Forum Home
PC World Chat
Thread ID: 126539	2012-09-03 10:03:00	Probably a weird question - fuel lights	pcuser42 (130)	PC World Chat

Post ID	Timestamp	Content	User
1298670	2012-09-04 04:21:00	I was always told to keep tanks full, as when empty moisture can condense inside and cause rust.	Agent_24 (57)
1298671	2012-09-04 09:38:00	Yes rust is a real problem with plastic fuel tanks ...lol	coldfront (15814)
1298672	2012-09-04 11:31:00	Please quit driving with less than 1/4 tank . It'll kill the fuel pump, which is mounted in the tank . The pump requires fuel to cool and lubricate it and when the tank gets low, the pump is not longer submerged in the fuel and you are damaging it . After you pay for a new pump, you will never allow your tank run low on fuel again . True . I burnt one out by running and starting on a near empty tank for a few months . Plus they can be troublesome to remove the entire pump carriage from the tank, without the risk of bending the float arm, or scraping the label type height indicator and the sender wires . For some reason there is a razor sharp circumference, which easily cuts your fingers . Then the feeling that fuel level never read proper when I replaced it . Learnt my lesson never again near "E" . Never knew they need petrol for cooling . I thought pumps were attached near the tank . My '77 929 Mazda electric pump certainly was .	kahawai chaser (3545)
1298673	2012-09-04 12:17:00	The pump requires fuel to cool and lubricate it and when the tank gets low, the pump is not longer submerged in the fuel and you are damaging it. Through all my vehicles over the years, and well over a couple of million Km's, I have always run my tank right down (knowing the normal average Km per full tank) and I've never had a petrol pump failure, in fact I've never heard of a petrol pump overheating, so could that be a US issue SJ, with your thirsty V8s etc do you think? I did see on the web a few US sites that mention the same issue, but I reckon the average Jap petrol sipper wouldn't heat up its pump in a month of Sundays. I don't for one moment doubt your experience, but I reckon there is either an application or a pump quality issue in there somewhere. A petrol pump shouldn't have to work that hard. Maybe it is the long hot runs you guys do? One of your Interstate runs, or just a day out in Texas would see us driving off the other end of the country here. :D Cheers Billy 8-{) Of course your PPs (GPs?) could all be designed by Lucas, and that would be a whole new ball game!	Billy T (70)
1298674	2012-09-04 14:58:00	The sole reason why the pump's on the tank is because of the high pressures and keeping leaks corralled in a controlled area - the tank itself . I've changed quite a few FI pumps (in tanks) from abuse by owners driving down to the vapors . Just trying to save house guys some money with my experiences .	SurferJoe46 (51)
1298675	2012-09-04 23:49:00	Yes rust is a real problem with plastic fuel tanks ...lol Depends on the vehicle... newer ones would be more likely to be plastic, but not all.	Agent_24 (57)
1298676	2012-09-05 11:38:00	The sole reason why the pump's on the tank is because of the high pressures I can see the logic for oil pumps Joe, but practical experience and commonsense tells me that since it takes about eight hours to empty my 65 litre tank, which is about eight litres an hour, that means the pump is struggling away delivering about 135ml per minute, or 1 litre every 7.5 minutes, give or take. Hell, I can pee about 20 times times faster than that without overheating, and I drain the tank every time! I know they run at around 2 Bar but they do have the through-flow to help keep the temperature down. If we were to calculate the amount of energy needed to deliver 135ml per minute (I estimate about 2.5A/30 watts all up at 2 Bar, losses included), I'd be surprised if that effort would raise the pump temperature by more than a modest amount, and bearing in mind that the gas is still sloshing around and in some cases through the motor, helping to keep things cool, and since it wouldn't be doing that with reduced external cooling until say the last 10% of the tank, then there seems to be a serious under-engineering problem somewhere back there. Surely modern 'intelligent' systems could pump 'according to demand' and hard on only if running at full noise, but it is still not a demanding task, and the motor should not overheat to the point of buring out. That outcome is usually saved for excess load problems where the pump motor slows, loses back-emf and consequently draws excess current. I guess a stonking V8 in a good 'ol US Truck would suck about 3 times the gas of my 2.3 litre petrol sipper, and I'm allowing for old age and inefficiency there, because it probably wouldn't be 6.9 litres and might not be very eco, but up to 400ml per minute is not exactly a major load. So, if pump burnout is a regular problem in the US, then I reckon that perhaps the pumps are under-engineered for some of your driving conditions, or put the other way around, perhaps the Japanese and Koreans have got it right. Cheers Billy 8-{)	Billy T (70)
1298677	2012-09-05 12:08:00	Please quit driving with less than 1/4 tank. It'll kill the fuel pump, which is mounted in the tank. The pump requires fuel to cool and lubricate it and when the tank gets low, the pump is not longer submerged in the fuel and you are damaging it. After you pay for a new pump, you will never allow your tank run low on fuel again. Seen the price of fuel down here?, I can only afford enough to moisten the bottom of the tank, never mind trying to submerge a pump. She had better run fine on vapors, because thats all shes gettin.	Metla (12)
1298678	2012-09-05 16:10:00	I can see the logic for oil pumps Joe, but practical experience and commonsense tells me that since it takes about eight hours to empty my 65 litre tank, which is about eight litres an hour, that means the pump is struggling away delivering about 135ml per minute, or 1 litre every 7 . 5 minutes, give or take . Hell, I can pee about 20 times times faster than that without overheating, and I drain the tank every time! I know they run at around 2 Bar but they do have the through-flow to help keep the temperature down . If we were to calculate the amount of energy needed to deliver 135ml per minute (I estimate about 2 . 5A/30 watts all up at 2 Bar, losses included), I'd be surprised if that effort would raise the pump temperature by more than a modest amount, and bearing in mind that the gas is still sloshing around and in some cases through the motor, helping to keep things cool, and since it wouldn't be doing that with reduced external cooling until say the last 10% of the tank, then there seems to be a serious under-engineering problem somewhere back there . Surely modern 'intelligent' systems could pump 'according to demand' and hard on only if running at full noise, but it is still not a demanding task, and the motor should not overheat to the point of buring out . That outcome is usually saved for excess load problems where the pump motor slows, loses back-emf and consequently draws excess current . I guess a stonking V8 in a good 'ol US Truck would suck about 3 times the gas of my 2 . 3 litre petrol sipper, and I'm allowing for old age and inefficiency there, because it probably wouldn't be 6 . 9 litres and might not be very eco, but up to 400ml per minute is not exactly a major load . So, if pump burnout is a regular problem in the US, then I reckon that perhaps the pumps are under-engineered for some of your driving conditions, or put the other way around, perhaps the Japanese and Koreans have got it right . Cheers Billy 8-{) Pump burnout isn't a regular problem in the US - it happens though and given the sheer number of FI'd vehicles on the road - almost every one since 1988 or so, it's a given that there'd be a lot of work for a mechanic just replacing them from normal attrition . However, most are damaged from running them low on fuel repeatedly as this is the sole destroyer of them from excessive heat and bearing failure . Almost to total exclusivity, all the FI pumps I've changed have been from owner's neglect by starvation and inconsistency in the keeping of at least 1/4 tank of fuel in the system as a minimum . This rears it's head most times in multiple tank systems where one can merrily run until one tank is empty and switch to the second tank and continue running off it . Then there's the pressures that most people don't understand . Many FI systems run over 13 ATM (for start up and then settle to 4 or 5 ATM during running - but know this: the pump doesn't actually drop pressure but the lower-running pressure is acheived by bleeding off the line pressure via a regulator after the fuel rail (supply line) and returning the excess to the tank to be recirculated . The pump, therefor, never rests and is screaming it's guts out all the time the engine is running and/or the key is in the 'RUN' position . Let it grab some air eg: in a low-fuel situation and it'll spin out of control, cavitating, trying to reach the designed-in operating pressure and (in times of this neglectful starvation) the bearings (which are not designed for such situations) cannot be lubricated at such high out-of-sight RPM nor can the heat generated be carried away because of insufficient lubrication/heat ablation in the bearings because of such a lack of fluidic circulation and thermal washing . There are however, people who get away with the most crass abuse of things-mechanical and even though all the projections and "typical-as-designed-run under 'normal' conditions" are and have been crassly exceeded, they still carry on blissfully unaware and unpunished for their lack of concept toward things mechanical . Bless their little pea-picking hearts but they are the bump or anomaly in the actuarial tables of logic and are members in good standing with the 'plays-with-fire' contingency that seems to be protected by angels or demons - I assume not which in this circumstance . These very same (oblivious) people are the reasons why mechanics, after a style, have no hair on their heads or an ulcer in their guts (mine: the latter) since they cannot be proven to the folly of their logic and ways . We call them: car killers .	SurferJoe46 (51)
1298679	2012-09-05 16:32:00	OK.. Here's a video I watched a while back from Airtex/Eric the Car Guy. (www.youtube.com) It seems a pump would overheat because they are so compact with little air space and many working parts. Think they would make them larger or more accommodating to the initial high pressures required. Then the filter - mine was grey as when I replaced the pump. This may add even more work/pressure to the pump, of which filters cannot be easily replaced like a oil/air filter. Though the Walbro's I think have higher pressure - at a much higher cost.	kahawai chaser (3545)
1 2 3 4