1st Gen R53 Cooper S Hard starting when below 1/4 tank of fuel

Not sure, but if you're going to replace the pump.... try this one!

DeatschWerks DW65v Uprated Fuel Pump for R53/R56 MINI Cooper S – Greene Performance

 

Ever change the filter?

They are NOT lifetime like MINI claims.

[ame="https://www.youtube.com/watch?v=rCppUQfNZQQ"]Replace Fuel Filter - Gen 1 MINI Cooper R50 R52 R53 - YouTube[/ame]

 

Add more fuel???

 

Sure, but its still less expensive than the OEM unit

 

It's weird that it would've just started, but I've had to redo customer installed fuel filters due to them either omitting the o-rings, or the o-rings not seating properly causing a bleed off of pressure.

Matter of fact I had to do this in my car when I first bought it due to the same predicament.

 

how long do you keep your pump running before you fully turn your key? You can hear the fuel pump pressurizing the system - when that sound stops, you should be able to start the car normally, or at least the fuel pressure should be up to spec and neither pump nor filter should impact the startup negatively.

It does sound like a filthy filter (they have less surface to filter when the tank is low, reducing flow just because once your fuel drops, only a small part of the filter surface is used, plus the crud usually collects most near the bottom due to gravity, plus it is the part of the filter that is always in use.

 

^^^ Exactly add more fuel or change your fuel filter.

Fuel is cheap now. :ihih:

 

I'd sure think so.

 

well, how long do you pre-pressurize the fuel system before startup? If the filter is clogged the pump has a hard time geting pressure built up. Once there is pressure, it recirculates back to the tank anyway. For most driving situations, once there is enough pressure, there's plenty of fuel available. Cold starts also require a surprisingly large amount of fuel.

And after you start the car and run it for a few minutes, will it start up fine after a brief stop? Fuel pressure will drop over a period of time, but it should not drop that quickly. If it starts up poorly even then, you have a very different problem

If the car starts poorly only after standing overnight, you may have a leak somewhere in the system, tiny, but enough to drain all the fuel from the line back into the tank. Starting with a full keyturn under those conditions will have the engine struggle to get going.

My filter caused problems only when I was driving up long mountain grades at a good clip, requiring a higher fuel flow over extended time (below 18mpg on the realtime gauge). Places like Vail Pass on I 80 would have the car cut out near the top of the grade, then bump start again as fuel pressure rebuilt during the hiccup, etc - idle it a minute at the side of the road and it was fine for a few miles again. No codes, just no fuel with a full tank or half a tank. Now that I think of it, the lower the fuel tank was on that trip, the more often the car would do that. However, startups and short bursts even at full throttle never were a problem with that dirty filter.

 

forget what I said about the low fuel and the filter being used only for the lower half of it's filter element. That's not how it works, actually. I somehow remembered this large thing in the tank, but that's just an enclosure, the filter is much smaller inside that thing and he pump pushes fuel into the filter enclosure through the filter. So unless you are almost totally out of fuel the filter will be fully submerged.

It's really difficult to make sense out of that 1/4 tank thing based on the setup inside the tank. the pump picks up fuel from the very bottom of the unit right on the bottom of the tank. Unless the pump intake is so clogged that it needs more fuel pressure by gravity to work well, there's just no way the fuel level would affect the performance of the pump.

There's a small pump under the fuel filter that is used to level the two sides of the tank, but if it failed you'd just run out of fuel earlier. Nothing that matters at engine startup.

Still would not be a bad idea to swap that fuel filter given the high miles you have on that car and the filter.

 

I have this one installed and have had no issues.

DeatschWerks DW65v Uprated Fuel Pump for R53/R56 MINI Cooper S – Greene Performance

 

Waterish gas at the bottom of the tank?