Well, let's summarize:

You have decided that Rover R&D stinks, so you whipped out all this on your own, along with an ECU chipset from someone that won't return your calls.

Despite the aerodynamics of a brick and a brake system not designed for the fast lane of the Autobahn you rawhide this puppy through the areas where you can.

There is some quirk in the fuel system, which has had plenty of things changed in it, so it is not exactly stock anymore.

You have a one of a kind vehicle that you, and only you, can really work on. When people have tried to suggest things, you shout louder that you have overcome every law of physics Rover tried to compromise on with immense expense.

But your fabulous creation does not work to your high standards. And it is Rover's fault?

Like I mentioned before, the stock ECU has a plan to deal with hot restarts, by changing the PWM to the injectors for a short period. There is no doubt in my mind that operation at 5,000 rpm plus and back to velocity = zero will produce a hot start condition. But you don't know what (if anything) your mod ECU does for hot starts.

Your pressure gauge, which probably costs more than my whole F250, is twitching. Now most fluids don't compress very well. In your mod of the fuel system, perhaps a built in accumulator space was deleted. For the plumbers among us, that would be like the pipe stub you build in above the shower and tub valves to prevent a water hammer. A small cushion of air in that dead end pipe absorbs the pressure pulses. In your case that might also come from injectors that flow at a different rate, etc. If you put on a new regulator you can tune this may go away, or you may find that a "T" fitting in the right spot with a short dead end fitting could become a simple accumulator. Since you experimented with everything else, why not that?

Since you only drive 1500 miles in two years, that's like 62 miles is a month. You have a well running pasture ornament. But it is a damn quick one. Bet it is frustrating that it won't run like you want it to, after all this work (looks like a lot more than one or two weekends).

BTW - you run stock radiator? Stock fan & fan clutch? Or something to provide more cooling? What temp stat? Maybe a larger fan or different coolant temp could provide soem help with this. As I'm sure you already know, plenty of fans and clutches from GMC/Chevy will fit.

 

Maybe it would help to have a fuel cooler, since this ain't mom's taxi. See Chrome Fuel Cooler for one that works on Jags. The extra radiant heat output of the overclocked Rover may be exceeding what the fuel line system can handle, unless you run around with no hood.

 

What's the outside air temp and relative humidity? What was it when it ran well?

 

Savannah, I appreciate and enjoy your active replies, keep 'em coming I needed a good laugh today.
"Bet it is frustrating that it won't run like you want it to" Nope your totally wrong it has been running better than I had planned after my efforts. My time, labor and machining at home are part of my machine shop background. A Bridgeport mill at home is almost as good as sex (wifey will kill me).
Cooling is not an issue, never overheats, booster fan after shutdown is also rare.
On "Rover's R & D" once you have seem the intake to head port miss matches on intakes, heads and exhaust manifolds you would throw up, yup that bad as well the exhaust there is room for serious common sense corrections vs sloppy high production rates Rover used.
Port matching plus later version injectors are simple more modern injector upgrades of the same 24 pound/hr replacements. Results a smoother running engine that starts 2nd or 3rd cylinder over comperession Lucas injectors never had. Matching injector pounds per/hr output, you tell me how this alters fuel demand? The intake extensions are of my own doing to reduce max TQ rpm's which it does perfectly as planned on paper and calculator working with intake lengths and sonic pulses. Oh you still there or a'm I over your head on basic Briggs & Stratton engine repair? Had to ask.
The RPI Tornado chip matches Rover's chip exactly with cold and hot restart features this is not some JC Whitney add on part besides it has been fueling this 4.6 perfectly the past 12 years as well no hard start problems, this has developed just the past couple weeks. No fuel cleaners added to break loose anything in the fuel system as well fresh fuel refills with tank drains testing different brands of gas.
This includes running with the intake extensions and other engine mods, yeah so radical the changes, yeah right passes smog actually too clean.
This chip feeds the engine properly vs NA version chip Rover has programed for the US market being too lean at best. I already swapped out the old ECU a virgin from my D1, yup still a hot start stumbling problem this using a chunk of brain tells me it's not the ECU with RPI chip a problem. It did run like a slug plus leaned down above 3,000 rpm's forcing me to shut down and lift throttle with the original ECU, why push it running lean and destroy a good engine?
With this chip last months smog test readings of 7 of 100 max HC at idle, 11 of 180 HC max at 2,500 rpm's, other gasses nats azz perfect and super clean plus I can pull 19.22 mpg on the highway keeping the speed down to 68 mph max. Now an ill tuned engine will not reward me with these good mileage numbers and performance. Stock 3.9 engine produced 15.7 to 16.3 mpg at best.
With the fuel regulator measurements all reading below factory minimum numbers and this again off another 95 D1 yesterday I have a bad feeling even a new regulator will read low and below minimum spec. An adjustable regulator available by RPI that can be set to within the Rover Workshop manual specs, lower or higher depending if on a 300 plus HP 4.8 or 5.2 liter Rover engine. Why spend $127 to $150 and gamble with a OEM Rover regulator that may possibly read below spec brand new, a waste of money when a little more added money a sure deal regulator that can be adjusted. The fuel pump for now is way cheaper and the first item i'll replace since it has shown fluttering needle but nor steady, can't be trusted plus old then off to order an adjustable regulator.
Yeah wow this is highly modified engine you mentioned, just a basic 4.6 that runs great that just developed a hot restart fueling problem.
No"pasture" to park in I live on an island in a city.
You must of got a deal on your "F250" and paid less than $49.12 for it? Congrats as that's what I paid for a fuel pressure tester. Cost me a 6-pack of Bud for a 70 F250 with a straight body I drove home, this a donor for the 68, disc brake conversion plus spare C6 core, steering box and column and driveshaft then sell the rest.
I have other vehicles to drive so no worries, I can wait until the rains stop besides the Rover still runs great only that 3-20 minute hot restart stumble of 5-15 seconds not a problem it's not dead on the street. The 68 F250 has a 454 in it my backup vehicle as the Rover is in the driveway most times covered up but used on my 58 mile highway loop trips.

Don't laugh, I have a 3" diameter x 4" tall stainless plumbing accumulator with an internal stainless bellows diaphragm as the thought had passed my mind to Tee it into the fuel rail schrader valve just for testing.
With now having solid gauge needle readings again I do not trust this 140K mile pump, it may be talking to me as well the 140K mile regulator with a "i'm about to fail" warning. Well below spec regulator is already suspect in my book but the engine can idle down to 9 psi rail pressure, this with the better designed 4-hole Bosch injectors where the Lucas single squirts the engine died at 14 psi minimum. That alone tells me something about later better designed injectors.
Savannah, "shouting back" replies that's your opinion we all have them, I never insult or belittle people so get a grip on your thinking.
On the RPI chip it takes days to a week to get a reply, a simple yes or no reply unless you nail Chris Crane at RPI down to a basic simple question to the point requiring a yes or no answer.
No second opinion or idea like "try this" seems to be how they reply, British dry humor?
Troubling yes but when 4-5 requests on one question that could be answered with one reply, just RPI's odd "Limey" thinking process.

"You have a one of a kind vehicle that only you, only you can can really work on".
It's almost stock with minor improvements to increase the enjoyment of driving a Rover.
The 5 speed plus Buick engine the only reasons why I purchased this D1 as i'm familiar with them back in the 60's.
MY Rover service manager tech friend plus a couple of his close mechanics are into Rovers not just at work they enjoy my visits twice a year to their service department to chew the fat plus i'll give the service tech a quick test ride on what I have added.
They have begged me to machine out and sell them intake extensions as well run up a batch of balanced Bosch 4-hole injectors for their personal Rovers. My engine has raised the standard they like being they are Rover off road hot rodders.
They see my engine as a basic engine easy to maintain, not a "only you can really work on" engine.
Granted the Pre-Oiler is a one off item install that works flawlessly 12 years also as well the modified sandwich adapter with hard piping and delay timer.
This was built as a soccer mom vehicle from 2000 to late 2009, basic simple to maintain being driven 14/7 a week.

With winter rains this will be a delayed project repair but no worries allows time to price shop for parts.
I have a custom built larger than stock capacity radiator, rock steady temps be it 30 or 115 degree weather. These hot restarts it's the same be I shut down in 38*F or in the paint room oven at 109*F, I have already tried this with the same results.
I drive by gauges, oil pressure included not idiot lights, A & P background has something to do with it besides being a gearhead and engine builder, Ford FE, 2.5L BMW and 356 Porsche engines.
I'm having a homebrew, Prost to you Savannah I enjoyed your replies.
.....~~=o&o>.....

 

This is your opinion and reply, not what I have ever said, try again Bud!

"But your fabulous creation does not work to your high standards. And it is Rover's fault? [/quote]"

Again another one of your off the wall statements coming from you.
If tuning for a clean running engine is considered "high standards" so be it, they are your words not mine.
Sounds to me a run of the mill ox cart would be fine for you even if one wheel fell off. There ya go, different standards.
What I have built and assembled has worked great for two years until this hot restart problem came about.
Even at the tiny 192 acre ranch in the hills feeding cattle in 114*F heat driving the trails with stop and go 5 to 30 minutes zero restart problems.

This must be time with mileage plus we have more alcohol added to our fuel.
End of life on pump with regulator to follow, hell 140K miles on them.

Smart to say I do not engage in pissing wars when I can not talk on the same level, if you have anything more to add is one thing, if BS keep it at the bars.
Prost.

 

My starting thread has gotten the attention with other Rover owners by the emails sent to me with questions.
Glad to help with my findings as well what you have found.
Seems i'm not alone as a few VIRGIN Rovers also have these hot start stumbling problems.
Mine is fueling not the dizzy amp thermo failure.
Emails are not a problem no worries.
.....~~=o&o>.....

 

I apologize for all my short comings. Let me try again.

You have highly modified a truck that was designed by Rover as a series of compromises. You are certainly wringing more out of it that it was designed to produce, which shows how far it could have been expanded, had the bean counters allowed the engineers a little more leash.

Now that you have pushed the envelope to the bleeding edge in one direction, it may be that you have run up against performance limits of something else, either (as you suggest) fuel delivery issues, or perhaps cooling issues. But now that you mention that it has been operated for short periods (1500 miles over 24 months) in warmer temps (114F), one would think that you should have hit this before if it was something that simple. Not sure what temp range thermostat you run, but with such short trips, you could afford the slight decrease in mpg and perhaps consider running a 180 or even a 160 F stat. A different stat is probably the least expensive thing you could do to the truck.

I think your idea of the adjustable fuel pressure regulator is a good one. Certainly quicker than dragging out the pump, if your pressure readings indicate a healthy pump (puts out more pressure than spec). I'm not used to fuel PSI guages twitching, but that certainly could depend on the system being examined.

I appreciate you not continuing a battle of wits with an unarmed opponent.

 

Savannah, I reread your reply post number 30,
"But you may find other forums may have a greater tech level participating on them".
"We are more newbies, off road modders, and DIYers over here".

This explains it all with general suggestions I understand this forum better now. Virgin Rovers ok, worked on or modified not good.

This means mounting my 255/65/16 Michelins vs 235/70/16 has me as modified again?
Mounting and balancing wheels and tires I do myself after seeing bent Rover rims by tire shops dealerships included.
Static balance with a spare hub and hard chromed and ground shaft on the motorcycle wheel balancer with flanged bearings for the radial balance. Remounted on another spare hub anchored to a vertical arm anchored to the ground.
The "shoe" remember them? This is applied to spin up and check for axial imbalance. Corrections taking time working with the total weight amount switching ratio inboard to outboard bead location. I mount all internal no weights on th outboard bead. When done turbine smooth wheels.

Double checking on a Hunter balance machine with a 3/8" thick disc that snuggly fits into the rim concentric mounting, center bore just fits the hunter arbor. This will still read zero and a perfect balance.
To use cones or stud spiders to balance is half assed and not off the concentric pads as run on the vehicle.
All in the details.
Prost....o&o>.....

 

Lots of guys here have all sorts of tires, deal with issues like rubbing on fenders, each claim to be better in the mix of mud and gravel that is local to them, etc. Many posters on here are trying to keep mom's taxi on the road until they can finish the payments and dump it. Some are guys who lusted after a Rover for years and finally bought an old beat up one and have been dragging it back to running condition. We have guys that drain the tranny fluid and add six quarts of oil to the engine and drive off. Hard to get some guys to understand that a nine year old battery is a bad idea. And then we have people at the other end of the spectrum, engineer/hobbyist, dismantlers who have owned and parted out hundreds of Rovers, pro mechanics relaxing, or guys in the bush in South Africa rebuilding part of a key fob with parts salvaged from a CD drive to deal with immobilization.

There are other forums where more engine builders gather. That's why Al Gore invented the internet, so people could freely exchange ideas.

You have taken a machine, improved upon it greatly, and now the only person that will fix this problem for you is..... you. You'll do it by exchange of ideas with others, and the light bulb will come on (the one between your ears, not the check engine light). You might have to prowl some of those UK forums where the Rover block was highly prized and polished and tweaked to even more extremes, then stuffed into a Morgan or a TR7.

Since you don't know how the new chip set handles hot restart, which on later D1s was dealt with by increasing the pulse width driving the injectors (while ignoring rich readings from the O2s I suspect); perhaps also you might consider if the new chipset is trying to learn your driving and engine, and is changing adaptive values, and changing parameters that you were happy with to start with. In other words you improve, it trys to work against that and de-tune. The lambda values are used with an internal formula to recalc the fuel air ratio corrections to the primary control range, and stored for use on the next engine start just before making the jump to closed loop. Well, at least on later versions of Discos.

Now, since I've exchanged ideas with you, and even gone out on a Sunday morning and burned some of my gas and rooted around in my junk box and dragged out a fuel gauge and given you a comparative reading from a just barely running Disco, I can confirm the the old saying that "no good deed goes un-punished."

Obviously, you come from the land of superior shade tree mechanics (a term of respect), because the height of your trees far exceed my simple magnolia grandiflora.

 

On stats a 188*F is used, below 180 cylinder wear begins, 170 ouch and 160 times 10 of 180 in wear. It's a nasty chart of wear x temps.
Savannah, on the engine build I went from factory spec of a 285 cam to a 260 cam, hell 25 degree reduction in duration is a lot to give up. The ramps are quicker allowing more chamber filling vs duration hence works perfectly on my build. Fear of the 380 box and diffs, can't be too wild. In anger this D1 will turn the tires on launch and second gear, quick clutch in them almost a switch. Break it your screwed parts not cheap.

Back to the cam;
On the other side of the coin this also allows for more dynamic compression the important one vs static compression which sells at the parts counter. There are limits of dynamic compression before detonation problems begin, retarding timing is not the correct way to correct detonation problems.
Lower compression with high advance degrees will pull a grade way better than a high compression retarded. There is a zone where both the above help, weight of vehicle, temps, fuel grade, altitude plus gearing and tire diameters.
BMEP numbers are the bible with building engines that can feed on pump gas.
Short cam helps with low end TQ, long intake track like I installed works along with the cam in harmony. Dizzy (love it) I can and did recurve the mechanical advance plus have a soft vacuum advance unit.
Matching and tuning the engine starts at the air inlet to the tailpipe, everything must work together. Big exhaust systemd you lose low end TQ, too small you have low end TQ but stuffed up by 3,000 rpm's as example.
Example a EVO Harley bagger heavy as hell geared tall for the highway, owner wants more power then installs a big fat high overlap and lift cam.
What he made was an engine that wakes up (provided intake and exhaust) can handle increased flows a high revving engine geared tall for low speed low rpm torque, a total mismatch of parts as well performance and gas mileage.
The secret is in the heads, port match, minimual porting to let them breathe good but keeping the air velocity high for ram air effect.This more important with a wet intakes like on a carbed engines vs MPI that are dry. Throttle body injection is wet like a carb, crappy crossover before MPI.

Add to this my 95 and older with a dizzy they have a restriction in the nipple that feeds the dizzy vacuum advance unit. This is for smog forcing a slow signal in and out for slow advance and retard of the vacuum can.
Talking 0.013 or 0.017" restriction hole of this ported signal.
Any little leak in the hose or diaphragm which I have found failed on 80-90% of dizzy Rovers end up without vacuum advance, less timing and a dog more than they need to be. Any leak even small or a larger leak results in reduced vacuum advance to none at all.
Back to my build, free flowing cats with Borla freed up the exhaust.
Cold dense ram air also helps plus being cooler less apt to have detonation problems. BTW the "jacket" under the plenum top just below the throttle plate allows very hot water to heat the plenum intake air charge allowing the engine to run leaner, a smog related idea you must know about.
This jacket gets hot within 30 seconds of cold start, place your hand on one on warmup. Less dense air like at altitude plus enhances detonation problems. Take a brass slug 1/2" long machined down for a tight forced fit into the hose deeper than the nipple it mounts on, this with a 1/16" hole down the center plus a 10-24 thread into the end of hose direction.
This allows installing a long screw extracting this restrictor if nee be.
Drill out larger if you live in a cold climate, I moderate in S.F. bay on the water. This a sneaky way looking stock but denser inlet air equals more free power.
While on this 95 engine the TPS holes I filed long vs round allowing the TPS to rotate slightly to a given voltage spec not a wild position.
This sends a higher voltage signal to the ECU which thinks more throttle is signaled than is applied richening up the fuel to throttle position ratio.
Now this thru RPI specs matching to their chip to properly set the TPS.
I return it to stock position, takes 5 seconds two srews for smog testing then back to the metered voltage readings again.
A clean strong pulling torque motor my build as this is a heavy vehicle, I designed an engine for this street duty not a high revving Honda four without toruqe under 4,000 rpm's.
I'm not a total racing *** on the road but enjoy the added powwer and torque.
Creeping stop sign is 2nd gear let out the clutch no slipping it, rpm's drop without throttle to 500-525 rpm's solid hookup thn throttle away.
Not bashing throttle light feeding the engine without lugging and pounding the engine and bearings. No way the 3.9 could do this even the 4.6 before the intake and injector install would of had a hard time to copy.
Hell 1st to 3rd then 5th with the higher gears at 1,100 with light acceleration not stupid heavy throttle pulls clean and smooth.
I built a very flexible engine from below idle to 5,900 but again a waste past 5,400 is beating the horse.
I could of and should of installed a bigger cam but this low end torque is addictive.

On the 68 F250 that 454 i'm surprised you didn't hammer on me with a chebbie 454 numbers posted in a Ford.
Bed time, we live to fight another day.
.....~~=o&o>.....