Technical Fiat Uno won't start anymore - only backfire

[EddieCochrane]

Hi,

I have a 94 Uno 1400.
I was driving one morning and suddenly the car just cut out.
Since then I can't get it going again.
The battery seems fine, as the starter turns, but engine does not start at all.
Funny though is that it only seems to spark when you stop turning the key in the ignition - then either backfire through carb or exhaust.

I have checked the distributor cap and that seems cool.

Tried another ecu, no luck either.

Any ideas ?

Thanks

Eddie

 

[circolo]

Hmm.

I was going to suggest the Distributor cap, but you said you've already check that.

Get someone to turn the engine over with the Distributor cap off, and check to see the rotor spindle is spinning correctly. You may be getting a spark, as you say in your post, but it could be too late/early caused by a distributor failure.

If you're getting backfiring that indicates you're still getting fuel too, as the backfiring is caused by ingnited unburnt fuel in the exhaust.

 

[alexGS]

Sounds like an ignition failure, perhaps with shorted pickup wires. That might cause a spark when you release the key, as there would have been no sparks with the engine turning over yet the coil is charged up from when you turn the key on (it produces a spark each time the power is cut off to the coil by the distributor). If you take out a spark plug and leave it connected to the lead, then rest on the engine, do you see a regular sparking as you crank the engine over? If so, then I guess you have a fuel problem and we can talk about that later.

If not, then perhaps remove the lead from the coil and attach a spark plug to it, repeat test, that will eliminate the cap/rotor arm as problems (sometimes the rotor arm develops a burned hole in its resistor which is obvious from inspection or a multimeter test). Since you could tell that the coil was sparking, the rotor and cap are probably fine.

So if still no sparks, the coil is a less likely suspect - more likely to be the module or the pickup. Remove the distributor and take apart to check the pickup wires - sometimes the insulation frays and the wires short. If everything looks fine, replace the module.

I can think of a horrible possibility - the distributor could have lost its drive due to a broken cambelt. Take the oil filler cap off and look in with a flashlight to see if the camshaft is turning... or of course check at the distributor as Circolo said. If the belt has broken, you'll need another engine for spare parts... or you could buy replacements for the bent valves... it does happen, it happened to an Uno that I bought... :bang: but I fixed it with spare FIAT 128 valves Three other engines I know of were not so lucky.

-Alex

 

[circolo]

Alex's answer is spot on

And as Alex states cambelt failure can be an issue. This is generally due to poor maintenance.

Often the roller/tensioner can perish over time, this then siezes up, or cracks apart, and takes the belt with it.

It happenned on my Punto GT I used to own, luckily no damage, but that was because the previous owner hadn't replaced the tensioner at the same time as the belt.

 

[Chas Uno]

I thought cambelt too, as Alex suggested, though being a 1400 engine it won't be guaranteed 'safe' like the FIRE engines. If the cambelt has snapped then there is a chance the engine might be ok, but it's hit or miss.

I had something similar happen on a 1.6 Austin Maestro yuck I had many years ago. The cambelt snapped, and though the engine still turned it only sparked on one plug. That's when I checked the belt and found it sitting at the bottom of the cam cover...

Another option could be the ignition switch. You say it sparks only when you release the switch, so maybe there is a dodgy contact there? Might be worth substituting another ignition switch to eliminate that possibility. They're easy to change as the switch is seperate to the ignition lock. Try a scrapyard for one.

Other than that, possibly a Low Tension wire has come off or got damaged? Really you need to check all the basic ignition components are in place and working as intended. Very much a case of methodically checking and eliminating possible problems.

Good luck!

 

[EddieCochrane]

First - thanks for all the advice.

I got home last night and decided just to check the distributor cap again.
Took the cap off, and yes it turned. But then we decided just to remove the inside cover aswell. And what did we have here.... somehow the middel pin or whatever you call it, ceased and this caused the little arm that is bound to the vacuum advance to be complete bend and destroyed, and with that the wires inside.

So today, I will be looking for a new distributor, and YES, it is about time again in the next 5000km to change the cambelt - this week!

Thanks again.

Eddie

 

[circolo]

Had a very similar thing happen to my Uno T I used to own. Which is why I suggested double checking the distributor spindle.

If you're in the UK, I'd suggest contacting Desira Diss parts (01379 650 111), they'll usually be able to get a new part for you straight away, and they'll always discount the price (if you ask).

If never fitted a distributor (weird, huh? all the years having fiats, and never fitted a distributor). But I'd imagine it's not a big job - not sure whether you need a gasket between the distributor and top end? I'd replace the cap and rotor arm at the same time, it'll need doing anyway at the next service, and for piece of mind and smooth running, it won't be much extra.

I'm glad to hear it wasn't anything too major.

 

[Peterg]

Eddie poss the finned module attached to the dis cap (i cannot recall the name of it at the mo) mine started backfiring and erratic stop start when hot traced it back to this module and a faulty earth.
Pete