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Stale Petrol

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Hi Chaps (and chapettes...)

Been lurking on here for a while, reading and learning, but this is my first post so be gentle on me ;-)

Basically, have acquired a 1989 110 N/A 2.5 petrol (fixed thrust, variable noise) hardtop. The plan, unsurprisingly, is to do the 200/300 TDI conversion. For which I have found loads of resources and articles on this site...

However, being the sensible, not taking on too many projects at once, sort of guy, I recently bought my first house (with a drive and garage, hurrah!!), and was using the truck to move my stuff. My not-so-bright mate found an old can of petrol in the shed of the old house, and promptly poured it into my tank, without my knowledge.

Result: Drove fine for about 10miles, then suddenly started losing power, backfiring, etc. The usual things you'd expect from past its sell by date go-juice! I pulled over to the side of the road, let the engine tick-over for five minutes, and promptly drove off again. I did attempt to dilute it with fresh petrol (£10 worth) It now drives fine, but will occasionally shudder, lose power and require a five minute rest before continuing. Interestingly, usually on an incline (going uphill).

What do you suggest as a possible remedy? I've heard talk of a small amount of paraffin in the tank? Or a belt'n'braces drain the tank? Probably won't bother with the latter, as I've moved now, and can start the conversion (assuming I can source a suitable donor disco)...but it would be useful to be able to use the truck should the need arise, without the five-minute rests.

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It's also worth disconnecting your fuel lines at the lift-pump and checking for them and the pump itself for guff. (Simply blowing through them will help in the short-term) The lift pump is placed between the tank and the filter in the fuel system and so has a habit of sacrificing itself to any cack that happens to be floating around.

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drain & fill with fresh petrol & change any fuel filters as well, a tank of clean fresh petrol should sort it.

Not necessary in my opinion. 'Rancid petrol' is a syptom of fuel that has been stored with a large amount of air present, so that it deteriorates, turns orange, and is significantly less combustible than fresh petrol. Diluting it with fresh petrol is fine, and the greater the dilution - the less effect it has on the running of the engine. Replacing filters is totally unnecessary - old fuel has no effect on it/them, so you you wouldn't benefit at all from doing it. If the the engine stutters on an incline, then it obviously can't be the the fuel, or indeed the filters, but rather water in the tank, or perhaps a small air leak somewhere - possibly from the tank. If you fill the tank and have no problems, but they return as the tank level reduces, then look at air ingress within the tank itself (pick up pipe perhaps).


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Thanks for your reply Les - I did wonder what exactly makes petrol 'stale'!

Things have moved on apace now anyway, as I appear to have acquired a donor disco with a 200 TDi lump in it. So will be replacing the filter anyway. Also, the 110 runs out of MOT next week!

However, obviously leaky pick up pipes and other means of air entering the system will be even more of a problem with an oil-burner up front, so will check the entire fuel system. I'm guessing that other than making sure the petrol is thoroughly drained out of the tank there isn't much more to do for the conversion? What with petrol being a powerful solvent, there's no point 'cleaning' the tank?

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  • 6 months later...

Hello all, with apologies for resuscitating a dead thread (and also my first post!), I thought I'd share that I think I've got to the bottom of this one, but it's thrown up a further mystery. Hopefully a grown-up on here will know the answer! Incidentally, I've searched the forum using the google trick, but drawn a blank :D


Fuel Pump by udderlyoffroad, on Flickr

As you can see my fuel pump output pipe is somewhat shorter than it should be, and I reckon the rusty stump was where the air was being sucked in! The flexible fuel hose was held onto said stump with a less-than-tight jubilee clip.

So it should be a simple matter of replacing it the assembly (+new seal!), which the parts catalogue on page 521 tells me is PRC7020, listed as 'Pump Fuel'? Er, not quite, as you can see from my build thread (linky below), I'm doing a rebuild and putting in a 200 TDi. The parts cat further states that for a diesel, I want NTC2156, 'Pipe Fuel Return'...

1) So is that assembly the fuel supply or return? Or are they reversed on a diesel I thought the return was the nipple on the side of the tank? (Supply sucks from bottom, return vents to top?)

2) Do I want the pump or pump-less version for the TDi?

3) Flexible hose appears to be the solution, anyone know a good source that will do 2+ metre lengths?

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