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Fuel guage reads "0" after fuel pump swap- a few questions

Old 01-11-2018, 05:41 PM
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Default Fuel guage reads "0" after fuel pump swap- a few questions

Hi all,

I pulled my sending unit to swap fuel pumps. While I was at it I also replaced the wiring with new wiring from Racetronix. After reinstalling, the fuel gauge reads completely empty (no lines) even though there is a half tank. Would that indicate that the purple wire is broken/not connected? Or is this some type of ground issue? The gauge worked fine prior to this.

I used a butt connector and it appears to have an okay connection when setup but obviously something isn't right. I have the sending unit out of the car at this point and have inspected but didn't see anything obviously wrong. Thoughts?
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Old 01-11-2018, 09:19 PM
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Originally Posted by qwiketz View Post
Hi all,

I pulled my sending unit to swap fuel pumps. While I was at it I also replaced the wiring with new wiring from Racetronix. After reinstalling, the fuel gauge reads completely empty (no lines) even though there is a half tank. Would that indicate that the purple wire is broken/not connected? Or is this some type of ground issue? The gauge worked fine prior to this.

I used a butt connector and it appears to have an okay connection when setup but obviously something isn't right. I have the sending unit out of the car at this point and have inspected but didn't see anything obviously wrong. Thoughts?
and sure enough with it out of the tank it works fine.... Time to try reinstalling it...
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Old 01-11-2018, 09:49 PM
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I cant offer any advise, but I am about to swap my fuel pump and would like to hear what ended up being the cause of the malfunction.

I am also using the racetronix kit.

On a side note, did you swap pumps as an upgrade or was your pump failing?
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Old 01-11-2018, 10:15 PM
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The restaurant escape is great but mine is a custom set up with a walbro 465 pump. Yours should be plug-and-play .

The weird thing with my sending unit is that when it's partially in the tank, the fuel level float works. When it is all the way and it goes completely to zero which is kind of the opposite of what I would expect to happen . If I push it too far I would kind of think that it would read artificially high
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Old 01-11-2018, 11:15 PM
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When the fuel gauge indicates "0", that means the car (CCM) is seeing a low resistance or short to ground. Sounds like two points might be toughing as you move the unit around.

You might try disconnecting the power connector and connect an ohm meter across the fuel sending unit so you can monitor the resistance as you move it around. If all is good, check the power connector and wiring.
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Old 01-12-2018, 12:43 AM
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Thanks! Got it figured out. There was a black wire on the outside of the sending unit that I was grounding causing the gauge to read zero. All is well now
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Old 01-13-2018, 04:27 PM
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update....

so the gas gauge works now that the black wire outside the sending unit is not grounded. However the pump isn't working because now it's not grounded. I must have done something wrong here.

Last edited by qwiketz; 01-13-2018 at 04:29 PM.
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Old 01-14-2018, 09:32 AM
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You may want to consider popping the pump out (you have done it a few times and see how easy it is) and rig up a "bench test" of some sort running wires and using the actual harness.

Yss, the purist freak when you lay the pump on your car, but the only (real way) to check the integrity of the WHOLE system is by testing the WHOLE system together. You simply just must "plug it in" to see if the fuel gauge, mote spins and ground work.

A bunch of alligator clips will be your friend.
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Old 01-31-2018, 10:01 PM
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strange results today bench testing.

internally:
pump red to red on the sending unit wire
pump black- to black on sending unit wire
purple - connected to level sensor
pump = walbro 465


There are two areas of question with my sending unit after using the racetronix bulkhead rebuild kit. There is a black wire on the top of the sending unit on the outside of it. It looks like a ground but I'm not sure exactly.

The second point of interest is what looks to be a grounding point on the body of the sending unit in tank. Without the ground connected to this, the fuel level indicator won't work.

With it connected the level sensor does work but I'm having issues with the pump not running.

A few times the pump did run, and you can clearly hear it squeak of sorts as it primes when you turn the key.

Here's the weird part. With the intank ground connected to the body of the sending unit, when you prime it (key on), a slight smoke comes out of the level sender. It's the weirdest thing. The level sender works but this obviously isn't confidence inspiring.

As a side note, with the black outside the sending unit connected to ground, still no pump. Pump is almost new with less than 50 miles on it so it should be good (I used it, swapped it for a aem 320 and am now going back since the aem is too small).

Here's more info on the racetronix kit:

https://www.corvetteforum.com/forums...-assembly.html

I'm wondering if I need to reverse the polarity of my pump but I still don't know about the crazy smoke!

I'm calling it a night and will try again later in the week to figure out what the heck is going on. I'll post some video and photos shortly.

Last edited by qwiketz; 01-31-2018 at 10:05 PM.
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Old 01-31-2018, 10:10 PM
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Photos with video to follow
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Old 02-04-2018, 09:53 AM
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I am having same issues after new pump and summit relay adapter. Worked fine for days then reads zero now after dash fuse blew out! I'm going to try to fix in spring.
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Old 02-06-2018, 11:25 PM
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did some continuity testing tonight.

I checked the red from the harness that plugs into the hotwire kit to the plug of the pump. It seems good.

I checked the ground from the harness to the pump plug and that seems fine too.

Finally, I checked the purple wire and that was good.

I guess my question would be are the gray and the red both 12v+ sources? If that is the case, it looks like I have everything wired okay and should check the pump which is almost new(less than 50 miles but it has sat for a while). About the pump, I did hear it spin at key on a few times but it isn't now.

Beyond that, I just need to know if I should ground the wire outside the tank to the frame or an other place.
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Old 02-07-2018, 11:32 PM
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did some voltage testing tonight. Tested voltage at the pump and have voltage at key on. Reconnected the pump and it doesn't run. The pump is almost new but it has sat quite a long time. I might try to find a way to "clean" it up a bit before ditching it and going back to the aem. The AEM was too small, but at least the car ran!
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Old 02-11-2018, 12:25 PM
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Qwiketz,

I dealt with this same issue last summer after replacing my stock pump with a HV Aeromotive Stealth pump, also used a racetronix harness. The pump worked fine on the bench; install it in the tank and nothing or maybe one on cycle than nothing….. what the ____ is going on? I must also add this was my second stealth pump as the first pump burnt out after one summer of driving.

There is always more than one solution to every issue, but this what I found in my situation:

Regarding your Walbro 465 pump, its consider a high volume pump which will draw more amperage placing considerably more stress on your stock wiring harness. I’m not sure about the Walbro install instruction, however the Aeromotive HV pumps require nothing less than 12 AWG wire.

I’m not sure which Racetronix harness one you have, in my case two of the harness pins needed to be relocated within the connector to match the proper flow of electricity. Ohm out the complete harness assembly (from outside connection to pump connection) and pay particular attention to high resistance values) which could indicate a harness conductivity issues as you may have already done.

In conclusion this is what I found to resolve my fuel pump issues:

1) My bulkhead connector pins where burnt / charred and causing very high resistance value. (Resistance goes UP, voltage goes DOWN). I couldn’t find a bulkhead connector and didn’t want to buy a new sending unit with the same small pin connector so I made my own compression type bulkhead which you would find on a race type fuel cell and passed the wires directly through it.

2) I also followed the pump installation instructions this time around which require a 12 AWG harness. I ran a completely separate fuel pump replacement harness which I purchased from Painless harness. These HV pumps need the larger harness as they draw so much more amperage than stock configuration.

I think your harness issue may also be at the bulkhead connector as the old and maybe worn stock pins can’t handle the extra amperage and will eventually burn and fail. Hope this helps.
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Old 02-11-2018, 05:52 PM
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Racetronix also makes a bulkhead connector harness which will work, however you may need to make adjustments to the yellow pin connector due to angle and clearance. (BCWA-C44 - C44 89-96' Corvette Fuel Pump Sender Harness Kit).

The bulkhead pin connector on my vett was the issue for me, the pin and connectors were in bad condition due to the added amp draw. This is an area you need to pay close attention too.
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Old 02-11-2018, 11:58 PM
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Vett1990, we have pretty much ran into the same things. I burnt the pin on my "regular 1992" sender before moving to a zr1 (which uses 2 pins). I did the racetronix bulkhead connector upgrade which caused my issues. I failed to pay attention to the details (also didn't have any instructions) and clocked the yellow exterior bulkhead connector 180 degrees out. So, since there are dual power lines, I was getting power but it wasn't setup right. Hence why I was seeing smoke out of the level sender because it was seeing 12 volts!

I posted on the racetronix support website and they got back to me with a very detailed response and once they reviewed my photos, they new exactly what I did. I was able to fix it and the car fired right up and the level sender is working.

As a side note, the pins on their unit are much larger than the stock ones so it clearly makes sense on how they handle more amps (in addition to being two instead of 1 on the basic sending unit).

Even better, the fuel pressure was right on which I was concerned about because last time I had the 465 hooked up, it was in the mid 50's due to the stock regulator. It couldn't handle the fuel volume. Outside of an injector switch and potentially a boost a pump, my fuel system is pretty much done (465 pump, aeromotive reg, hotwire kit, bulkhead wiring and 60lb injectors).

Last edited by qwiketz; 02-11-2018 at 11:59 PM.
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Old 02-12-2018, 08:52 PM
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Thats awesome to hear your fuel system is working proper, the racetronix website is a great place for C4 harness updates. When your dealing with a little extra HP and performance there are always troubleshooting issues which cause you to pull your hair out, however when you find the solution its very rewarding.

Just curious as to what engine package you have as it seems to have high fuel pressure and injectors.... i;m always looking for more Hp.

My 383 is tuned at 50 psi on the fuel with a 30 pound injector and is dynoed at 376 hp at the wheels @ 6000 - 6200.
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Old 02-12-2018, 09:21 PM
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It's currently setup for 39psi fuel pressure (relatively stock fuel pressure). That may change over time. It's a low compression supercharged lt4 with 14lbs of boost.
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Old 02-13-2018, 10:35 AM
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Originally Posted by qwiketz View Post
did some voltage testing tonight. Tested voltage at the pump and have voltage at key on. Reconnected the pump and it doesn't run. The pump is almost new but it has sat quite a long time. I might try to find a way to "clean" it up a bit before ditching it and going back to the aem. The AEM was too small, but at least the car ran!
Had something similar. Put some wd-40 into it and could see the impeller. I was able to move it with a long pick and broke it free. Then put power to it and it ran.

Also if you have a variable power supply what can put out 15- 20 volts or so and 10 amp you might try momentarily hitting it with a quick higher voltage. Go up from 12 a volt or two at a time and see it a higher voltage will break it free. What do you have to lose if the pump does not currently run.
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Old 02-13-2018, 01:28 PM
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hi guys. I have it working again! Fired right up after re-clocking the bulkhead.
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