Technical 850 setting points

[sizzles]

Hello,
Looking into why my 850 sport spider is so reluctant to start when cold. Thought I would check the points gap as a first step. Distributer cap removed, I have undone the set screws and removed the rotor arm. Under there is the mechanism of weights and springs that advance the timing. But this seems stuck on the distributer shaft. How do I remove this from the shaft? With it in place I can’t see how I can check and adjust the points. Any suggestions?

 

[Pugglt Auld Jock]

Although mostly familiar with Lucas/Delco/etc (i. e. distributors on old British cars) which tended to have their weights in the base under the plate which the points screwed to, I've managed to dig up an image of the distributor for your car and I have come across this design somewhere before. The rotor arm unscrews with a set screw on each side so you can get slightly better access by removing it however you are very unlikely to be able to remove the balance weights without the 4 lobe cam having to be removed as well? I've never come across a distributor of any type before where the balance weights need to be removed to renew or adjust points so I would bet the manufacturer does not intend these parts to be removed - anyway, if you disturb the 4 lobe cam you probably won't be able to gap the points at all. As you'll know, replacing points (& condenser) at every big service - typically yearly - was pretty standard procedure on these older cars so, although sometimes slightly "fiddly", it was usually a pretty simple procedure. Setting points by gaping with feelers is not especially accurate anyway and I'd strongly recommend you buy yourself a Dwell meter and learn how to set points by Dwell angle - done correctly doing it this way can contribute considerably to a well running engine.

 

[Pugglt Auld Jock]

PS to the above. Thinking about your poor starting. If the distributor shaft bushings or shaft are worn (always one of the problem areas with distributors - the Delco distributors on the old Viva were very poor for it) you can expect poor starting and erratic tick over. Check the distributor shaft for any side to side play simply by gripping it with your fingers and trying to waggle it. There should be virtually no side to side movement at all. If the shaft can move sideways then, as you set the points, it will push the shaft to one side so when the engine runs and the shaft tends to centralize in it's bushes, the points will be wide which will increase the degrees of turning during which the points are open so decreasing the number of degrees for which the points are closed which is when the coil is being energized. This both upsets the timing and can cause miss fires. If you have a dwell meter you can see the dwell will not be constant as the points gap differs from lobe to lobe of the cam. Even easier to diagnose on an oscilloscope - but that's maybe going a bit far for us "simple minded" driveway grease monkeys?

 

[sizzles]

Thanks for your detailed reply. That’s very kind. Will look into those ideas.

 

[portland_bill]

I'm not familiar with the 850 distributor, but the weights above the points was often a feature.
Many Fiat distributors were made to have the dwell adjusted with the engine running. These would have a hole in the distributor body, through which a small allen key was inserted, and turning this adjusted the points gap, which changed the dwell. (Dwell is the time the points are closed, so charging the coil)
When new points are fitted, they should come set close to correct, so the engine should run adequately. Then start it, get it warm, so ticking over as normal without choke, attach the dwell meter, and adjust through the hole. Inserting the allen key will bring a few sparks as it provides an alternative earth path, but this does not affect running, and won't bite you. Practice inserting the key with the cap off, so you can aim it well, although stuffing it into a moving part should be difficult.
You will probably need to adjust the dwell, reset the tickover, and maybe check/adjust the dwell again. Repeat until correct.

Used to be a feature on most Renaults, so they would be Ducellier distributors. My Panda (classic) 750 had this feature too, but I think that was a Marelli distributor.

 

[sizzles]

Makes sense. Thanks for taking the time to reply. Looks like I need to invest in a dwell meter.

 

[timmycm850]

Yes. I'm familiar with those dissys. Its often easier to set these first with the dissy out of the car. The fixing bolts of the points are best approached with a small spanner rather than screw drivers. Note the couple of slots in the points that allow you to fine tune the points position with the slight twist of a blade of a screwdriver.

Do check some other things though.
On the 850 it takes about 10 compressions of the engine to prime the carb when the car is stood for sometime and also check the fuel pump spacing too.

Tim

 

[timmycm850]

difficult starting cold on the 30dic carb could also be the choke butterfly is not giving you fully closed and hence not full choke

 

[rusty500]

On an 850 distributor, you can set the points gap or even replace them without removing the weights assembly. It's awkward, though, and it may be worth removing the distributor to get easier access. If you do, don't forget to mark where the rotor was aligned, or you'll have to reset static timing.
As long as you've got it open, it's a good time to make sure the weights move freely and the springs aren't shot, either of which can mess up the advance.
I agree with @timmycm850. It can take a while to get fuel through the carb if it's been sitting for more than a day or two. So, if it starts up once it's turned over for a little while and it keeps running without a lot of gymnastics on the gas pedal, there may not be anything wrong.

 

[timmycm850]

The 850 dissys dont do the adjust with an allen key through a hole thing and the points dont come set, in fact you have to assemble them onto the base plate. ant points gap adjustment will reset the static timing too so you will need to reset the timing anyway.

Tim

 

[timmycm850]

Saying that. I did find this pointless box recently