Some of you may have seen my introductory thread where I gave a quick run down of the issue, but I'm going to dedicate this thread to it.
I recently bought an '01 XJR that had been sitting for 7 years. I drained the old gas, put in fresh, replaced the fuel pumps, and it started (but for other issues, I had to shut it off after just a couple of seconds). Once I was ready to fire it again about a week later, it no longer starts, it just cranks and cranks.

I have verified that it has spark.
I have verified that the throttle is opening slightly when cranking so it should have air.
I have verified that it has 45 psi at the rail on cranking.
The car is not throwing any meaningful codes (using a basic generic scanner).

So, to me, it must be one of 3 unlikely things.

1. The injectors all got clogged after firing it the first time.
2. The ECU is shutting off the injectors for an internal fault that I can't see.
3. The engine somehow lost compression after the first start.

None of these seem likely at all, but I'm now at a loss as to why it won't start. Any input is appreciated.

 

Check the CPS (crank position sensor), you only need to remove the sensor and check for build up (which prevents it from measuring marker rotations) and the harness itself.

 

Does the engine sound like it cranks over very fast with a fully charged battery? If so, it sounds like borewash to me. I never put any oil in the cylinders though like you will read about. I use friction from the cranking to create heat within the rings to seal it back up. You must have a really good battery and have jumper cables from another running car onto your battery to overcome the loss of compression though. But, that’s just me! If you hold the accelerator pedal to the floor the entire time, crank it for about 10-15 seconds. Let off the key about 30 seconds, perform this same function about 10 times. When you turn the key back on after the tenth or so time, crank the engine over without touching the go pedal and see if it at least farts a few times. I’m quite sure other people will chastise me on here but remember, this is the method I use.

 

I can check the crank sensor tomorrow, but I would imagine if it was bad, it would throw a code and not attempt to crank.
The engine doesn't sound abnormal to me when cranking, but at this point it can only be injectors or compression, so I'll test compression as well, that's a good point. If compression is that low, I'll try squirting oil in there.

 

Crank sensor will allow you to crank and crank and crank and crank but never allow the engine to fire. If you have spark the crank sensor is good enough to start the car.

If you shut the car off right after starting there is a very good chance you will lose compression. Just crank crank and crank with the throttle open and when you let go it will catch.

 

Looks like it is bore wash. I checked two of the cylinders, and they read 60 and 80 psi. I pulled all the plugs, put in ~3 squirts of oil (5w30) from a can, did 6 x 15 second WOT cranks, but to no avail, the compression is still about the same. Did I not use enough oil? Should I try putting in ATF?

 

You may have a valve problem. Apply compressed air to those cylinders with the piston at tdc and see if the air comes out the throttle body, exhaust pipe or crankcase.

 

I'll rent a leak down tester tomorrow, but it's very unlikely that something in the valvetrain broke just from briefly running it.

 

Maybe the MAF

 

Update:
I changed the oil in the car, and added 5-6 more squirts in each cylinder. I began compression testing each cylinder but managed to only properly test the driver's side bank before the battery started to die, so I'll finish tomorrow.

Driver's side front to rear:
95 psi
100 psi
20 psi
80 psi
Pass side front to rear (again, battery was on it's way out, so it began cranking very slowly)
80 psi
65 psi
xx
xx

By my understanding, these numbers alone should be enough for it to fire or at least stumble.

Summary:
Car has fresh oil
Car has new spark plugs that are sparking during cranking
Throttle body is opening during a crank (I don't think it's the MAF as when I try to crank with it unplugged, it'll throw a code for MAF performance and Intake Air Temp fault. When I plug everything in, the car doesn't throw any codes)
Car has 45 psi fuel pressure at the rail, and the spark plugs smell like gas after an attempted start.
During a crank, I can see the driver's side center cam spinning from the oil cap, so timing is not broken, and given the fact that it's an interference engine, I would imagine that I would hear a valve/piston contact during cranking, but I don't, the cranking sounds fine.

With all of this combined, I have no idea why it won't fire now. I really don't want to give up on this car, especially when it ran 2 weeks ago.

Thanks all for the help so far.

 

I experienced bore wash when I had my 02 xj sport. It was weird. My dad just sprayed starting fluid in the TB, throttle pedal pushed and we just kept on cranking. It fired. I was like wtf was that.

 

I've heard of starter fluid working on the base V8's, but I question whether or not it'll work through the supercharger, I haven't been able to dig up much about it.

 

I’ve had quite a few frustrating times using the “squirt oil in the cylinders” method which is precisely why I haven’t done that in a long time. Oil is going to continuously foul out the plugs now. What I’d do if I was in your position is to pull all the plugs back out, clean (I use brake cleaner) and immediately blow them off with compressed air. I would then pull out both of the fuel pump relays and floor the gas pedal. What your trying to do is get that oil back out of the cylinders. After several times of cranking, I’d put the plugs back in, reinstall both fuel pump relays and then try again with a strong battery cranking it over to hopefully start.

 

I think that makes the most sense, when I pull the plugs now they're wet from the threads to the tip, I'll try that tomorrow.

 

Alright, I tried pulling the spark plugs and cranking it for awhile to try to reduce the oil in the cylinders, thoroughly cleaned the spark plugs, and still nothing, no change. The engine doesn't even stumble or try.
It has rail pressure and the plugs smell like fuel when I pull them. With a plug and coil outside of the engine (grounded to the supercharger) I can see it sparking, and this cylinder tested at 100 psi after the oil treatment.

I have absolutely no clue what is preventing the car from even trying to stumble, It has air, fuel, spark, and compression, but it doesn't make a sound...

 

Did you pull both of the fuel pump relays out while you were trying to clear the cylinders?

Also, while you were cranking the engine over, did you hold the gas pedal to the floor the entire time? This is still during the “clearing the cylinders” stage that I ask.

About how many times and for how long did you try clearing the cylinders for?

Do you have a good battery charger on it while cranking?

 

Try Battery or Mass air flow sensor, when i dropped a engine in my 01 xjr it didnt start right away just kept cranking lower than 1 rpm so changed crank sensor then still kept cranking with no start, then we started spraying starter fluid in past the MAFS while i sat inside cranking the car and boom it fired after a little while.and have been driving it for 3 years no problems.

 

Yes, both pump relays were pulled, but I don't recall if I had it at WOT (shouldn't matter if the pump relays are pulled).
To clear them out, I believe I cranked it twice for about 15 seconds with the plugs out.
The car is now on its second new battery (they're under warranty so whatever), so battery power is not an issue.
I've tried dousing it with starter fluid through the throttle body, but still not even a stumble.

 

I suggest you check/swap/replace the TB, Ignition and Injection relays inside the ECM box (diagram for AJ26 supercharged):

 

The TB is opening on crank, so that relay works.
The vehicle is getting spark (tested outside the cylinder) so ignition relay works.
The spark plugs/cylinders smell like gas after an attempted crank, so I know injectors are at least partially working.