Problems with pajero starting/not starting

[ThaProphecy]

Hey there everyone,

I have a 1992 pajero 3.0L V6 petrol and for the last roughly 8 months it has been in a way I can only describe as "tempermental" with regards to whether she will start or not. Turning the key allows the engine to attempt to fire over but it's like she's not sparking to fully kick over. In saying that have definitely checked spark plugs and leads and as far as giving a spark everything is working. Some days she runs like a dream and then out of no where she'll struggle to kick over and fail and then usually won't start again until I've given up and left her alone for an hour or two. Sometimes when it fails to kick over I can hold the key on and the accelerator open until she kicks but she struggles for a while, other times I can clutch start her. Also on occasion after she has played up and finally kicked back over she revs high for a few minutes before settling (around 3000rpms in neutral) and blows a lot of whiteish smoke. I have had a dozen or more people looked over it already and everyone is dumbfounded at what could be causing the problem. To date I have replaced the following parts hoping to come up with a solution: fuel pump, fuel filters, starter motor, spark plugs, spark plug leads, distributor cap, distributor rotor. I have cleaned up battery terminals and tightened the power cables. I am replacing the coil pack this Friday but my hopes are not high.
I was hoping somebody on here has faced similar issues with their pajero or knew of what could be causing this to happen? Any advice would be greatly appreciated before this blows a bigger hole in my bank account lol

[rykiel575]

Are you loosing coolant?

Possible head gasket?

[ThaProphecy]

@Rykiel575 yes it's losing coolant from the radiator cap and overflow bottle, rubber inside radiator cap has eroded. I have a new cap to go on but was told to leave it off until I can flush and clean radiator to avoid pressure building back up inside head and blowing that? Does that sound right? Sorry if I'm coming across as a noob I only have minimal mechanical knowledge lol I just don't want to throw away the pajero she's a solid, sturdy beast when she's going

[spot01]

I agree with Rykiel575 - white smoke can indicate water/coolant in the combustion chamber.
If there is a slight leak in the head gasket, it can also force the coolant out through the radiator cap & overflow bottle, as you describe. Also check the engine oil for any "milky" residue from a coolant leak (inside the oil filler cap is best place to look).



Have you done a cylinder compression test?
Have you had the cooling system tested to ensure it holds pressure?


Whilst putting the cooling system under normal pressure may cause an issue to become worse, it would likely get worse anyway in time.



IMO, better to get it properly diagnosed rather than continuing to throw expensive parts at it in hope.

[rykiel575]

I had a suspected head gasket leak in my old car.

It would be hard to start on occasion. Once it started it would misfire with a rough idle heavily for a few seconds with white smoke coming out of the exhaust.

Later i suspected what was happening was coolant was entering one of the cylinders and since water cant be compressed it would lack the compression to start.

Easy way for you to check is to take the spark plugs out and see if one of them is very different to the others.

[ThaProphecy]

@Spot01 I am definitely getting sick of spending money for no results but have been going off what I've been told as different people look over the car (they'll say "oh it might be such and such causing this" so we replace it just to be sure)

In regards to her blowing smoke she doesn't blow smoke all the time it's specifically only when she's been playing up and not starting.

Have just been told by another mechanic it could be a faulty crank sensor and with some quick searching that looks like a $200 fix so don't want to run out to spend that without some sort of confirmation lol

[ThaProphecy]

I had a suspected head gasket leak in my old car.

It would be hard to start on occasion. Once it started it would misfire with a rough idle heavily for a few seconds with white smoke coming out of the exhaust.

Later i suspected what was happening was coolant was entering one of the cylinders and since water cant be compressed it would lack the compression to start.

Easy way for you to check is to take the spark plugs out and see if one of them is very different to the others.

@Rykiel575 have had spark plugs out of car multiple times over the duration I've been trying to fix this and originally they came out a little black along the thread just from wear but a quick scrub with a wire brush brought them back to like new appearance. They are all fine, and have pulled them instantly after trying to fire over and the ends aren't wet which I was told would be an easy way to tell if it's a head gasket problem?

[erad]

One way to check the head gaskets is a compression check. It is not a definitive check, but if you find lower compressions on one (or two adjacent) cylinders, that is a sure sign. Good readings on the pressures may not totally isolate the gaskets as a cause, because if the leak is slight. it may seal at colder temperatures and nnly open up when hot. This is not likely to be the case with your engine.


As for Rykeil's comments about water being incompressible, this is true, but any slight leakage will either leak past the rings or be small enough so as not to fill the combustion chamber when at top dead centre. Only when you have a massive leak will it hydraulic and stop the engine from cranking over.

[RUGGA]

.

Have just been told by another mechanic it could be a faulty crank sensor

Considering how random your symptoms are, this is not a stupid consideration - however, has the car ever died while you have been driving it? (not just a start up issue?)

[ThaProphecy]

@RUGGA nope never died while driving it's only doing it when trying to kick over. Also something that happens EVERY time it plays up that is weird is the 4x4 lights on the dash that represent 2H gear is selected flash continuously (the top two tyre lights on the little car symbol)

[spot01]

@RUGGA nope never died while driving it's only doing it when trying to kick over. Also something that happens EVERY time it plays up that is weird is the 4x4 lights on the dash that represent 2H gear is selected flash continuously (the top two tyre lights on the little car symbol)

At the risk of introducing a "red herring", I think the Paj uses vacuum solenoids for 4WD selection, so I wonder if there is some issue with the vacuum system &/or hoses/leaks that is contributing? Others might know more about this?

[nj swb]

At the risk of introducing a "red herring", I think the Paj uses vacuum solenoids for 4WD selection, so I wonder if there is some issue with the vacuum system &/or hoses/leaks that is contributing? Others might know more about this?

The vacuum is only for the front free wheeling mechanism. Without vacuum there is a spring bias towards 4H, which would make the front wheels flash until there is sufficient vacuum to return the mechanism to the 2H position.

On the petrol models vacuum for this system is drawn from the inlet manifold. If there is a significant vacuum leak allowing air to be sucked into the inlet manifold other than through the MAF that would make it difficult for the ECU to provide the correct amount of fuel for starting.

Edit: I've been back through the thread and I believe a vacuum leak explains all the symptoms. Start at the MAF sensor and work towards the engine, looking for loose hose clamps / split intake hose / loose bolts on throttle body / plenum / manifold. From memory, there's a moulded black plastic thing that hangs under the intake - something to do with resonance in the intake. Check that for holes / splits too.