count cells as they were so I hopefully their behavior doesn't change while I try to dial it in further.
Last edited by JimMueller; 09-12-2021 at 09:56 AM.
Owner granted permission to publish, but he doesn't want his name associated with the files. He says he never ran it down to E, but when it was completely full, the needle was directly on the F hash mark (not past it).
I'm curious if this is related to my issue?
On the old sending unit we pulled out about a week ago, empty is 40 ohms and full is 250 ohms. Gauge behavior remains the same after swap.
OEM Min AD count = 20, divide by 51 to get voltage = 0.40V
OEM Max AD count = 150, divide by 51 to get voltage = 2.95V
When I completely fill up the tank, the fuel sender output voltage is 2.27V which is only 116 AD counts, which says fuel volume is 11.6 gallons throwing off the gauge
On my stock tables, it doesn't reach 15.5 gallons until the AD count is 130 (2.55V)
I don't recall the Racetronix kit from 2010 including a different sender, but the whole kit I installed about a week ago included everything inside the tank.
Perhaps it's simply a different sender than it came with from the factory and I need to scale it for a different voltage range? Or else it's the same and I need to perform additional testing between the bulkhead connector and the PCM? Hypothetically, I suppose three different shops that each installed float arms over the past decade could have all gotten it wrong, but the gauge behavior has been consistently off.
Shbox had this blurb: To test back to the gauge, ground the purple wire on the body side of the connector back toward the gauge (key ON). The gauge should read empty. With the connector unplugged and no ground applied, the gauge should read full.
Last edited by JimMueller; 09-12-2021 at 04:50 PM.
I now have a draft Word document I could send you for your review to see if it makes sense. PM me your email address if you are interested in seeing it.
I've been logging my fuel level voltages every time I fill up to correct my fuel volume vs A/D count table. With the recent fueling kit swap, it appears the pump starves when making U-turns, and sputters a bit on straight-line acceleration, with 2 gallons remaining in the tank. Does that seem unusual? I also randomly get an EVAP code (although I've cleared it before noting the number) since the pump kit was installed.
I've pulled and changed my 98 fuel pump assembly too many times to count. First was Racetronix 255 fuel pump upgrade with harness. Next was Racetronix 340 fuel pump upgrade with upgrade harness. Last was the Racetronix dual 255 fuel pump upgrade with harness. During that time I have pulled and connected the purple fuel sender wires countless times and have never had an issue with fuel gauge level.
The 98 purple sender wires are polar neutral (doesn't matter if they get crossed). That said the purple wire connection plug ends are very small with small tangs to hold the plug end in place. The female ends easily bend to a point where they will NOT connect after insertion into the grey plug the connects to the underside of the yellow bulkhead connector that contains four male terminals.
Since this issue started after the initial harness upgrade, IMO, the issue was caused due to a faulty connection of one of the purple wire plug end terminals where the grey plug connects to the yellow 98 bulkhead connector. Or one of the pins in the yellow bulkhead connector coincidentally failed when unconnected or connected.
There are four male terminals on the yellow connector. Two pins are for the purple sender wires, a third pin is ground and the fourth pin for the pump.
In the Racetronix instructions the purple wires are NOT to be removed or tampered with. But if they were pulled out and reinserted it's very easy to reinsert but fail to assure that they SNAP into place and do not easily pull out (tangs on plug are bent). As a result the female plug ends don't mate with the male terminals on the underside of the yellow bulkhead connector. This happens frequently on coil plug ends and/or injector plug ends.
If it were me, I would start over with a new modular style bulkhead connector. Perhaps it has been the issue from the get-go.
Cut a hole inside the car over the tank and remove the fuel pump assembly rather than dropping the tank.
Remove the yellow bulkhead connector plug and replace with the newer style modular plug and harness.
IMO it is very difficult to install the 98 assembly back into the tank and not bend or dislodge the float arm. At the same time make sure the filter isn't pushed loose and the assembly hanger doesn't interfere with the metal divider on the floor of the rear of the tank. The metal divider keeps fuel from moving from the rear of the tank forward when braking. The pump draws fuel from the rear of the tank.
Never take the chance of running under a 1/4 tank of gas. Doing so will just burn up the fuel pump. Been there done that when I ran low on fuel on my 95 Z28. GM would NOT warranty it because I ran it low on fuel ( with less than 8K miles).
If you view the hanger assembly and the fuel pump location with the hanger in the tank, two or three gallons splashing around the bottom of the 15 gallon tank doesn't allow many inches of gasoline on the floor of the tank for the pump to draw fuel.
FWIW - I did find a terminal in a new grey plug I received from a vendor where the wire was NOT connected to the male pin. The wire obviously pulled loose when the wire and plug end were inserted into the plug.
The question with the hydramat is the form factor and if will attach to the pump and still not interfere the metal fuel divider on the rear bottom on the 98 metal tank.
- Any chance the EVAP code (whose number I forgot to document before I've cleared it) is related to drivability problems and/or premature fuel starvation symptoms?
- Neither me not the shop have any desire to use a trap door. I'd only pay a shop to install the trap door if they fully acknowledged they accepted any and all risk with the change (they won't). Yes, I understand others like the convenience. I won't do it.
- I'm using the drop-in kit linked below, which came with all new harnesses. I think I'll just order the replacement bulkhead connector. What could cause the fuel sender to send a slightly lower voltage range to the PCM compared to how it was shipped by GM? http://www.ws6project.com/user_stor/...oducts_id=6821
- I did watch the shop owner insert the new kit into the tank, they did appear to be careful and reviewed the part fitment inside the tank prior to mounting it to the car.
- I did run out of fuel once when the fuel system was completely stock, around 1998-1999. I don't recall doing so since then, I know it never stalled while making U-turns in the past except for when there was a loose ground on the back of the head. But the actual volume in the tank at the (miscalibrated) E level was more like 3-4 actual gallons of fuel remaining in the tank, so I had not let it get down to 2 actual gallons remaining in many years due to the gauge miscalibration. I also seem to remember that I could (albeit not recommended) drive the car down to E without it starving. I was able to drive from home near Orlando almost to Atlanta on a single tank of fuel (roughly 31MPG). I (mistakenly) expected the aftermarket parts to behave in the same physical manner as the OEM design.
- The suspension and tires are significantly improved over stock, perhaps the additional mechanical grip exacerbates an already known weak point in the OEM fuel system. Some people need to keep >1/2tank full during autocross, didn't expect to experience it at 2gal remaining on simple street maneuvers.
I did inquire about hydramat in the past... it never gained much traction and I didn't pursue it.
So my takeaways thus far:
- Don't let fuel volume drop below 3gallons (I'll set the gauge needle to read E at the 3gallon level)
- Replace the bulkhead connector. This will be completely plug and play even though it's a new style?
- Figure out what is causing the new (since recent fuel kit install) EVAP code and repair. Hopefully it doesn't involve dropping the tank.
- Any chance the EVAP code (whose number I forgot to document before I've cleared it) is related to drivability problems and/or premature fuel starvation symptoms?
- Neither me not the shop have any desire to use a trap door. I'd only pay a shop to install the trap door if they fully acknowledged they accepted any and all risk with the change (they won't). Yes, I understand others like the convenience. I won't do it.
- I'm using the drop-in kit linked below, which came with all new harnesses. I think I'll just order the replacement bulkhead connector. What could cause the fuel sender to send a slightly lower voltage range to the PCM compared to how it was shipped by GM? http://www.ws6project.com/user_stor/...oducts_id=6821
- I did watch the shop owner insert the new kit into the tank, they did appear to be careful and reviewed the part fitment inside the tank prior to mounting it to the car.
- I did run out of fuel once when the fuel system was completely stock, around 1998-1999. I don't recall doing so since then, I know it never stalled while making U-turns in the past except for when there was a loose ground on the back of the head. But the actual volume in the tank at the (miscalibrated) E level was more like 3-4 actual gallons of fuel remaining in the tank, so I had not let it get down to 2 actual gallons remaining in many years due to the gauge miscalibration. I also seem to remember that I could (albeit not recommended) drive the car down to E without it starving. I was able to drive from home near Orlando almost to Atlanta on a single tank of fuel (roughly 31MPG). I (mistakenly) expected the aftermarket parts to behave in the same physical manner as the OEM design.
- The suspension and tires are significantly improved over stock, perhaps the additional mechanical grip exacerbates an already known weak point in the OEM fuel system. Some people need to keep >1/2tank full during autocross, didn't expect to experience it at 2gal remaining on simple street maneuvers.
I did inquire about hydramat in the past... it never gained much traction and I didn't pursue it.
So my takeaways thus far:
- Don't let fuel volume drop below 3gallons (I'll set the gauge needle to read E at the 3gallon level)
- Replace the bulkhead connector. This will be completely plug and play even though it's a new style?
- Figure out what is causing the new (since recent fuel kit install) EVAP code and repair. Hopefully it doesn't involve dropping the tank.
I don't remember the DTC code either (0440 0446 maybe). However, immediately after installing the dual pump kit I got the DTC error.
Dah! Forgot to connect the harness that attaches to the vapor control solenoid just in front of the gas tank. A solenoid turns off and on to pull gas fumes/vapor from the gas tank and runs thru a line up to the intake manifold where it enters on the driver side of the intake where the gases are recyled thru the intake. Make sure the electrical connection is secure at the solenoid and that the vacuum line is connected at the manifold vacuum port as well (driver side front - can't miss it). The vacuum hose has silver heat tape on it.
This is what the harness will look after removing the yellow bulkhead connector harness. The fuel pump harness below will plug into the modular style yellow connector. Don't remember which but one of these plug ends plug into evap cannister on front of thank. Would take a pic for you but car is not on the lift. Pretty sure it is the middle plug end.
Or you might have a cracked seal on the gas cap.
HTH
Stock bulkhead connector harness that controls the pump and fuel sender. Note the purple wires for the sender.
Last edited by dlandsvZ28; 10-06-2021 at 08:59 PM.
Reason: edit content
Sorry for my lengthy posts. I didn't look closely at the pics of the kit you received from the WS6 store. That kit is different than the stock kit.
If those pics are correct, then you already have the newer style upgraded modular yellow plug with an upgraded harness that plugs into the yellow bulkhead connector.
So if you already have the upgraded yellow modular bulkhead connector then doubt it is the issue. In order to replace it you have to drop the tank since the yellow plug is secured with a press fit clamp on inside of the tank. That said there t still might be a wire connection issue inside the tank if the full and empty sender wires are crossed (see pic below - easy to make a mistake).
Is there a way you can check the ohms from the terminals on the plug and also on the two external purple wires on the harness that connects to the yellow plug?
I wrote myself some instructions as an aid if I ever had to remove the dual pumps. It identifies each plug on the yellow connector (in tank side and atmosphere side).
I have sent you a PM containing those instructions.
Some of the wiring instructions in it refer to the modification necessary because the harness to the yellow plug was changed. Pay attention in the instructions when it refers to the terminal on the full side of the sender and the empty side of the sender on the atmosphere side.
If the harness is similar to my dual pump harness, then also pay attention to the modifications necessary to attach the full tank side and empty tank side where the harness attaches to the bulkhead connector on the panel just aft of the back seat near the brake lines.
Note in pic below: even though the tank side purple wires are not polar specific, there is a full side purple wire and empty side purple wire from the sender. The full side goes into the full side slot on the connector and the empty side plugs into the empty slot on the underneath side of the yellow plug.
If those wires are crossed either on the inside of the tank or outside atmosphere side (as explained in my instructions) verify that they are routed correctly. As a precaution, I would examine each plug end as well to confirm that the wire end hasn't pulled loose from the plug end.
Last edited by dlandsvZ28; 10-07-2021 at 09:52 AM.
Reason: edit content
I already ordered a pair of the bulkhead connectors (without harness) from Racetronix, but that's okay, they'll sit with the rest of tons of spare random parts I've collected. I thought the connector I ordered was what the harness connected to on the rear floor pan. I know where the EVAP solenoid is near the driver fuel rail connection.
The shop that did the work is is very backed up and getting my car on the lift there is quite the ordeal, so hoping any quirky remaining behavior is resolved without dropping the tank again (or even taking the car back to them). Also don't want to be in a finger pointing match between parts provided by WS6Store and quality of labor.
I know how to measure the ohms with the pump assembly out of the tank, but I didn't think to measure it on the new kit before installation. I measured it on the kit we removed and the swept range is 40-250Ω. I also found the link below which lets you measure the resistance at the floorpan connector, but it's technically for a '95 F-body, unsure how the 98's may differ.
I'm making good progress on recalibrating the fuel tank tables. I'm more curious than anything on why I need to change them at all. I'm guessing an original GM part that came on the car is no longer available, and the 'stock' replacement has a different output range which is incompatible with the stock PCM tables. I've tweaked the gauge to show 3gal remaining at E that will hopefully minimize running too low on the street. I can't do much about accurately scaling gauge levels below 3gal though.
I already ordered a pair of the bulkhead connectors (without harness) from Racetronix, but that's okay, they'll sit with the rest of tons of spare random parts I've collected. I thought the connector I ordered was what the harness connected to on the rear floor pan. I know where the EVAP solenoid is near the driver fuel rail connection.
The canister vent valve is near the front of the bottom of the gas tank. I named it wrong in above post.
The harness that connects to the top of the fuel assembly includes two wires and a plug that branches off from it down to the canister vent valve. That short harness plugs into the canister vent valve. See harness in previous post. It's easy to forget to reconnect or it has come loose. The plug connects on back side of the canister.
You can see the vent valve in the pic below. Hard to see in mess of wire harness's and fuel line.
You might call Lonnie's and ask if the instructions to change the fuel tanks values is correct. Last time I talked to him, he wasn't very impressed with aftermarket fuel assembly's and suggested I keep what I have if it wasn't broke. 98's are one of a kind.
As you can see in previous pic - the sender in the tank is pretty simple. Just sweeps back and forth and as the float rises and lowers. I can't see the resistance face of your sender, but the rest of the sender looks nearly identical to the sender on my swing arm. If there is a change in resistance it would be in the wire as the arm move up and down.
As you can see in the pic. The swing arm is not secured in place. It secures by snapping into the plastic tabs on the sender.
This is what the original harness and plug looks like on the stock 98 fuel pump filter assembly. It provides power to the pump and sender. The yellow plug will melt and short out if a bigger pump requiring more amps is installed.
Last edited by dlandsvZ28; 10-08-2021 at 01:44 AM.
Reason: edit content
My guess at this time, is that the '98-specific kit' I bought has the wrong fuel sender on it (just like what I received with the Racetronix kit back in 2009ish). I'll deal with it in the calibration and perhaps see if I can find the correct sender for the next time we're in the tank.
Edit: The EVAP code I'm receiving is P0452. I broke out my Helms manuals and searched around. I located the vapor canister behind the driver wheel well and the vent valve forward of the tank. I didn't try reseating any connections due to poor arm clearance but both appeared to be connected. I'll add it to my list of things to chase... I do have a new vent valve on hand but not a new vent canister.
Last edited by JimMueller; 10-13-2021 at 02:11 AM.
09-07-2021, 06:22 PM
Help with fuel gauge level 
I left a message for WS6Store tech support but haven't received a callback yet.
