Hot start / warm start / restart issues again!

[Laney760]

Originally Posted by Laird Scooby

See if it does it again Ellie, might be just a quirk and a one-off just to remind you to take it in for service etc tomorrow.

Has the whine calmed itself down yet?

Cheers Dave, the whine has gone but the restart/hot start problem has been intermittent now for a couple of years or so. It started up again at the beginning of the summer, then went away and now it's started up again at the start of the autumn/winter so I can't even tie it down to the outside temperatures! As you know almost everything relevant has been renewed on the car, the throttle body is always kept clean. Been a while since I had a new lambda probe, that was the cause of my terrible hot start problems back in 2014-15, I've done about 50-60 thou since then, maybe thats worth renewing!

[Laird Scooby]

Sorry Ellie, i thought i'd replied to this last night. I doubt your Lambda sensor is playing up again but when did you last have the LPG system serviced? I'm thinking filters and possibly injectors may have a slight leak on them or need a cleaning agent put through them. A slight bit of dirt on them might cause enough of a leak to give hot restart problems especially as it will always start on petrol whether it's hot or cold. Could be leaking just enough gas to not want to start with WOT when hot but the ambient temperature is not hot enough for that gas to evaporate quickly - i think that makes sense.

You could probably try my theory by switching to petrol a few minutes before switching off so it burns off any excess gas from the alleged leak before switching off, if that stops the problem then you know you're in the right area.

[Laney760]

Originally Posted by Laird Scooby

Sorry Ellie, i thought i'd replied to this last night. I doubt your Lambda sensor is playing up again but when did you last have the LPG system serviced? I'm thinking filters and possibly injectors may have a slight leak on them or need a cleaning agent put through them. A slight bit of dirt on them might cause enough of a leak to give hot restart problems especially as it will always start on petrol whether it's hot or cold. Could be leaking just enough gas to not want to start with WOT when hot but the ambient temperature is not hot enough for that gas to evaporate quickly - i think that makes sense.

You could probably try my theory by switching to petrol a few minutes before switching off so it burns off any excess gas from the alleged leak before switching off, if that stops the problem then you know you're in the right area.

Hi Dave

Thanks but I tried switching to petrol a few miles before switch off many times down the years and it made no difference and I have this issue even when I am running on petrol for weeks and there has been no lpg in my tank for weeks so it's nothing to do with lpg.

The lpg system was serviced today as well and all was ok :-)

[Laney760]

Hi to All!

All winter I started with ''foot to the floor'', Bob's excellent tip that gets me out of trouble and starting. Then, I forgot to start with foot to the floor one day this Spring and she started first time and I haven't had to start with foot to the floor all summer. Exactly what happened last year!

Suddenly this week and immediately after the heatwave I experienced the starting problem again, and remembered the foot to the floor tip and sure enough she will start that way but she has to be started that way every time now, whether she's been switched off for a minute or an hour or a day.

I had spent all summer thinking I had seen the back of this starting problem and thinking that maybe the head gasket renewal and head skim had been something to do with the end of the problem. Clearly I was wrong!

I've just spotted from a previous post on this thread that this problem re-started last autumn but its started a bit earlier this year! But the issue did re-start after a very big reduction in temperatures! I suspect something in the car's computer system reacted to this big drop in temperature like it normally reacts to the drop in temperature from summer to winter?

I am wondering if this problem could be the ECU? Its probably just about the only thing I haven't replaced?

[bob12]

Hi Ellie - sorry to hear that the problem has reappeared.

On my 745 with LH2.4 etc Bosch changed the engine management ECU after 6 months in about Aug 1990 apparently because of problems with it. Then with the 900 Series they removed the cold start injector and again introduced new ecu's.

The problem is definitly ambient temp related. After years of head scratching and changing bits and pieces I tend to your thoughts on the problem being with an ecu rather than a fuel evapouration/pressure/temp sensor etc loss/problem.

I have spare original ecu's for my car but have never got round to swapping them as starting 'my way' if needed causes me no agrivation. I guess the original starter motor may require love sometime though (got a spare in a box somewhere)!

Bob

[Laird Scooby]

Saw your post last night Ellie and couldn't think of anything useful to try but Bob has echoed the majority of my thoughts on it.

Except one that is. What petrol are you using? I know you mainly run on LPG but as i also know you know, it starts on petrol. Some time back i decided to try one of my cars on normal unleaded to see if the "new" E10 stuff would give any improvement in power, economy or anything else. It didn't but it also brought a hot starting problem in warm weather.
Switched back to E5/Super unleaded, problem solved. A bit of research revealed the higher ethanol content can evaporate (and cause vapour locks) easier than the lower E5 ethanol content in hot weather. As your normal running is on gas, when you switch off all the heat of the engine bay can work on the petrol in the fuel rail evaporating the ethanol content causing a vapour lock.
Bear in mind that it should be relatively cool while running due to constantly recirculating back into the tank, the heat would be very local to the fuel rail.

Also on another forum i'm on, someone has performed tests on E10 on a variety of cars, mainly Honda and a couple of motorbikes and has reported difficult hot starting on E10 as well as reduced power and economy.

If you're using E10 even just for starting it might be worth a try switching to E5?