GS difficult to start

[Oldsmoker]

My GS is a pain to start from cold and needsway too much cranking to get to go which is of course wrong. Plugs and leads are relatively new though i baulked at the points due to the need to take the dizzie off. I'll be doing that this week. However, I suspect compression may also be an issue so I've tested number 4 which is only 80psi (5.25kg/m3) this seems a little low, does anyone know what it should be. I'll be testing the rest later today.
I also serviced the carb when I bought it as it was tricky to start then and it can wiff of petrol when parked up in the garage. I'll be checking the float again but are there any bad habits here.

Thanks

[myglaren]

I found that points wear was a constant problem and frequent adjustment required.

I had an acquaintance who used to import them and DSs, refurbish and sell them. Once saw him start one by pouring petrol into the carb throat while cranking it

[Oldsmoker]

I thought you were going to say he poured petrol over it. Anyway there's a guy on youtube demonstrating the same problem so it's not just me. Typical French to put the most frequent problem in the ost inaccessible place.

[citronut]

have you checked the fuel is being pumped up, if there is a smell of petrol you could have a split fuel line between the tank and pump, this would cause it to suck air,

what duzzy is on the car, if conventional points they are easy enough to sort,

just tipex across the base of the dizzy onto the mounting point

were are you located

[2cy]

re. Oldsmokers question regarding compression test.. Does anyone have an indication of what it should be ?

I'm about to check over a 1015cc G10/612., in an Ami-Super-Berline, and the only guide I have to hand is in the French 'Revue Technique' # 330 magazine which says 9:1 compression.. 'pressure of compression : 13 +/- 0.5 kg/cm2.'

Converting this, I get 185 psi which is about 70psi more than the 1950's Sunbeam motorcycles I'm more familiar with.. Can anyone confirm that 185psi is in the right ball park, and whether this is a hot test or cold.?

Thanks, Peter
in Suffolk

[Stonehopper]

Rule of thumb would 170psi and over good; 150psi moderate; 130psi a bit on the low side. All for 9:1 compression ratio.

Test needs to be done on a warm engine with all four spark plugs removed, and throttle wide open. Remove the feed to the coil lead so as to not have sparking mis-haps. Start with No.1 cylinder and follow with the rest (just logic really). All measurements should be within 10% of each other.

[2cy]

Thanks Derek that's really useful.

Might I enquire if the test can be done cold, as I'd like to check the engine before running it ?
...and if so how would that effect those figures ?

cheers, Peter

[Stonehopper]

Never done a cold test to compare with a hot one, so can't say for sure. It could be that cold thicker oil would increase the readings - or hotter oil having been circulated increased the readings. I'll ask a man who should know.

- and the man said: -

"because a cylinder expands outward when hot, the rings will open up to accommodate and the oil will be thinner. Engines are always hot when they are working so you test it in its normal state. Nobody should give a toss what an engines state is stood still switched off but it is a rather popular notion forwarded by some.

BTW its hot and the throttle wide open as a partial throttle will skew the results too."

Sean, from 2cvGB.

[2cy]

Thank you Derek, it was kind of you to enquire on my behalf.

Alas, it sounds as if Sean is a man with his own opinions.. "Engines are always hot when they are working " ...Try telling that to an engine just starting, after sitting out all winter night ! ...or the missus who wants warm feet !!

"..as I'd like to check the engine before running it" . . . ie., when it's still cold ...then to me at least it is not a stupid question.

Context : I've just bought a car that's been standing. The condition of cam belts, fuel pipes, electrics, etc.. are questionable.. And I'm simply trying to determine whether to disturb the cylinder heads (and barrels) now, or to just change the belts, pipes, etc..

Because.., to my mind there's not a lot of sense in pulling the front of the car off and change the belts, etc., and to put it all back together again.., only to then find out that the engine won't start because there's insufficient compression, or else it's so lack lustre in performance that it all has to come out again.!

Conversely, because the car is 1200 miles away.., I'll have to pay someone else to do a job I can do. And given the choice I'd rather not pay someone to remove an engine and rebuild it.. unless of course I know that it needs doing straight away..

So, whilst I concur that a simple cold compression test may not be absolutely accurate.. all I'm after is a set of guideline figures. *

Furthermore, if the engine is "in a normal state" then Hey, I don't need to do a compression test !

* On the 1950's motorcycles I restore - we cold test ...And we have to manually turn the engines over ! But still, from real experience, we know that the bikes are unable to run on anything much below 70psi, whereas a good engine reads upto 120psi. As a datum ; those two figures, and the range inbetween, are rather useful as a guideline. But still, we have no idea what those figures should be on a hot engine.

And on a final note ".. because a cylinder expands outward when hot, the rings will open up to accommodate" yes But.. as the coefficient of expansion of an aluminium piston is greater than that of the cast iron barrel, the piston-in-bore clearance is very much less. In a good engine it will be practically oil-film tight, which of course lessens blow-pass (and piston slap !).

I'll stick with your own answer Derek..
"170psi and over good; 150psi moderate; 130psi a bit on the low side"

Again I thank you,
Peter

[Stonehopper]

Ken Hanna has also pitched in:

"Also, don't forget that the valve clearances in an A series engine *decrease as the engine warms up, so it's vital that they are checked (and adjusted if necessary) prior to carrying out a compression test.

*To the point that, at working temperature, a valve can be held off its seat if regular adjustment has been neglected."

It should be noted, that both these gents are very able and competent restorers of A series, and Sean races them, their opinions are based on a great many cars and engines.

I think if I were looking at a new acquisition in terms of cars, I would plump for the 'cranking it over by hand' compression test (if there is none, well at least you'll know) and if it started and ran, then a proper test would need to be done later. If such is not possible - then buyer beware! Checking any engine when cold will not show up what could be several faults when hot. I have driven several cars as new acquisitions over 150 miles, and always had that nervous feeling, hoping I would make home!

So from the above replies, and my own guesstimate, a cold test will produce possibly a higher reading than hot. As the fireside is of greater attraction just now, I'm not about to venture forth in the wet to discover same

You're into bikes! Good man. Have tinkered with them since 16yrs of age. Never compression tested with any device other than the foot until nine months ago! - And then only on the cars. Sunbeams are nice. Current bikes are basket cases in need of . . .

[CitroJim]

Ken Hanna has also pitched in:

"Also, don't forget that the valve clearances in an A series engine *decrease as the engine warms up, so it's vital that they are checked (and adjusted if necessary) prior to carrying out a compression test.

*To the point that, at working temperature, a valve can be held off its seat if regular adjustment has been neglected."

Just a little off-topic but I thought I'd chuck it in for a bit of interest. whilst the above generally holds true it does not in the PSA XU(D) 8V family of engines. Just the opposite in fact.

Here the valve clearances are tightest when stone cold and this in turn can lead to starting difficulties due to the clearances going negative and holding valves off their seats. This was a problem especially on the 1.8 diesel...

[Stonehopper]

I'm sure this is all to do with engine design, materials used, and layout. Whilst the XUD engine is a pretty strong block and overhead camshaft, the A series have long aluminium pushrods which will expand at a greater rate than the cast iron barrel, so the cold valve clearance will be greater that hot. The opposite of the XUD.

Good point though.

[2cy]

pssst Derek.. this is "GS difficult to start" (clue's in the title )

[xantia_v6]

Measure the voltage been the live side of the coil and the engine block while the starter is cranking the engine. If it is dropping below about 8 Volts, you can go looking for a voltage drop somewhere.

[Stonehopper]

pssst Derek.. this is "GS difficult to start" (clue's in the title )

It was two years ago . . . I think it should have started by now . . . !