Hey guys,


A friend's Punto was taken to a local garage because it was originally misfiring on two cylinders and then wouldn't start/run at all. We wanted it taken to a specialist (Sheldt & Pettet) but the idiot tow truck driver would only take it somewhere local. Anyway, these yeehaws reckoned the timing belt skipped and it had bent valves. When i got the car it had all the parts with it, but no valves. (Also no signs of valve collision on the pistons.)

This is how it was towed from their shop to me:




I have since rebuilt the cylinder head (16 new valves, new headgasket set, new timing belt and tensioner, etc.)

The old plugs didn't look great, so i put in a new set of plugs (And oil + filter) the car also has a new ECU and a new coil pack. I have double- and triple-checked the timing, which is correct. It seems to be getting fuel (There is fuel to the rail, the fuel pump runs.) but no spark. All i can think of is that the crankshaft position sensor is faulty. There is no camshaft position sensor on this engine. I have checked that the pulley is installed correctly, which it is.

I made a video of it turning over:

[ame="http://s7.photobucket.com/albums/y290/chrismca/?action=view&current=MOV00979.flv"][/ame]

It doesn't always backfire like that, only has done once or twice.

I hooked my multimeter up to the crankshaft position sensor, when the engine is stationary i get this reading:



When turning over, i get these readings:




The range in resistance also leads me to believe that it is the sensor that's at fault. It is also the only sensor that tells the ECU when to fire the injectors and spark plugs. However, with no cam position sensor, i don't know how it knows the position of the cams though?

Is there something i've missed?

Any help would be greatly appreciated, i'm out of ideas here. Usually all i work on is VWs and Audis, i don't have compatible diagnostics for this car.

Thanks in advance,
-Moosey.

Looks like the timing is 180 degrees out, don't know the 16v engines but that pipe the smoke is coming from is the air intake is it not? If so then Re-time it 180 degrees

bredsticz said:

Looks like the timing is 180 degrees out, don't know the 16v engines but that pipe the smoke is coming from is the air intake is it not? If so then Re-time it 180 degrees

Click to expand...

180 degrees?

The crank rotates twice for every rotation of the cams. If i re-timed it, then turned the crank once the cams would only turn 180 degrees.

I have checked the timing, you lock the cams (locking tools) then set all 4 pistons in line (with indicator tools). There's no way to change it by 180 degrees.

Yes, the smoke is coming out the intake.

Sorry, i don't really understand what you mean.

Yes, turn both camshafts 180 degrees and the pistons will all line up in the right place again. a 4 stroke engine goes past the same point twice in one full cycle if you understand that.
Keep trying the engine the way it is atm and there is a chance you can blow a hole through the intake manifold.

bredsticz said:

Yes, turn both camshafts 180 degrees and the pistons will all line up in the right place again. a 4 stroke engine goes past the same point twice in one full cycle if you understand that.
Keep trying the engine the way it is atm and there is a chance you can blow a hole through the intake manifold.

Click to expand...

So set it up to time it, all pistons in line as it is now. Then remove the timing belt, rotate the cams 180 degrees, leave the crank as it is and refit the belt?

Thank you.

Exactly, once the cams are turned 180 degrees all the pistons should line up again.

If cams were 180 deg out, that is similar to crank 360 deg out. You'd still suck air in inlet and blow it out exhaust but the fuel injection would be on wrong cycle (spark would be OK as these engines used wasted spark).

If blowing out of the inlet, the cams are 90 degs out or conversely, the crank is 180 degs out. Need to lock the cams as before, remove belt and turn CRANK through 180 degs. Pistons will be level again but the ones that were going down are now coming up.

red.

P.S. Crankshaft sensor outputs a series of pulses so you won't be able to deduce a lot from various resistance readings. You'd need an oscilloscope really.

If it's out by however many degrees get a piece of paper and work out what you've got to try.

If the bottom end is out either way check the top end too and work out all the possibilities and write them down and try them one at a time.

I had the same problem on my Mk1 16v and it was the bottom end out and i'd swapped the top end over numerous times in confusion.

The bottom end of the engine turns twice for every single rotation of the top, hence the suggestion that you are 180 degrees out.

Cheers

SPD

Thanks guys, i understand what you mean now about it being 180 degrees. I was thrown off by the whole thing about setting all the pistons in line, but now understand how it was off.

I retimed it and it's made a huge difference, it now sounds like it wants to start, but still won't. Now when i turn it over, it acts as if the battery is flat. I have checked + charged the battery, even tried jump starting it and bumping it, but still no start. When trying to jump it, it acts as it does when i try to start it under its own power, like it has a flat battery. The key code light goes out, i have both fuel and spark, the fuel pump runs as it should.

It seems like something is sucking the power. I have checked the alternator (I fitted it when i rebuilt the top-end) and that's wired correctly, not causing a short. I removed the earth strap that goes gearbox-chassis-battery, cleaned all contacts and refitted it but still nothing.

Any ideas?

Thanks for the help guys, really appreciate it.
-Moosey.

Moosey said:

Thanks guys, i understand what you mean now about it being 180 degrees. I was thrown off by the whole thing about setting all the pistons in line, but now understand how it was off.

I retimed it and it's made a huge difference, it now sounds like it wants to start, but still won't. Now when i turn it over, it acts as if the battery is flat. I have checked + charged the battery, even tried jump starting it and bumping it, but still no start. When trying to jump it, it acts as it does when i try to start it under its own power, like it has a flat battery. The key code light goes out, i have both fuel and spark, the fuel pump runs as it should.

It seems like something is sucking the power. I have checked the alternator (I fitted it when i rebuilt the top-end) and that's wired correctly, not causing a short. I removed the earth strap that goes gearbox-chassis-battery, cleaned all contacts and refitted it but still nothing.

Any ideas?

Thanks for the help guys, really appreciate it.
-Moosey.

Click to expand...

Does your engine have a removable bottom pulley that the crank sensor looks at?

Is it on the right place?

Cheers

SPD

Yes, it does. When i refitted the pulley i lined up the little hole with the dimple in the toothed timing belt pulley behind it. It's in the correct position.

After a couple hours of electrical testing i found that there was a big drain somewhere when cranking.

Tried the old ECU for the hell of it and it started! Must be a short in the new ECU, so i'll get on the blower on Monday and see if i can get my money back for it. Not impressed.

It will run with the old ECU, but will sometimes misfire. I had it running almost perfect with a little blip every now and then, other times it will start an will have a constant misfire on one of two cylinders. (Usually missing on cylinder 4 when it does this.)

Confused as hell now. But still think it's the ECU that's at fault. Grrrr!

First of all, I know you've sorted the valve timing but I needed to get my head round it for future reference. Here's what I think:

For SPI the ECU sparks two plugs and injects some fuel every 180 degs of the crankshaft, which is every 90 degs of the camshaft(s). The ECU doesn't need any signal from the camshaft(s), it times spark and injection from the TDC sensor on the crankshaft. If the crankshaft were locked and and the camshaft(s) rotated 180 degs, it would make no difference. It's the same as locking the camshaft(s) and rotating the crankshaft one complete revolution.

For MPI the ECU needs to know which of the four injectors to open so there needs to be a camshaft position sensor. It is therefore important that the camshaft sprocket(s) are fitted to the camshaft(s) in the correct orientation (usually by the use of a key). As with SPI, rotating the camshaft(s) 180 degs with the crankshaft locked makes no difference, provided that the camshaft sprocket(s) are correctly orientated.

If setting the valve timing (i.e. fitting the timing belt) when pistons are all level, it is possible to get the crankshaft 180 degs out. The result is inlet valves open when pistons are rising, hence smoke/air/whatever pumping out of the inlet manifold. The fix is therefore to lock the camshaft(s) and rotate the crankshaft 180 degs or to lock the crankshaft and rotate the camshaft(s) 90 degs.

Now, back to your problems. You started off the thread with misfire on two pots and not start/run. That is symptomatic of a coil failure. You report fitting a new coil pack - was that just the one for the misfiring pair of pots? Was the original misfire on pots 1 and 4? (you report current issue is with pot 4). The "old ECU" that you have now refitted may have sustained some damage from the faulty original coil pack so you may just need a good ECU (or a repair to the old one).

red

red said:

First of all, I know you've sorted the valve timing but I needed to get my head round it for future reference. Here's what I think:

For SPI the ECU sparks two plugs and injects some fuel every 180 degs of the crankshaft, which is every 90 degs of the camshaft(s). The ECU doesn't need any signal from the camshaft(s), it times spark and injection from the TDC sensor on the crankshaft. If the crankshaft were locked and and the camshaft(s) rotated 180 degs, it would make no difference. It's the same as locking the camshaft(s) and rotating the crankshaft one complete revolution.

For MPI the ECU needs to know which of the four injectors to open so there needs to be a camshaft position sensor. It is therefore important that the camshaft sprocket(s) are fitted to the camshaft(s) in the correct orientation (usually by the use of a key). As with SPI, rotating the camshaft(s) 180 degs with the crankshaft locked makes no difference, provided that the camshaft sprocket(s) are correctly orientated.

If setting the valve timing (i.e. fitting the timing belt) when pistons are all level, it is possible to get the crankshaft 180 degs out. The result is inlet valves open when pistons are rising, hence smoke/air/whatever pumping out of the inlet manifold. The fix is therefore to lock the camshaft(s) and rotate the crankshaft 180 degs or to lock the crankshaft and rotate the camshaft(s) 90 degs.

Now, back to your problems. You started off the thread with misfire on two pots and not start/run. That is symptomatic of a coil failure. You report fitting a new coil pack - was that just the one for the misfiring pair of pots? Was the original misfire on pots 1 and 4? (you report current issue is with pot 4). The "old ECU" that you have now refitted may have sustained some damage from the faulty original coil pack so you may just need a good ECU (or a repair to the old one).

red

Click to expand...

Red, yes the timing was out by 180 degrees. How it was set with all pistons in line the pistons were going up when they should've been going down, hence it seeming like the timing was fine when i checked. If you set the timing with cylinder 1 (or any) at TDC, then the piston can only go down from there, and there's no confusion in the timing. I have now corrected this.

Thanks to bredsticz for his correct diagnosis on this problem.

There is no cam position sensor on this engine. It has multi-point injection and is a wasted spark engine with a single coil pack. I don't know how it times the injectors. The cam pulley (The belt drives the exhaust cam, with a pair of gears driving the inlet cam off it.) does not have a woodruff key, you set the timing and tension the belt, then you use a pulley holding tool to tighten the pulley bolt. I followed the timing instructions from Autodata for this.


Originally there was a constant misfire on cylinder 4, and an intermittant misfire on cylinder 3. I tried a new coil pack and there was no difference. Cylinders 1 and 2 always fire fine. Injectors, maybe? There is no injector warning light coming up on the dash, and no engine warning light either.

The new ECU is definitely faulty. I did a number of electrical tests (With a friend's guidance.) and the new ECU is causing a massive electrical drain somewhere. ~4v voltage drop during cranking. I tried running a lead from the battery live terminal to the starter solenoid, with the ignition turned off it turned over like it should, with the ignition turned on it was the same, as if it had a flat battery.

I put the old ECU on and it started right up (via the ignition) and ran. Still misfiring. (Although it was running on all 4 for a bit, with a little "blip" every now and then. It only did this once, its misfiring is not consistent and its pattern seems to change every time i start it. However, aside from that one time, it always misfires on cylinder 4.) I moved it and it was still severely down on power, but i was damn glad i finally had it running!

I'm trying to get some diag gear (Snap-on dealer has offered to lend me his demo Solus Pro.) to run it for codes. But as i said, no warning lights.

I'll try swapping the injectors over and see if the misfire follows them.

Thank you for the help guys.

The management light will not show up an individual injector fault.

It shows up a sesnor fault that effects the injection system.

If one cylinder is occasionally missfiring and thats due to a sticky injector, the management system will not see anything wrong.

If, however, the missfire was caused by an ignition problem, unburnt fuel would pass into the exhaust which the sensors wouldn't like, would try to adjust, and if they failed (most likely) would flash up the management light.

Cheers

SPD

ECU failure cause misfire on 2 cylinders. Maybe replace and hope 3rd time lucky with them?

Otherwise the timing might still be a bit off

I pulled the fuel rail today, swapped the injectors around and there was no difference.

While pulling leads to check which cylinders were misfiring i saw that occasionally the spark jumped out the side of the lead boot. Had not seen this before. A new set of leads later and it runs perfect.

This explains why no check showed an issue with the leads, it was a break in the insulation on the cylinders 3 & 4 leads.

A new set of leads and it's perfect. I wish this had been picked up on before the cowboys pulled the head etc.

But at least it's all fixed, and can now be returned to it's owner tomorrow.

Thank you for all the help, guys, much appreciated.
-Moosey.

Moosey,

Well done mate for sticking with it. That feeling of triumph of man over machine is hard to beat!

red.

red said:

Moosey,

Well done mate for sticking with it. That feeling of triumph of man over machine is hard to beat!

red.

Click to expand...

Thank you, Red.

It certainly is a hard feeling to beat, i was well pleased when i started 'er up and she ran perfectly. No misfiring, no stumbling, no loss of power at all. It was driving me crazy, but it's all fixed now.

Unfortunately, since the idiots stripped it all down and tore the ass out the engien, the bill for parts is £444.