Hilux '93 3L 2.8L Timing Issue

[KneeDeepInGrease]

Greetings to one and all from Australia.

I have just replaced the head gasket on my engine and after replacing the timing belt, getting the injectors serviced etc. The engine won't start. I gather it is a timing issue as I am getting fuel ok to the back of the injectors.

My question:

The crankshaft mark should be at almost 12:o clock, the Fuel pump mark should be at 12:o clock and the Cam shaft mark should be at 6o:clock.

The crankshaft pulley has a notch which is an indicator for timing it turns 2 revolutions to one revolution of the Pump and Cam.

I fear I have muddled up the timing in my battles and am unable to determine what TDC is anymore?

What is the best way to determine TDC by turning the crankshaft with the head still on?

Hoping all are safe and well.

KDIG

[Mud Dog]

Hi and welcome Bahram.

I'm nor familiar with the timing marks on your motor and where they should be but I suspect that you might be 360° out on the crank.

It's a 4 stroke motor, i.e. 2 up and 2 down which means that there are 2 TDC positions per cycle, one TDC compression and TDC exhaust. (That's why as you say the crank turns two revolutions for each single revolution of the cam and pump.) You need to be on TDC compression for no. 1 cylinder.

You don't need to remove the head (it won't help you anyway), but you need to remove the tappet cover so that you can see what the valves are doing as you rotate the crank. As you rotate it and watch the rockers of no. 1 cylinder the intake and exhaust valves will be rocking between exhaust and then intake at TDC exhaust. Continuing to rotate in the direction that the crank runs, (some motors will run clockwise and some anti-clock), the intake valve will rock while the exhaust valve remains closed (rocker in the up position). As the intake valve closes both valves will be closed (both rockers in the up position) the TDC mark on the crank pulley should be on or close to the TDC mark, lining it up perfectly will be TDC compression where you are supposed to be. Then check that the timing marks on the cam and pump are spot on.

[KneeDeepInGrease]

Hi Andy,
Many thanks for your reply.

I should have mentioned, it's a diesel engine.
I gather the inlet/outlet valve and crank relationship is the same for both petrol and diesel.

Do two revolutions of the crank pulley mean a complete cycle of engine?

I have encountered moments, where when I attempt to turn the crankshaft, i seem to "tap" something within the engine.
Of course, I am doing it very gently and with very little force.
Is this the top of the piston meeting a valve?

Thanks again,
Bahram

[Mud Dog]

Crank, cam, valve relationship is the same in diesel and petrol, although I was aware you were referring to diesel. On petrol it might still run if you are a tooth out on the cam / valve timing, but on diesel it's more critical.

Which brings me to the next point ... there should be no knocking or hard spots at all when you turn the crank. This could indeed be a valve fouling against the piston - could also be a sticking valve. The crank and cam timing has to be precise, so just check that you are not a tooth out. If that's not the problem then physically check the valves themselves while someone turns the crank for you.

To answer your other question, yes, two revolutions of the crank per cycle.

[Thabogrobler]

180 degrees Andy... and it will be on the cam afaik.

[Mud Dog]

I make it 360° on the crank, i.e. TDC exhaust instead of TDC compression ... same thing as 180° out on the cam and pump (cam / pump = 360° and crank = 720° in a cycle). Apparently his timing marks are lining up as they should. Cam and pump are both 360° per cycle so that's why I termed it as 360 out on crank instead of saying 180 out on cam and pump.

[Mud Dog]

Probably also the reason why a valve might be fouling with a piston.

[KneeDeepInGrease]

Thank you so much Andy and Thabo.

I will have a better look today.
Saw a handy video on youtube about the compression and exhaust strokes.
I am feeling lucky that it is such a basic engine, I cannot imagine how a sensitive modern engine would cope with my clankings.
I was sensing the fouling while the timing belt was off.

I imagined that since the cam was stationary while the crank was being rotated, it meant that eventually the piston would rise and meet with the valve.
So I would then rotate the cam another 1/4turn and then the crank could freely continue clockwise.

I figure there would be a point in the crank's revolution where all pistons are midway meaning the cam could do a full 360 without interference.
I was concerned I may have to take off the head if there was no way to avoiding the interference for the sake of setting the timing.

The biggest challenge I see now is determining which of the two revolutions of the crank is the Cylinder 1 TDC compression.

This is fascinating stuff!
If only my wife felt the same about it

I am very grateful for your time and attention to my questions.

Bahram

[Mud Dog]

There is another way you can do it that might be less hassle worrying about the valves. By now you might be confident enough to try it.

Remove the timing belt. Turn the crank (it will be easy to turn if the glow-plugs are out) so that it's 180° away from the TDC position (this is where the pistons will all be in the midway position). Then you can rotate the cam freely. Doing so, bring it onto the valve timing mark when no.1's rockers are both in the up position as described earlier. Make sure the pump pulley is on the injection timing mark. Now fit the belt while holding of the belt tensioner (you won't be able to do it by hand and I don't know what it looks like on your motor but a large screw driver might do the trick). When the belt is on let the tensioner take up the slack and check that you are still exactly on all three timing marks (pulley, cam and pump). Rotate the crank through 720° to check if there are any tight spots ... just for peace of mind and to make sure there are no sticking valves.

If all is good, you're good to go.

[KneeDeepInGrease]

Thanks heaps, Andy.

Much appreciated!

In this video: https://www.youtube.com/watch?v=M1h9eU9YH5o

at 1:06 into the video, it shows all the cylinders midway in their respective strokes.
Does this mean that the cam could go 360 degrees around without interference from the pistons?
ie. no risk of damaging valves?

Would this point where all the piston are at mid stroke be when the crank is 180 degrees from the Notch (TDC)?

Next question:

Watching this video suggests that a single revolution of the crank will see pistons 1 and 4 go down and up and 2 and 3 go up and down.
So one crank shaft revolution makes each piston do a reciprocation cycle (down and up for 1 & 4, up and down for 2 & 3) in their respective cylinder.

It is when we factor in the Valves and the Fuel pump, that we can determine the stroke type (Power, Exhaust, Compression & Induction).

When all notches and timing indicators are on the marks:

Cam "should" be such that both valves are closed for Cylinder 1 (piston is up with compressed air with fuel sprayed in)
Pump "Should" be just about to pump fuel into Cylinder 1.
Crank "Should" be about to bring Cylinder 1 down.

I guess my main query is, how can the crank be 360 out at the point when I set the timing marks and notches?

The crank doesn't know about Exhaust TDC or Compression TDC, it is after the cam and the pump come into the picture where the stroke type is "defined".

Regards,
Bahram

[Mud Dog]

[quote="You]at 1:06 into the video, it shows all the cylinders midway in their respective strokes.
Does this mean that the cam could go 360 degrees around without interference from the pistons?
ie. no risk of damaging valves?[/quote]

Yes.

I guess my main query is, how can the crank be 360 out at the point when I set the timing marks and notches?

The crank doesn't know about Exhaust TDC or Compression TDC, it is after the cam and the pump come into the picture where the stroke type is "defined".

You're right, it shouldn't be out. How clearly defined are the timing marks? Could there be a confusion where the correct positions should be? Maybe it's not 360° out but just a tooth or two?

[KneeDeepInGrease]

Hey Andy,

I must thank you, sincerely, for staying with me this far.
I will give it a go to see if the pump needs a bit of pampering with a tooth here or there.

Still haven't given up on the concept of being out 360 or 180 degrees and such but I need to do the mental gymnastics to work it out.

Thanks again.

Bahram

[Mud Dog]

What bothers me is that there's a hard spot when you rotate the crank, that's not normal. If it's not a valve that's fouling, what else is causing it .... Why did you need to replace the head gasket? Was there another issue maybe? Could something have fallen into the motor (cylinders) while you were busy working?

What motor is it? 3L / 5L or KZ ?

[KneeDeepInGrease]

Hey Andy,

I think it is a valve.

Imagine the cam stationary (timing belt off) and the crank turning ( ever so gently ;) ). Inevitably, a piston will touch a protruding valve.

If it happened while the timing belt were on, I would be crying.

I'm about to don the overalls now and go up and have another tinker. Will come back with details.

Cheers!

Bahram

[KneeDeepInGrease]

Oh... I replaced the head gasket because of losing coolant. Timing belt was due so I figured I would delve deeper.
Curiosity killed the cat etc.
With the cam stationary and the crank turning, there are no peculiar noises.
I am thinking it best to remove the rocker cover and take a look at the show with the timing belt on.
All the things a pro would do prior to reassembly.
A cul-de-sac of sorts.

[KneeDeepInGrease]

Andy!!!!

The reason why it wasn't starting is too embarassing to mention.
I tried on countless times to try and figure ouut why my timing could be cuasing it but...
Drum roll...
The glow plug energizer was shorting on the inlet manifold because drongo here didn't arrange the isolator properly.

It kicks over and purrrs in a way that only an old toyota diesel can.

So the moral of the story is this (I reckon).

If all the timing marks are on their respective setpoints.

Everything is ok, one can't be 180 out on this particular engine.

I tip my hat, sir. If ever you come to the Sunshine Coast, QLD Australia. There's a beer waiting for you!

Regards,
Bahram

[Mud Dog]

Absolutely good to hear! At least there wasn't any major issue.

I got a brother-in-law and some mates living in Brissy and another BIL a little further south in Coff's Harbour but doubt I'll be visiting soon. Thanks for the offer of a cold one though.