Fuel sender unit or fuel pump issue?

[808inthe949]

Hey there. Sorry to ask something asked before but I havent gotten a solution just from reading. Purchased Libby a month ago. I have done a gauge sweep and gas gauge works. My gauge is not always on E as it sometimes read correctly (or at least as correct as it did before the issue was noticed). I havent watched the gauge fall to E so im not sure when it actually occurs. I can have the gas light come on and it read E and then sometime later in the drive it will show the correct level but still have the gas light on. No CEL.
I understand how to resistor works in the sender unit. My jeep sometimes takes an extra second of cranking to start up, almost like the fuel pump isnt building full pressure. I have no driveability issues with acceleration or idle, so I'd assume the fuel pump its self is okay.
I know that I need to do a fuel pressure test on the passenger side fuel injector rail at just before start up to tell me if the pump is actually good. Will do in the coming days.
Is there a way i can test the actual sender unit? I dont mind dropping the tank as I plan to fab a skid plate at the same time, but I dont want to have the jeep down for days while waiting for the part to come in. I can order the fuel pump on RockAuto or just the sender assembly. But, theres also a full pump housing assembly. Does this contain all the peices in the tank?

 

[808inthe949]

Also if anyone has the resistance specs for the fuel sender unit on my 05 3.7 4x4 kj that would be great!

 

[Bikeflyer]

There is a full range of specs in the KJ manual. Mine had a dead spot in the sender wiper reading at 95 pecent full for a long time. The harder starting/bleed down is an issue with the sending unit's check valves. I just replaced my whole unit to correct it and found the replacement wasn't a whole lot better. Makes better PSI but still bleeds down. Going to try warrantying it to see if it gets better or if I have to change up brands. That was a Schnorkel brand from Amazon. I know, but they have a good cust service. I hope...

 

[808inthe949]

Is that a manual like the Hanes or is that from the FSM? Please update this when you hear back from the company you purchased from. I'm nervous to replace anything in the tank as most people seem to not get much life out of the replacement unit. Id rather spend money/time fixing the stock unit if it can be done.

 

[Bikeflyer]

https://colorado4wheel.com/manuals/Jeep/KJ/2006-KJ-SM.pdf

 

[808inthe949]

https://colorado4wheel.com/manuals/Jeep/KJ/2006-KJ-SM.pdf

Thanks a ton!

 

[808inthe949]

There is a full range of specs in the KJ manual. Mine had a dead spot in the sender wiper reading at 95 pecent full for a long time. The harder starting/bleed down is an issue with the sending unit's check valves. I just replaced my whole unit to correct it and found the replacement wasn't a whole lot better. Makes better PSI but still bleeds down. Going to try warrantying it to see if it gets better or if I have to change up brands. That was a Schnorkel brand from Amazon. I know, but they have a good cust service. I hope...

Any luck with your fuel pump replacement? Im gonna replace the whole unit too, but unsure which brand.

 

[Bikeflyer]

I got the amazon vendor to warranty it out, but ended up replacing the injectors too. Seems it was partially the pump and partially injectors, or the bad pump threw grit at the injectors.

 

[808inthe949]

Ah so you went ahead and replaced everything except the fuel rail and lines going to the pump? I think I'm gonna order that one on Amazon, the Schnorkel brand one. Wish me luck. The only problem I seem to get is the bleeding of pressure for startup. When it's running and idling it has proper Pressure. I checked my plugs (less than 1000 miles on then I think) and they didn't show signs of being lean so I'll just do the fuel pump assembly for now and see what that does for me.

 

[Bikeflyer]

The injectors seemed to do more for the startup than the pump did. Both are good to do though. If you flip the rail over with the injectors mounted, check if they seep with pressure. The counterintuitive thing is if one or two of them are dirty they can jam slightly open and bleed down the rail pressure, at the same time flood that cylinder, and restrict flow. In hindsight I probably had bad/dirty injectors for a very long time showing randomly.

 

[808inthe949]

I haven't removed the injectors or rail yet. There's a local place that will do the cleaning if I bring them just the injectors. But for the price I imagine I could just buy new ones. Is it recommended to do any improvement with the injectors like a bigger size or better brand?