M

MGT

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I'm having trouble starting the motor when the engine is warm/hot.
It will (up to now) start eventually but I don't like cranking it over and over and need to find the fault.

I've changed the battery to new (and also tried an old but fully charged spare, and it's not cured it.

I've tested the alternator, so it's not that.

It DOES start when cold though, so I am ruling out glow plugs.

Once started it idles as normal.

So I thought that leaves starter motor, and I was about to take it out and replace it. However, when I went out after it had been standing for a couple of days it started first turn of the key.

I'm guessing it is most likely still starter motor in the throes of intermittent fault before dying completely but I wondered if there was another possible fault that causes the car to fail to start when the engine is warm.
 
Slow or failing to start when cold could be the HP pressure regulator seals failing. When the fuel is warm, it's thinner, so gets past the seals easier than when it's cold thicker. That's where I'd start locking.
 
Thanks Nodge. It starts ok cold, but not when warm. Unless I have misunderstood your answer. Do you mean the thinner warm fuel will be leaking out the seals so I am not getting enough fuel through to start it? Anyway, I can easily check, so thanks for the reply.
 
MGT said:
Thanks Nodge. It starts ok cold, but not when warm. Unless I have misunderstood your answer. Do you mean the thinner warm fuel will be leaking out the seals so I am not getting enough fuel through to start it? Anyway, I can easily check, so thanks for the reply.
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I think you'll need to check the fuel rail pressure to determine if the regulator is leaking. You won't actualy see a 'leak' as it will (presumably) be draining back to the tank. Not sure what pressure you need to see when its cranking.
 
MGT said:
Thanks Nodge. It starts ok cold, but not when warm. Unless I have misunderstood your answer. Do you mean the thinner warm fuel will be leaking out the seals so I am not getting enough fuel through to start it? Anyway, I can easily check, so thanks for the reply.
Click to expand...
The pressure regulator works by dumping excess fuel back to the low pressure side of the pump. However if the seals aren't able to hold the fuel tightly, the fuel pressure bleeds back to the low pressure side via the seals.
If you have access to diagnostic live data, you can check the rail pressure when cold and hot to see if a lower pressure is measured when hot.
 
Nuisance, I don't have diagnostic kit. I suppose I could haul it along to one of the local Land Rover specialists I trust. But if the seals are leaking, wouldn't that affect throttle performance? What about idle? Wouldn't that go rough?
 
MGT said:
Nuisance, I don't have diagnostic kit. I suppose I could haul it along to one of the local Land Rover specialists I trust. But if the seals are leaking, wouldn't that affect throttle performance? What about idle? Wouldn't that go rough?
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Not all the fuel is being lost through this seal, there will be some pressure while its cranking.

However, I believe that the ECU will only open the injectors if it sees sufficient fuel pressure.

Once it is running of course, the pump will be running faster to maintain or building on that pressure.

If you put your foot to the floor at lower revs, it won't open the injectors to their maximum flow to protect the engine and because of the smoke map. You'll only get maximum fuel flow into the engine at higher revs when the pump is running (basically) at its fastest.

You'll only lose so much through the leaking seal, until it gets really bad presumably. So If you manage to start it, it should run without any sign of problems until it get really bad - then I presume you'll find the engine going into limp mode or what ever - but the likelyhood is that you won't have been able to start it to get to that situation.

This is my understanding from reading threads about this sort of thing.
 
GrumpyGel said:
Not all the fuel is being lost through this seal, there will be some pressure while its cranking.

However, I believe that the ECU will only open the injectors if it sees sufficient fuel pressure.

Once it is running of course, the pump will be running faster to maintain or building on that pressure.

If you put your foot to the floor at lower revs, it won't open the injectors to their maximum flow to protect the engine and because of the smoke map. You'll only get maximum fuel flow into the engine at higher revs when the pump is running (basically) at its fastest.

You'll only lose so much through the leaking seal, until it gets really bad presumably. So If you manage to start it, it should run without any sign of problems until it get really bad - then I presume you'll find the engine going into limp mode or what ever - but the likelyhood is that you won't have been able to start it to get to that situation.

This is my understanding from reading threads about this sort of thing.
Click to expand...
Thanks. That would explain it.
 
Alteredtech said:
Hi,

Crank sensor can gives issues when the engine is warm.
Any codes ?

Regards.
Click to expand...
Don't have any diagnostic kit. But crank sensor is easy replacement. IN fact, now you mention it I think I swapped it out a while back for one I had off my donor vehicle. Can't remember why though. I think I was swapping bits to try to eliminate another fault. Ok, I will look that up. Might get lucky. Thanks.
 
I thought I would just confirm that it looks like it was the o rings deteriorating. Although they looked ok when I got the regulator off when I put the new ones on and put it all back together there is a huge increase in pressure if the boost to the rev counter is any guide. I've a residual problem with leaking return hoses on the injectors (new since I changed the o rings), which i've mentioned in another thread, but as far as the advice given re the regulator it looks to have been spot on. So thanks again.

By the way, whoever said you can get the regulator off without taking the starter motor off must have magic powers.
 
I was not jocking, I had once to stop my car because there was a very strong gasoil smell. The return hose break, lot gasoil near the injectors, gasoil dripping everywhere.

I changed that part before driving again the car, and also put a fire extinguisher in the car.
 
Alteredtech said:
I was not jocking, I had once to stop my car because there was a very strong gasoil smell. The return hose break, lot gasoil near the injectors, gasoil dripping everywhere.

I changed that part before driving again the car, and also put a fire extinguisher in the car.
Click to expand...
That's a shame . It could of been one less freeloader on the road 😂😁😁
 
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