How do I start a Pajero jeep with Low compression ?

I bought a pajero sport 2007 2.5 a few months ago that always had trouble starting.
I would heat it 4 times then crank and she would pick up with a puff of smoke then run fine.
No problem starting when warm.
Having ruled out the plugs (replaced) the relay (12 volts) a local garage man did a compression test and
told me that two of the cylinders had low compression
We were going to run some oil additive through it to see if that would help
But now the B**ch wont start at all.
it cranks fine but wont pick up.
Its outside the house and I am waiting for the mechanic to get time to do a house call.

I was wondering if there is any sure fire way of starting it up with slightly low compression so that I can run some 
oil additive through it 
or if I get it started what is the best treatment to put through it.
also If I have to open up the engine how complicated and expensive would it be
I have a mechanic friend coming to stay with me in a few weeks what are the minimum tools needed?

Cargorm (author) 2 months ago

Thanks for all the advice lads , turns out the glow plug fuse was blown with all the warming, so its going again. but still hard to start

I am going to wait til my friend arrives and take the head off to see what the story is with low compression

rickharris2 months ago

1. get the low comp fixed or it will always be a problem and may well get worse.

2. Impossible to say until the top is lifted off, could be a simple thing 0 leaking gasket or may be expensive - cracked cylinder bore.. Can't tell

Cargorm (author)  rickharris2 months ago

Would you reckon the engine definately needs to come out to have a look?


No, only the head needs to be off to start with. Follow Vyger's tricks, then PeterCD's compression testing with oil first.

Vyger2 months ago

Is it gas or diesel?

Lots of miles, like over 150,000?

Chances are good its a head gasket going bad. It can be expensive depending on how hard it is to replace. One of those things that getting to it is harder than replacing it.

If its a gas engine that has been under a heavy load a lot it could also be burned valves. That requires pulling the head also.

You need to have a mechanic that you can trust and not one that is going to take advantage of you.

Cargorm (author)  Vyger2 months ago

92K miles only

Its diesel. it belonged to the council dog pound and so prob did very little towing.

"You need to have a mechanic that you can trust and not one that is going to take advantage of you."

aint that the truth , thats why Im trying to gather as much info as i Can


Vyger Cargorm2 months ago

Diesels are made to go lots of miles so that few implies there is another problem. I have a VW rabbit diesel so I have played with it a lot. Two other factors that could be at play here are: 1. The timing could be a little off. The mechanical timing has to be dead on for it to start. The fuel has to be injected just when it will be compressed enough and the valves need to be closed to contain the compression. Once its running it can tolerate a little bit off. Your timing belt could have jumped a notch. The second thing is the fuel injection pump. The pump could be out of adjustment. I had to replace mine and got a rebuilt one which worked great at first. Then it somehow changed its adjustment. Under the advise of a very good diesel guy I took the seal off and reset the pump and it worked fine again and started. I would check those things.

As far as low compression that might be able to be fixed by re torquing the head bolts. A diesel head is under a tremendous amount of pressure and the bolts can actually stretch, They are supposed to be re torqued after having been in operation for a period. You need a good torque wrench and you need to follow a specific pattern which will be in the repair manual for the engine. Diesel head gaskets are more expensive than gas ones and require extra care in changing, A diesel engine compression is often 400 lbs or more which is almost 4 times as great as a gas engine. The re torquing process is usually to back of the bolts a specific amount, like 1/4 turn and then cranking them down to the specific torque.

Finally, if it has a manual transmission it can often be pull started to get it going so you can analyze what the problem is. Pull starting turns the engine over at a lot higher speed and will often be enough to get even a cranky engine started. Once started you can see how well it runs. If it is putting out white smoke (a leaking head gasket or cracked head) or black smoke meaning the injector pump is putting in to much fuel and needs adjustment.

Vyger Vyger2 months ago

So, this is what I would have the mechanic do ---

Take off the valve cover and check the timing alignment. Set to TDC the valves, the pump and the crank should all be on their marks. Then follow the manufacturer specs and re torque the head bolts. put the vale cover back on and pull start it so you can see if the fuel settings on the pump need to be adjusted.

Cargorm (author)  Vyger2 months ago

Many thanks for all that.

Ill suggest these things things to the mechanic, and Know exactly what he is talking about if he mentions them.


petercd2 months ago

A diesel by its very nature needs high compression to run, the only
thing an additive will sort out is stuck rings, which I strongly suspect
is not the case here.

Might be a blown gasket like others have suggested.

If your radiator water is clear ie no diesel or oil traces, or your dipstick isnt popping out due to pressure in the sump, and you cant hear a whistling canary anywhere in the engine bay, then you've pretty much ruled out a blown gasket.

A teaspoon of oil in the low reading cylinders is the classic check for worn rings, all you need is a suitable compression gauge for diesel engines, the oil gives a much higher reading if the rings are worn.

A selection of spanners and 1/2" drive sockets to remove the head bolts and a torque wrench to properly fasten them again would be the minimum.

Cargorm (author)  petercd2 months ago

So the water looks fine so the head might be ok

are you saying that it might be possible to look in the cylinders without removing the engine??


petercd Cargorm2 months ago

Sure, you only need to remove the head to look into the cylinders not the entire block.

Sometimes its possible to pull the sump cover with the block still in the engine bay and work from the bottom as well, provided you dont have obstructions like cross members or such like.

But rule out all the easier solutions first, Vyger seems to have a few more items to check before you dive into the head removal route.

Cargorm (author)  petercd2 months ago

Thanks again

Cargorm (author) 2 months ago

Keeping that in reserve for now

Cargorm (author)  Cargorm2 months ago
steveastrouk2 months ago

Get the head off and LOOK.