1989 xj40 stalls out on hot days after during long drives...

My cat's seemed to have developed a problem. When I do on extended drives over 4 hours long,on hot sunny days she just stalls out like I'm out of gas,however there is still over half a tank on board. It was suggested by a 'jaguar specialist' assured me it's the fuel pump & filter,well $300 later and the problem consist. Now it's been suggested that it may be a small crack in the Ignition coil.Has anyone heard of this and could it be a possiblity? Thanks to all who help and love the greaest motoring machine in the world. jim

Reply to
Bongo Fury
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I'm not a specialist on the XJ40 but it looks like a well-known problem. Have you removed heat-shields from the engine or have you put insulation under the bonnet leading to overheating the fuel-lines? Is it correct that after cooling down everything is OK? In that case, try driving for a testperiod, which normally causes stalling, with the bonnet opened up. That worked for my old cars that had a problem with it. Fred

Reply to
toppie

Reply to
peter williams

The fuel pressure regulator at the end of the fuel rail is subjected to heat expansion and fuel pressures get inadequate at idle. I learned a hard lesson to get this knowledge. My 1988 XJ6 VDP had the same dilemma when coming to a stop and the engine dropped to idle speed. I followed the advice of the Haynes automotive manuals suggestion to install a second fuel pump. I piped it into the blank fitting on the front of the fuel rail. Two weeks later an overpressurized fuel line burst while I was driving on Interstate 95 and sprayed raw gas into the engine compartment and ignited an engine fire which destroyed the car in minutes after the line burst. Just as you have experienced, even the experts didn't see this one coming. I've handbuilt custom intakes and fuel systems for carbureted, injected, turbo-charged and superchaged engines for classic 6 cylinder Chevy's and a couple of 70's era Kawasaki 4 cylinder superbike motors and I've never came across a fuel delivery system as complicated as the on the 1988 Jag that burned or my current cat, an '89 XJ6. Do you hear what sounds like a tapping rhythm a bad valve lifter would make, somewhere near the firewall when you come to a stop and are at idle? You can only hear it when your inside the car. The sound is similar to "water hammer" in a piping system when you shut off a valve in a system without a damping standpipe. Same thing is happening to the fuel pressure regulator. When the injectors click shut, a good regulator will absorb the back pressure created in the fuel delivery cycle without losing synchronization to the ignition timing. When the diaphragm in the regulator expands from heat or ages, the regulator loses synchronization at high fuel pressures which occur at idle. Once the engine load is off idle, the fuel back pressure drops dramatically to supply the now hungry injector flow and the regulator functions adequately. That explains the "experts" suggestion to find an ignition timing fault. The CPU controls injector timing based on feedback from the ignition sensors and fuel pressure sensors. The back pressure leak through the regulator changes the fuel delivery volume and the now fuel delivery volume tells the CPU a false value and it corrects with an ignition timing adjustment and the fuel pressure at idle is inadequate to open the injectors. Sort of like a leaky heart valve in a human. This is what I believe caused the burst fuel line in my '88. I was at highway speed, (for my '88 that was usually between 85 and 105mph) I let off the accelerator and an instantaneous but brief backpressure in the fuel lines from the air flow snapping shut, told the CPU to reduce injector flow. At that instant both fuel pumps were delivering high volumes through the regulator and the backpressure leak blew the dual pumped fuel rail line. Have you ever seen a "top fuel" nitro car blow a supercharger off the engine on a burnout? Same physics here. Bad fuel delivery timing and back pressure into the fuel lines. Nitro burners react violently to lean fuel to air ratios !!!

"Bongo Fury" wrote in message news: snipped-for-privacy@4ax.com...

Reply to
John M Shedlock

Possible reason for the knocking sound is because the in-line damper is in need of replacing (disc shaped object in engine bay near fuel rail with inlet and outlet hose for fuel).

Another possible likely reason it stalls is because there is no fuel cooler in the delivery side if the fuel line as there is with the series I - series III cars (4.2L 6's and 5.3 V12's). You can retrofit one from an xjs v12.

I would hardly call this fuel system complicated?! 6 Injectors, 1 regulator,

2 dampers, a delivery and return line, a pump, a coolant temp sensor, a MAF meter and an ECU. All pretty standard stuff.

HTH (these are direct fixes to actual problems I have encountered in the trade)

Cheers Nick

Reply to
Nick

Since my original post, I have replaced the coil,which seems to have taken care of the problem,,,,well so I thought,Went on a drive to Indianapolis on Oct

29,only to have the engine stall out again on me,this time though there was no restarting it because opon closer inspection I discovered that the valve cover gasket had given out nad allowed oil to accummulate arould the spark plugs and basicly drown the in oil so the spark was gone.Now that I've repaced the gasket,everythings been running great.....well except for the little bastard that put a screwdriver into the oil cooler las month,I've never seen so much oil in my life.I was actually affraid the EPA was goin' to bust me. So after another $575.15 fix I happy to say I'm back on the road.hoping to find the little vandal and possibly make the human gene pool a little cleaner....

Happy driving to all

jim

Reply to
Bongo Fury

Actually, The FIRST person you should be going after is the guy who charged you $575 to fix the oil cooler. They list NEW for $120 to $136.12 (Part # CAC8509) -- used they are about $50. Sad how some Jag owners continue to insist upon being ripped off!!

Cheers Webserve

Reply to
webserve

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