X308 Compression Test
 

New to forum.
1999 XJ8 X308 84k miles. I've had the car for about 2 yrs without any major issues. Car is now hard to start, misfires when it does start. Had it to my jaguar mechanic to try several things and no luck. However, at this time, my biggest concern is the compression test results (as follows)
1. 110
2. 120
3. 110
4. 90
5. 90
6. 90
7. 85
8. 85

I understand this car may be one of last nitrasil engines. I am trying to decide how to proceed. The car is in beautiful condition and mechanically and electrically in great shape. I know the dollar value on a car like this isn't great, but I would like to evaluate options with the engine. I would appreciate any input on rebuild, replace or conversion.
Thank yo so much.
Pete

recently parked or moved briefly?

may just have to run for a while

Those compression ratios represent an awful lot of "blowby". In some engines I have had in the past,
I used a higher viscosity oil and continued to use the engine for a while, but it will need either a rebuild
or replacement with a known good engine.

You need to check the compression with the engine up to operating temperature.

You likely have a bad ignition coil? Can you get a code from the engine management?

Don’t worry about the Nikasil engine. That issue was resolved decades ago.

It’s also possible that your MAF sensor is dirty and/or you have a crack in the bellows of your intake tube causing a hard start. Brake cleaner or MAF cleaner can clean out the sensor following by drying it with compressed air. When you have it in your hand looking down inside that tube, it may have a fuzzy appearance on those 2 resistors. If so, they’re dirty and needs cleaned out to tell the ECM how much air is entering the engine for proper air/fuel mixture so your engine can run its best.

It is true that a warmer engine will provide better results than a cold one, but usually only about 10% or so.
In most cases a sudden condition of hard starting is not attributable to compression but other causes.

What is a good number for a compression test?

the specific number is less important than the consistency between holes. In denver, you'd get less compression than in death valley for instance.

I'd say 130-150 is fine, but the large difference between good and bad is the issue

Jaguar doesn’t list a spec on actual compression numbers. As long as it’s within 15%.

Thanks to all who responded. Might look for a replacement motor.

I think you will come out ahead going that route. I have seen some that come complete
with all the "bolt on" still on the block. That may or may not suit your needs, however if
a core is required, it could give you some parts that you may eventually need.

I still think you have a flooded situation. I wouldn’t go scouting out an engine yet.

I’m assuming you have good fuel, enough fuel in the tank and good fuel pressure? Is the MAF sensor clean?

To contend with a possible flooded situation you must have a strong (FULLY CHARGED) battery in your car preferably with another vehicle running with jumper cables attached to yours. This next procedure will deactivate your fuel injectors to help build cylinder pressure in the combustion chamber by introducing friction heat to seal the rings to the walls. Gas pedal to floor and crank no more than 15 seconds, turn key off and let rest for 15 seconds, foot to floor and crank 15 seconds. Do this “on” 15 seconds and “off” 15 seconds about 8 full cycles. After this, foot OFF the gas and try cranking the engine over. It may spit and sputter at first but keep on cranking, however no more than 15 seconds at a time because the starter is getting a serious workout while the battery is being drained of its juice. That’s why the running vehicle is keeping the battery charged up in your car.

The difference is those ratios seems odd to me. You might do all those things the guys above listed and then do a recheck. These engines will run a very long time if you keep oil and water in them. I can't imagine the cylinder walls are scored or the rings are shot. Of course that's just my opinion. Of my cars, Jag 3, has the engine from my wrecked 2000 VDP which has about 300K on it. The engine runs perfectly and is as spunky as Jag 2 that has about 125K.
I do run 20-50 most of the year and 10-40 in winter here in the Atlanta GA area in my cars. All of the 308 Jags I have owned use a bit of oil so you need to check it about every 1000 miles.

You never know what a previous owner did or did not do that ultimately caused a failure.
Jaguar engines are usually fairly bulletproof, however poor maintenance can extract a toll.

AJ27 Valve pitting and compression / leak rate / poor running
 

The AJ27 engines are highly susceptable to valve face and seat pitting, some in as little as 30K miles..

When I rebuilt my 2001 AJ27 heads at 106k miles, the dimples in on both the valve face and the valve seats looked like someone took a tiny ball pein hammer to both surfaces.
I had some real bad compression values across all 8 cylinders and a leak rate test showed every one of the 32 valves were blowing by, even with the valve lash within spec.

So I tore down the top end, decarbonized the engine, lapped in the valves with a suction cup adapter for my power drill.
I achieved to a good valve to seat seal checked first with mechinist blue, replaced the stem seals checked all 32 valve spring rates, and reset all the valve lash adjustments back to spec.
I got the engine back to almost zero leak rate, zero with a squirt of oil in each cyclinder, and compression ratios were all in the range of 165PSI +/- 2-3 PSI with composite/steel head gaskets.

The engine ran better at 106k miles than when I bought it at 60k miles, and oddly enough all of my rogue codes dissapeared.
Then after about 2K more miles with it running about perfectly and all the niggles sorted out, I rolled it at 80mph :icon_bricks:

My 2000 x308 had the same done at about 70K miles by the previous owners mechanic.

Listen to xalty. If the car was started and then shut off in a short time you could be suffering from bore wash. As he posted above if you can get the car running that will usually correct itself.
This is a thread that talks about bore wash and how to get past it. But you need to fill us in on when and how this started? Because I may be guessing wrong?

Bore Wash

Try starting the car with the gas pedal pressed fully to the floor. This allows you to crank the engine without the fuel injectors pumping more fuel into the engine. I have also used a bit of starting fluid to get it to start and clean out the excess fuel.
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It couldn't hurt to try the bore wash fix and if you get it running and starting well,
then see what your compression is The fact that you had a "Jaguar" mechanic
"try several things with no luck" is not promising. Bore wash would be one of the
first things he would probably check.

Hard / no start on kickover
 

I have had something similar to the "borewash" symptoms three times on different AJ27 engines. I am not coinvinced it is borewash, but lets call it that for now.

There are programming features in the ECM that if the engine does not start in a certain number of revolutions depending on the throttle position, many things are disabled, and there are typically no useful codes stored during the initial or elongated tickover. There is only a pretest to make sure the sensors are active "ready to start" like crank position sensor and throttle position, injector continuity, oil pressure, but only a couple of sensors are actually briefly logged during tickover, unless you have an IDS attached with proper probes.

So it may be useful to first record the DTC's, then clear the ECM DTC codes including any other modules that inhibit starting like the TCM and ignition / instrument modules, verify you have a "ready to start" signal , meaning you can actually crank the engine with the key engaging the starter.

My opinion is if I cannot see what the various modules are doing, you are pissing into the wind.

The first two times I had a no start with a few cylinders intermittently firing but not enough to start the engine I removed the coils and plugs, cranked the engine to blow out the excess fuel. carbon and then a very short squirt of oil, crank again for distribution and then a short squirt of starting fluid in each cylinder and reinstall the plugs and coils.

On those two cases the engine then started almost immediately. When that did not work I did a compression and leak rate test.

The third time was very different. I had to put two batteries and a charger to crank as it would turn over and almost catch, but not quite start the engine and if the battery voltage goes below 12 volts on tickover you get all sorts of things turning off and it will never start. So after repeating the above sequences, I cranked and it took about 2-3 minutes of cranking continuously while watching the available volts stayed above 12.5VDC before the engine would catch and start. That was very odd, but then after starting, I had no more issues.

There were no leaking injectors, no bad coils, perfect fuel pressure, all sensors had been verified operatonal using the IDS/SDD.

I actually believe there is a particular sequence the ECM gets locked up that is not resettable using simple OBDII tools and needs software capable of interrogating each module in detail with a proper diagnostic power supply attached.
I have seen that too many times where one module error kept the ready to start signal off to crank the engine.
Once my local dealer shop foreman verified my findings, there was a code he was also not able to reset, showed me where to find it, which was when I replaced my ECM with a rebuilt one, started at the first twist of the key. The second ECM I located was for the last series AJ27 motors and after installing that one, started with the first twist of the key, many of the annoying DTC niggles vanished, including reduced performance.

We have to remember that the people programming these engine management systems may not be thoroughly competent engineers, but programmers working for someone operating under a strict production timeline to get something out that "works", and then the rest is troubleshot by the dealer network - that is the way 3 automanufacturers I have done work for have sold their new cars for decades.

Off to go fix my X350 :icon_deal:

what you are describing is something else.

low to no compression across the board with an otherwise ready to start condition is common borewash. these things only happen with very low tension rings, pretty much exclusive to the nikasil engine.

Pete you have had some good responses?
Has any of this helped?
Is your car starting now?
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