Xantia Cold Start fault diagnosed at last.

pete woods · Post by **pete woods** » 17 Oct 2003, 17:12

After 11 months of trying to sort it out I finally admitted defeat & took the thing (1996 1.9 TD) to a diesel specialist.
The problem is a lack of Compression. This means either rings or valves. As it uses next to no oil & doesn't smoke I suppose it has to be Valves. The odd thing is I would have expected the problem to be worse when hot not better. Has anyone come across this before & is the cure as simple as adjusting the valve clearences to make them more gappy?

bxbodger · Post by **bxbodger** » 17 Oct 2003, 17:43

When the compression test was done, did the diesel specialist do the test twice- wet and dry?
"Dry testing" being without putting some oil into the cylinder and "wet" being with putting in some oil; they should have done both- if the compression increases significantly "wet" then it is rings (the oil temporarily seals the rings) if no change then it would be valves or possibly head gasket.
Were the compression figures the same for all cylinders, or were they different on some? it could be the head gasket not sealing or the head being warped.

bxbodger · Post by **bxbodger** » 17 Oct 2003, 17:44

When the compression test was done, did the diesel specialist do the test twice- wet and dry?
"Dry testing" being without putting some oil into the cylinder and "wet" being with putting in some oil; they should have done both- if the compression increases significantly "wet" then it is rings (the oil temporarily seals the rings) if no change then it would be valves or possibly head gasket.
Were the compression figures the same for all cylinders, or were they different on some? it could be the head gasket not sealing or the head being warped.
Whatever, its going to be fun to sort out![V]

pete woods · Post by **pete woods** » 17 Oct 2003, 17:59

None of the above. I was done using an electrical tester of some sort.
I just wanted to see if I had missed anything obvious in the past. All the tests checked out ok bar the compression one. In view of the value of the car I dont want to spend lots to diagnose a problem thats going to cost a few hundred to sort out + it's due for a clutch as well. I think its time to cut my losses & take it to an auction unless there is a cheap fix.

bxbodger · Post by **bxbodger** » 17 Oct 2003, 19:31

I am a bit confused[?]I can't see how a compression test can be done electrically; its usually done by removing a glow plug or injector, or in the case of a petrol motor, a spark plug, and screwing in a compression tester which physically measures the pressure in the cylinder at the end of the compression stroke; a proper test like this can tell you all sorts; it may be a good idea to go back to the "specialist" and find out exactly what they DID measure, or go somewhere else to get it done properly.

AndersDK · Post by **AndersDK** » 17 Oct 2003, 20:47

BXbodger -
The electrical compression test Pete mentions - is the most common compression test done by garages & speialists.
The way it works is simple :
The power (Amperage) consumption is measured on the starter motor while it cranks the (non-started) engine.
Any deviation in the cylinder's compression will also most accurately give a deviation in the starter motor's power consumption.
The method is in fact very accurate to determine relative compression between cylinders - and lack of compression - but does not give a clue to the cause of it.
The method you describe is the only correct method to find the CAUSE of lack of compression.
Clearly there's large differences in labour spent on the 2 methods.
The electric approach is indeed very easy/fast to use.

pete woods · Post by **pete woods** » 17 Oct 2003, 21:03

Thanks Anders I couldn't have put it better my myself

Jonesy · Post by **Jonesy** » 17 Oct 2003, 21:10

Pete,
If the problem is the valves, unfortunately you won't just be able to adjust the clearances as the seats themselves will be in poor condition.
Also, it could be that the compression rings are in poor condition and not the oil control rings, hence the reason it burns little oil. Have you tried to see how much blow-by you have by removing the oil filler cap with the engine running. This is a surefire way to see how the compression is. There should only be a small amount of pressure coming out of the filler.
One last thing is that the compression may well be higher when warm because the ally pistons are expanding and so creating more compression. What sort of mileage has it done?

pete woods · Post by **pete woods** » 18 Oct 2003, 15:19

The thing has done about 110000 miles. I realise the seats may be in poor condition but i thought that adj the gaps (if they are tight) may improve things a little. i rang the local Citroen specialist & he didn't want to tackle the job of adjusting the clearences!
Is it really that bad a job? I done the shims on 16 valve 750 Honda's in the past. Is it just the usual access problem or is there more to it? My biggest problem is lack of time so any advice will be very welcome

jeremy · Post by **jeremy** » 18 Oct 2003, 15:47

So far as the valves are concerned you can have one of 2problems, either they are not shutting properly or they or the seats are pitted and burnt.
So far as the clearances and starting are concerned as long as there is some clearance WHEN COLD (not necessarily the correct clearance) then the engine will start and run. The clearance will tend to get larger as the engine warms up and the head expands more than the steel valve gear. If you have no clearance then the valve will not shut properly and you will loose compression.
So the simple test is to remove the rocker cover on your engine when it is cold and see if there is some or no clearance. If there is some clearance then your problem is either valves/seats or rings/pistons/bores.
I should add that if the engine has been running with very tight clearances for any length of time then the valve seats are probably damaged due to overheating partly caused by the valve being open for longer than it should be.
The valves are adjusted by shimming. To shim them you must measure the existing slearances, remove the cambelt and then the camshaft, remove the cam followers and the shim underneath, and then substitute the correct sized shim. - just like your Honda I expect.
I know you would expect loads of fuming from a worn engine but I had a Triumph 1300 many years ago that would not start from cold reliably and did not fume. When I bought it I found that the thermostat was stuck open and I think previous owners had driven it with the choke out to compensate. Went beautifully after rebore!
Jeremy

Richard W · Post by **Richard W** » 19 Oct 2003, 05:08

I had a similar problem with my '98 xantia it had done round 100000 took it to a diesel specialist who found a few problems,ie. air leaks, cracked filter housing pump timing slightly out.and sorted these out to find it a pig to start when cold, no bother at all when even slightly warm. It turned out to be tight clearences on the valves with no gap at all on one cylinder. he suggested taking off the head to grind in the valves as it should be done or take a risk and adjust the gaps in situ, which I opted for saving quite a few quid! it worked ok and has been fine for the last 10 months maybe you have the same problem best of luck.
Richard

Dave Burns · Post by **Dave Burns** » 19 Oct 2003, 18:22

Park the bitch on a hill and bump it from stone cold, if its compo it will start easily and instantly in second cog, if it doesn't........!!
Too many variables and too much uncertainty for that method of comperssion testing to be any real use, pot to pot maybe, but not overall, I wouldn't be taking the head off on the strength of it.
Dave