Electrical / Fuel Issue
Turbo Mini Forums

Mini is currently off the road at the moment with a pretty terminal fuel / electrical problem. Here's what happened. I'd just returned from a rolling road tune at Slark Engineering (see my other threads) so the car had been put through its paces.

Cabin began to fill with smoke from melting electrical wire. Washer pump then cut in and I pulled over. Found wire to fuel inertia switch on one side was melted. Disconnected the washer pump, and bypassed the (then suspect) inertia switch to get home. Found rest of wire back to fuel pump (SPI tank) also started to warm up and melt, cue more smoke and trip home on a trailer.

When the ignition is on, the fuel pump is audibly intermittent. Battery is now disconnected until I can figure out the problem.

So I'm suspecting one of the following:
1) heat from turbo during tuning has meted some cabling, causing a short circuit somewhere between the washer pump and the fuel pump
2) Fuel pump is faulty and drawing too much current.

I obviously need to strip back to find out exactly whats melted and needs replacing, but I'm really looking for some other opinion as to what might have gone wrong so I can solve the root cause.

Just bought the car and desperate to get it on the road for the Castle Coombe meet on the 24th...

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

sounds like no 2 to me, is the pump fused?

I suspect not, but it soon will be!

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Well if the wire is melting all the way to the fuel pump the issues must be at or near the pump.

Try connecting the pump directly to the battery, by-passing the loom and measure the current drawn.

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A man without a project is like a like a woman without a shopping list.

Is it the SPi pump in the tank? How much boost where you running? You may have over worked the pump as they don't flow enough fuel for lots of boost.

Okay, so by way of an update. Traced the loom back today. The wire from the interia switch to the relay is totally fried, with the damage less severe towards the relay end. Damage to the rest of the loom is minimal, and there is no damage between the relay and the fuel pump.

I haven't tried wiring directly to the fuel pump yet to see what the power draw is.

Having read some of the other info on here, a little surprised to find the relay was a 30 amps, and wonder if this was why I was getting the wire melting and the circuit didn't fuse, or perhaps the relay itself is faulty. There was some scorching around the relay contacts.

I plan to replace the relay with a lower rated one anyway. Will test the fuel pump tomorrow. If the pump needs need replacing, I was thinking of using a higher rated pump as suggested elsewhere on here to avoid the problem apbellamy suggested. I'm only boosting at 10psi at the moment though, so surprised if that's the problem. I'm suspecting that a better rated pump wont massively affect the setup?

Any additional advice would be welcome!

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

ignore the relay rating, its just a current rating like a wire, it wont make the current it jsut means it wont fail as easily.

I have known a couple of pumps to draw excess current before, but its pretty rare.

bare in mind that if the pump is drawing a lot of current then its likely to be getting hotter than intended, and personally I wouldnt want anything that has fuel in it getting hotter than intended.

get an amp meter on the pump and check the current, it should be maybe 5 amps at the most. IIRC there should be a 10-15A fuse in line.

An intermittent short on the 12v wire to the fuel pump to ground would cause the pump to be intermittent and could cause the wire to melt if the fuse rating is incorrect. If the washer motor wire is in the same loom it also may be missing some insulation somewhere and shorting to the fuel pump supply causing it to run. (long shot..) Basically you need to have a good look around and poke about with a meter. If the wiring is bad enough for shorts like that then it needs a proper looking at.

I'd be re wiring to the fuel pump completely for starters. I have to agree with Joe C on being careful where fuel is concerned.

hmmm wire to pump shorting on a hole or clip on the floor ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

SO clearly there was no fuse protection ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Fuel pump is good, drawing 2.8A. Reckon a faulty relay leaking current into the relay switching line or a dodgy cable. Either way, they're both going to be replaced....

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

and add a fuse before you end up with XL5!

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

Okay. These things are never simple. I've put all the wiring in the loom. Tested the continuity all the way along, connected everything up and fuel pump was working perfectly with the ignition on. BUT.... turned the key to start the engine then click and nothing. Now I've lost all power. I'm guessing another short somewhere, but goodness knows where to start. Any suggestions!?!

Knackered starter solenoid perhaps? Would that explain no power when turning the key though?

Edited by daveg79 on 20th Sep, 2011.

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

Dug around a bit more....
Have 12 V at the starter solenoid, and at the live that feeds the ignition
Live voltage drops to 0.5V with the key in the ignition to the first position (no idea if this is normal). No power elsewhere.
All fuses are fine (I think I've found them all!)

My build thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=440970

Go for simple stuff first.

Battery, earths leads etc

In the 13's at last!.. Just