23 replies to this topic

[Merryck]

Ok, so I've got a decently modified 1275 engine. It's in a Midget - but that aside it's very much in the Mini wheelhouse, so bear with me!

 

It's been sat since 2020. It ran ok when I parked it up. It wasn't great and needed a tune, but it ran ok.

 

The problem I'm having is that when I'm trying to start it it gets really slow to turn over. I charged the battery and it did the same, so I tried a spare battery, but it was the same with that. It's since had three batteries and I've tried to jump it off two cars (one of which was a 200tdi Land Rover) and all cases showed the same behaviour.

 

It spins ok to start with - maybe a little slower than I'd like but ok, then after a few seconds it slows down again. Just gets really slow. I just bought a new battery for it today and it did exactly the same with that one - brand new straight off the rack.

 

I've had the starter motor out and it spins happily, all functioning as it should.

I've changed the plugs

I've rebuilt the carb (it's getting plenty of fuel)

 

I did have the distributor out to get to the starter motor and I was fairly certain it went back in the same position (the Midget has two locating bolts so it's easy to get it in the correct position). I thought maybe I'd allowed it to spin 180 degrees out, but I've just tried putting the rotor arm mechanism back in place 180 degrees opposite to where it is and it doesn't seem to want to sit in that position, which leads me to think it went back in the right position.

 

It has a spark, fuel and air. It should go bang but there is no bang.

 

I haven't done a compression test on it yet, but that aside has anyone got any suggestions?

 

My main concern is the starting fast then slowing down. I can't think what would cause that.

[DeadSquare]

When you removed the distributor, I hope you didn't disturb the shaft to the cam gear.

 

I can't think of a reason why the engine cranking speed would be slow, but if you disconnect the oil and ignition bulbs, you could try a short spin over with two batteries in series, ie: 24 volts.

 

Is there anywhere that you can tow the car in gear, so that the starter isn't taking power from the battery and you have full 12 volts for the coil.  I have often found that having started an engine this way once, the starting corrects its self.

[KTS]

worth checking the earth straps from the engine to the body, and battery to body are good 

[Merryck]

I did consider bump starting it - with the thinking that it's worked with motorbikes in the past - so why not. I'll try and give that a go.

 

I don't think the earthing is a problem, I've connected the starter directly to a battery and the negative to the engine block and it has the same results.

 

It's currently in a warehouse at work. I'll see if I can grab a pair of hands before everyone knocks off this evening and give it a push start.

 

If anyone else has any ideas keep them coming! I'm completely out at this point!

[Ethel]

You could take plugs out & see if it turns easily by hand, or rocking in gear. Just to eliminate mechanical seizure. My money's still on it being a bad contact somewhere though. What sort of starter is it, inertia or pre-engaged?

[red81]

The plate of the solenoid is earth so add another cable to one of the retainer bolts to ensure a known good earth.  For what it costs get a new solenoid, they don't like sitting for any period of time.  Also check what solenoid you should have i.e. 3 spade connectors or 4.  My understanding is that, On the 4 connector ( MG Midget 1500) you get increased voltage when starting which reduces when running, something to do with the ballast resistor,( behind your dash clocks), which may be faulty, so worth a look and read about.  

 

Steve

[sonscar]

Deadsquare hit it,it is likely too advanced.Remove plugs and use a timing light.At least you will then know.I was always drilled to actually verify the timing before attempting a start.
A poor connection on the live or earth circuit or a failing starter needs thought,more turns,gets hotter,higher resistance,turns slower.Just my experiences,Steve..

[Merryck]

Ok, so I had another go after work. Bump starting it is a no go as it seems the clutch isn't disengaging, so the engine will be coming out anyway at some point.

 

I gave it a good go starting it and felt the battery cables afterwards. The earth was beginning to get warm.

 

I can't remember the details of the ignition system. It's got electronic ignition, but in terms of which solenoid etc. I'd have to take photos to check.

 

Current plan is find a timing light, check the timing, remove the slave cylinder and try to re-engage the clutch and bump start it if I can. After that it'll be engine out and I'll sort and and all electrical connectors at that point.

 

Ideally I'd like to get it running before I remove the engine, just to rule out anything I do after that point, but I'm not going to muck about with it forever. It's a shame as it's a cracking engine, and I was really excited to get it going!

[DeadSquare]

I don't expect that I'll live long enough to get around to it, but for a few years I have been mulling over slipping a BMW K1600 six cylinder motorcycle engine into a Midget.

[Clip]

My money would be the starter motor, especially if you have electronic ignition. The starter motor will be sucking all the juice out of your electrical system and not leaving enough for ignition. I would be grabbing a known working starter motor and trying that before anything else.

[weef]

If the starter motor is slowing down after several attemps I would suspect it as being faulty. But before you condem it do some  volt drop checks across the main starter motor circuit cables to see if you can identify a problem there.

To try and start the car, once the engine timing is set correctly, is to use two fully charged and functional batteries. Use the "on board" battery to power the starter motor and isolate the ignition circuit from the car,  "hot wire" the ignition using the second battery, this ensuring you get a good supply voltage for the ignition irrespective of the on car system.

[Merryck]

Excellent advice everyone, thank you very much! I'll see if I can spin the starter separately from the ignition system and go from there. It span happily on the floor when it was out of the car, but obviously that's a far cry from it having any kind of load on it.

[Merryck]

I don't expect that I'll live long enough to get around to it, but for a few years I have been mulling over slipping a BMW K1600 six cylinder motorcycle engine into a Midget.

 

there's a great thread on retro rides of a chap who's put a 1275cc Nissan CG engine in one mated to a suzuki engine. It's a pretty good conversion and designed to be reversible if he chooses to go back to an A-series.

[gazza82]

The Nissan engines were developed from the A-series. Probably were the Mini engine would have been had it lived on.

[Merryck]

I only discovered the CG engines were based on the A-series a few years ago. Can't understand why it wasn't the go-to for conversions over the K-series and VTEC. Nice and small, five speed box, 16 valves, overhead cams, fuel injection and it's the baby of the Nissan family, so power upgrades can be taken from other cars quite cheaply. The 1.3 I've got puts out the same as the equivalent year Rover Cooper, but is restricted by it's inlet and exhaust. A better inlet and exhaust sees an immediate power bump, and there's plenty of room to go higher before you get into forged internals etc.

 

Anyway, back to the matter at hand. I had the starter out again and had it spinning on the bench. It's not spinning amazingly fast, but we couldn't stop it when we wedged a piece of wood against it to create some load. 

 

I found a thread on mgexp from 2017 of a guy having the exact same issues and his were solved by a new starter. To further diagnose the problem I connected the battery to the ignition system, then connected another directly to the starter motor. Either battery individually showed the same symptoms as before, but with both putting power through it nearly fired.

 

It was up on axle stands, so tilting backwards. Spraying easy start in got the best results so I suspect either my carb rebuild has caused me to set the pickup in the carb wrong or the axle stands were causing issues.

 

Just charging the batteries and will try again later with the car on the floor. Failing that I'll take the carb off and check my work.

 

Still not 100% on where the issue is coming from, but I suspect a new starter will be needed.