13 replies to this topic

[nospamprl]

I own a 1989 mini 30th with the 998cc.

The car is only used for weekend ramblings and sometimes it refuses to start for the first 4 or 5 attempts.

Once it starts, it keeps starting on the first try for the rest of the weekend.

Is it possible for the carburator/pump to dry after a few days and need some cranking befire it gets enough fuel to start?

Would using starter fluid help?

Starter, coil, etc seems to be ok.

Thanks

[cal844]

If the car has a mechanical fuel pump check that the engine oil doesn't smell of petrol... If it does then you need a new pump.

[Retro_10s]

I wouldn't recommend introducing starter fluid as part of the normal starting procedure. It 'should' be as simple (assuming your 1989 has an S.U. HS4 carb) as pulling the choke out, turn the key and away we go.

How long have you been noticing this behaviour for? There's quite a few things that could be causing this but for now, making any adjustments to fuelling is best left as a last resort.

Your HS4 carb has a float bowl on the side where the fuel enters from the pump, by removing the airfilter (assuming you have the standard air filter housing) you can gain access to this bowl,.. it should be full of fuel even after after 4-5 days of rest... If it is not we need to find out where it's going!

As mentioned by cal844,.. it's possible you have a deteriorating mechanical fuel pump, specifically the rubber diaphragm inside,.. have you been running the new E10 fuel? It will cause all old rubber parts in the fuel system to turn brittle and crack. You can get e10 'proof' parts from minispares or another trusted supplier.

You could always fit an inline transparent fuel filter between the pump and carb to see if you can see the fuel flowing, or not.

[timmy850]

I’d make sure the choke cable is properly adjusted, and that you’re pulling it as far as it goes to get the starting mixture correct

[Ethel]

If it's a HS carb unscrew the float lid & look at the fuel level before you attempt to start it, then do the same straight after it's run. That'll tell you if it's losing fuel while it's standing - probably from where the jet screws in to the float bowl.

 

You could also crank it over with the fuel hose squirting in to a jar to see if there's much delay in it delivering fuel. I'm assuming it has a mechanical pump.

[nospamprl]

If it's a HS carb unscrew the float lid & look at the fuel level before you attempt to start it, then do the same straight after it's run. That'll tell you if it's losing fuel while it's standing - probably from where the jet screws in to the float bowl.

You could also crank it over with the fuel hose squirting in to a jar to see if there's much delay in it delivering fuel. I'm assuming it has a mechanical pump

 

 

I drove the car yesterday, so probably today it would start ok anyway.

 

I just unscrewd the bowl as suggested and the fuel level (after removing the float) is about half of the bowl. I guess this is correct after removeng the float).

 

The I started the car and i fired at first try (so probably the fuel level in the bowl hadn't have enough time to go low. After that I checke again the fuel level in the bowl and seems the same.

 

I won't start the car car again and will check next week.

 

 

 

Additionally, there are 2 hoses at the top of the bowl. One comes from the pump but the other seems to go to the front of the car above the clutch and then maybe to the starter motor area. What is this hose for? It's broken where it fits the bowl but doesnt feel like it is doing anything (no fuel, no vacuum). The car seems to run normal even if I disconnect it.

 

Thanks again for all your help.

Edited by nospamprl, 23 October 2022 - 04:11 PM.

[Lplus]

 

If it's a HS carb unscrew the float lid & look at the fuel level before you attempt to start it, then do the same straight after it's run. That'll tell you if it's losing fuel while it's standing - probably from where the jet screws in to the float bowl.

You could also crank it over with the fuel hose squirting in to a jar to see if there's much delay in it delivering fuel. I'm assuming it has a mechanical pump

 

 

I drove the car yesterday, so probably today it would start ok anyway.

 

I just unscrewd the bowl as suggested and the fuel level (after removing the float) is about half of the bowl. I guess this is correct after removeng the float).

 

The I started the car and i fired at first try (so probably the fuel level in the bowl hadn't have enough time to go low. After that I checke again the fuel level in the bowl and seems the same.

 

I won't start the car car again and will check next week.

 

 

 

Additionally, there are 2 hoses at the top of the bowl. One comes from the pump but the other seems to go to the front of the car above the clutch and then maybe to the starter motor area. What is this hose for? It's broken where it fits the bowl but doesnt feel like it is doing anything (no fuel, no vacuum). The car seems to run normal even if I disconnect it.

 

Thanks again for all your help.

 

The second hose is the float bowl overflow pipe intended to divert overflowing fuel away from the hot exhaust.  It shoud terminate just behind the starter gear housing on the clutcch cover.

[Ethel]

It's also a vent to let atmospheric pressure in to the fuel bowl. If it was blocked you'd get some vacuum that would stop petrol being sucked through to the engine. So it's another potential contributing factor, but doesn't fit your symptoms quite as much - the vacuum would increase as the float chamber emptied. 

 

If you're careful to keep it level, you can get a feel of if the float is holding the float valve shut before the lid is properly seated as the lid would be pushing the valve seat down as much as the float is pushing the valve up.

 

It's worth checking all bits on the fuel supply side though as they're all interconnected:

 

The float isn't holed or dinted; its pivot isn't worn & moves freely; the float valve & seat are debris free and haven't worn a groove; the float height is set something like - 4mm drill bit (usually), but google images should find you a diagram & let you identify what goes for your pattern of float. 

[nospamprl]

It's also a vent to let atmospheric pressure in to the fuel bowl. If it was blocked you'd get some vacuum that would stop petrol being sucked through to the engine. So it's another potential contributing factor, but doesn't fit your symptoms quite as much - the vacuum would increase as the float chamber emptied. 

 

If you're careful to keep it level, you can get a feel of if the float is holding the float valve shut before the lid is properly seated as the lid would be pushing the valve seat down as much as the float is pushing the valve up.

 

It's worth checking all bits on the fuel supply side though as they're all interconnected:

 

The float is holed or dinted; its pivot is worn & moves freely; the float valve & seat are debris free and haven't worn a groove; the float height is set something like - 4mm drill bit (usually), but google images should find you a diagram & let you identify what goes for your pattern of float. 

 

Last week I opened the float chamber and the fuel level (without the float) was about half of the chamber. 6 days later the level is only about 1/4th of the chamber, so either it's leaking or evaporating.

 

I noticed the vent hose on the top is broken and I don't feel any dampness below the float or carb. Could the fuel evaporate because of the broken vent hose or a small leak that on the bottom that dries fast enough to make it unnoticeable by touching it?

 

Thanks.

[Lplus]

 

It's also a vent to let atmospheric pressure in to the fuel bowl. If it was blocked you'd get some vacuum that would stop petrol being sucked through to the engine. So it's another potential contributing factor, but doesn't fit your symptoms quite as much - the vacuum would increase as the float chamber emptied. 

 

If you're careful to keep it level, you can get a feel of if the float is holding the float valve shut before the lid is properly seated as the lid would be pushing the valve seat down as much as the float is pushing the valve up.

 

It's worth checking all bits on the fuel supply side though as they're all interconnected:

 

The float is holed or dinted; its pivot is worn & moves freely; the float valve & seat are debris free and haven't worn a groove; the float height is set something like - 4mm drill bit (usually), but google images should find you a diagram & let you identify what goes for your pattern of float. 

 

Last week I opened the float chamber and the fuel level (without the float) was about half of the chamber. 6 days later the level is only about 1/4th of the chamber, so either it's leaking or evaporating.

 

I noticed the vent hose on the top is broken and I don't feel any dampness below the float or carb. Could the fuel evaporate because of the broken vent hose or a small leak that on the bottom that dries fast enough to make it unnoticeable by touching it?

 

Thanks.

 

Either is possible, though I would suggest it is simply evaporating out of the vent pipe.

Edited by Ethel, 29 October 2022 - 10:28 AM.
Yes, Mexico is likely a bit hotter, drier & higher than here!

[Ethel]

Not because of the hose so much, but it could evaporate. The biggest factor is likely to be how much heat is around the fuel bowl after the engine's turned off.

 

Starting a carb car is all analogue. You need enough fuel in the air between the plug gap and enough potential across it to create a spark that catches & creates enough of a burn to get the next cylinder to do the same. Everything is variable and affects everything else. A bigger plug gap can contain more fuel, but needs more volts to jump it. A richer mixture reduces the resistance so needs less voltage...

 

Understand the system so you can make your own judgement calls:

 

Is difficulty in starting because the engine has had long enough to cool down to need a richer mixture than it's getting or so much longer that fuel has evaporated, or leaked, from the carb. Does it need cranking more to refill the fuel bowl, or get the fuel air ratio rich enough? Is the ignition working as well as it could...?

 

Starting with the ignition is usually the best tuning approach as it doesn't require the right fuelling to get a stronger spark or check the timing against the specs.

 

 

 

By "4 or 5 attempts" I think we've been assuming that means 5-10 seconds of continuous cranking each time. As I'm sure you're aware a carb is nothing like a diesel injector, even if an A Series squishes & burns almost as well. If your car fires on the 1st turn it'll be because the inlet manifold was still wet.

[Lplus]

Not because of the hose so much, but it could evaporate. The biggest factor is likely to be how much heat is around the fuel bowl after the engine's turned off.

 

Starting a carb car is all analogue. You need enough fuel in the air between the plug gap and enough potential across it to create a spark that catches & creates enough of a burn to get the next cylinder to do the same. Everything is variable and affects everything else. A bigger plug gap can contain more fuel, but needs more volts to jump it. A richer mixture reduces the resistance so needs less voltage...

 

Understand the system so you can make your own judgement calls:

 

Is difficulty in starting because the engine has had long enough to cool down to need a richer mixture than it's getting or so much longer that fuel has evaporated, or leaked, from the carb. Does it need cranking more to refill the fuel bowl, or get the fuel air ratio rich enough? Is the ignition working as well as it could...?

 

Starting with the ignition is usually the best tuning approach as it doesn't require the right fuelling to get a stronger spark or check the timing against the specs.

 

 

 

By "4 or 5 attempts" I think we've been assuming that means 5-10 seconds of continuous cranking each time. As I'm sure you're aware a carb is nothing like a diesel injector, even if an A Series squishes & burns almost as well. If your car fires on the 1st turn it'll be because the inlet manifold was still wet.

It seemed the OP was talking about the level dropping from half to quarter after 6 days, so iI'm assuming the engine wasn't started in that period.  However I do note the OP is in Mexico, so it could be a good deal hotter than here.

[Ethel]

Seems a lot for evaporation, but it's a very subjective measure. The jet tube seals were always a bit delicate, easily over-tightened & now we have ethanol. Could be lots of things & quite likely a little bit of all of 'em.

[nospamprl]

Apparently the problem has been solved by replacing the vent hose with a new one. Really cheap (free) repair for something that has been annoying me for a couple of years).

 

I have left the car parked 2 times for 6 days each time and the engine started at the first try both times.

 

Thank you all for your advice. This forum is great! (specially for us far away from the UK where this cars are not common).