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BMC 1500 will not start when hot


Bobby b

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1 hour ago, StephenA said:

is it a manual stop or electronic?

 

Now  that is a good thought. I don't think 1.5s ever had a stop solenoid screwed into the pump like 1.8s but who knows. I if it has it may be energize to run so a dodgy connection could stop it starting.

 

Even if it is a manual cable maybe the outer slips in the clamp when hot.

 

Certainly worth investigating in any case.

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10 minutes ago, Tony Brooks said:

 

Now  that is a good thought. I don't think 1.5s ever had a stop solenoid screwed into the pump like 1.8s but who knows. I if it has it may be energize to run so a dodgy connection could stop it starting.

 

Even if it is a manual cable maybe the outer slips in the clamp when hot.

 

Certainly worth investigating in any case.

 

If its manual then I was wondering if the stop control gets stiff when hot so when you push the stop back in it doesn't move but the cable bows and then when it cools down the bow in the cable pushes the stop back, and so it can start again.  And possibly if its a solenoid that engages to operate (which I know the Buhks did because you could burn them out leaving the keys in the stop position) and relies on a spring to push it back - if the stop control is stiff enough when hot to stop the solenoid from returning.....

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20 minutes ago, StephenA said:

 

If its manual then I was wondering if the stop control gets stiff when hot so when you push the stop back in it doesn't move but the cable bows and then when it cools down the bow in the cable pushes the stop back, and so it can start again.  And possibly if its a solenoid that engages to operate (which I know the Buhks did because you could burn them out leaving the keys in the stop position) and relies on a spring to push it back - if the stop control is stiff enough when hot to stop the solenoid from returning.....

Could be ether, probably best to remove the cable from the lever on the pump and operate by hand, ditto if its a solenoid acting on the pump lever as I think the Bukh ones you describe. The DV36 and I thin the 1.8 uses a solenoid screwed into the pump. I THINK that if such a solenoid is removed and a thumb put over the hole the engine should start. Take the thumb away and fuel spews out and the engine stops - I hope, so that gives a way to test a  screw in solenoid.

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7 hours ago, Bobby b said:

Hi I can confirm  the stop mechanism  works correctly,   it has a external  solenoid connected to the stop leaver which is energised  to stop position  and spring  load to closed.

 

But have you disconnected it from the pump lever so the is no mechanism  attached to the pump and then running the engine to hot. Stop it by ha d at the pump, push the stop lever up against the stop to the run position and try to restart.

Such solenoids have been known to get sticky when hot, often as a result of them being left energized for a long period and it is possible  the levers in that mechanism sticking when hot.

  • Greenie 1
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I had a Range Rover with this exact problem, engine was a BMW 2.5 6 cylinder, when hot would not start. Pump wear diagnosed, new one cost a kidney but as it was linked to the ECU a little unit from ebay for 30 quid wired into the ECU tricked it into thinking engine was cold and added more fuel when starting, worked perfect. Not relevant to your engine but fault is the same, i bet your pump has some wear. 

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3 hours ago, john.k said:

Even if it wont go,you get 10 out of 10 for such a tidy little engine installation........its quite lovely .........if only you had a practical motor like a Gardner to work with.

9.95, the engine mountings seem to overlap the bed and the copper pipe out of the exhaust manifold  does't seem to have any 'barbs'.

Seriously, beautifully prepared. I'm off to give my 1.8 a good talking to 😁

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1 hour ago, Tracy D'arth said:

Looking at the solenoid and the linkage, there is a fair weight pulling the stop lever down. Is it pulling the lever as the engine cranks?

Hi There is no issue  with the stop mechanism  as mentioned  a heavy duty spring is holding  it in the run position all the time, so the solenoid only momentarily  pull it to stop for 5 seconds  then realise  to run position 

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Im  sure the OP has disconnected the stop lever as part of his thorough investigation.....in any case the motor starts OK when the pump cools .............and as I stated right at the start,IMHO ,the cause is a worn hydraulic head assy on the pump............Its also mentioned this is the second recoed pump?............but is it ?.......he s got an exchange pump,or has he.......due to the rarity of unworn hydraulic head assys,has he twice been given his own pump back with new seals etc in a fancy plastic bag?...is there any evidence a new British made (not Indian) hydraulic head assy has been fitted?.............My opinion of Indian stuff is that they would be incapable of making a hydraulic head to the exactitude needed to run a tiny motor like a 1.5l 

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7 hours ago, john.k said:

Im  sure the OP has disconnected the stop lever as part of his thorough investigation.....in any case the motor starts OK when the pump cools .............and as I stated right at the start,IMHO ,the cause is a worn hydraulic head assy on the pump............Its also mentioned this is the second recoed pump?............but is it ?.......he s got an exchange pump,or has he.......due to the rarity of unworn hydraulic head assys,has he twice been given his own pump back with new seals etc in a fancy plastic bag?...is there any evidence a new British made (not Indian) hydraulic head assy has been fitted?.............My opinion of Indian stuff is that they would be incapable of making a hydraulic head to the exactitude needed to run a tiny motor like a 1.5l 

 

but why would a worn pump head mean not enough fuel is being delivered to start when hot, but not cause running problems when the engine is hot?

 

would a pump really cool off enough in 20 minutes on a BMC under a closed deck? Our engine certainly doesn't cool off much

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There is a simple answer to this.   If the engine is getting fuel but not starting it will emit clouds of white smoke if you persist in trying to start it.

 

If there is no smoke, there is no fuel. 

 

Then you have to establish why there is no fuel. I would take that air cleaner off and spray fuel into the intake to see what happens.

If it runs then loosen all the injection pipes off and see what comes out whilst cranking.

Edited by Tracy D'arth
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Just once I had a 1.5 that would not start but once started would run well. What we found has some bearing on what John k  says. It turned out to water in the fuel (tank breather too low) and the water  was causing the hydraulic governor to stick in the no fuel position. We solved it temporarily by taking the governor head off and carefully cleaning it. That got the boat back to base so we could do all the work needed to solve it long term. In that case the pump went to the pump shop.

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Once the motor is running,there is a flow of cold fuel through the pump...........if you look at temperature/viscosity tables for hydrocarbon liquids ,you can easily see the reason...............and as I mentioned,Ive seen this effect many times with DPA pumps on 4/108 Perkins motors.

Edited by john.k
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5 hours ago, john.k said:

Once the motor is running,there is a flow of cold fuel through the pump...........if you look at temperature/viscosity tables for hydrocarbon liquids ,you can easily see the reason...............and as I mentioned,Ive seen this effect many times with DPA pumps on 4/108 Perkins motors.

 

OK but will the temperature in the pump really drop enough in 20 minutes for the viscosity to rise enough for the pump to start working again? As I've said our BMC sitting under a closed deck doesn't cool off much at all in 20 minutes.

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