Technical 2 wet plugs & 2 dry ones

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Technical 2 wet plugs & 2 dry ones

rusty500

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In my 600D (I know the Forum says 850, but where else to go?), I'm tracking down a problem with starting and idling. It only starts occasionally, and it won't idle when it does. I'm still checking on various things, but I noticed something curious yesterday. When I pulled the plugs, expecting to see them all wet from flooding, 1 and 4 were bone dry while 2 and 3 were wet like I expected.

The theory that I'm pursuing is that 2 and 3 have a weaker spark because of a problem somewhere in the circuit. I have confirmed that they spark when dry.

What I'm wondering, though, is if this could be a symptom of a carb problem causing unvaporized gas to be leaking down into cylinders 2 and 3? If so, what would it be? Carb's been recently cleaned and rebuilt. No leaks on the bench with a full float chamber.
 

bugsymike

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In my 600D (I know the Forum says 850, but where else to go?), I'm tracking down a problem with starting and idling. It only starts occasionally, and it won't idle when it does. I'm still checking on various things, but I noticed something curious yesterday. When I pulled the plugs, expecting to see them all wet from flooding, 1 and 4 were bone dry while 2 and 3 were wet like I expected.

The theory that I'm pursuing is that 2 and 3 have a weaker spark because of a problem somewhere in the circuit. I have confirmed that they spark when dry.

What I'm wondering, though, is if this could be a symptom of a carb problem causing unvaporized gas to be leaking down into cylinders 2 and 3? If so, what would it be? Carb's been recently cleaned and rebuilt. No leaks on the bench with a full float chamber.
First I assume all four compressions equal and good.
Any chance of a hairline crack in distributor cap across those two cylinders.
Spark plugs in good condition and correct heat code for your environment. Never wire brush plugs to clean as the metal particles cause breakdown of insulation and misfire.
No wear in distributor cam lobes i.e. same points gap on each lob when opening points.
No head gasket issues, water or oil losses.
Are your HT leads copper cored or radio suppressed carbon string. Test with multimeter Ohms setting to check for continuity, similar on all four leads plus HT to coil.
Re carb cleaning, does your carb have an idling jet and if so is it possible to remove the emulsion tube below it as some carbs store dirt and water there. No leaks with full float chamber as you say, but were you able to test needle valve by blowing (with a clean tube so you don't taste petrol all day;)) then keep blowing as you turn carb upside down so float shuts valve etc. without sticking.
This is all general knowledge from fifty years in motortrade, I did have a Fiat 600d with suicide doors around 1972 and a Fiat 500 around 1978, but none recent.
Final thought for today inlet manifold air leak / warped etc. between center cylinders. Sometimes you can hear this with a length of tube placed to your ear and other end run along between head and manifold.
(y)
 
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rusty500

rusty500

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I just remembered a detail that I didn't pay attention to when I dismantled my carb last week...the gasket between the carburetor cover and carb body was soaking wet with fuel.
That's an indication that there is something wrong with the float and needle, isn't it? (Or too much fuel pressure, but that seems unlikely.)
 

bugsymike

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I just remembered a detail that I didn't pay attention to when I dismantled my carb last week...the gasket between the carburetor cover and carb body was soaking wet with fuel.
That's an indication that there is something wrong with the float and needle, isn't it? (Or too much fuel pressure, but that seems unlikely.)
Worth a check, although would have thought if starting with a set of clean plugs it would still rev up until it got too rich to run cleanly and I would have thought the rich exhaust would be fairly obvious, like a car with the manual choke right out.
 
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rusty500

rusty500

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Follow up: still not sure why my carb was flooding my engine so badly, but in the meantime, I've put another carb in and replaced the spark plugs. Started right up, and it is idling smoothly and evenly below 1000rpm now. Hoping to take it for a test drive in the next few days.

(All of this is follow-up to an engine rebuild because of low oil pressure where it turned out the bearings were worn and the rings were +.6mm while the cylinders/pistons +1.0mm)
 

bugsymike

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Follow up: still not sure why my carb was flooding my engine so badly, but in the meantime, I've put another carb in and replaced the spark plugs. Started right up, and it is idling smoothly and evenly below 1000rpm now. Hoping to take it for a test drive in the next few days.

(All of this is follow-up to an engine rebuild because of low oil pressure where it turned out the bearings were worn and the rings were +.6mm while the cylinders/pistons +1.0mm)
Glad it all sounds good now :).
Strange about the odd mix of ring and piston sizes, I suppose with older cars you never know who has been working on it in the past.
Trust the engine been "run in" gently since rebuild along with early oil change and filter, head retorque and valve clearance checks?
If so should be good for many miles to come(y)
 
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rusty500

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Engine hasn't been run in yet. Still working to get it on the road for the first time after the rebuild.
 
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Mike raised some very salient and informative points above but, given the outcome that it seems to be running well on a substitute carb all seems to point to a problem with the rebuilt carb. Without having the advantage of being able to inspect and "fiddle" with it, I'd be suspicious that it's something to do with the needle valve or float. Have you checked the float level? I remember when I rebuilt the carb for my old Austin Ambassador I just couldn't get it to run well. Had it in pieces several times and just couldn't find anything wrong. Then I noticed that the float level given in the Haynes manual for that vehicle was different to that given in another Haynes manual for basically the same carb on a 1500 Allegro - SU HIF for those who remember them. The HIF stood for Horizonal Integral Float - I set it up to the Allegro spec and it ran beautifully. Wrote to the Haynes people - who I'm not knocking by the way, I've used their excellent manuals for years and this is the only discrepancy I've ever found - who wrote back saying I was correct and apologizing for the error (don't know if they tried to rectify it though?). I think you should check your float setting and maybe check the float doesn't have a wee hole in it?

On a more general note, and for the benefit of our less experienced people, I also noticed that Mike raised the "hairy old" subject of whether to clean spark plugs or not. I am firmly in his "don't wire brush them" camp. The argument goes that if you wire brush them then small traces of the metal the brush is made from gets rubbed off against the insulating "nose" which then encourages the current to track down the outside of the insulator to earth rather than jumping the gap to the side electrode. At worst this can lead to actual missfires but also I believe it can lead to a diminution of spark energy if some of the current "leaks" but still has enough "left over" energy to jump the gap but with reduced force? I believe that, a few years ago, the manufacturers (NGK for sure) stopped giving a glazed finish to the ceramic insulator "nose" (you can clearly see the nose is now matt in appearance on a new plug) I believe this type of finish attracts the metal particles even more?

If your engine is in good order and not allowing excess lubricant to enter the combustion chamber then modern spark plugs are, to a large extent, self cleaning. Just look at these plugs which came out of Becky (2010 1.2 Panda Eco Dynamic 60hp) last year at service time:

P1100551.JPG


The first thing to notice is that they have, in common with many plugs today, extended "noses" which project the centre electrode well into the combustion chamber which allows normal deposits to be burnt off during running. Look a little closer:

P1100553.JPG


You can see there's been some degradation due to heat - you can see the discolouring of the ceramic nose - and erosion of the electrodes due to spark jumping that gap - Look at the centre electrode and you can see it's corners are a bit rounded off, so far no metal has been leached from the side electrode. These plugs have been in the engine for a couple of years and are looking pretty much as I would expect them to look, which is - No great build up of carbon deposits. Some evidence of wear to the electrodes (metal gets burnt away by the spark over time) Threads looking good and undamaged thus indicating that the threads in the head are probably in good order (they unscrewed without jamming up too which is another good indicator). I'm sure I could have just stuck them back in and the engine would have run on them just fine but maybe with a little reduced efficiency. If I was doing this I wouldn't have done anything to them except check the gap. However they've served me well for the last couple of years and there's always the increasing possibility of electrical breakdown of the insulation due to age so now it's time for new ones. These are normal, some call them "copper cored" plugs, which my local factor sells very cheaply so that's what I run both my Panda and my boy's Punto 1.4 8 valve on (NGK ZKR 7A-10). I could choose to fit "long life" iridium tip type (ZKR 7AI - 8 I think?) and "forget" about them for 60,000 miles/10 years? but that's not for me as I like to pull my plugs every year at service time and examine them so they can "speak" to me about what's going on inside each cylinder. Also by removing them every year it pretty much ensures they'll never have time to corrode/seize in place.

For those reading who don't have much experience of examining plugs here's a new one - on the right - compared to a well worn one - on the left. Just look at how much the centre electrode has burnt away:

P1100556.JPG


Close examination will show the side electrode is also suffering slight erosion as it's tip is slightly hollowed - I've seen them much worse than this with side electrodes almost burnt away and. usually the engine missfiring - which is why the customer has brought the car in of course - nothing to do with them having missed the last 2 services?!

If your plugs look like this:

P1100562.JPG


Where the plug is heavily contaminated with black carbon (soot basically) Then you've got an over fueling (running rich) problem and it's not at all uncommon to find this will be due to the air filter needing to be renewed! Of course other problems can be the cause also but checking your air filter should be a first stop check.

Or

P1100557.JPG


Wet and "gungy" with often heavy deposits inside the end. Oh deary me! this is due to oil being burnt. might be something "simple" like a blocked crankcase breather but more often due to a worn engine - commonly valve stem seals, sortable at a price - or, more seriously, piston/ring/bore problems which often means a new engine needed as labour to "fix" it will be prohibitive. By the way, Any "clever clogs" reading this will probably recognize this oily plug is actually from a 2 stroke but I didn't have an oil fouled plug from a 4 stroke to take a picture of - sorry! So, at the end of the day, If the plugs are nice and clean burning like mine above which you saw in my first picture then, if the electrodes are in good order, you can reuse them, just screw them back in. If they don't look "good" then, if it's just electrode wear renew them but if it's contamination you need to sort out the problem, no amount of wire brushing will sort that.

Just to finish off, again for the information of our less practical brothers (and sisters), here's what the business end of a couple of "long life" iridium/platignum/whatever plugs looks like:

P1100563.JPG


You'll notice right away how different the centre electrode looks - very thin and "pointy". These centre electrodes are very brittle and should not be abused with gaping tools as they can easily snap off! The manufacturers claim the plugs are pregapped and should be fitted without attempting to adjust them. I still check visually just to be sure they haven't been damaged in transit. The NGK "jobbies" have a hard cardboard tube in the package which protects the threads and electrodes, I've never had a damaged one.

If course if your engine only has a long life plug specified - like my IBIZA - then that's what you should use, but I'm very happy to go on running "copper cored" plugs in our wee Fiats.

Finally, another thing which "bothers" me is the length of the treaded part of the typical plug on modern engines. Just look at those two Iridium plugs compared to a couple of older plugs:

P1100564.JPG


As you can see the long life ones are on the left. To their right is first an N9Y (NGK equiv BP 6 ES) - found in so many cars form the 60's and 70's and a short reach from a wee DAF. I know modern plugs have sacrificial thread coatings (NGK call theirs Trivalent I believe?) but a thread that long, and I've seen longer, I think the KIA uses an unusually long one? https://www.eurocarparts.com/search...Sy-ftHBzMAwvVerZfNYVZNO-FHPCmZzxoCHpgQAvD_BwE surely must be subject to greater possibility of seizure after 6 or more years? And yet they are telling us not to lube the threads with copa slip or other antiseize. On the strength of this I've been putting them in "dry" for a couple of years now so time will tell I suppose?

EDIT Ps. DO NOT clean plugs with abrasive papers, 'specially not anything with carborundum. and don't even think of using one of those old style sand blasters. In my opinion the chances of managing to ensure none of the grit gets left behind up in the recess is unacceptable and any grit which then gets into the cylinders will wreck havock|!
 
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rusty500

rusty500

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Thanks for this. It's very helpful. My particular situation is that my engine had multiple problems when I bought it, and I'm still trying to get it running well, with the added complication that I leave at an elevation of 6300ft/1920m. I'm trying to get the timing right and the carburetor properly jetted for the elevation even though I don't have a ton of confidence in either the distributor or carburetor. In the process, I can't help fouling the plugs periodically by either flooding the engine trying to get it to start or running too rich because of the elevation. Once I get everything set right, I will put in a new set of plugs and leave them alone, but for now I am trying to clean the ones I have when they get wet or fouled to be good enough to do the next round of testing.

As far as the carb I swapped out is concerned, I have adjusted the float level, tested the float for leaks and replaced the needle valve and seat. I'm stumped about why it was flooding the engine consistently, but I'm not worrying about that as long as I have one carb that is working.
 

bugsymike

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Re the old plug s and cleaning, I just put them on my gas cooker burner for a while, it works well for two stroke chain saw plugs also and doesn't involve wire brushes.
Re the flooding , assuming no higher powered aftermarket fuel pump fitted and the float level set correctly, if the needle jet is in good order, with the carb in your hand and a clean tube to inlet if you blow through the tube with carb in normal position easily and then as you turn it upside down the jet should shut so impossible to blow and when turned correct way up again it blows through easily again.
Re centre two plugs fouling, assuming compressions high and even, I would look to the inlet manifold /gasket area for warping or cracks.
I wouldn't presume to advise you on jetting as your local knowledge at that elevation is much higher.
On timing I assume the distributor isn't worn on the advance balance weights area allowing it to over advance, so all I can say would be use the highest octane/quality fuel available and trial and error to get to the optimum, much as we had to do when fuel companies stopped our five star petrol, advance timing to just below "pinking/knocking" when fully warmed up and under labour pulling up a hill.
 
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rusty500

rusty500

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For anyone following along, I have discovered that the problem (or at least a problem) is the thing that I dismissed right from the beginning. I had too much fuel pressure.

The last person to mount the fuel pump before me did not put in enough gaskets to space it far enough from the engine. As a result, the shaft that pushes the diaphragm was protruding into the fuel pump too far. I continued the problem when I remounted the fuel pump because I just used the same number of gaskets that they had in there. I've now put in enough gaskets so the shaft only protrudes 1.2mm into the fuel pump at it shortest. (I could not find specs for the 600, but that's the spec for the 850, and they seem to use the same pump.)

It started right away and no evidence of too much pressure any more. Fingers crossed, I'm one step closer to this thing finally running as it should.
 

bugsymike

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For anyone following along, I have discovered that the problem (or at least a problem) is the thing that I dismissed right from the beginning. I had too much fuel pressure.

The last person to mount the fuel pump before me did not put in enough gaskets to space it far enough from the engine. As a result, the shaft that pushes the diaphragm was protruding into the fuel pump too far. I continued the problem when I remounted the fuel pump because I just used the same number of gaskets that they had in there. I've now put in enough gaskets so the shaft only protrudes 1.2mm into the fuel pump at it shortest. (I could not find specs for the 600, but that's the spec for the 850, and they seem to use the same pump.)

It started right away and no evidence of too much pressure any more. Fingers crossed, I'm one step closer to this thing finally running as it should.
Regarding gaskets at pump, most pumps and carbs around that time had a thick fibre insulator block with a paper gasket either side to prevent heat transference which could vapourise the fuel and cause problems when hot.
Glad you are having some progress:)
 
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