The car turned over and would even sort of start if the pedal was held to the floor but it was extremely rough - barely running (I would have never attempted it if I had known it was a cam chain issue).
Had it towed to British Automotive locally and we lucked out, no valve/piston contact, just jumped timing on one cam. New metal tensioners and it runs like a top.

 

Worried that we are getting confused here. Broken t/c tensioner and skipped cam on an early 4.0L has little or no bearing on the later 4.2L, for which this built-in frailty was never an issue.

Karl's good advice to focus on one thing at a time is sound and since your fuel rail pressure is sub spec, then disappears once not cranking, this is the logical place to start. However, I am further worried that brand new plugs are "wet" and/or "fouled" . . . perhaps implying not a lack of fuel but lack of ignition and/or correct ignition timing.

What worries me most is that this was a slowly deteriorating fault spanning several weeks of worsening fuel consumption that was resolved, not by successful diagnosis and repair, but by engine eventually refusing to start. Two relevant questions . . . where in this process, and why, did you swap in the XF fuel tank, pump and delivery system? . . . and if so, how long was the car running at full optimum performance with all the XF stuff before fault/s first emerged?

Best wishes,

Ken

 

Yes, there is some smoke. I can pull a plug and ground it while cranking to verify, but it seems like I'm getting spark. I'll be at the car again today, and I plan to pull the rear seat and see if I can get at the fuel pump's check valve. Rest of the parts don't start arriving until tomorrow.

Those OEM fuel pressure sensors are starting to be hard to find. Might be wise to get one, if you have a car which it fits, while they are still somewhat available. The local Jag dealer couldn't sell me one, so I ordered direct from Ford.

 

The car went into the dealer years ago, with the leaking fuel tank problem. As far as I know, my car is the prototype for the XF tank and pump swap repair, which has now been performed on at least one other forum member's STR. The car ran great for a long time after that. I started seeing symptoms of a vacuum leak. Replaced the "PCV valve" (I know it's not what it is, but you know what I mean), and the eval solenoid and assembly. Lean codes went away.

I started getting a stumble and RP lights after that. Found out my intercooler pump was dead, and the wiring harness body plug up there had shorted out and was loosing injectors randomly. Fixed that, and replaced the DCCV valve while I was at it. Ran well for a good while, then started my current adventure.

 

Do I need to start entertaining the idea of a dead PCM?

 

Lots of folks here have an ELM327 and seem happy with it. Be careful because there are a lot of cheap knockoffs out there.

I'm running an Xtool Bluetooth module on my '02. I went with this because it's one of the few advertised to work with an iPhone:


It works well with the free app. No dealer-level stuff, but it does handle all OBD II functions and can graph live data.

If you have an Android phone, you have a lot more options.

This is one of those times a scanner, even a basic one, is worth its weight in gold. It will immediately tell you if the fuel pressure sensor is putting out an inaccurate signal, so you'd know how best to proceed.

 

Powertrain Control Module? Unless faulting itself, not very likely.
​​​​​

 

PATS LIGHT Goes out when I crank the engine over.

 

Hmm, that is eirily like what I'm seeing. Foot to the floor and it almost stumbles to life. 4.2 is not supposed to have that weakness, though. I'll be checking the fuel pressure problem tomorrow. I'll know more then.

 

Is there a quick way to diagnose a loosed/jumped timing chain on the 4.2 V8? I know a quick trick for older engines with a camshaft-driven distributor, but that's no help here. If there's a simple method for this engine, by all means have at it.

Just beware of making the symptoms fit a pattern failure, especially when that failure is very rare for this engine. Need some personal examples of troubleshooting the hard way? How much time do you have?

I hate to bring it up again, but you're really flying blind without a scanner. They are super cheap these days, and indispensable for observing inputs such as fuel pressure and CKP output.

 

compression test ,
or remove the cam covers and check the timing flats of the cams , with the flex plate TDC slot lined up with the CAS mounting hole .

 

Any progress? The suspense is killing me...

 

I don't see any reason to. Last item in the car to suspect, roughly.

 

I'm taking the day off from fretting about my car. I have in hand a NEW, OEM CKP sensor, and a NEW OEM, FRP Sensor. FRP will go on tomorrow evening, and I'll recheck the pressure output.

I do have an OBD to USB adapter - if that's what you're talking about by "scanner". It tells me a different story about fuel pressure than the manual gauge, which is definitely suspicious. I don't know how to read CKP output (there isn't a PID for that specifically) - unless that's where it gets its RPM information from, which I said before is something like 150rpm while cranking.

I can do a compression test. In fact, I had planned to, but my compression gauge won't go down into the plug holes. I need to get an extension for it.

 

If you can see revs while cranking I suspect that means the sensor is OK.

 

Re: Scanner - Yeah, by that, I just meant something able to read live data via the OBD II port. This is as opposed to a code reader, a much simpler device which can only (wait for it...) read codes and not much else.


What is the scanner saying for fuel pressure? The mechanical gauge shows 38, right?

 

I would measure the fuel pressure with a fuel pressure tester. You have a test port on the passenger side fuel rail. These can be borrowed for free from the parts stores but you might need to track down an adapter? My personal gauge had the correct fitting.

You need 55 psi as has been posted. If less you will have problems even if you can get the car started.

1. Fuel pressure with key on-engine off. If NOT 55 psi or so. Cycle key off and on several times without cranking the engine. What is that number?

2. If you can get the car started post the running fuel pressure. As stated above it's referenced to the intake vacuum/pressure and should jump around as you rev the motor.

3. I was able to drive around with the mechanical fuel pressure gauge installed. Ran the hose up by the wipers and closed the hood.

You should have codes if the fuel pressure is too high or too low but I did not see that you posted any codes?
.
.
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I was getting 0193 regularly and 0171 infrequently.

I've been super-busy, and haven't been able to get back to it and swap out the fuel pressure sensor. If I can get it started with that, I'll run the mechanical gauge on it while I drive around. There's a moderate chance I'll be replacing the fuel pump as well. Some major changes are coming down the pike in my life that will make me more able to tolerate my beautiful car's eccentricities. This is a good thing

 

Ok, update time:

- swapped in the OEM FPS. Still doesn't start. However, using my scan tool, I can see the fuel pressure - as delivered by the new FPS - is 60psi and solid when cranking. When I stop cranking the pressure drops to about 56psi and then ever so slowly drops down a 1/10 of a psi every minute or so.

I think my mechanical fuel pressure gauge might be shot. Well, that and perhaps there is some kind of issue on the right side of the engine (where the schraeder valve is).

I get a very strong fuel smell when cranking. This isn't a new behavior. This has been a constant throughout this adventure.

Things I haven't done yet:

- pull a plug and coil, ground it and crank to make sure I'm getting spark.
- compression test
- smoke test

I have a smoke tester device coming tomorrow. There is an existing evap leak issue, but I don't think that could be causing this no-start condition, could it?

Ken

 

Has the P0193 now gone? (And not back even as pending.)