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Discussion Starter #1
Hi all,

Does anyone know what fuel pressure would normally be on the 5.0 V8 S/C engine?

My engine runs unevenly from start-up. After 30secs to a minute, the engine note changes and it runs evenly. I've observed on my OBD II datalogger that this coincides with a sharp increase in fuel rail pressure. I'm getting the following approximate readings:

Start-up - briefly reaches 20,000 kPa/2,900psi
Cold idle, with no previous application of throttle - 400 kPa/58psi
Idle, after 30secs to 1min - 17,000 kPa/2465psi

In the Tech Training manual I see the following spec, but my numbers appear somewhat different...
179486


If I apply some throttle after start-up rather than leaving it, the fuel rail pressure increases to circa 17,000 kPa and doesn't drop. I'm trying to establish what it is that changes the engine note after 30secs-1min. Alternator perhaps... does anyone know if the 2 HP fuel pumps come online straight away or after a similar period of time?

For background, the car has had an engine-out rebuild. I have a fuel pump timing tool (JLR-303-1621) on the way so that I can determine if I have correctly set that during the rebuild.
 

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One would assume that if it reaches fuel pressure after revving it a bit then the fuel pump is ok and timed up correctly.

I'd suggest looking at things after the fuel pump such as injectors or and other pressure relief valves etc.
 

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EGR valve?
 

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Discussion Starter #5
Thanks for the thoughts Gents. I scanned the car again this morning (from cold this time) and it ran rough for a longer period of time, even cutting out sometimes. During this time the fuel rail pressure was in the range of 35-55psi, which seems awfully low for a DI engine. It gave a new code, P0087 fuel pressure too low. Even applying some revs, the fuel pressure was falling back to these low figures.

Once the car was up to temp, and I revved again, the fuel pressure increased and stabilised on the scanner and it ran fine thereafter. This makes me think injectors are okay, and it's some kind of fuel control electronics issue during warm-up?

If anyone has experience of fuel pump pressure relief valve failures, EGR or leaky injector symptoms I'd be intrigued to hear it.

If anyone has the ability to x-check my fuel rail pressure readings during warm-up against a known-good engine, I'd be very grateful.
 

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How long has it stood unused? Is this a low battery issue?
 

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Discussion Starter #8
I've started it up and ran it up to temperature each day for the past 4 or 5 days. I have taken it up and down the street a couple of times only, as it does not yet have an MOT. It keeps throwing the MIL, and so I won't be able to get it through an MOT as it stands.

The battery is new but over the weeks of working on the engine rebuild it went flat - I have since charged it up. However I've also noticed the infotainment screen going on/off by itself which I've read may be due to low battery? I'll put the battery on charge again today and be more diligent keeping it topped up :)
 

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Discussion Starter #9
Just for some thread closure on this one. After a long wait for the JLR-303-1621 special tool, it finally arrived and indeed the fuel pump timing was out - the tool didn't fit. Anyway, all re-assembled now and the fault code is gone and the fuel pump is much quieter! For anyone out there tacking this in future, to get you "in the ballpark" the large notches in the pulley need to point approximately towards the bolt holes in the housing, with the "FoMoCo" branding at the top, reading from left-to-right. If you fit it the other way, your timing will be 180 degrees out. Finally re-fit the tool and check it fits; if it does then the timing is correctly set.
 

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Nicely done and thanks for letting us know Blanco. :cool:
 
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