Thread: SU problem

Originally Posted by Mudhog1974classic

Hi all,

I'm running SU's on a 3.9 Disco motor in my Classic rangie with dual fuel.

When I change from Lpg to petrol I get a splutter, which then when I turn the switch half way to Lpg again, the engine kicks into life until the petrol runs out!

Can anyone help or suggest what to try

A couple of questions:

1. Does the LPG conversion have fuel cut off solenoids in the petrol line and are they functioning?
2. is there an electrical cut off to the fuel pump and is it working?
3. Is your electric fuel pump still functioning properly - the Bendix ones can be beasts at times (am assuming yours wasn't an EFI type with a submerged pump)?

Diana

Mine actually stopped as soon as I switched from gas to the middle position then to petrol (or striaght to petrol). I just thought it was because the carbs don't hold as much LPG as petrol therefore I stopped switching that way. Worked no probs from Petrol to gas.

Also, it may take time for the fuel pump to kick in and send the petrol back up the line to the carbs?

Only guesses from my experience but there IS a reason why my rangie's off the road at the mo...

Originally Posted by Lotz-A-Landies

A couple of questions:

1. Does the LPG conversion have fuel cut off solenoids in the petrol line and are they functioning?
2. is there an electrical cut off to the fuel pump and is it working?
3. Is your electric fuel pump still functioning properly - the Bendix ones can be beasts at times (am assuming yours wasn't an EFI type with a submerged pump)?

Diana

Hi Diana,

1 The solenoids have been checked and are working
2 No electric fuel pump cut off,
3 Fuel pump is working normally and not an EFI type

does it run on the petrol.....?


how long has it been since it ran on petrol......
and have the dampeners in the carbies still got oil in them.....?


if the carbies are working fine......then i would expect the splutter when switching from petrol to lpg......

Originally Posted by DEFENDERZOOK

does it run on the petrol.....?


how long has it been since it ran on petrol......
and have the dampeners in the carbies still got oil in them.....?


if the carbies are working fine......then i would expect the splutter when switching from petrol to lpg......

It was running fine on petrol about 4 weeks ago.
Will check the oil levels.

What type of oil do I use?

How full should they be?

we use to use transmission fluid.......


as you drop the plunger in...it should have resistance just before the threads touch the carby......


so what you are saying....is....it wont run properly on petrol......?
but it runs fine on gas.....?

Originally Posted by DEFENDERZOOK

we use to use transmission fluid.......


as you drop the plunger in...it should have resistance just before the threads touch the carby......


so what you are saying....is....it wont run properly on petrol......?
but it runs fine on gas.....?

That's what's happening!

Now to summarise:

• You have checked the fuel filter and it is good/not clogged.
• There is no electrical cut off on the electric fuel pump.
• There are no cut-off solenoids on the petrol lines/or they are working O.K.
• The electric fuel pump is working normally. (making clicking sounds & petrol comes out the end of the fuel line at the carbies if you disconnect it ?)
• The solenoids on the LPG tank and evaporator are functioning.
• The change over switch has been tested and is working O.K.

The symptoms:

1. The car runs normally on LPG.
2. You switch to petrol - the engine dies.
3. you switch back to LPG the engine runs fine.
4. You switch back to petrol and the engines splutters runs for a bit and dies.
5. the engine wont start on petrol.

Is that correct?

Have you checked the needle and seat in the fuel bowl on the SU is not clogged? (The little cylindrical chamber with a hex nut on top to the side of the air inlet.)

Diana