Hello,

New member here, though I've been previously trawling the site and getting lots of useful information - thanks.

Anyway, I've just replaced the upper timing chain tensioner on my AJ16 and once I'd put it all back together, it was really hard to start. It's up and running now and drives ok, but if I rev the car in neutral, as the revs fall back to idle, it stalls and is then very hard to start again (lots of pumping the accelerator when cranking). I'm pretty sure I've got the cam sensor lined-up correctly and can't see any loose vacuum hoses, so a bit stumped.

Good news is that the timing chain rattle has ceased, though!

Any pointers much appreciated.

 

Welcome ...Roy!

Lots of stalling around here lately... with a variety of causes and solutions. Don't know if the cam position sensor could cause stalling, but for sure it could cause hard starting! A small degree of rotational adjustment of the CPS can make a big difference in starting. Give it a slight twist either direction, and try again. Likely it is a bit off, since you had it out to get to the tensioner. See if the hard start is corrected, then let us know if the stalling continues and we'll go from there.

 

Good idea. Will have a go at that later - thanks!

 

Mine was doing it as well, but under heavier breaking, when still in gear but clutch all the way down to the floor. Topped up clutch fluid and it's never done it again.

 

Well, it's stopped the stalling now and runs ok, but is still pretty hard to start.

I'm taking it on a 3000 mile trip around Europe in a few weeks, so will need to get this sorted. Wife thinks I should just take it to a mechanic......

Will have a mess around with the cam position sensor thing tonight and see if I can get things to improve.

 

The chance of a mechanic knowing that the cam position sensor affects starting ease is nil, unless he's a jag mechanic. Don't go to one until you try this out, it is your most likely scenario! Tell the wife that if this fixes it, she will get a gift with all the money you saved!

 

Hmm....not sure I'll be taking it around Europe now.

Wouldn't start at all yesterday so I called the breakdown recovery people who diagnosed a total loss of compression and a new engine needed. Find it hard to believe as I was driving around in it quite happily on Sunday, but there we go. Just considering my next steps, now.....

 

No start after Cam sensor twist adjustment? Are you certain you replaced it in the same exact position as removed when doing the tensioner?

Your service people probably heard of the first gen Jag V8 and it's compression problems and passed it off as such. Did they actually do a compression check? Did they check for fuel, air, and spark?

Sounds like bull-bunk to me.

 

Didn't see them doing a compression check, but he said it was turning-over too fast and didn't sound right, so suspected loss of compression.

I'm guessing cam-sensor is way out now as both of us have been messing about with it try to get it started. Will get it lined-up and try again - got nothing to lose now.

Definitely had fuel and spark, though.

Thanks

 

There is a method to get the cam sensor timed properly in relation to the rest of the engine. I don't remember how it's done but hopefully someone else knows straight away and will post up.

I've never heard of an AJ16 losing compression to the point of no-start. Anyone else?

Good luck and good day.

 

is this is a 4.0 xj6 1995 then
i don't know if the valves aj16 interfere with pistons but if you get timing off to much on a Honda you will bend all valves after a short run and loose compression. it turns over easy because it has no compression. or compression test it. if camshaft sensor is unplugged it will be difficult to start but will start and rough idle. this is what regulates the timing for injectors fuel air mixture.

my crankshaft sensor was out of spec. where the gap was .048 and adjusted by bracket to .025 inches
remove negative on battery.
timing: oil fill cap open examine 4th cam lobe should be straight up and timing on camshaft through window should line up in circle. AND THE CRANKSHAFT SENSOR POINT SHOULD LINE UP WITH OPEN TOOTH ON CRANK. DON'T LINE IT UP WITH TIMING MARK POINTER. if lobe is down rotate crank shaft approx 180 degrees with
1-3/8" short socket till cam lobe is STRAIGHT up and cam shaft is centered in circle. take off cover temp. to see if you are close. camshaft sensor normally doesn't throw a code and can run smooth at under 2000 rpm after it gets warm it can eventually through code ck engine lite p0727, p1775, p1790 but if you are off 1 tooth you will get misfires and hard to start.

once it is running put a vacuum Gauge in the intake manifold. if it holds at 18 lbs vacuum steady you do not have a blown engine. if it jumps like 10 to 18 during idle you have a problem.if you hit throttle full open momentary it will rise to 22 momentary and drop to zero and back to about 18 steady that means all valves are seated and good compression and cat is OK.

 

Right....mechanic has got the car running, so that's good. He said that there was no compression in any of the cylinders due to the flooding, but it's up and running now, although still tricky to start on occasion.

Having a full service done, new thermostat and the crank sensor bracket changed for the fancy one that advances the timing.

Just have to wait for the bill now.....

 

GENERALLY NO COMPRESSION MEANS VALVES ARE OPEN OR BENT OR HOLE IN PISTON AND FUEL TYPICALLY DOESN'T CAUSE NO COMPRESSION. IF ANYTHING IT WOULD INCREASE COMPRESSION. Generally hard to start is the camshaft sensor out of adjustment / spec. Once you verify previous alignment points . If you still have problems. Look at something else. I have had temperature cause camshaft sensor to fail after the car starts and runs smooth for about 15-20 min. Make sure the gap on the new crankshaft sensor is gaped to about .025"
spec says .018 to .042 you get the most signal at this adjust. Sound like it been running rich with carbon on plugs that could be tps jumping from 14 to 64 and not moving smoothly as depressing throttle. Which causes it to misfire occasionally and sometimes backfire.

 

I think he said that the fuel had washed-away the film of oil that maintains compression around the pistons. If the car is kaput, I've got my eye on a couple of XJR6s that are for sale.....

 

Car is back and working now. Needed a new ECU and a couple of coils fitted. Had ignition advance bracket fitted at the same time and the car seems great. Much quicker than before.

 

i dont understand how your mechanic went from no compression to ecu and coils. but glad its all fixed now.

 

i had the starting problems with my jag and it was one of the injectors fault - always open - so the cylinder was getting filled with the gas. fixed the injector - car back on road.

I do not understand how mechanic could get back car to life without changing piston rings if there was no compression at all. sounds like he's bull shitting you.