GS 1300 Lumpy idle and running any ideas please.

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GS 1300 Lumpy idle and running any ideas please.

Post by falling-out-with-my-car » 26 Nov 2015, 12:38

Hi, My Father who is in his 80's and getting top a point where I need to help him
out quite a bit has a 1300 GS Hatchback and it runs like a bag of bolts, things we know
fuel supply is good and filters are ok plugs are good to the car starts up and runs well its just very lumpy.
perhaps a carb rebuild any ideas please?

secondly we rebuilt her engine about five years ago with a brand new clutch and she hasn't done much mileage
the clutch is slipping and no matter how we adjust the cable the clutch still seems to slip.

I own a 2cv and I was wondering if like the 2cv the clutch cable required an inch or so of slack in the top of the cable?

your thoughts constructive comments much appreciated.

regards.
Nigel.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by Stonehopper » 26 Nov 2015, 16:28

Regards the clutch cable, there should be between 3.2mm and 3.8mm play at the point where the cable adjuster butts against the bulkhead fitting, and 15mm - 20mm at the pedal face from 'off' to taking the tension of the cable.

Rough running. Check your timing and dwell before tackling the carb. If the former is as per book, then take the top off the carb, soak up and empty the float bowl, then tackle the jets cleaning each one in turn. Another item to check is for air leaks either side of the carburetor base to manifold; inlet pipes to cylinder head, and exhaust manifold to cylinder head. Leaks there will usually result in a popping on the over-run, mostly noticeable when using the engine as a brake descending hills.

If you have a Weber carb., there is a little electric cut-off valve attached to the carb tucked under the air hose to the cleaner. Had trouble with one myself which needed replacing. The Solex might not have this - uncertain.

One other thought: how old is the fuel in the tank? Water can be absorbed by modern fuels and will settle at the bottom - just where the pick up is located.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by falling-out-with-my-car » 01 Dec 2015, 13:32

Thanks Derek,

I had a feeling there should be some play in the clutch cable not unlike the 2cv.
as for the carb I shall have to check which type it is first, I have a feeling its not a Webber.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by 2cy » 11 Dec 2015, 23:19

Stonehopper.

might I ask 'timing and dwell'.. Do you mean by this the timing and points gap ?

or else how does one set the dwell. ?

Thanks, Peter
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by xantia_v6 » 11 Dec 2015, 23:30

Dwell is the measurement of the proportion of each revolution that the points are closed. It is measured by a dwell meter (some timing lights had this function). It is adjusted by adjusting the points gap.

On some engines it is difficult or even impossible to set the points gap statically due to the shape of the cam or other factors.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by 2cy » 11 Dec 2015, 23:59

Thanks xantia_v6

you learn something every day.. !

Of course the instant the points open is when the spark happens, x degrees before TDC.., so why does it make any much difference when they close again / the proportion ?

Apologies if the rest of the world knows something I do not.. but I often find that !

p.s. On many A-series the points have been replaced with electronic (optical or magnetic) units. As I hear the GS points are equally awkward to attend to, is this not also a practical proposition on the flat our engine. (mine being the Ami-super 1015cc)
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by xantia_v6 » 12 Dec 2015, 01:03

2cy wrote:you learn something every day.. !

Of course the instant the points open is when the spark happens, x degrees before TDC.., so why does it make any much difference when they close again / the proportion ?

If the dwell is too short (points gap too wide), then at high RPM, the coil does not have time to charge its magnetic field, and you get a weak spark and misfire.

If the dwell is too long (points gap too small), then on some engines, the coil (on average) draws too much current, and runs hot, which can also cause a misfire. In reality, the usual problem with running excessive dwell is that as the cam-block wears, the points open less and less until they don't open at all and the engine stops.

2cy wrote:p.s. On many A-series the points have been replaced with electronic (optical or magnetic) units. As I hear the GS points are equally awkward to attend to, is this not also a practical proposition on the flat our engine. (mine being the Ami-super 1015cc)

You can fit electronic ignition to almost any engine, as long as you can get or adapt a pick-up assembly to fit in the distributor. All the big vendors have long lists of pickup assemblies and adapters for most classic cars.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by 2cy » 12 Dec 2015, 15:55

Thank you that's clear as to the why's and wherefore.

I assume because most don't have access to a dwell meter then the practical compromise is to set the ignition timing by strobe with the correct points gap.., and the dwell ends up close enough (assuming the cam lobe(s) are in decent order).

I appreciate your taking the time to explain these things, and in particular the importance of the dwell with regard to coil recharging or overheating.

Peter
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by sandybx » 13 Dec 2015, 00:09

Dear Peter :)
GS engines have two types of distribtors Peter. They have ducellier type distributor has 2 pieces and SEV marchal witch have only one peice cassette points ( niether are inter changeable )
A points gap of a 15 thou feeler gauge will give a dwell angle of 57 degrees ( which is what the dwell angle should be ) Peter
I hope this clears up this problem :)
Vince :)
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by Stonehopper » 13 Dec 2015, 20:58

Sorry, I missed the query! But Xantia V6 and Vince have answered perfectly. :snowman:
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by xantia_v6 » 13 Dec 2015, 21:54

I remembered something else about dwell vs points gap:

When the distributor shaft gets worn with use, it floats around a little, dynamically altering the points gap and dwell. It is easier to take account of this by adjusting with a dwell meter.

I see that Luminition list a kit for the GS with Marchal distributor, but not Ducellier, although they have kits for other Ducellier models which maybe could be adapted.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by 2cy » 14 Dec 2015, 16:39

Thank you again Vince, Derek, & Xantia_v6

From a photo I took when viewing my Ami-Super (M10 engine) for the first time - it looks as if I have the Ducellier distributor. My engine mileage is thought to be low, so I'm hoping things are not too worn.

I like the accuracy and maintenance free of electronic ignition, but also like things to be easily switchable back to points (in case the device decides to fail - as I had that once, a long time ago). In due course I'll speak to Luminition and ask if they can help me out. They've given me very good service in the past.

Peter
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by macplaxton » 17 Dec 2015, 04:06

I think the problem with the Ducellier ignition kits is that unlike Renault stuff with an open area under the cap:

Image
2014-10-03_22-43-28_306 by macplaxton, on Flickr

The one on the GS has a top bearing plate to get in the way of things such as tall hall sensors and beam choppers:

Image
Distributor internals 3 by macplaxton, on Flickr

If you want the "best of both", upgrade a Marchal to electronics and keep the Duc with points in the boot for a quick swapover.
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by 2cy » 17 Dec 2015, 13:33

ah ha ! ..that makes sense (..and would why it's reputed to be a pain to adjust in situ !)

Your 'best of both' sounds like a plan.

Thanks, Peter
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Re: GS 1300 Lumpy idle and running any ideas please.

Post by CitroJim » 18 Dec 2015, 10:40

Back in the day I never relished the task of points adjustment and in the GS I'd relish it even less!
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