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The only place for a coil spring is up Zebedee's arse.
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Joined: Feb 25 2020
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Great job so far! Following with interest ...

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Joined: Jan 05 2016
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Not a lot of progress of late - I've been away on a course and its been too hot for my liking to be working on anything outside.

I have however started work on the fuel system. Being a Thor, it had a returnless pump setup and the filler neck obviously wouldn't fit a diesel nozzle. So both had to come out.

Controversy time - yes, I could have dropped the tank. But I a) couldn't be arsed and b) sods law would dictate if I did it that way, I'd get it all back in place and down off the stands, and then have forgotten something or something would leak, not work etc, and I'd be doing it all over again. So I've cut a hole in the floor. I will need access to it again sometime over winter to fit another dip tube for the Webasto diesel heater - so now I have easy access. Once all is said and done, I will secure the flap back down and seam seal it, so its semi-permanently sealed.

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Out with the petrol filler neck.

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Diesel filler neck in. They look the same... you'll have to believe me :)

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The pump locking ring put up a fight coming loose... but a bit of reshaping and painting - it'll be fine.

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New aftermarket diesel pump setup in place. Of course, the plug is different.

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This is the bracket that held the Thor evaporative emissions canister under the car in front of the fuel tank. I have repurposed it to hold the return fuel cooler and the BMW pre-supply pump, that takes the supply from the lift pump in the tank and bumps it up to 4bar before supplying it to the HPFP on the engine. Said pump will have its supply taken from the wiring to the in-tank pump. The wiring looks more than capable, and the in-tank pump is now a very low pressure (0.3bar I think) job, so the 5 amps the BMW pump needs won't be an issue.

Highly complex bent bit of bar welded on along with some rivnuts to hold the cooler. It isn't ideal being under the car, but I figure when under way it will get some air flow - more than it would in the hot engine bay anyway.

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And then we have breakdown #2... had to take the RR to get enough fuel in the tank to cover the pump before I dared turn it on, given it was now void of petrol, but not petrol vapour...

I'd put the new ECU in which has been mapped... and on second application of mild-loud pedal, big bang and lots of smoke out the back :)

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Pipe work was temporary to get it home - time to address that I think. Luckily had literally only a 7mm socket and ratchet in the car.

Can confirm though - definitely (if not briefly) had more spank. I look forward to giving it a proper hooning, and seeing what falls off next.

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Joined: Aug 19 2019
Posts: 233

I guess the argument is that it's not that difficult to drop the tank, but I think the lack of an access panel for the fuel pump is one of the few design flaws on the P38. When I got the Disco, I had a fuel gauge fault. With the panel it was very easy to access and troubleshoot, then reinstall the panel until parts arrived.

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Joined: Dec 30 2015
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Looking good! Can't wait to go out in it with you once pipework is sorted and see what it's like...

I'm on the fence about the cutting vs dropping tank, but get both sides to be fair... I took the tank out on my '98 (originally so I could get under there and wire brush/paint the chassis, but I think I'm going to scrap the '98 now - another long story) and Sloth was actually there to give me a hand.

Whilst it wasn't too much of a pain to 'drop' the tank, a couple of the couplings that were supposed to be 'quick release' were an utter pain to do and I think one of them has probably been damaged in getting it out. Which as it's now not going back in, it isn't really a problem. But if you had all that to contend with when you're just doing the pump then it would be a proper pain.

I don't see why LR didn't fit a hatch on the P38 either - would have made life a lot quicker/easier!

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Joined: Jun 17 2018
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How does it drive now compared to the V8?

I'm guessing it is lightyears ahead of the 2.5's!

Time for a "3.0 DHSE" badge for the back

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Joined: Sep 14 2016
Posts: 518

Seems likely that the solid floor over the fuel tank without an access hatch for the pump may have been due to a proposed regulation or regulation interpretation thing floating around when the P38 was designed.

Having direct access to the fuel tank from inside the car, especially a plastic one, is the sort of thing that would be seriously frowned upon by more modern regulatory authorities so designing with the tank outside of a solid floor might well have been the safe option. With quick detachable connections and everything pretty accessible if the car is up on a ramp only draining the fuel would seem to be a major downside from the design staff viewpoint. Realistically its not as if things need frequent attention.

(Often wondered how Bristol got away with their layout. A whacking great alloy tank immediately behind the backseat with a (very) thin alloy sheet self tapper screwed on between tank and seat. Glass fibre parcel shelf above, no metal. Couple of simple straps to keep it in place. Seems to work but ... The strong steel panel is between the tank and the boot. Structurally essential because the chassis ends about there with the back axle and Watt links overhung out back.)

Clive

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Joined: Dec 30 2015
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Top Work, you must be proud!!
I'm for cutting. It's not a nice thought at first but if you ever get fuel pump issues you'll be glad of the hatch. You can easily make it vapour tight.

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Joined: Dec 29 2016
Posts: 447

This is looking great. You’ve got it all knocked out very quickly and have done a really neat job of it!

David.

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Joined: Feb 25 2020
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I am also eager to see the results here!

Cutting vs. dropping, I had the change to go at it while the car was "naked", but I decided against it. The moment the pump goes, it will not be a bad idea at all to remove a +20 years' old tank and give a good scrub to the entire area, and the tank itself as well. Knowing you might end up doing this just once in the lifetime with the vehicle, might as well do it all and proper ....

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Joined: Aug 05 2019
Posts: 135

Your pump dies, you are going to drop the tank to replace it, but the tank has 80 litres of fuel in it. How do you de-fuel the tank with a dead pump? Asking for information not trying to be smart.

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Joined: Jan 05 2016
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I don't feel bad having cut the floor to be honest - if it was a like for like replacement, I'd have swayed more towards dropping the tank, as it should only have had to come out once. But who knows.

The P38 is about the only car I know of that doesn't have an access panel - I've had both newer and older cars that have all had panels under the rear seats. Really odd that it doesn't.

Last night it had its first test drive without a breakdown! We welded beads on either end of the alloy tube that blew off the other day, but I was still quite light footed as there is another leak from somewhere I haven't found yet and didn't want to risk something else popping.

Driveability around town - it is very smooth, with only downshifts when you come to a halt being a bit late. I haven't ever driven an M51 P38, and honestly I'm not sure how to compare it to the V8 entirely. My V8 at least had instant torque off the line as you'd expect from an N/A vehicle, but that very quickly lost enthusiasm and fell a bit flat. This has no problem moving from a standstill, and then the power just starts to build. The only 'old' diesel I have to compare to is an old 2.2 Saab 9-3, which had the Vauxhall (or Isuzu, depending on who/what you believe) direct injection 4 cylinder. That was terrible for turbo lag - pull away in haste and it was nothing nothing nothing POWER nothing. This engine is more like 'righto, gently does it but lets get a move on and not piss about'. That is to say... at the speeds I've driven around town in it so far, it drives like a petrol. Planting it I suspect will have some noticeable delay compared to the V8, but not a great deal.

The late downshifts are I think because the final drive ratio in the compushift isn't setup correctly, so it thinks the vehicle is moving faster than it is - which the readout certainly suggests. I'll look at this tonight.

Otherwise... it is very smooth. Cruising at 40-50 just...works, and it doesn't feel like its working hard. Climbing a long incline was about the only time I felt I wasn't gaining speed as much as I'd like, but I was also only just on the boost because pansy and didn't want to risk it where I was.

On the few occasions where I did blip the pedal a bit more underway and felt it start to really come on - you could feel there was power ready to go. Soon. Sooooon.

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Joined: Feb 25 2020
Posts: 239

Sorry Marshall (glorious brand of great RIB of a bygone era), I missed on this one.
I run on LPG so fuel tank holds just a handful as needed. And I can force-start on LPG if necessary.
In any case, I know when the time comes it will be a drop tank operation ....

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Joined: Jan 05 2016
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Bit of an update

Having issues with the turbo VNT at the moment. Boost is unpredictable. Sometimes not enough, sometimes too much. Accompanied by a nasty screeching noise at times too. Need to inspect the business end of it - I'll be surprised if its got excessive play in it - it was fine and operating correctly before the incident.

Assuming their isn't excessive play in it, some data logging is needed to see what is going on next.

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Still having VNT issues, but I think getting there. Not spending as much time as I'd like looking at it - but other things are just in the way.

Have been using it for a few days taking it to work - and will this week too. Currently at a point where it is making boost - but it doesn't appear to be all there and when the adjustment is tweaked just a bit too far, there is more power, but it starts screeching when hot. Unsure if turbo is the happiest.

Since adjusting more I haven't been able to get it on the motorway at a decent speed - unless I want to drive all the way to work on a weekend, the motorway in both directions from home is a 50 average limit at the moment till you get so far. As of Thursday when I last had it up to 70... it was somewhat disappointing it must be said. Taking a lot of pedal to maintain speed, and acceleration up inclines was poor. It has been so long since I've driven a V8 I can't remember. I know its a boost issue too... cos the clouds I've been leaving behind me would really piss Greta off. And the back end is getting black spots :)

To be honest if I do get the boost in line with where the ECU wants it and its still lacking - I am going to be at a lot of a loss as to how much power this thing needs to get it moving. Turbo upgrade would be next on the cards, and further mapping.

Did find today that if I shift it manually, it'll pretty quickly do 40-50 in 2nd, but leave it to its own devices and the current Compushift mapping doesn't downshift enough at in 3rd, it'll rev to about 3k and then struggle to keep going. I really need to do the ASBO thing and abuse the industrial estate at work on a weekend to do some straight line runs with it locked in each gear while data logging - see what is going on.

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Joined: Jun 17 2018
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I feather mine at 70 and beyond "ahem"

No need to mash it..

A DSE however needs a fair bit of pedal to maintain a set speed.

No idea on the Hp of the M57.

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Joined: Jan 05 2016
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The map I currently have should be good for 220hp and 450nm. So hp on par with the 4.6, and a fair whack more torque. In theory...

Will see how it goes. There will be a reason.

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Joined: May 05 2020
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The M57 in my 90 is a standard map at 184hp and it's not slow. I'm not brave enough to test the top speed but even on a good incline it just pulls and pulls and I have to lift off. It has so much torque too, it's very responsive and you can apply power in any gear and we're off. Not a trace of smoke at any time. If you get you're boost issue sorted I'm sure you will be pleased with it. The boost control vac solonid/pressure regulator can be a cause of boost issues so that might be worth looking into?

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Joined: Jan 05 2016
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I think I have either a leak, or the turbo is on the way out. It's fine when cold... but once it has some heat in it, something starts making a fairly unhealthy noise that is definitely boost related. It hasn't really changed or gotten worse so I'm not too afraid of impending turbo boom, but that is next on the list to look at.

In other news... I've adjusted the shift pressures and points and it is sooooooo much nicer to drive around now. Smooth changes on throttle at low speed, much more eager to change down appropriately etc.

Boost is now, despite the noise, meeting demand. Power is generally much better. I feel I will probably want more in the coming future - which may mean the early E60 turbo is on the cards, but I'm not sure. I've lost track of what the upgrade paths are at this point.

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Joined: Jan 16 2016
Posts: 426

Your Nanocom obviously can't read the boost pressure directly as it is a different engine.
I think I would fit an aftermarket boost gauge to see what the boost is, if you can find a suitable tapping point.
Just a length of plastic tubing and mount the gauge temporarily on the dash.
Is there a waste gate on the turbo? I have got a VNT turbo here that I was going to fit to my M51 engine. I made a boost control system for it.

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Sorry when I say the boost is meeting demand - that is from data logged from the ECU. The ECU spits out what it wants, and what it is seeing from the MAP sensor in the inlet. It is now very close. Power is getting predictable, and it is driving quite well. I just need to deal with the angry noises.