Fiat engine rough running..

[milliemarlin]

Re: Fiat engine rough running..

<snip> the Chrysler study I read detected the first degradation at 70,000 miles <snip>

That sounds like an interesting study – do you have link to it? I guess that the engine was run fairly continuously for the duration avoiding degradation due to oxidisation, moisture and pollution. Almost all wear happens in a cold engine.

I agree that changing the oil filter when changing the oil is essential. Personally I change the oil every 12-18 months regardless of mileage.

I might be stating the obvious but any air filter should be cleaned or renewed before adjusting the mixture.
Paul

[b_caswell]

Re: Fiat engine rough running..

This makes interesting reading !! but have never heard of "oil spy"

http://www.kewengineering.co.uk/Auto_oils/oil_degradation.htm

[element]

Re: Fiat engine rough running..

Hi Element,
Do you have the Haynes manual for the Mirafiori?
chris

Yes I do - and the one for the 131 Argenta from which the engine was sourced. I know where the mixture screw is but access is the problem - as suggested I'll have to remove the louvre side..

[element]

Re: Fiat engine rough running..

Did you change the oil filter with the oil change? If so just check that the oil filter is tight, if you have a leak where you never had one before it might be seeping past the filter seal.

Yes I changed the oil filter too (always do so). Until I can really get underneath I can't tell yet where the oil comes from - this evening I'll have a better idea.

[element]

Re: Fiat engine rough running..

A number of sources agree that changing the leads every 5 years or less is advisable. It's a very easy job.
Paul

My leads are 2 years old and in otherwise perfect condition - nice new silicone type.

[greyV8pete]

Re: Fiat engine rough running..

Sorry to keep on but that rusty plug connector looks u/s to me. Some silicone leads are still like the carbon type. The decent Magnecor ones are wire wound and really work well. Peter.

[duncan]

Re: Fiat engine rough running..

That sounds like an interesting study – do you have link to it? I guess that the engine was run fairly continuously for the duration avoiding degradation due to oxidisation, moisture and pollution. Almost all wear happens in a cold engine.

That was 20 years ago! - so no links - but I do remember that the cycle was normal driving and I believe they were measuring the capacitance of the oil to detect a change -

[element]

Re: Fiat engine rough running..

Spent 2 hours last night removing the louvre side of the engine bay. This morning I thoroughly cleaned the oil away and then doused the area with talc then got it running nice and hot and the leak was obvious.

It is coming from the oil pressure dashboard gauge supply valve. The instrument on the dash has a capillary pipe (transparent plastic or nylon) which carries the oil pressure from a valve on the oil pump. This valve has a brass pipe sticking out of it onto which the plastic pipe is fitted. The first thought I had was that the valve was leaking and it appears to be a hexagonal stud screwed into a hexagonal nut that is itself screwed onto the horizontal (hexagonal again) fitting that is sticking out of the oil pump assembly. The pictures show it better than I can describe it..

So I thought I’d just tighten up the valve stud, it wasn’t tight and I gave it a wee turn, whilst holding the nut immediately beneath it. Then as I did so – I realised that the horizontal shaft below wasn’t tight onto the oil pump assembly & so I gave that a turn. In so doing I now realize that the problem is that the valve (sticking uppermost) cannot allow the lower shaft to tighten anymore becase the brass tube (surrounded by the plastic pipe) is now touching the side of the engine and cannot move anymore; it looks as though the brass tube inside is a little bent at an angle as a result of the lower shaft being tightened in the past.

So… as I see it – the only way to fix this would be to empty the current engine oil and remove the shaft ‘thing’ (I don’t see what purpose it can serve other than to accommodate the valve; there is no electrical fitting on it). Then maybe put a copper washer on the thread of this shaft and retighten it into the oil pump assembly again in such a way as to ensure that the entry point for the valve stud is more towards the left side (my side as I am looking at it). All the while it is the way it is – the valve can’t be tightened adequately.

I am beginning to doubt the continued service of this valve and tube now that the brass pipe is bent the way it is.

Your thoughts?
Can I just fit a washer to get the shaft to be tight in a position so that the valve is then orientated outwards to enable it to be tightend up more? Can I get a replacement valve like this? If so where! Also how would I get the new valve inside the plastic tubing – or do I have to buy a replacement whole unit – valve, tube and dashboard instrument? (it is a 'Smiths Instrument')

Thank you for your advice!

On a positive note… I have adjusted my fuel mixture screw & it runs far better now.

[wiggiesworld]

Re: Fiat engine rough running..

Interesting conundrum. I've been considering this and just have a thought that may, or may not, help.

Just_an_idea.jpg

I've put a couple of arrows in your piccie to help me explain. Looking at the design you would think there is no way it would have been created with the part indicated by the yellow arrow being actually screwed into the LHS block for the obvious reasons you've indicated (namely that the take-off hex interferes with the boss at the back). There are a couple of possible ways around this:

1. The hex indicated by yellow is in fact just a sleeve to hold the take off and that the hex indicated by the red arrow is the way to tighten this up?
2. Indeed they have designed it such that you have to shim the yellow hex to put the take-off in the correct position before you actually can fit the take off?

Just some random musings.

[h_m_cumming]

Re: Fiat engine rough running..

The yellow arrow shows a normal gauge take off adaptor on a oil pressure electrical switch installation. just put a copper or fibre washer between it and the block to get the gauge take off in the right position and reconnect the oil pressure pipe up in the best position. The bend in the pipe will have no effect unless it's leaking.

[element]

Re: Fiat engine rough running..

Ok,
Been away for a couple of days, back now to inspect more. The yellow arrow item looks to be one of these:

https://www.merlinmotorsport.co.uk/p/oil-pressure-gauge-t-piece-m12-x-1-5-tp-m12x15

It does screw in to the left and although it appears to have some kind of electrical sensor switch screwed into it on the right - there is no longer an electrical contact for it - it is long ago broken off - so its actually serving no purpose. Whilst I could remove it and just fit a plug end cap to this T piece; its not really in the way so I'll leave it and re-use it.
The inner brass tube within the clear nylon pipe had a crack where it was up tight against the engine wall and is no longer useable. On taking it apart I have now identifed it as one of these:

http://www.minispares.com/product/Classic/Gauges/Cables,%20pipes,%20etc/OL.aspx?1402&ReturnUrl=/shop/classic/Gauges/Cables,~pipes,~etc.aspx|Back%20to%20shop

It looks identical, even the 5' length sounds right because behind the dash there's a coil of this nylon pipe. The only thing I don't know is whether the Mini one for sale is correct in size for the adaptor valve. At £5.86 its a small cost for a fix.

I have removed the 'yellow arrow' t piece & measured the thread size & have just ordered a copper washer to fit it.. If that isn't enough to give me the orientation where I need it - I can try using ptfe tape as well.

I'll call the minispares people tomorrow to ask whether the end caps on the nylon pipe are 3/8ths or not - if so I'll order that too and the car will be back on the road again shortly. However the engine bay side panel I removed was held on by lots of old fashioned big 'cross head screws and nuts & spring washers' - I will use Stainless M6 bolts & nyloc nuts to refit it..

[h_m_cumming]

Re: Fiat engine rough running..

Well done, you're getting there.

[b_caswell]

Re: Fiat engine rough running..

The can on the right is the oil light switch, worth replacing while your at it.

[Ye Ol Ripper]

Re: Fiat engine rough running..

Hi I understand you have adjusted the mixture screw and gained an improvement with the idle which is now satisfactory. On many Weber carbs the idle mixture jet (not the screw you've adjusted) has a small black o ring that provides a seal. If it's cracked it will suck in air along there and you may find that your idle will change again in the future . So before refitting the louvre panel remove it and check if it had an o ring & it's condition.

If you cannot find it in your Haynes etc then let me know as it's very likely that I have an exploded & labelled parts diagram for your weber carb

The nature of our Marlin cars is that they often spend a lot of time parked up.

The petrol evaporates and often leaves a clay type residue in the float chamber bowls, this in turn clogs up the idle and main jets. It is a good idea when the car is next being stored, to remove the top of the carb for an inspection and clean out with carb cleaner and also an airline.

Whilst the cars still in use .The Weber the idle jet can usually be unscrewed inspect the small hole in the jet isn't blocked and spray where it fits with carb cleaner and then blow through with the airline.

A blocked main jet will also cause the engine to run weak and cause the engine to run hot.

This used to be a common problem on the carb you have fitted.

I would also recommend checking the ignition timing is correct using a Strobe light as it may also be running too far advanced and pinking when going up hill which could damage a piston, as well as cause it to run too hot.

[milliemarlin]

Re: Fiat engine rough running..

Hi Element,
I’m pleased to see the rough idle has been sorted.

For the oil leak Europa do an extra long “T” piece:

https://www.europaspares.com/oil-pressure-gauge-t-pieces.html

I don’t think you have room for that. I have also seen a straight take off at the engine with a short pipe to a nearby bracket or bulkhead mounted “Y” or “T” connector.

All of the connections I have seen like this are tapered pipe threads. Sometimes they can be tightened an extra half turn – but this has a risk of thread stripping which could be very very annoying. I know from experience that these tapered threads from different manufacturers look similar but are not the same. You can fit them and they look and feel ok when you tighten them but will leak under pressure. Perhaps, someone who is familiar with the Fiat engine can tell you exactly what it is.

I’m not keen on packing on this type of connector. It doesn’t seem like a sound engineering solution. If it is a tapered thread packing will defeat the purpose of the taper – to create a tight seal.
Paul