Technical Two of my 500 engines wont start

[Fiat500sos]

Hello,

I have spent days trying to start two engines on 500 and no luck.
In my opinion I have tried everything and now is time to ask for help

So, engine was staring fine and tomorrow morning nothing.
It has enough petrol, there was spark but I have found that block has a crack so I had other engine from a car where I know it started fine, but not in this car so I have started replacing the bits:
coil, points, condenser, distributor cap, rotor arm, spark plugs, fuel pump, spark leads ... but no luck

I need to say that before putting that engine in the car, I had took it a bit apart just so I can jet wash it , clean it and paint certain parts.
There was no luck for days.

Then I remember that in the back/front there is a screw with hole in it that goes into the head and I have made a mistake and didn't put it in the back and instead put normal screw.
After change it engine was starting just fine. Hm. I though I fixed it until friend of mine said that it has nothing to do with it and he seemed to be right as tomorrow I couldn't start it again.
I might have touched something that got it working.

After trying everything for two days again I did the same thing with different engine but still can't start it.

What else could it be wrong ????????

There is spark, swaped cleaned and checked two carburators ...

WOil dbe nice if somebody can help.

Thanks
Marko

 

[fiat500]

Marko, I think it's difficult to help you because there is no way for us to eliminate possibilities. It definitely is not the hollow bolt. Did you try new spark plugs?

 

[Toshi 975]

I just supplied a cylinder head to a guy whose engine had been fitted with normal bolts. When the head gasket blew the hot gas had to find its way out and burnt a channel across the head to the extent that it was beyond skimming.

 

[jjacob]

First, tell us how you know you have spark. How did you check this?
Next, you say you have fuel. Pull one of the spark plugs. If you have fuel going into the cylinders and the engine is not starting, then the plugs should be wet with fuel. If you are using the same carburetor on both engines, then the carburetor could have a problem.

You need spark
You need fuel into the cylinders
You need compression
You need the spark to occur at the right time. Check timing
John

 

[fiat500]

I just supplied a cylinder head to a guy whose engine had been fitted with normal bolts. When the head gasket blew the hot gas had to find its way out and burnt a channel across the head to the extent that it was beyond skimming.

That's an interesting point I hadn't thought of
That groove is a pretty unusual feature as far as I know and would possibly prevent serious damage that would hurt most engines.
But If Marko is asking, all things being equal, could the wrong setscrew in those holes actually be a direct cause of non-starting....obviously it couldn't.

 

[Toshi 975]

These engines will generally fire up on one cylinder if all is set well and no load is applied. If you have a dodgy cylinder they will often cut in when the engine is warm and the revs are up which is when problems can get worse. Like when a valve starts burning out as even the exhaust valve is more vulnerable than the harder valve seat so an ally head v a cast iron head is no contest. Unlikely to be the case here but I thought it worth mentioning as I know those hollow bolts can be a real pain. They seem to be made from a casting rather than machined from solid and you have to make sure you get a good grip on them with a socket or ring spanner if they are tight. I made my own from suitable stainless socket head screws.

 

[fiat500]

I put mine in with lots of copper grease...it might work.
When I stripped the 650, the head must have been blowing into the grooves for ages as they were caked-up in hard carbon. So I was surprised to find no evidence of damage or even a prticular blow-by point.

 

[Bambino]

Hi Marko,

Given the the engine was running and then packed up after you cleaned a few things, guess my only contribution is twofold -

The guys are right - the hollow bolt is not the problem. Well not at the moment, that is.

Make sure the plug leads are on correctly. If they are reversed the engine will not start as the plug will fire but the cylinder will be on the exhaust stroke and not the compression stroke. This assumes that it's not a wasted spark ignition - unlikely as these were usually found on the 650 engines (Fiat 126/Niki 650 etc.)

Chris

 

[Fiat500sos]

Hello,
I am away to Italy at the moment and friend of mine has fixed it.
Yeeeeessssss
Will update you fully on Friday what the issue was and many, many thanks for your help and posts.

Marko

 

[Fiat500sos]

They were spark plugs even though I put the new once in.
My problem was that I was checking the spark between spark plug and nut in my case and I should have checked the spark inside the gap of the spark plug.

It was the issue on both engines and somehow I got some bad new spark plugs first time.

Thanks to everybody