In theory, if you run a car until the fuel runs out, what would happen?
Will the engine suddenly die?
Will it cause any permanent damage?
If you refill the car with fuel will it restart as if nothing happened? Of you have to tow it to garage to do some special tricks?
How an electric car would handle this differently?
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>> In theory, if you run a car until the fuel runs out, what would happen?
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>> Will the engine suddenly die?
on a modern car
Its likely the engine will throw up a low fuel pressure warning
>> Will it cause any permanent damage?
In theory its possible the fuel pump can be damaged due to lack of lubrication, but the low fuel pressure sensor should prevent it.
>> If you refill the car with fuel will it restart as if nothing happened? Of
>> you have to tow it to garage to do some special tricks?
In theory it will restart, the pump(s) self prime tho the low fuel pressure warning will remain in fault memory.
In an old car, it runs out of fuel, it stops, you fill it up, it cranks forever and eventually starts, having sucked up crap from the tank, the filter gets blocked, the carb jets or the injectors get blocked, you break down again about 50 miles later.
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>> How an electric car would handle this differently?
It goes flat, you stop, you re-charge it runs.
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If your electric car runs out in an area remote from charging points can you call out an emergency service to give you a fast re-charge?
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Not sure about a fully electric car, but here's an interesting experiment a bloke did on a Chevy Bolt (same as my Ampera)
www.greencarreports.com/news/1109431_what-does-a-chevy-volt-do-when-it-runs-out-of-gas-and-battery-charge
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>>If your electric car runs out in an area remote from charging points can you call out an emergency service to give you a fast re-charge?
No - they will tow or flatbed you to a recharge point that works.
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>>In theory it will restart, the pump(s) self prime
Most (if not all) modern diesels don't have an LP pump and will need to be manually primed - and some can be difficult to get liquid up to the pump to make it go; and even then it might need 3 or 4 goes before it will run OK. I suspect that most punters would need the services of a breakdown man to get it going again!
Most modern petrols, given a reasonable delay after switch on to allow the pump to prime, will start as if nothing has happened.
Last edited by: RichardW on Sun 3 Dec 17 at 16:24
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>>modern diesels don't have an LP pump
LP?
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>> >>modern diesels don't have an LP pump
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>> LP?
>>
A low pressure pump to supply fuel to the high pressure injection pump.
Last edited by: Old Navy on Sun 3 Dec 17 at 16:42
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Did not know that. Thanks.
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Sorry, more. Why don't they have one?
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My diesel cars covered the transition from injection pumps that supplied all the injectors individually to common rail systems. LP or lift pumps as they are sometimes called seemed to dissapear on my cars when common rail systems were introduced. I assume that the common rail high pressure pumps provide enough suction to lift fuel from the tank. My current (petrol not battery) car as a fuel pump in the fuel tank which supplies the fuel rail.
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>>Will it cause any permanent damage?
On a newish car probably not.
On my 180,000 mile 735i it sucked a bunch of silt into the fuel pump and it died a few days after I ran out of fuel.
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MD of once company had a Ford Scorpio 2.8. He ran it out of fuel. Two days later, the engine failed and would not restart - dirt in injection system.. ££££s
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I remember reading in my Mazda6 manual about the manual priming process if you ran out of fuel... made me think I don't want to have to do that.
I'd never run a car low on fuel though because of problems with a Fiesta I had in the mid 90s. When I bought it there was little fuel in it and it had probably been moved around on fumes. Couple of months later was having problems with it spluttering a bit.
Took to my friendly garage and on listening to the engine said it sounded like there was something mechanical wrong... so booked into their recommended engine place. Engine did have problems and I elected to get a recon engine (warranty covered 50%).... and when I got it back.... the spluttering continued!
Went back to the original garage and they blew out the fuel lines with compressed air but the problem kept coming back. So they fitted an inline filter for me (for free too) and the problems went away. Sold it a few months later when I started racking up miles so got a business need company car and used hire cars until one was available.
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Some diesels do have a lift pump in the tank and some don't. Difficult to be model specific,but most VAG models do,while most Fords don't. A CRD high pressure system pump (which is actually not a pump at all)more of a fluid transfer device,needs a good fuel supply to operate.If you run out of fuel with no lift pump in the system,then restarting the engine can be a real pain.
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I'm involved with a '30s Austin that has an autovac as a fuel pump. It only works when there's an inlet manifold depression, so it only works when the engine's running. It's used intermittently and the non-return valves aren't as good as the were eighty years ago.
To start this we have to remove the carburettor float chamber and fill it with an eggcup-full of petrol, that lets the engine run long enough to for the vacuum to get the autovac to work.
Old cars are fun!
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Shirley spraying starting fluid through the intake would be less hassle?
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The modesty filter does not like my link to Start ya B*****d.
Last edited by: Old Navy on Sun 3 Dec 17 at 21:22
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>> Shirley spraying starting fluid through the intake would be less hassle?
Yep! I don't think the owner's would be pleased with the (alleged) damage that would do to such an old lady.
I understand the stuff wipes off any lubrication on the cylinder walls.
I'm quite happy to spend a few minutes going through the rigmarole of getting the thing going.
That means checking the oil and coolant levels, setting the ignition to full retard, setting the (ignition?) switch to accumulator, putting a clothes peg behind the choke knob (the friction don't work any more), pushing the clutch in (to reduce any transmission drag) and pressing the starter button.
Once it's running, check there's oil pressure, switch the ignition to dynamo, adjust the advance/retard for a 'sweet' spot and continue to adjust as it warms up (no thermostat).
Old cars are fun!
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They certainly are Tombo. The Jowett has never started well from cold. I've used both Eezy Start or a bit of petrol poured down each carb air intake. Lucky in this respect as the air cleaner goes up with the bonnet leaving the tubes clear. I've just sorted out the camshaft to sprocket relationship and she started first kick with a little choke. Looking forward to better running from now on.
I made clips out of brass sheet to hold the choke out...no modern clothes pegs in my motor house ! But then, 65 yr old pegs would have been ok. I removed the mechanical pump and fitted an electric one...no Lucas for me, our local ancient auto electric place had a new AC one for a Morris Minor in stock. Equal capacity to that which the car required and it was the last one !
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>>I don't think the owner's would be pleased with the (alleged) damage that would do
Not a lot of lubrication in petrol either - maybe they should use petrol/2-stroke mix when starting...
More likely the fannying about is an integral part of their enjoyment and a quick and sensible solution goes against their luddite sensibilities ;-)
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>>Old cars are fun!
Prefer tinkering with older women these days, knowlmean.
:)
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I've never understood the "crud in the tank getting sucked through if you run the level right down" scenario.
I agree anecdotally it sometimes appears to be true, but the fuel gets sloshed around anyway, and the pick-up point must obviously go to the lowest point, so what is the crud doing normally? Sitting around somewhere cunningly avoiding being caught?
It might happen if the tank has a floating pick-up, perhaps, but most don't - they just have a pipe tapped into the lowest point or a pipe down from the top with a filter at the bottom.
I suspect the stories are more likely to be simply that a car will run despite neglected maintenance until something causes it to stop, like running out of fuel, and then trying to restart it shows up the other things that need attending to.
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I expect I’ll be able to let you know next weekend! I started our old Audi convertible yesterday; it hasn’t really been driven since last December, and it was looking a little grubby after a year of dust and rain so I decided to give it a clean. I left it idling with the interior fans on max most of the afternoon to air it out, but when I went to turn it off it was spluttering slightly and was clearly running on fumes. I’ll chuck 5 litres of Shell’s finest unleaded in in next weekend and see what happens...
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Going back a few years I ran my Citroen C8 out of diesel virtually outside a filling station. It has the 2.2 HDi engine with, I believe, a low pressure lifter pump and a high pressure rail pump. The engine hesitated once, then stopped. After blagging a 100 yard tow round a roundabout and onto the forecourt and buying a fuel can, I put 5 litres of diesel in the tank and switched on. There was the usual muted growling that I get when unlocking the car or opening a door that I take to be the lifter pump working. I switched off and popped the bonnet and undid the fuel filter drain, letting an eggcup-full of diesel onto the undertray. Switched on again and the engine started immediately. 55K miles later there appear to be no ill effects.
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Restarting car after fuel runs out - Zero
