V8 engine shuts off after 4 minutes, code P0627-00 (6C) Fuel pump A control circuit/open

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gsxr

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Another update. I was able to finally drain the tank. I made one last attempt today (after spending 20-30 mins yesterday, unsuccessfully) to get the siphon hose into the tank. Today it worked! But, I was only able to siphon 6 gallons out (estimated 14 gallons remaining).

Next was pulling the filler pipe connection. More fuel leaked out than I expected, but the flap at the tank did not leak so it was "only" a few ounces (which is more than it sounds like). With the filler pipe removed, I was able to push the flap open with a screwdriver and drain a pint or two at a time into a bowl, which was then poured via funnel into a gas can. After repeating this a dozen or more times the flow was down to a trickle.

Next was sticking the siphon hose into the tank fill port and siphoning directly out of the tank. Total drained ended up around 17 gallons. I had estimated there was 19-20 in the tank, so draining all but 2-3 gallons was fantastic.

Now I'm having fun getting the tank disconnected and lowered out of the chassis. Those quick-connect pipe fittings are poorly named. More like torture-connect. When you can't easily get your hands/fingers on the fitting, it's a PITA to squeeze hard enough while also twisting/pulling. Finally got the front pipe connections separated.

Removing the electrical connector at the flange was 10x harder than it should have been. I don't know what JLR was thinking, since you're supposed to separate this with the tank only lowered 250mm (~10 inches). After 30+ minutes of fighting and using a mirror to view the locking tab, it finally released. Just ridiculous. Fabulous engineering study of how NOT to design a connection in a limited-access area. *shakes cane*

I'm now stuck at separating the vent piping at the rear. The large diameter pipe torture-connect fitting is fairly easy to access and I'm confident I could separate this. The small diameter pipe... appears to connect waaaay back, buried above/behind the differential. Another great example of terrible engineering. This was designed for manufacturing, not for maintenance / service / repair. I gave up for now, will try to figure out if I'll remove the small vent pipe above behind the differential, and snake the tube out... or disconnect it from the tank instead.

Really frustrating, all JLR had to do was design accessible fittings at the front+rear of the tank, but nope.. had to save those seventeen cents. A pox on those who designed this, and approved the design.


o_O


UPDATE: Tank has been successfully removed. Those stupid fittings are just the worst. Clearly, these are connected on the production line with a bare frame, before the body is lowered onto the frame. With the body removed, there's plenty of access. With the body in place, there's very poor access. The FSM is just plain awful with no text descriptions, and not-very-helpful colored drawings. I'll post more info & photos on the only tank removal thread I could find on the forum (here).
 
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gsxr

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Success! Problem solved. :thrasher:

Root cause was a failing electrical connection at the flange, INSIDE the tank. Photos attached below.

Had I known what the normal resistance of the pump motor was, I could have figured this out much sooner. The new VDO pump assembly measures 0.3 ohms. At the old flange connector (top side / external) I measured 1.0 ohms, which is a substantial difference.

There was no visible problem until the flange was removed, and electrical connector separated from the flange on the underside. One of the terminals had signs of overheating and corrosion on the terminals. This increased resistance of the connection, resulting in intermittent pump operation. The resistance directly at the old pump motor was normal at 0.3 ohms, identical to the new pump motor. The bad connection was entirely at the flange connector.

The FPDM was likely seeing different-than-expected current draw and triggered the unhelpful P0627 code. Or, after a few minutes of pump operation, the connection could have gotten bad enough to be "open", or close to open (infinite resistance). The only way to measure this from above is to expose the FPDM (seen in this post), remove the connector, and measure the resistance at the appropriate sockets on the harness. It should be 0.3 ohms, maybe ±0.1 ohm. Anything higher likely indicates a bad connection and/or a bad motor. It would be impossible to check this otherwise, without dropping the tank enough to remove the flange connector and test directly at the flange - it's easier to get to the wiring at the FPDM and measure there.

Since my truck had not yet received the new style flange/filter per dealer recall RCRIT-21V635-5779, and I had to replace the flange anyway, I bought the new parts and did the upgrade myself. Part numbers are in post#8. I'll create a separate thread about this, AFAIK nobody else has done this as DIY at home. I have detailed photos of all the new parts too.

I considered performing the modification for "Fuel Gauge Operation Inaccurate" (LTB_00566NAS4), since the fuel gauge has always been wonky (despite new senders installed by the dealer under warranty at 49kmi). However after examining the harnesses I decided to skip this. The wires are insanely short, there's just so little slack to work with, and this "locks" the senders / pump / filter together so they can not be separated. If you cut anything in the future, there may not be enough wire left to re-connect! If the gauge gets any wonkier I might do this in the future. Maybe.

BTW - this was the original fuel pump from 2010 with 160kmi, so a new one made sense. Just replacing the connector may have also worked but it wasn't worth the risk, given the labor/effort needed to drop the tank and repeat the job if the old pump was near death. Be careful when shopping, there are a lot of aftermarket garbage pumps (ÜRO, for example). If you can't find OEM VDO, I'd shell out for OE/Genuine, unless you don't mind repeating the job.


Total parts cost: $500 (new OEM VDO pump, all TSB parts, new low pressure sensor, spare used FPDM)
Total labor: Estimated 10-12 DIY hours over multiple days (includes quite a bit of time cleaning, and trying to empty the tank)
Total downtime: 4 weeks, mostly waiting for parts to swap & test


Hopefully this will help the next person who encounters P0627 along with the engine shutting off.

:driver:
 

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gsxr

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Forgot to mention: When installing the tank, I double-checked each quick-connect pipe fitting. Or so I thought. Of course when running the fuel pump priming sequence (thanks for the tip, @scapistron!), I heard an odd sound. After a few seconds I figured I should check, and yup, raw gas was spewing onto the floor. The fuel feed pipe at the front of the tank had not been fully locked in place. Re-connected that and TRIPLE checked, and all was fine.

The other 3 pipes are all vents, and of course the one I messed up on had to be the pressurized fuel line. D'oh!
:musicus:
 

gsxr

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A few photos of the new / updated flange and new pump.
 

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gsxr

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Pics of the tank being dropped, along with separating the tank from the metal shield to remove all the rocks trapped in there.
 

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gsxr

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And finally, I created a thread detailing the new fuel flange/filter as part of the TSB:

 

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