Aargh! TU5JP4 engine recon

davek-uk · Post by **davek-uk** » 13 Mar 2008, 15:22

Guys, last night I pinned the flywheel and market TDC on the sump and the crank pulley. I stuffed a wire up the tube of no 1 cylinder plug and used an old fashioned strobe from the wire to ground and got a light. The crank pulley rotates clockwise and the strobe flashing clearly showed up a steady view of the mark on the crank pulley. It was nearly an inch to the left (clockwise) of the TDC mark on the sump. This indicates (doesn't it?) that I'm running 10 or so degrees after TDC. This didn't alter as the engine warmed up. I watched it for a couple of minutes, by which time the engine was really hot.

I have phoned a few more garages and no-one seems to be able to think for themselves any more! Their views are to get it diagnosed professionally. Oh, yea - good idea IF I could drive it there...

Any more ideas? Any tests I could do? I'm going to resort to a Basil Fawlty thrashing with a tree branch soon...

AndersDK · Post by **AndersDK** » 14 Mar 2008, 18:44

citronut wrote:how can this led strobe proove wheater you have or not got HT at the plug side of the coil pack, if you are only getting your pick up from the low tention feed wires

regards malcolm

Malcolm please think it over :

The strobo is not used to test the HT power - but the TIMING of the engine. The ignition timing is derived from the TDC sensor, which is the engine reference timing then. Therefore this approach will instantly VISUALLY show you the whereabouts on the engine timing, leaving out any guessworks.
To test the HT power you need other test gear. The strobo will trigger on even a faint plug spark, as the current is sensed in the HT cable. Thus the strobo will not tell you if the HT power is right.

Back to the topic :
Dave I tend to follow Malcolm on the possibility of a defective coilpack. These coilpacks are nothing but 2 x double ended ignition coils, like any other standard coilpack with HT cables used on earlier models.
The major difference is the elimination of the HT cables - and hence lack of testing access & possibilities.

YES - I know that a new coilpack is a small fortune.

But before you go spend this small fortune, its actually possible to test the coilpack quite easily :
The reference here is, that a spark gap of 1mm in free air approximates 1KV of high tension voltage. A good coil pack should provide 16-20 KV no problem at all.
But 16-20mm spark gap will make the spark jump anywhere on the coilpack, so you should limit the gap to some 10-12mm, which is controlable.

You will have 2 beaker inputs and a 12V input on the low tension plug of the coilpack. Sometimes there is an extra 12V "feedback" pin on the plug, to provide 12V for other circuits (pump, ECU, etc.) ONLY if the coilpack pluck is fitted correctly.
These connections yo must first identify on the coilpack.

Now connect the coilpack to a +12V line - via a safety fuse

Then connect a free ended wire to either of the breaker inputs.
Insert screw drivers, rods or wiring into 1&3 - or - 2&4 plug connectors.
Arrange for the inserted rods to have approx 10mm distance to any chassis ground members - by use of dry cloths etc.

Now strafe the free ended breaker input wire across a clean chassis ground area.

You should see a series of good loud ticking blue sparks from both spark plug connectors.
Move the free ended wire to other breaker input and test remaining spark plug connectors.

I bet one pair of the coilpack spark plug outputs will be rather inferior.

This is by the way the method of testing ANY coilpack or ignition coil type.

citronut · Post by **citronut** » 14 Mar 2008, 18:58

ok Anders
but my point was refering to the HT comming out of the coil pack to the spark plug,

as i said earlier buy 4 spark caps fit the to all 4 spark plugs, then fit the coil pack on top of the flashers, this will show you which or if any part of the coil pack is down
regardcs malcolm

Post by **CitroJim** » 14 Mar 2008, 19:17

Dave,

This really is odd

That was a very good way you devised of checking the timing

Gosh, that is retarded and no wonder it is so hot!

The timing will be determined by two main sensors, one that detects TDC and the knock sensor. Now I don't know these engines at all, my experience is XUDs and XU10s only, so I don't know where the TDC sensor is but it'll be worth searching it out and seeing what it senses against and see if the sensor has moved relative to what it senses. A moved Dragons teeth ring perhaps? Also, the function of the knock sensor is to retard the timing if it detects engine knock. Is that the problem? Somehow the sensor has got too sensitive and is retarding far too far? Try disconnecting it.

Also, some engines have a cam position sensor so that the ECU knows where the cams are. This may be duff or out of position?

The TDC sensor might be worth a swap but usually they either work or they don't. It might be worth checking the air-gaps on the sensors as too wide and it might make then very slow to respond and affect timing. Another thing, check the screening of the sensor cables is well intact. Timing could be badly upset if the cables are picking up interference from the ignition sparks. The sensor cables should have an outer earthed braid like co-ax cable.

Finally, to get the timing that wrong, the only other thing it can be is the ECU itself but if that was the case, I'd expect to see the engine management light on.

Sorry, I know this is all idle speculation from someone who would not know one of these engines if one came up and slapped me but I hope it helps a bit..

AndersDK · Post by **AndersDK** » 14 Mar 2008, 19:51

Ouch -

Completely overlooked the fact that you actually prooved that the timing is retarded.
Though I dont agree its by 10 degrees. Its got to be at least double that

The dynamic timing should be some 8-10deg BTDC at normal working conditions. That cannot be caused by a defective coilpack

The only thing I could think of, is in fact described here in details - a few days ago : the drive belt pulley slipped and failed on the crank because of a dodgy allen key.
Except in this case it must have happened to your crank timing belt cog.
Note : in your case with the TU5JP4 engine you have the drivebelt pulley bolted on to the timing cog, which in turn shares its allen key with the innermost oilpump chain cog.

I can only advice you to closely inspect all parts involved exactly in this location.

AndersDK · Post by **AndersDK** » 14 Mar 2008, 22:56

Juraj - about the LED drop resistor :

Each LED (white clear or almost clear with a blue tint) drops approximately 3.3V across itself with a drive current of 20mA.
When calculating, you should set the battery voltage to 14.0V as this is very close to the maximum expected charge voltage on the battery while engine is running.

Most mini-torches uses a single center bulb/led and 5 or 7 LED's in a ring formation connected in parallel. They are driven directly off a couple of batteries - via a standard power microcircuit that selects single center or ring or ring blinking. The serial connected batteries internal natural resistance takes the place of the series drop resistor.
Cut the wire for the center LED/bulb, as this will not survive the modification otherwise.

Calculation of drop voltage over the drop resistor :
14.0V - 3.3V = 10.7V
Calculation of current consumption through the drop resistor :
1) 5 x 20mA = 100mA = 0.1A
2) 7 x 20mA = 140mA = 0.14A
calculation of drop resistor value (U=RxI -> R=U/I)
1) 10.7V/0.1A = 107 ohm (nearest standard value = 110 ohm)
2) 10.7V/0.14A = 76.5 ohm (nearest standard value = 75 ohm)
Calculation of drop resistor power consumption (P=UxI)
Always go for the next higher wattage type (casing size) of the resistor
1) 10.7V x 0.1A = 1.07Watt -> 2Watt
2) 10.7V x 0.14A = 1.5Watt -> 2Watt

It should be fairly easy to calculate any drop resistor for other counts of parallelled LED's.
NOTE : this design is not efficient as a light torch driven off the car's battery, as then the drop resistor will get very hot.
If you want a LED torch driven off the cars battery, you should series & parallel connect the LED's to minimise power losses in the series drop resistor(s).

dnsey · Post by **dnsey** » 15 Mar 2008, 09:41

Do you (or a friend) have a dual-trace oscilloscope?

If there's no mechanical problem (such as a damaged keyway, as suggested), I'd scope the signal from each of the sensors, referenced to the 'CB' pulse. That should show up any ECU problems.

If you can't do this yourself, I should think one of the 'home tune' chaps would be able to do similar tests.

AndersDK · Post by **AndersDK** » 15 Mar 2008, 13:08

Why bother dnsey ?
Its beyond ANY doubt that this engine has a mechanical timing issue

dnsey · Post by **dnsey** » 15 Mar 2008, 17:20

I agree that it's almost cerainly mechanical, but there's a slim possibility that the input signals to the ECU are correct, but it's outputting severely retarded pulses.
Just suggesting a way forward if a mechanical inspection turns nothing up.

juraj · Post by **juraj** » 17 Mar 2008, 12:48

hi

thanks for the electronics clacs anders,

if the suggestion is that the timing cog has slipped then surely the mechanical timing will be most likely out too, the cam will be out of timing with the crank and quite possibly pistons ought to be colliding with valves,

bye

MikeT · Post by **MikeT** » 17 Mar 2008, 15:40

Well either way you don't want to be running 10 degress ATDC for too long as the valves will begin to melt, if not already. I'm surprised the plugs came out other than spotless! In those temperatures they should have got a thorough cleaning if not melted.

juraj · Post by **juraj** » 17 Mar 2008, 15:58

by the way

what is theoretical basis for the engine running hotter with timing retarded, intuitively i would have thought that since the fuel/air mixture is being ignited after it begins to expand that this would not make any difference

bye

Post by **CitroJim** » 17 Mar 2008, 16:19

juraj wrote:what is theoretical basis for the engine running hotter with timing retarded.

As I understand it, the mixture is still burning very well as the exhaust valve opens and combustion continues in the exhaust manifold, hence the exhaust manifold glowing red hot under retarded ignition conditions.

Normally the fire is out by the time the exhaust valve opens. As Mike says, it's hard on the exhaust valve..

juraj · Post by **juraj** » 17 Mar 2008, 16:26

makes sense

thanks citrojim

MikeT · Post by **MikeT** » 17 Mar 2008, 18:19

If I may supplement Jim's statement - Additional oxygen creates a leaner A/F mixture.