Right - first post here so hello everybodypeeps!

Short Version

Felicia 1.3 (single point injection) won't fire - it turns over. There's a spark from the coil, there's fuel from the injector, there was sparks from the dizzy yesterday. Tried WD40 around the HT leads/dizzy and all the electrical connectors. Unplugged temp sensor, made no difference. Flywheel position sensor looks to be ok.

Long Version

I was given a 1996 Skoda Felicia 1.3 (carb/spi) by a friend, as she didn't want it anymore and it was basically scrap (bodywork is battered, rust on all the panels, blowing exhaust, stuttery engine). I've replaced the exhaust, replaced the HT leads which did help the starting/stuttery issue a little, hammered the oil filler hole to dent it slightly so the cap doesn't keep falling off (who though push-fit oil caps was a good idea?)

Recently, it's been struggling to start - taking 2 or 3 attempts, cranking for 10 seconds or more before showing any sign of firing, often firing on just 2 cylinders, then 3, then 4 after some revs.

Last night, it decided it couldn't be bothered to start anymore. I tried for an hour to get it going, before giving up and getting a lift home. Today I went back to it, put some more petrol in, WD40 around all the sensors and HT leads, new battery (flattened it last night), and 5 attempts or so, it just about fired up. Drove to petrol station, put some go juice in, then it wouldn't start. Pushed it out the way, then it started right up. Drove back to the workshop, got it inside, switched it off, had a cuppa, wouldn't start up. It has started ONCE since, out of about 50 attempts.

I've tested the ignition coil by connecting a spark plug directly to it, then grounding it and cranking - sparks lovely. I've cleaned up all inside the dizzy cap, including sanding down the contacts inside and on the rotor arm. I've tried WD40 in all the connectors - ignition coil LT, HT leads, temp sensor, crank position sensor, ECU, TPS, air temp sensor - no luck. I removed all the air inlet, adjusted the throttle cable (it was loose anyway), remove the fuel hose from the carb and my lovely go juice came out, so theres fuel at the carb. I removed the injector, more fuel came out, so there's fuel there. Fuel pump primes every time I switch ignition on too, so he's fine. Used my phone's camera to watch the injector as I cranked the engine (I have no friends) and it seemed to be spraying a nice mist on the throttle plate, so all seems well there. Still not even a hint of firing.

The temperature gauge does get a bit special sometimes, in that it will read way over the red line, until I hit it, then it's fine, so I thought maybe the temp sensor was busted. Someone on here said they disconnected it, and the car fired straight up - I didn't have that same luck, so I guess it's the actual gauge at fault (which would make sense, as a good whack fixes it)

Crank position sensor LOOKS fine, but no idea if it is actually working correctly - I assume it is, as 1% of the time, the engine runs ok. I've removed it and cleaned it, but no difference.

Since I've known the car (about 3 years), it's always struggled to accelerate when you put your foot down, but it's been a lot worse recently, to the point I sit for AGES at roundabouts, as that's when it decides it doesn't feel like moving, which is freaking dangerous.

Gonna test for more sparks tomorrow, as well as check the injector again to make sure fuel is definitely coming out (sure looked like it). Either it's overfuelling and flooding, or the laws of physics have changed in that petrol is no longer flammable. I'm a fire dancer/performer, I can vouch that petrol is definitely flammable!

Any other ideas folks? Sorry for the long post!

Edited 24 August, 201114 yr by HughieW

Sounds like fuel and ignition are fine...check valve clearances aren't tight and that the cat/exhaust isn't blocked.

Thanks for the reply!

My mechanical skills are fairly limited - how do I check valve clearances? I'm assuming I just whip the rocker cover off with those two nuts on the top, then check for clearance between the rocker arms and the valves?

Exhaust shouldn't be blocked - I've just replaced the mid pipe as it fell into two pieces (sounded great with just a pipe coming off the cat). Backbox needs replacing but only due to the baffles being ruined, it still functions as a pipe

Forgot to mention, I also tried earthing the engine to the neg battery terminal with a jump lead, in case a faulty earth was causing it (happened to my mums poogeot 106) but that didn't help.

More reading suggests I crank the engine with the dizzy cap off to ensure the rotor arm is turning (it should be, it was sparking yesterday at cylinder 4), and possibly check the yellow wire going to the starter motor, so I'll try those after work too

Edited 24 August, 201114 yr by HughieW

Latest update:

Ignition coil is good

Distributor is good

HT leads are good

Spark plugs are good

Injector is good

Fuel is good

Bodywork is not good but that's a seperate issue

So, there's fuel going into the throttle body, and there's a spark inside the cylinder, so the only thing left in the magic fire triangle is compression.

When turning the ignition off after cranking, occasionally I'll get a backfire through the throttle body (whisp of white smoke after a chuff sound). I also noticed when testing the spark plugs, that turning the ignition off causes a spark at the plug. Dunno if that's meant to happen but that would explain the backfire (unburnt fuel, sparky spark, poof, smoke, yada yada yada). The fact that it was running yesterday suggests the timing chain is alright, so the valves are ok.

This leads me to think believe that the ignition timing is the problem, so tomorrow, if I can get one for peanuts, I'm gonna swap the crank position sensor (might need to book the day off work as it's a big job...)

Unless any of you Skoda Genii know better? I know Mazda's, but not so much about Skoda's!

Edited 24 August, 201114 yr by HughieW

You've already proven the crank sensor works, if the crank sensor is faulty you won't get any sparks at all.

The yellow wire to the starter motor must be fine because the engine won't crank over without it.

I'd agree with what dave has said above, check the valve clearances aren't too tight before anything else, it's not easy to describe the process but you are on the right lines by saying that you check the clearance under the rocker arm, I'd suggest seeing if your local library has a Haynes manual for a felicia, it's fairly well covered in there. However, judging by what you say about it popping back to the intake it does sound like you put the ht leads on the dizzy cap in the wrong order.

Surely the crank sensor controls the injector timing rather than the spark timing (which would just be controlled by the rotor arm in the dizzy, maybe finely adjusted by the crank sensor). If not, what does control the injector timing??

Yep I figured yellow wire was the one to fire up the starter motor but it was worth looking at I guess!

The firing order hasn't changed since it was running yesterday though, I've labelled the leads to ensure they don't get mixed up :S Anyone got a photo of the dizzy and plugs with the leads attached so I can check it against mine? I'll have a browse on here after I've posted this.

I've got a haynes manual for it at the workshop, I read over checking the valve clearances today - seems straight forward, just need to get some feeler gauge thingies (borrowing some from a family friend tomorrow hopefully).

There is definitely fuel going in, and there's definitely sparks, so my last guess is that either the ignition timing is sometimes completely out, or the injector timing is sometimes completely out (i say sometimes, because it did start and run a couple of times yesterday, with a fluctuating idle speed, and little power under load).

Plugs smell of fuel, and are wet if I remove them immediately after cranking for 20 secs or so

EDIT: Ok I'm 90% sure the leads in the same order as this:

I posted a video on my stalkbook yesterday of the engine running. I couldn't pause to get a good frame to look at the leads, but I've watched it over and over, and traced the leads - fairly certain they match.

Edited 24 August, 201114 yr by HughieW

The dizzy is there only to distribute the sparks to the correct cylinder, the actual ignition timing event is derived from the crank sensor and is mixed with data from other sensors like the coolant temperature to 'trim' the actual ignition advance angle.. The ecu needs the crank sensor so it knows where tdc is, then it fires the ignition driver slightly before tdc, the faster the rpm of the engine the more advanced the ignition timing event will be

In this context the injector timing is irrelevant because it fires every revolution of the engine, and its attached to a common plenum where all the cylinders feed from it, the important 'timing' value for the injector is how long it stays open for, and that Is done in a similar way as above based on rpm (from the crank sensor) and engine load from the map sensor

I am not trying to confuse you

What happens if you hold the throttle open a touch when trying to start?

See I thought the coil put out a constant voltage, then the dizzy just distributed as necessary. Then the weights inside the dizzy move as it spins faster, adjusting the advance of the rotor arm, therefore advancing the ignition timing. Guess you learn something new every day!

The injector firing every revolution would make sense, as it sprayed the throttle body in noticable pulses, at the same sort of rate the spark plugs were sparking at.

Holding the throttle open a touch makes no difference - be it slightly, or full throttle, still won't fire.

Could it be that the crank position sensor is working, but is faulty? As in, sending the wrong signals, so it's firing the sparks/fuel at the wrong time?

EDIT: Checked this morning using the above photo, HT leads are definitely in the correct order :( gonna try reducing the gap in the plugs tonight, then try swapping the plugs from my mazda (by coincidence, they're the same size/thread, but the mazda plugs are much newer)

Edited 25 August, 201114 yr by HughieW

Used my lunch break to take another look, and got it started 4 times in a row! I think I need a new set of plugs and dizzy cap.

Brought my timing light with me from home (yeah because you need one of those in your house), hooked it up and saw no light on any of the leads while cranking. Also took the rocker cover to ensure timing chain was good, rockers moved just fine when cranking. Rocker cover back on, reduced the gap on all the plugs, whipped a spark plug out the Mazda, stuck it in the skoda, fired on first turn of the key, but didn't properly fire up until that spark plug burned away the excess fuel, then it ticked over just as good as it always did. Nology Silver plugs are great! Still struggles as soon as I go near the throttle though, so I assume the dizzy cap isn't quite letting enough juice through. Spark plug connected directly to the coil produces a brilliant white spark. Connected to the dizzy produces a much smaller, but still white spark.

Gonna get some new spark plugs tonight if I can whip up some dosh, then hopefully pick up a dizzy cap on my way to work tomorrow.

Thanks for your help Tom, hopefully she'll be running as slick as ever tomorrow

See what I did there? Slick? TeflonTom? Teflon = non stick? Not working? No? Still not funny? Okay :(

id try a new rotor arm too... ha.. the police gave me the nickname teflontom many years ago

If I can get the cash together (hopefully I can) I'll pick up some sparkies from HellFrauds tonight, then I'll pick up a cap and rotor arm from Central Auto tomorrow morning.

Is that because you kept getting away? Or always came up with excuses? Or just greasy/dirty?

lol, well Teflon interestingly is the slipperiest substance on earth,

FACT

it's used it large civil engineering jobs when oil is not a good enough lubricant, normally it's used in the construction of bridges when they slide the 230,000 tonnes bridge section over each other, the temperatures get so high in the lubricant that no grade of oil on this earth can take, teflon is the only substance that can

Edited 27 August, 201114 yr by Sonner