Technical Non starter! HELP PLEASE!

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Technical Non starter! HELP PLEASE!

crazypierre

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Hi,
(Fiat 126 652cc engine fitted in a 1970 Fiat 500.)

This car had sat for over a year and it started immediately, although with an erratic idle (kept dying unless foot on accelerator.)

Drove it about 5 miles and it ran OK although it kept cutting out at lights but started again OK.
Then, the next day, driving along about 50mph, it started spluttering and coughing, revs dropped and it cut out.

As I had not tool, I called the AA who removed the carb, cleaned all the jets, put it all back but it just wouldn't start for the AA man so he towed me home.

Today, I removed the carb, cleaned all the jets again, checked the needle valve is cutting off fuel and it's all fine.

Removed the plugs, cleaned them and checked they spark which they do. It's a Weber carb- see attached picture.

But still it won't start! Checked plugs after trying to start it and they are wet with fuel so it's getting through to the cylinders.

It has electronic ignition so no points.

What could be wrong that it was running and then spluttered cut out and now won't start?

One other thing I noted: the fuel return from the carb to the fuel tank has been blocked off so there is no way for excess fuel to make it out of the carb.
Could it be flooding the carb due to this?

But that's how it was for years before when it was running fine so don't see how it can be that?


Any ideas?

Thanks
Peter
 

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Hi, as you are getting fuel through to the cylinders I would Replace the condenser, if it is faulty it won’t start as the spark is to weak. I always keep a spare with me as I went through 3 on my return journey from Italy, poor quality replacements.
 
Have you drained the fuel tank and installed fresh fuel. Modern fuels can go off after even a few months and then doesn't ignite so well - so it's possible that the fuel can wet the plugs even if they are sparking correctly. Afaik, the volatile components evaporate out of the fuel and it can also absorb moisture from the air in the space above the fuel, both of these factors will affect ease of starting and cause running problems.

If there's very little old fuel remaining you could try putting a couple of gallons of fresh fuel in the tank and give it a stir, fresh fuel will get to the carb with a bit of running.

The lack of a fuel return shouldn't prevent the engine running normally - many other owners have cars with the return blocked off - and you said the car was running this way in the past. Only way it could affect it is if the carb needle jet is worn, float level is incorrect or float is perforated (unusual). - and you've checked the carb out and it appears ok and was running in the past.

If the car has electronic ignition, I don't think it will be fitted with a capacitor (I might be wrong on this) and in any case you were getting a spark when you checked?

Does the car start if you do a push/tow start? If it does I'd run it at a fast idle until fresh fuel gets through.

Al.
 
Hi, thanks both for your advice.
I don't think it has a condensor as it's been fitted with electronic ignition.
The fuel is fresh and it ran for about 5 or 6 miles then just started spluttering and died.
I've ordered some new plugs and will see if that starts it.
Haven't tried push starting as has a new battery and turns over fine.
Will let you know if it starts.
PC
 

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Have you checked for spark? I've never fitted electronic ignition as I've found some of them to be unreliable. ..stick with points and condenser simple to get going should you break down. Just check gap and maybe change a condenser
 
Is it easy to change back to a distrubutor and condensor and coil?

Sometimes.

Some electronic ignition systems use a different coil and modified/different distributor. So all components need to be returned to standard. Can you post pics of your ign. coil and the distributor with the distributor cap removed - someone can then advise you if they're standard and suitable for conversion back to the original points, condenser and coil system.

I just noticed your picture in post#4 above. Your picture above of the coil is not from a 500. It appears to be from a later 126. If it has 2 plug leads coming out of it, it sounds like it's the later 'wasted-spark' ignition system and afaik, can't be easily converted back to the original 500 coil and points system. Others on here, will no doubt be able to give you an accurate answer (I'm not familiar with the later 126).

Al.
 
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Hi, thanks both for your advice.
I don't think it has a condensor as it's been fitted with electronic ignition.
The fuel is fresh and it ran for about 5 or 6 miles then just started spluttering and died.
I've ordered some new plugs and will see if that starts it.
Haven't tried push starting as has a new battery and turns over fine.
Will let you know if it starts.
PC

Are you absolutely sure that there is no blockage in the idle circuit in the carb (I know you say you cleaned/checked the carb).

Running for 5-6 miles and then spluttering and dying sounds more like a fuel issue. One possibility is a blocked vent on the fuel filler cap, this causes a vacuum to build up in the fuel tank, restricting the flow of fuel after a few miles. When it happens, remove the cap, if you hear an inrush of air, this is probably the problem, the car should restart after a bit of turning over to prime the fuel line to the carb.

Another possible cause is something still lodged in the idle circuit, restricting/stopping the flow of fuel at idle. Thus is why I suggested trying a push/tow start, this will spin the engine over faster than using the starter motor, so should get the engine started if the idle circuit is indeed blocked.

Ignition faults usually result in the engine cutting out suddenly, as if you turned off the ignition switch. Running short of fuel tends to result in rough running, spluttering a little before finally cutting out.

Some people have reported similar problems traced to an ignition coil going faulty. Often the car will restart normally when the coil has cooled down. Whenever this happens, it's useful to check if you still have a reliable spark when the engine cuts out, not wait until later to check things out. When it happens, try touching the ignition coil, it shouldn't be unbearably hot.

The usual procedure for fault finding on an engine that cuts out is to immediately check if you have a spark and fuel. Disconnecting the fuel pipe at the carb inlet should show fuel present. Spinning the engine over with the plug leads connected to spare known good plugs earthed to the engine tin-ware/ cyl. head should show good sparks.

As I said earlier, if the sparks stop, the plugs will become wet with fuel - doesn't necessarily mean that the carb is faulty in some way e.g. leaking float valve.
Be aware that brand new spark plugs may foul with fuel quicker than used plugs. If the existing plugs spark ok when removed from the engine, I doubt they're faulty. If fitting new plugs, make sure you fit the correct ones, a wrong heat grade will cause problems.

I was going to suggest checking if you have a resistor type (suppressed) rotor arm fitted, but if your existing ign. system is 'wasted spark' type, (2 plug leads coming from the coil to the spark plugs) there won't be one fitted.

Please keep us informed of progress.

Al.
 
Hi,
Thanks for the reply.
I think you may well be right- that this is most likely due to carb rather than ignition problems. The symptoms when it stopped were not a sudden dying of the engine......
There is definitely fuel filling the float bowl as I filled it manually. Not sure where this idle jet might be? I unscrewed them all as did the AA man at the breakdown scene......

Wondering if I get some of that spray starter thing and just spray it into the venturi as I start the car. That'll tell me if it's carb I guess.....

Will keep trying!

Regards,
PC
 
I can't recommend the use of 'starter spray', some claim if used frequently, it can cause damage to the pistons. Most of the starter sprays I've seen use Ether, a volatile gas which can cause detonation within the cylinders, hence the possible piston damage.

The idle jet is accessible without stripping the carb. It's a largish brass screw with a slotted head situated just above the throttle spindle/linkage. This idle jet is in 2 parts, the screw is the jet holder, the idle jet can be separated by pulling the 2 parts apart. The idle jet will have a number stamped into it, possibly 45? The idle jet holder also has a rubber 'O' ring to seal it to the carb. body.

Make sure you separate the idle jet from the jet holder (it just pulls out) and check carefully for any dirt inside the parts. The tiny hole in the chamfered end of the jet is the metered part, there is also a larger cross hole along the idle jet, closer to the split end tube. This larger hole is how the fuel gets into the jet and then it is metered by the smaller hole (remember the 45, that 0.45mm) and flows to the idle discharge drilling inside the carb just below the throttle disc (butterfly valve) when it is closed. So hopefully you can now understand the need to separate the 2 parts when cleaning. A tiny speck of dirt inside the idle jet can block the outlet hole.

If the engine is difficult to start and you suspect it's down to the idle circuit, try blocking off all or most of the carb air intake using your hand - this will richen the mixture and help the engine to start when cold, similar to using the choke.

One old trick to clear a partially blocked idle jet without removing it from the carb was to get the engine running, rev it up fairly hard, release the throttle and as the engine is slowing down, quickly place your hand over the carb. air intake (as above) - the increase in vacuum being applied to the idle jet might just clear a small blockage. Try this a few times, just remove your hand from on top of the carb. before the engine slows down fully to idle, otherwise the engine will cut out.

Al.
 
You don't mention if you have a workshop manual for your car - this would greatly help you with working on your car.

If you don't have a manual, it can be downloaded from the 500 Classic section in the Downloads section at the top of this page (it's in the blue line)
The workshop manual gives lots of info on fault tracing and also covers the carb.

Al.
 
Hi Al, is this the idle jet? Stamped 50. Do the 2 parts come apart as they seem stuck together? Also is that the O ring on the end?
 

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Hi again,
OK, so I removed and cleaned the idle jet (there were no blockages).
Still wouldn't start.
So, took the top of the carb off, (there was plenty of fuel in the bowl).
Removed all the jets and blew them all through again.
Still not starting.
Check the plugs and they're wet with fuel.
Changed the spark plugs with new ones, still not starting.
I can hear it trying to fire but maybe just once.
Check the spark plug for a spark and it sparks.
So, fuel getting through, plugs sparking.
I can only assume it's the electronic ignition that's not firing at the right time?
Getting stumped now....
PC
 
Hi Al, is this the idle jet? Stamped 50. Do the 2 parts come apart as they seem stuck together? Also is that the O ring on the end?

Yes, that's it. Iirc it separates into two parts at the end of the thread. The part on the left is the metered jet, size 0.50mm hole in your case and the bit on the right with the slotted screw head and threads is the jet holder. The rubber O ring can usually be re-used unless split. If you examine the end of the idle jet, you'll see that it has a tapered end which seats in the carb.

As I said, the idle jet assembly needs to be separated into 2 parts (jet and holder) to allow it to be cleaned properly. I've seen cases where it was just blown through while in one part (as it is when unscrewed from the carb.), leaving a little speck of dirt that occasionally moved around to block the metered hole.

Al.
 
Hi,
Yes, I managed to separate the two parts and cleaning it thoroughly.
Still no joy.
Good sparks at the plugs, fuel on the plugs. Just not firing.......
Is it the mixture is not rich enough? But I'm using the choke.......
PC
 
Hi again,
OK, so I removed and cleaned the idle jet (there were no blockages).
Still wouldn't start.
So, took the top of the carb off, (there was plenty of fuel in the bowl).
Removed all the jets and blew them all through again.
Still not starting.
Check the plugs and they're wet with fuel.
Changed the spark plugs with new ones, still not starting.
I can hear it trying to fire but maybe just once.
Check the spark plug for a spark and it sparks.
So, fuel getting through, plugs sparking.
I can only assume it's the electronic ignition that's not firing at the right time?
Getting stumped now....
PC

For an engine to start you need compression, air/fuel in the correct proportions and a good spark at the right time relative to piston position. (i.e. just before the end of the compression stroke).

Plugs get wet with fuel usually because they're not being fired, Also can be because there's little/no compression, fuel has gone off or spark is occurring at the wrong time in the engine cycle i.e. incorrect ignition timing.

I think your conclusion is possibly correct i.e. incorrect ignition timing.
You could make a mark (e.g. with a Sharpie or Tippex) on the distributor body to mark it's position relative to the engine block/crankcase. Then loosen the distributor slightly and have someone try starting the car while you try turning the distributor body slowly in either direction. If the engine kicks back against the starter the timing is too far advanced, if it either doesn't attempt to start, or makes an occasional feeble effort to start, it's likely too far retarded.If this doesn't make any difference, you can reset the distributor to it's original position by aligning the marks you made.

Only other thing I can think of is that your spark is not strong enough - it's takes a bit more voltage/energy to fire a spark plug when it's under compression pressure in the cylinder, than when it's removed. This is not usually a problem, i.e. if a plug can be fired outside the cylinder it's usually fine when re-installed.

Yes, maybe try adjusting the ignition timing.

Al.
 
Hi,
Yes, I managed to separate the two parts and cleaning it thoroughly.
Still no joy.
Good sparks at the plugs, fuel on the plugs. Just not firing.......
Is it the mixture is not rich enough? But I'm using the choke.......
PC

If the plugs are getting wet with fuel, then there's sufficient fuel getting through to start the engine.
The choke on this carb is a fuel enrichment device i.e. more fuel is allowed in, it's not a moveable flap in the carb intake to restrict air going in. It's theoretically possible for the fuel enrichment system to be not working but I think this is unlikely in your case as the plugs are getting wet with the stuff. This is why I suggested placing your hand over most of the carb intake while turning over the engine, this act should provide all the enrichment needed to start any engine even if the choke is not working.

I'd leave the carb alone for the moment and concentrate on the ignition system - maybe try adjusting the ignition timing while turning the engine over?

Al.
 
Hi,
I've had a look at the ignition system and it has a set up whereby the points are still in the distributor but the rotor arm and HT leads from the distributor have been removed. There is a wire from the distributor cap to the electronic ignition module and then the 2 HT leads come out of it to the plugs.
(See picture.)
So from what I can tell, the points are still acting as the switch or trigger for the ignition module to send the charge to the plugs.
I could alter the timing by rotating the distributor as you suggest but it's fixed solid. How would the timing have gone out of alignment if it's fixed tight against the block.....
 

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I don't know how that later ignition system works but if it was my car I'd turn the engine to where the points are fully open and check the points are clean and the gap is 12 to 16 thou (0.3 - 0.4mm). if the gap needed adjustment, I'd try starting the engine after adjustment.

If the gap was more or less ok, I'd try a known good condenser/capacitor in place of the one fitted, no need to use the exact same type/same mounting, you could borrow one from another engine, using crocodile clips to connect it up temporarily. Again I'd try starting the engine if I fitted a different condenser.

Have you checked out all wires/cables in the ignition system for possible loose connections? The low tension lead where it attaches to the distributor often causes problems, examine this connection carefully.

Haver you checked that you have a reliable 12v at the ignition coil with the ignition turned on?

Have you checked out the spark plugs lead with an ohmmeter/multimeter? try stretching wiggling them slightly when checking them in case of any internal breaks.

The distributor usually has a clamp fitting or a mounting with a slot in order for the ignition timing to be set/adjusted. I've never seen one without this feature when contact breaker points are used.

It might be the case that your ignition coil/electronic ignition module is failing, perhaps intermittently, or is giving a poor output? With this in mind and looking at your pics, it might be quicker/easier/cheaper to convert back to old-style points and coil ignition- you did ask about this earlier.

It would appear that any ignition coil designed for a 12v system (i.e. not a ballasted system) would do the job, if you don't want to bother with getting the correct item for a 500/126 - you might be able to get something for any older classic car provided it's a 12v one from a local motor factors or online.
Going on you pics, you'll also need a distributor rotor arm to suit that distributor/cap and a HT lead to go from the new ignition coil to the centre of the distributor cap.

I just went to the bother of checking out www.fdricambi.com on your behalf...… (There's lots of other suppliers, I tried this one as they stock a wide range of parts).

You can get a replacement electronic ignition coil same as yours? for Euro48.65

Or an original ign. coil for a 500/126, 12v. for Euro 31.50 and also buy a rotor arm and make/buy a coil ht lead if you want to convert back to standard points/coil ignition

Or if you want to convert back to standard points/coil ignition, and very good value @ Euro 46.50, you could alternatively go for a 126 Ignition set. This includes a new cap, rotor arm, plug and coil ht leads, spark plugs. points set, condenser, plus rubber seals (for the spark plug leads where they go onto the cyl. head) PLUS buy the above original type ign. coil.

Hth,

Al.
 
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