10 replies to this topic

[smurfomatic]

The 998 in my Mini Marcos has developed an annoying issue recently... 

 

Once it's been sitting in traffic for a while, then you pull away, it will accelerate OK up to about 45-50mph then it splutters and cuts out, on and off, for a while before clearing.

 

If it's really stuck in traffic for about 10 mins or more, the car cuts out and needs to be left for around 10-15mins to "cool" before it'll start. When you try to start it before this, it'll fire for a second or two before cutting out.

 

Other than this, it takes a few attempts to start on cold mornings but other than this it runs fine. I do 20 miles (mostly dual carriageway) each way every workday, so it's getting a good run.

 

The car isn't overheating on the temp gauge, stays just below normal (and it will go higher than that as I've run it without the fan for a while to check it'll go up). I suspected a fuel issue, but last time it broke down I disconnected the hose from the carb and it was pumping fuel OK. by the way it's a single HS4 carb with a K&N conical filter on it.

 

I recently fitted a new exhaust manifold (end of June) and haven't had problems - driving every day - until recently. Caveat on this is that it wasn't driven much in August and early September as I had my appendix removed so couldn't drive.

 

I suspect the new manifold may be causing fuel vaporisation? The new pipes have a crossover where the old one was "straight" so this will have possibly caused the issue. PS - this took several hours to fit past the bulkhead so I hope the solution isn't to replace it!

 

Looking at the carb there doesn't seem to be a spacer on it, never had one in the time I've had it but maybe needs one now? There's not much clearance to get the filter in if there's a spacer but the bulkhead could be modified to fit.

 

What I've tried:

 

Cleaned out carb float bowl

Cleaned fuel filter

Tightened alternator belt

Checked dashpot oil

Put some petrol cleaner in with the last tankful

Flushed cooling system

 

I'm hoping that it'll be something as straightforward as heat shielding the fuel line (which doesn't run too close to the manifold) or putting some kind of heat shield by the carb - no-one seems to make single HS4 shields though.

 

Thanks for your time reading all this waffle!

[lsto]

Have you checked if your getting a decent spark when the car gets hot. I had a car with this type of fault which turned out to be a duff coil when it got hot.

[smurfomatic]

Thanks - I will check, but it had new plugs & leads not long ago plus a new coil about a year ago. Strange that it'd only happen after being stuck in traffic, as I'd expect the car would get just as hot driving around town.

[MiniMonty]

Dodgey thermostat ?

[69k1100]

The engine will get much hotter sitting in traffic as there is less air circulating through the grill. This is why thermo fans rarely cut in while driving around.

 

What sort of fuel pump are you using? Does it have some age to it? Also if the Pump is getting warm (If its mounted in the boot or near and exhaust) that could be vaporizing the fuel too.

 

Try running it up to temp in the drive way, can you replicate the problem? If so take the bonnet off, see if it helps. Or open the boot if that's where the pump is.

[smurfomatic]

Monty - the thermostat, that seems fine in a pot of boiling water.

 

69k1100 - I think the fuel pump may be the issue. It's a Fuelflow, mounted inside the O/S wing, fitted in Jan 2013. Just had the car running on the drive for about 20 mins, the pump was getting warm and the level inside the fuel filter (fitted between pump and carb) had dropped noticeably. Also, while looking at the filter, there were bubbles coming through from the pump (checked connections and they are all tight, so would think this is vapourised fuel?). Car didn't cut out but was definitely running worse than when it started.

 

Any recommendations for a replacement pump? Preferably one that would be able to go in the same place and last more than 15,000 miles!

 

Edit: Having done a little research, seems a Facet 501 would suit my needs... http://www.minispare...ssic/SS501.aspx

Edited by smurfomatic, 19 October 2014 - 10:16 AM.

[69k1100]

You'd need to find a low pressure pump, most pumps these days are high pressure pumps designed to "push" the fuel up to the carb, as opposed to "pulling" it up from the tank.

[smurfomatic]

So would the Facet not be suitable then? They do a model (40104) ranging from 1.5 - 4.5 psi which should do the job (I think!)

[69k1100]

It's the location that's the problem. Many moons ago they used to put them /near the engine but the fuel in that configuration is drawn up, lowering the pressure allowing the fuel to vaporise in the lines.

A pump that "pushes" the fuel (mounted near the tank, preferably under it) tends to have a better chance of keeping the fuel to vaporise.

[smurfomatic]

OK thanks. There's no easy place to mount a pump in the back, as it's a Marcos there's not really a boot only a space behind the seats.

 

I'll have to see how it goes with the Facet pump, as I will need to replace the current one ASAP before it decides to cut out completely!

[smurfomatic]

Update: new Facet 40104 installed and seems to have cleared the worst of the problem - tested in a 20 min traffic jam after going for a drive to get the car warm. Stuttered a bit when finally pulling away but nowhere near as bad as in similar situations.