Starting issue LPT

[Rversteeg]

Sometimes one of the LPi injectors slightly leaks.
The engine always starts on petrol before switching over to petrol. A slightly leaking LPi injector will fill the inlet manifold overnight with LPG. On first start attempt, the engine gets a mixture of LPG and petrol, which is too rich to ignite. Longer cranking or restarting is then needed to get the engine picking up.
This is typically worse when the engine has not run for a whole night than when the engine has not run for a few hours.
Idling is no problem, as the leaking of the LPi injector is far too small to disturb the air/fuel ratio.

[Delta66]

Originally Posted by skidje

Still need by default 3 attempts to make it run. Perfect at idle.
But when the 940 starts at idle it runs perfect. Best to stay away from gaspedal since that makes starting more difficult.....
Is it an idea cleaning the injectors and changing the pressure regulator?
Is the ECU confused with wrong temperature sensor signals? Need for changing the one for the coolant?
Any input appreciated..

Note: the volvo runs LPI / LPG and when running it we do not have any issues. When running petrol it tends to stalk after a while but this doesn't explain the starting issue.

The ECU can be reset by

Remove fuse No1
Wait 20 seconds
Replace the fuse

That may assist any confusion and it worked for me when there was an emissions issue over a leaking inlet manifold gasket.

[Laird Scooby]

Originally Posted by skidje

Note: the volvo runs LPI / LPG and when running it we do not have any issues. When running petrol it tends to stalk after a while but this doesn't explain the starting issue.

Originally Posted by Rversteeg

Sometimes one of the LPi injectors slightly leaks.
The engine always starts on petrol before switching over to petrol. A slightly leaking LPi injector will fill the inlet manifold overnight with LPG. On first start attempt, the engine gets a mixture of LPG and petrol, which is too rich to ignite. Longer cranking or restarting is then needed to get the engine picking up.

Have i missed something here? LPi - Liquid Phase Injection LPG?

[TonyS9]

If not starting, always check the rpm needle to see if its moving atall, it should be getting ignition pulses after <1 turn finds TDC (a little slow compared with other designs). If not suspect crank sensor or ignition amp.

Slow fuel pressure build or not holding pressure when off could be FPR.

Does it start if you just hang on the starter motor for ages?

[Rversteeg]

Yes, LPi is a LPG system made by Vialle. It is actually injecting liquid phase LPG in the inlet manifold, just like the petrol system. The evaporation of the LPG is done in the manifold / cylinder, so there is no need for a cooling water heated evaporator.
The inlet manifold has four additional LPG injectors added. The system is under a constant 5 bar pressure, so if one of the injectors slightly leaks, the inlet manifold will be filled with evaporated LPG over time. Not uncommon.
I believe such systems are unusual in the UK (are they even allowed?). An advantage is that there is no power loss (even small power gain because of an intercooling effect) and the injectors are basically controlled by the original petrol fuel system (ECU).

[Laird Scooby]

Thanks for that Rob - i think that LPi systems are allowed in the UK as i've seen some sellers selling them, i just don't think they've caught on as yet, not to mention the fact the front end/ECU kits seem to be about twice the price of the more conventional SGi kits.

I do have a query though - i understand the fuel rail needs to be kept at 5bar while the engine is running but surely there's a shut-off valve that feeds the fuel rail?

If so, adding a temporary manual switch to the feed for that would give a means of diagnosing the problem - flick the switch off while still running LPG and wait for the engine to stall once the fuel rail is empty. That would minimise any LPG leakage from an injector overnight.

[skidje]

Originally Posted by Laird Scooby

I do have a query though - i understand the fuel rail needs to be kept at 5bar while the engine is running but surely there's a shut-off valve that feeds the fuel rail?

If so, adding a temporary manual switch to the feed for that would give a means of diagnosing the problem - flick the switch off while still running LPG and wait for the engine to stall once the fuel rail is empty. That would minimise any LPG leakage from an injector overnight.

The specialist told me to run 3 days on petrol before we can exclude the leaking injector. The line remains filled and can keep leaking for a nr of days.

Moisture in petrol?? Wouldn't this be vapored out if the tank has proper breetherlines?

@ RVersteeg: Thx for the support/diagnoses. Will meet you soon in Amersfoort. Are you on Volvo700vereniging?

BDP-Sensor: When the car starts (best without hitting the throttle) it runs perfectly idle immediately. Should I consider this sensor as a cause?

Removing Fuse one could be an easy attempt. I recently replaced the fuel pump with a new original Bosch so perhaps the fuelamount is higher than the ECU learned in the past.

Also the petrol-filter will be changed this week. Anyone know the dimension of the need sealrings?

Will give all of the above a read tonight/ Thx so far for all input.. All the best Joseph

[Laird Scooby]

Originally Posted by skidje

The specialist told me to run 3 days on petrol before we can exclude the leaking injector. The line remains filled and can keep leaking for a nr of days.

Moisture in petrol?? Wouldn't this be vapored out if the tank has proper breetherlines?

@ RVersteeg: Thx for the support/diagnoses. Will meet you soon in Amersfoort. Are you on Volvo700vereniging?

BDP-Sensor: When the car starts (best without hitting the throttle) it runs perfectly idle immediately. Should I consider this sensor as a cause?

Removing Fuse one could be an easy attempt. I recently replaced the fuel pump with a new original Bosch so perhaps the fuelamount is higher than the ECU learned in the past.

Also the petrol-filter will be changed this week. Anyone know the dimension of the need sealrings?

Will give all of the above a read tonight/ Thx so far for all input.. All the best Joseph

My idea would save 3 days waiting as (in theory at least) it would exhaust the excess LPG pressure before switching off.

Moisture/condensation in the petrol will ALWAYS sink to the bottom of the tank, where the pick-up pipe is for the fuel for the simple reason, water is 1g/cc and petrol is about 0.8g/cc so petrol will ALWAYS float on water.
By adding the meths, it forms an emulsion with the water and is carried through and burned off in the combustion process.

Can't remember the seal sizes on the fuel filter, usually they come with new copper washers, 2 small, 2 large, a pair for each end.

[skidje]

Originally Posted by Delta66

The ECU can be reset by

Remove fuse No1
Wait 20 seconds
Replace the fuse

That may assist any confusion and it worked for me when there was an emissions issue over a leaking inlet manifold gasket.

This seemed to workout at first start (after replacing fuelfilter and pressure-cooker regulator) this evening. Lets see tommorrow with a cold start. Also running better on petrol with hardly hesitation.

[skidje]

Originally Posted by Laird Scooby

My idea would save 3 days waiting as (in theory at least) it would exhaust the excess LPG pressure before switching off.

Moisture/condensation in the petrol will ALWAYS sink to the bottom of the tank, where the pick-up pipe is for the fuel for the simple reason, water is 1g/cc and petrol is about 0.8g/cc so petrol will ALWAYS float on water.
By adding the meths, it forms an emulsion with the water and is carried through and burned off in the combustion process.

Can't remember the seal sizes on the fuel filter, usually they come with new copper washers, 2 small, 2 large, a pair for each end.

Feel a bit of reluctance doing the meths method. First next step will be cleaning injectors and check all sensors (clean contacts) related to ECU. Final step could be yr suggested meths.thx for your excessive tips and trips laird... Nice to Pick up yr meths solution. Though reluctant i might do it soon. Be aware the volvo switches to LPI soon and with LPI it really runs like a swiss movement...