Xantia V6 a bit slow to start

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xantia_v6
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Xantia V6 a bit slow to start

Post by xantia_v6 »

My "new" V6 is a bit slow to start when cold, it takes 3 - 5 seconds of cranking, wheras my "old" V6 has always started within a couple of revolutions of the crankshaft. Once running it is fine, and it generally starts OK when warm.

There are no faults logged in the ECU, and I did not notice any abnormal sensor readings. I thought that it might be a problem with learned parameters in the ECU, so I swapped in the ECU from the old car, but it was still slow to catch.

The car has done 15,000 miles on the current spark plugs, but I would be surprised if they caused this problem.

Any suggestions?
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Re: Xantia V6 a bit slow to start

Post by CitroJim »

Ahh, I may have the answer... Recently I've had a head off a V6 engine and removed it (as you can and do) with cams in place. I was a little bemused to note that ALL valves were fully closed.

This would appear to be because all the oil has drained out of the hydraulic followers and they have compressed to their shortest length.

It follows that on a first start attempt the followers will have to fill with oil under pressure to allow the valves to open enough to get the engine running. This might take a little more starter spinning then expected.

Just a thought...
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Re: Xantia V6 a bit slow to start

Post by DickieG »

If the oil was draining out of the hydraulic followers overnight then I'd have thought that would be a significant problem/fault on a high mileage engine, OK after a couple of weeks but overnight? :?

I take it you have checked for vacuum leaks/unmeasured air getting into the inlet manifold?
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Re: Xantia V6 a bit slow to start

Post by xantia_v6 »

To be honest I have not checked anything carefully yet, and the Lexia session was before I noticed that it is always reluctant to start from cold (even after 2 hours).

The car has done 94,000 miles and has been very well maintained. It idles very smoothly and quietly. I am suspecting an idle stepper motor fault, or maybe fuel draining back to the tank. I will get the Lexia back onto it when I see some blue sky.
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Re: Xantia V6 a bit slow to start

Post by CitroJim »

DickieG wrote:If the oil was draining out of the hydraulic followers overnight then I'd have thought that would be a significant problem/fault on a high mileage engine, OK after a couple of weeks but overnight? :?
Well, I know Old V6 could be a bit 'tappety' and reluctant from time to time, especially when starting from hot.

Interestingly, I've just returned from Chris570's where we've been resealing the camboxes on his 'new' V6 engine. I was somewhat surprised to find the tappets on this engine were all still springy, suggesting they'd held oil. This engine has not run for getting on for two years or more and is quite a youngster with, I think, about 115,000 miles under its belt. Chris's old engine had 172,000 miles on it and all tappets were found to be solid - suggesting they were fully drained of oil and that engine last ran not so long ago.

Looking at the tappets they show some wear, especially around the oil hole groove.

The rest of the engine appears to be in fine fettle. Honing marks are still plainly visible in the bores and not a mark on the cams.

So yes Richard, I'd say there's a good chance the tappets do wear. We need to examine more high-mileage V6 engines to be sure though. One swallow doesn't make a summer and all that...

I'll do a bit more on the V6 disassembly in my blog later and post up some pictures.

It's a beautiful engine, a work of mechanical art 8-)
Jim

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