14 replies to this topic

[purple_fly06]

Hi Everyone,

 

It's probably something that i can figure out myself but I'm wondering what peoples thoughts on the subject are.

 

Here's the situation:

Around 6-7 months ago i tucked my mini up for winter, when it was put away it was running as sweet as a nut and i had no issues. 

 

Due to being busy/ forgetting i only started it up yesterday    but it turned over and fired up straight away... BUT it wont tick over (even with the choke out) and as soon as i touch the throttle it backfires.

 

Its obviously fuel related but why would it have changed if it has been sat there... could it be that some of the spark plugs are corroded and hence not sparking so the fuel is burning in the exhaust?

 

Ill be giving it a full service and once over this weekend as i plan to let it out for the spring and summer so that should hopefully sort it.

 

Any ideas would be appreciated.

 

Thanks,

Josh

[JetBlackEreg]

What spec is the engine? 

[purple_fly06]

What spec is the engine? 

1.75" SU Carb. 1275CC.

 

Nothing majorly fancy as i use it as a daily in the summer. 

[paulsv24]

Has it got points? if so, it might be worth having a quick look at them, the gap might've closed or corroded and inside the cap could be damp etc. Check the dashpot level too.

[purple_fly06]

Has it got points? if so, it might be worth having a quick look at them, the gap might've closed or corroded and inside the cap could be damp etc. Check the dashpot level too.

Nope electronic ignition. Im thinking it could just be the old fuel? Or it has a mind of its own....

[paulsv24]

Could be, but fuel tends to last better these days. Have a check on all the breather pipes are still connected etc and clean up the plugs. Put some new petrol in from a can and give that a go, hopefully if you can then get it running it'll blow the cobwebs out. Can't think of anything else that would change if left apart from damp etc.

[ChopperHarris]

Could be, but fuel tends to last better these days. Have a check on all the breather pipes are still connected etc and clean up the plugs. Put some new petrol in from a can and give that a go, hopefully if you can then get it running it'll blow the cobwebs out. Can't think of anything else that would change if left apart from damp etc.

Sadly untrue The problem begins with today's modern fuels. These so-called "clean" fuels typically deteriorate at much faster rates than fuels made 20 years ago. While all fuels suffer from the problem, most at risk are the EPA mandated reformulated gasolines (RFG) that contain oxygenate additives, derivatives of methyl alcohol and ethyl alcohol. We've seen gasoline have shelf life as little as a month—particularly if it is subjected to heat and moisture.

[dklawson]

You said the car backfires.  Is the backfire out the tailpipe or carb?

 

If the backfire is out the carb, you are dealing with a lean condition.  Though it normally doesn't happen in 5 to 6 months, evaporating gas in the float bowl can leave behind fuel gum and varnish that blocks the jet.  The solution is to replace any fuel filters, clean the carb jet & needle, and clean the float valve.  Reset the float valve height if necessary.

 

If the backfire is out the tailpipe, check/replace the points and condenser.  Leave the distributor in the block when changing the points and condenser so as not to disturb the ignition timing.  Though it will not hurt to check the spark plug wires, cap, and rotor... it is not likely to be the plugs themselves.  

[purple_fly06]

Its out of the tail pipe, and it has electronic ignition.

 

I'll put a new cap, ht leads and plugs in when i do the service, that should eliminate those being the issue.

[dklawson]

With the car having an electronic ignition and a tailpipe backfire, you may also want to take a peek under the dizzy cap at the advance plate.  Make sure it is free to move and is not bound up.  While there, look underneath the plate at the bob weights.  Make sure they are free to pivot and that their springs are not broken.  Finally, grab the rotor and give it a twist back and forth.  You should feel springy resistance and be able to move the distributor shaft a bit.  If not, the advance portion of the shaft may be seized onto the part that goes into the block.

[carbon]

 

Could be, but fuel tends to last better these days. Have a check on all the breather pipes are still connected etc and clean up the plugs. Put some new petrol in from a can and give that a go, hopefully if you can then get it running it'll blow the cobwebs out. Can't think of anything else that would change if left apart from damp etc.

Sadly untrue The problem begins with today's modern fuels. These so-called "clean" fuels typically deteriorate at much faster rates than fuels made 20 years ago. While all fuels suffer from the problem, most at risk are the EPA mandated reformulated gasolines (RFG) that contain oxygenate additives, derivatives of methyl alcohol and ethyl alcohol. We've seen gasoline have shelf life as little as a month—particularly if it is subjected to heat and moisture.

 

+1 for ChopperHarris comments about modern fuels, in particular petrol with ethanol content which is now in most pump petrol in UK.

 

When left for long time any ethanol left in carb float chamber can absorb water and then starts to do messy things like corroding the alloy float chamber and can end up with load of gel-like substance which doesn't help fuel flow.

 

If checks on the ignition don't clear the issue I would suggest the carb would be next in line for attention.

[David128]

also if firing at tdc will be too far retarded

[russo]

Fuel can deteriorate in as little as a month. You say it has been in storage for 6 - 7 months. Way too long. Drain the fuel tank and fill up with fresh fuel.

[purple_fly06]

As said above,

 

I didn't drain the tank as there wasn't much in there, i just put 5L of fresh fuel in. After a few bang's and pop's the 'newer' fuel eventually pumped its way down and now its back running like it used to.

 

Thanks for your help guys!

[Dusky]

Im going to bore you with a 'funny' fuel story. My dad had a fair few cars, most of them just old and rusty ( saved from the scrapyard to salvage usable parts).
It took us 3 days to get his race mini started, that mini stoof for 5 years. The fuel went stale, it really smelled funny too!
Few weeks later I want to start one of the old cars for fun, the car is a fiat strada, stood for 24 years.. 10 second crank with a new battery and it started! It did have Electronic ignition tho, but amazing how easy it starts!