Rebuilt engine won't start

[RobinJ]

I have a Land Rover 2.5 engine in my boat, which I have just rebuilt after the crankshaft died. It's been a complete rebuild with rebore, new pistons, new valves. Every part that went back into the engine checked out as perfect.

 

Compression test showed all four cylinders at 240 psi. This seems a little low to me but I'm told that a cold engine will read low.

If its the one I'm thinking of, you can set the timing chain up on the cam and crank, but have to lock the injector pump drive up too, before fitting the chain.

The compression ratio given of 22 is not true, its the ratio of compressed volume to uncompressed, actual compression will be nearer 10-12. 380psi is probably the expected pressure, but above 250 it should still run, probably low because of lack of oil?

[Yamanx]

Eh, how????

 

Richard

 

This would only be the case if the was an extra link in the drive chain on the drive side, as this would change the gearing. You may find you have to rotate the cam back a little to get the slack out of the chain on the drive side.

[Justme]

This would only be the case if the was an extra link in the drive chain on the drive side, as this would change the gearing. You may find you have to rotate the cam back a little to get the slack out of the chain on the drive side.

 

 

It matters not which way you are out.

 

If your out by one tooth you stay out by one tooth.

 

It cant change.

[bizzard]

I doubt if the valve timing is out by any more than two maybe three teeth or a valve would probably have collided with a piston.

[Bee]

I don`t know these engines but I would try advancing the injection timing, I think white smoke is too retarded, others may correct me, a retarded engine will be hard to start and very `flat`, in fact so flat that it won`t pick up and run.

Good luck

[gazza]

tother way round, retarding the timing means the injection point is at an earlier point on firing stroke, making it easier to start but results in reduced power.

Edited December 12, 2012 by gazza

[Bod]

I can only add "Back to Basics"

Enough Fuel (clean & fresh)

Enough Air ( no dropped rag in air intake!)

Enough compression ( what does the manuel say it should be?)

Enough Exhaust ( no dropped rag in exhaust!)

Enough Rotation (engine turns over freely, not in gear)

Enough Timing ( you did time on No.1 cylinder not No.4?)

 

Bod

[FadeToScarlet]

 

Enough compression ( what does the manuel say it should be?)

 

Que?! (Sorry!)

[Justme]

If the compression is low check the tappet clearances & valve timing.

 

Then check the injection timing.

 

 

Its very very easy to get both 180 degrees out from each other.

[notaminga]

Thanks for all the replies. It's been helpful to know that I have been going through all the same sorts of issues that you have raised.

 

I think I have found the problem. I could find absolutely nothing wrong except for the low compression, so I decided to bite the bullet and take the head off again. It does seem like a head gasket sealing problem. When I took the head off I found that there was a path for gas to escape between the cylinders. This was caused by the new hotspots that I had fitted. Now the manual states that maximum hotspot protusion is 0.76mm - I checked mine and they were 0.45mm, so I foolishly assumed that the head gasket would allow them to bed in - they did not. The gas escape was around the edges of the hotspots.

 

I could kick myself now because I had the head skimmed before fitting new hotspots, now it will have to go back to the machinist to skim the hotspots down.

 

I'll report back again when the head is fixed.

 

Mari

[koukouvagia]

I think I have found the problem.

 

I'm glad you've tracked down the problem. I refrained from offering any advice because you'd said that the "head gasket was tight and not leaking." However, I had identical symptoms on my BMC1.8. I was stumped and it took the local wizard mechanic a day to trace the fault to a tiny gap in the head gasket between two of the cylinders.

[RobinJ]

I think I have found the problem. I could find absolutely nothing wrong except for the low compression, so I decided to bite the bullet and take the head off again. It does seem like a head gasket sealing problem. When I took the head off I found that there was a path for gas to escape between the cylinders. This was caused by the new hotspots that I had fitted. Now the manual states that maximum hotspot protusion is 0.76mm - I checked mine and they were 0.45mm, so I foolishly assumed that the head gasket would allow them to bed in - they did not. The gas escape was around the edges of the hotspots.

Glad you found the problem!

I thought the manual stated they should be faced level?

Are you sure it doesn't refer to insertion depth?

[notaminga]

Glad you found the problem!

I thought the manual stated they should be faced level?

Are you sure it doesn't refer to insertion depth?

I don't think so, as it gives a measurement for both recession and protrusion. Eitherway, they will now be machined flush.

[notaminga]

Well, I had the head re-skimmed and checked over again at the machinists; they told me it was in perfect condition. So, I re-fitted it and guess what - no different.

 

I went back to checking the compression again. This time I squirted some oil in to test out the piston rings - made no difference, I was still getting a steady 200 psi, which, as has been pointed out is far too low for dieseling to occur.

 

Ok, head off time again. I took out all of the valves today and double checked them, lapped them back in again, but still couldn't see a problem.

 

Then, as I was staring at the block, considering how much I would get for scrap, I realised that the pistons at TDC do not reach the top of the bores! I measured a 1cm shortfall in the stroke! The same on all cylinders. This would certainly account for my lack of compression. I know that the cylinder crowns on this engine should come flush with the top of the block.

 

I've yet to strip down the engine again, which I know I will have to do, but I'm left wondering what could cause this problem - I can only come up with the possibility that I have got the wrong pistons or the wrong crankshaft. I've double checked the part numbers and they all check out. I'm completely puzzled by this. How come pistons and crankshaft both fit perfectly in every way except the stroke seems way to short?

[Timleech]

Well, I had the head re-skimmed and checked over again at the machinists; they told me it was in perfect condition. So, I re-fitted it and guess what - no different.

 

I went back to checking the compression again. This time I squirted some oil in to test out the piston rings - made no difference, I was still getting a steady 200 psi, which, as has been pointed out is far too low for dieseling to occur.

 

Ok, head off time again. I took out all of the valves today and double checked them, lapped them back in again, but still couldn't see a problem.

 

Then, as I was staring at the block, considering how much I would get for scrap, I realised that the pistons at TDC do not reach the top of the bores! I measured a 1cm shortfall in the stroke! The same on all cylinders. This would certainly account for my lack of compression. I know that the cylinder crowns on this engine should come flush with the top of the block.

 

I've yet to strip down the engine again, which I know I will have to do, but I'm left wondering what could cause this problem - I can only come up with the possibility that I have got the wrong pistons or the wrong crankshaft. I've double checked the part numbers and they all check out. I'm completely puzzled by this. How come pistons and crankshaft both fit perfectly in every way except the stroke seems way to short?

 

Have you still got the old crankshaft and pistons, for comparison?

[steven wilkinson]

There is always the length of the rods to consider now! But that would be an extreme issue I would have thought! But you have ended up with a cm short somehow!

Crank throw? Rod length? Piston height? All combine to result in the overall movement of the piston!

[notaminga]

Luckily the con rods are the originals, so can't be the culprits.

 

Yes, I do have the old pistons and crankshaft for comparison. I am confused as to what I might have been given in error, as both the same crankshaft and pistons are fitted to the petrol version. Any older engine, such as the 2.25, only has three bearings on the crank, so would not fit.

 

Does anyone know of any pistons or crank of other models that I might have ended up with by mistake?

[John Holden]

Luckily the con rods are the originals, so can't be the culprits.

 

Yes, I do have the old pistons and crankshaft for comparison. I am confused as to what I might have been given in error, as both the same crankshaft and pistons are fitted to the petrol version. Any older engine, such as the 2.25, only has three bearings on the crank, so would not fit.

 

Does anyone know of any pistons or crank of other models that I might have ended up with by mistake?

 

Pistons for a petrol engine?

[Timleech]

Luckily the con rods are the originals, so can't be the culprits.

 

Yes, I do have the old pistons and crankshaft for comparison. I am confused as to what I might have been given in error, as both the same crankshaft and pistons are fitted to the petrol version. Any older engine, such as the 2.25, only has three bearings on the crank, so would not fit.

 

Does anyone know of any pistons or crank of other models that I might have ended up with by mistake?

 

Measuring the throw of the crank, and the height of piston from pin to crown will indicate whether or not you have the right parts.

Of course, that's likely to mean partially stripping the engine again...

 

You can measure the crank throw with the head off, just by checking the piston movement, but would need to take a piston out to get the height.

 

Tim

[gazza]

Any chance the con rods are wrong?

 

Stupid phone. Rods are originals doh. Screen does no always show full post..

[ditchcrawler]

Any chance the con rods are wrong?

Original

[steven wilkinson]

rods are original but crank and pistons are replacements?

[notaminga]

Measuring the throw of the crank, and the height of piston from pin to crown will indicate whether or not you have the right parts.

Of course, that's likely to mean partially stripping the engine again...

 

You can measure the crank throw with the head off, just by checking the piston movement, but would need to take a piston out to get the height.

 

Tim

That's a thought, I'll check the throw before I take everything apart. Having said that, I have to take almost everything apart to change the pistons as the sump won't come off in situ. Am I right in thinking that the piston movement will be equivalent to twice the measurement from centreline of the crank to centreline of the big end?

 

Yes to Steven Wilkinson, the rods are original, but the crank was sha**ed and the block needed a rebore.

[Arthur Brown]

Do you have a real LandRover book for the engine? It MAY show pictures of the piston crowns to be expected on petrol and Diesel engines -usually the swirl pattern is different on the crown. Do any of your invoices show the part numbers of the new crank and new pistons -these should confirm whether the correct parts were supplied. Can you view the PCMI or Fiche copy of the parts catalogue -always used to have "things to look for" highlighted to avoid crossovers in the stores (I did that in the 70s )

[notaminga]

I've been researching on the net all evening and I think I have the answer. For a short period in the early 80's Land Rover changed their crankshafts from 3 bearings to 5 bearings, whilst keeping the capacity to 2.25. Shortly after they increased the capacity to 2.5. I think I have been sold a 5 bearing 2.25 crank - the difference in stroke between the two is just short of 1cm, which is what I am seeing!

 

Tomorrow will tell, as I am back to the boat to start the long process of stripping it all down AGAIN!