2003 S-Type 3.0: Fuel Pressure Drops when Hot - Restricted Performance, Stalling, No Start.

Started with Restricted Performance then immediate stall while driving.. let sit for 5 minutes, car would run normal. Seamed random, Occurred once in a while 1 to 2x per month. No Codes. IDS only showed stalling condition.

Then one day it started happening every time I drove the car more than 15 minutes. let sit for 5-10 minutes and would drive for 5 -10 more minutes. Still No Codes. IDS only showed stalling condition

Followed the procedures here for MAF to TPS cleaning, sensor connector waterproofing, and air filter swap. (Everything was remarkably clean already, except the air filter.)
https://www.jaguarforums.com/forum/s...ics-faq-50741/
-Afterwords ran car at idol for 15 minutes and stalled with RP. Still no codes.
-Car now won't start(cranks but won't turn over) for 15 minutes, then can only drive it 3-5 minutes before stall and RP.

Swapped out crankshaft position sensor. (At the advise of two mechanics) No change.

*Started reading live data for further troubleshooting(on cheap code scanner, IDS wasn't helpful for this). Found fuel pressure drops first, then RP engages, and stalls. (within a second or two from start to finish)

Swapped fuel filter.
-Fuel pressure now creeps up from 53-56psi to 65psi as engine warms up, then suddenly drops to 20-30psi, then immediate RP and stall.
-Finally was able to rev the engine a little after pressure drop before stall, and received codes P0191 and P1338.

Swapped primary fuel pump. (Had a new one handy)
-Fuel level had been inaccurate since purchase of car. Car would be out of gas at 1/4 of a tank.
-Found both fuel pump and sender with housings had been replaced recently. Primary fuel level sensor was stuck between fuel line cables.
-Fuel level sensor now swings freely
-Replaced only the pump.
--Test drove and pushed it, Drove better than ever. Fuel pressure stayed right on 55PSI +/- 1PSI with less variance for the entire extended 40 minute test drive. Did pop up above 60 only on wide open throttle. Quickly returned to 55psi.
--Turned off car, car wouldn't start. Fuel pressure 3-10PSI across multiple attempts.
--Fuel pump and fuel sender both make a sputtering sound when ignition turned to on, then neither run.
--No codes.
--Car starts again normally after sitting overnight.

Though I have some ideas, I'm ready for some help with this before proceeding further. Any help would be appreciated.
-Full disclosure: I do get an ABS sensor code plus P1000 all the time since I bought the car, which I excluded here. I also get A/C codes in IDS - same since purchase. I don't think they have anything to do with the problem.
-Backup Toyota's engine blew last week so I am currently immobile without my S-type running.

Thanks.

 

Hmm, sounds like good troubleshooting so far.

One thought that comes to mind is the fuel pressure regulator. I'd have to do some research, but I seem to remember that the intake manifold vacuum was part of the equation. I'll have to dig through some documents tomorrow. If I'm on the right path, perhaps some vacuum issue is part of the problem.

Are you able to watch fuel trims as the engine misbehaves, or does it happen too quickly? Just thinking out loud, but maybe some vacuum actuated component has a major leak, but is only commanded open after the engine is fully warm. A big vacuum leak by itself would be enough to make the engine run poorly. And if my vacuum/fuel pressure theory is correct, that would be a double whammy.

 

Thanks for the reply. Would a vacuum leak of that nature cause the pumps to fail before trying to turn over the engine? When the problem is occurring, the pumps stutter and stop but don't pump at all when the key is in the on position(without trying to turn over). When it is working properly you can hear the both the sender and the pump start working when key is in the on position(without trying to turn over).

 

Well, looks like I'm in left field again. My vacuum theory makes no sense then.

How about the fuel pump relay? Have you replaced that? If marginal, it could certainly heat up internally and misbehave. I think it's R15 in the trunk. Try swapping with a known good relay from another position.

 

I will try the relay swap. I wasn't sure if heat would be a factor there, thanks for the advise.

 

 

What an odd & unusual problem! Good troubleshooting & data so far.

I thought fuel pressure should not get anything like as high as 65psi.

If I'm right then that must be a big hint though what it means... I can't figure it out, sorry. hmm... if it's too high then is it reporting something that's to blame (fuel pump won't stop running or some such) or is it a fake reading? Just thinking aloud here.

I'm struggling to see how a relay could cause it but it's an easy thing to check out - do check if that's the right one, though. (Not saying it isn't.)

I wonder if a failing fuel pressure sensor could cause this?

If that sounds "maybe" then any chance of watching a physical gauge on the fuel rail as it happens, to see if it matches the sensor? Would it have time to react and be seen? I suppose that comes down to how rapidly the behaviour occurs.

 

Found the details on fuel pressure, see page 109 here:

http://www.jagrepair.com/images/Elec...E%20Update.pdf


The specs are 3.8 to 5.0 bar, which translates to 55 to 72.5 psi. More details of the pump control starting at pages 57 and 97.

I'm still drawing a blank finding the reference to the fuel pressure sensor also monitoring intake manifold pressure (vacuum, actually, depending how you want to label it). I found a reference on the earlier models, but nothing definitive for 2003+. I think the later models also do this, but can't prove it. I guess it would be easy enough to inspect the sensor and see if it has a vacuum line on it. If so equipped, at least make sure the line is in good condition. However, the more I think about it, a failure of the vacuum sense portion shouldn't kill off pressure entirely. It might command the fuel pressure to one end or the other of the 55-72.5 psi range, but not shut it down entirely. So in the meantime, I'll continue scratching my head.

Could the fuel pressure sensor itself be faulty, as opposed to my previous thinking of an incorrect vacuum input? Maybe, but the scanner is showing fuel pressure dropping off just before the engine dies. If the sensor was mistakenly reading high, and thus commanding the pump to reduce output, the scanner would still show high even if the actual pressure was too low. As suggested, a mechanical gauge would be a big help here for verification.

My present theory, which I've held for over 12 hours (a personal record!) is something funky is going on with the pump. Either the electric circuit is acting up (burnt relay?) or there is a physical problem in the plumbing, such as a clogged pickup sock.

 

And the winner is.... kr98664... Bad Fuel Pump Relay.

Got the car hot, turned off, wouldn't turn back on, Put the accessory relay in the fuel pump relay plug and car started. put the bad relay back in and car wouldn't start, switched again to the accessory relay and car started and continued to run for another 30 minutes no problem. Going to pick up a new relay for a 2003 Lincoln LS at the local parts shop for $15.

JagV8: The high fuel pressure that crept up to 65psi at idol was resolved when I changed the fuel pump. As the fuel pump and the relay were both getting out of spec, I am thinking one caused the other to start having problems. Fuel pump was only $10-15 back when I originally got it so well worth the swap out even though it didn't cure the primary stalling/not starting hot issue.

Thank you both for all your help. I'll try to post back with an update after putting the car back into service for a while.

 

Sounds good but yes please see how it goes for a while.

 

I've marked the thread as resolved, please update if there are any problems.

 

Um, you do realize it's considered bad form around here to compliment me, right? It makes my head swell up and I become unbearable. From now on, for any vaguely related problem, I'm going to suggest replacing a relay. Heck, the problem could even be a flat tire, and I'll still suggest a relay. I'm sure the others will back me up on this...

All seriousness aside, please pop off the cover of the failed relay and post a picture. I'm wondering if it shows evidence of arcing, like the picture I had previously posted.