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Fuel and fuel systems Petrol vs Diesel, LPG Conversions, premium fuels, and all that gas

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Old 16-10-18
ProfJ ProfJ is offline
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Default Fuel starvation - a cautionary tale

Hey folks,

Thought I would post this warning tale because I have had a lot of great advice off this forum over the years. I have a 2001 3.5 GLS LWB. I don't drive it that often because I work from home and live in a tiny village so walk everywhere. About two weeks ago I parked it in front of my house, left it a few days. Then had an early morning flight to catch, jumped in the car at 6am in freezing temps, and NFW, the engine would crank but it didn't ignite at all. So I took the wife's car (a Toyota Highlander, how embarrassing) and left her with a dead Paj, this is why you get married, right?

Anyway I got round to fixing it a couple of days ago. I pulled a sparkplug, plenty of spark there, so it must be a fuel problem. I split the high pressure fuel line at the junction on RHS of the firewall. First surprise - no pressure in that line, a tiny leak of fuel was all that came out. I tried running the pump by hotwiring it from the fuel pump relay, but no fuel coming out.

I also squirted some start-ya-bastard ether into the opened air box, the engine fired up fine and ran a few beats. So, not an ignition or timing belt or any of that. Must be fuel.

At this stage I'm thinking fuel pump. I open the hatch under the RH back passenger seat, and the hatch under that (who f%&*ing designed that arrangement, you have to bend the under hatch to get it out of the hole?) I remove the high pressure hose and get the long suffering wife to key the ignition. Now some fuel does actually pump out, not as much as I expected for an HP pump, but what do I know?

I was thinking the fuel tank might be low - the car is parked on quite a steep road, not crazy steep but you do breathe a bit heavy walking up to my house. The gauge was showing about 1/8th tank, the warning light hadn't come on yet. I didn't have a full size jerry can around but used a 10L one, put another 10L in the tank on top of the 1/8th tank, no change.

Now what? I was thinking maybe immobiliser (because it cuts the pump, and maybe injectors?) I try the spare keys. No joy. I also opened the HP fuel line again - I was going to manually inject some fuel in there - but it actually did have fuel in it, just not under pressure.

I tried to start the car with the fuel pump hotwired, thinking that maybe the fuel pump relay powers the injectors and this will bypass an immobiliser. Now the engine actually kicked, ran a while, died. Classic fuel starvation. It couldn't quite sustain an idle.

OK, maybe it's the in-tank fuel strainer? So I open the f#$#% under-seat hatch again, wrestle the electrical and pipe connections off the pump top, get the six fiddly 8mm nuts off. I lift the pump out. The pump and strainer look perfect, like they were put in yesterday.

BUT...I look in the tank, and there is no petrol to be seen. The pump seems to sit in a kind of small sump, with walls or baffles around it, about the size of the bottom of a 2L milk jug. Not quite bone dry, but you can see there's nothing for the pump to lift.

So a pour a couple of litres of gas in there, put the pump back in (which is FIDDLY, take your time getting the pump and its hold-down ring and the lugs all lined up, or you get some excitement when you top up the tank. Ask me how I know). And of course the engine fires up and runs perfectly.

So, I spent two days diagnosing that I didn't have enough gas in the tank (although it was nearly a quarter tank when I got it on level ground).

I think what happened was that when I left the car standing for days, the pressure leaked out of the HP line (it is supposed to hold pressure with the car off). Normally, you probably drive off out of these situations before that happens, on the fuel in the pipe, and the fuel sloshes around the tank before the pump starves.

I can't believe that a moderate slope is enough to starve the fuel pump, with at least 1/8th tank.

Anyway, I have seen a number of posts about Paj's which run badly on low fuel tanks, it is generally blamed on the tank strainer but I reckon this is probably the issue at least in some cases.
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Old 16-10-18
RUGGA RUGGA is offline
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Very interesting, thanks for sharing.

Could the small "sump" be there to hold fuel in the event of car stalling on a steep 4wd track incline/decline? To keep the pump always "wet" and ready for a re-start, get moving and sloshing what fuel is left in the tank (if low) around?
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Old 16-10-18
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marcthelegend marcthelegend is offline
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I'd be inclined to check the fuel tank for a dent in the middle, I've smashed mine in twice now and just live with it only going down to the 1/4 mark haha

They're in quite a vulnerable position and the fibreglass "protection plate" just bends around it!

Cheers,

Marc.
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Old 16-10-18
ProfJ ProfJ is offline
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Yeah, I reckon it's something like that.
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