Fails to idle when hot [Solved]

[owent2005]

Evening all,

I have recently refitted my 009 points dizzy after the electric ignition I installed failed. I took the bus for a drive and after about half an hour she started to cut out at low rpm, i.e. coming to a stop. She started again straight away and I just kept the revs up at low speeds. The dizzy was timed with a strobe when hot and when I got home I double checked and it was still fine. I’m thinking idle screw on the carb but I’ve not touched this for a long time, has anyone any thoughts on other things I could check?

I have a stock 1600 with single soles 34 carb.

Any thoughts would be welcome!

 

[ozziedog]

Hard to say from that description, but usually it’s the very last thing you touched :mrgreen:
I’d start from the beginning and do the basics. Gap and clean your plugs and points and check / replace condenser, then do your valve clearances as that’s a likely suspect and I’d probably do that first because you can only do that with your motor cold and apart from a couple of gaskets, it’s free. Check your rotor arm and cap and look for stray sparks in the noise cupboard with the lid mostly down. If everything is sorted then move on after that, as it’s very hard to get anything else right if any of the above are a bit out.

Ozziedog,,,,,,,,,,, 100% sure the lecky one failed ??? :mrgreen:

 

[owent2005]

After a warm afternoon working in the boot I have checked the following; condenser is fine, dizzy, cap and leads are all fine as are the spark plugs, the fuel pump is also ok.
I’m baffled the only thing I did was swap the dizzy back and retime, now it won’t idle once warm. I’m thinking carb, but it’s not been touched.
Is there any other info people might need to give me some pointers?
Thanks!

 

[ozziedog]

I don’t know of a reliable way to check your condenser and the same goes for the coil. My stand by / go to type plan with those is buy a spare one or borrow a known good one and just replace. If it’s still “exacterly “ the same then put the old one back on as you now know it wasn’t that and you have just bought a spare. Pop the points out and double check the wiring underneath and the grommets through the side.

Ozziedog,,,,,,, What went wrong previously??? :? :?

 

[K@rlos]

Sounds like fuel starvation

 

[subheatadey]

First 1/4 of throttle is idle jet so maybe its blocked?

 

[atafonso]

It could be that the timing is retarded, did you check at idle or at full advance?
Abel

 

[owent2005]

Hi,
Thanks for the thoughts guys, yep to check each item I swapped them out and still had the same problem, I haven’t checked under the points though.
I have taken out the idle valve and cleaned it and this didn’t do anything although I swapped the valve for one with slightly larger holes. The result was that it idled but I couldn’t get it less than 1600rpm. I originally timed it with a strobe at both idle and max advanced.
The original problem was with an electronic ignition fitted I was driving along and then got nothing, at first I thought it was the accelerator cable or fuel. The breakdown man said it was the signal from the ignition back to the coil had failed which seemed to be backed up by the way the van ran when I put the old dizzy back in. Unfortunately I didn’t take it for a long drive to check everything and I didn’t notice the idle problem until I went for a drive a week after the breakdown.
I’m now thinking maybe where the idle jet screws into the carb?

 

[sparkywig]

Before you start on the carbs, if it was running fine before your ignition problem I'd run it with another coil just to eliminate that.

 

[owent2005]

Is the coil required to continually run the engine? I thought it was just to get it going?

 

[sparkywig]

Is the coil required to continually run the engine? I thought it was just to get it going?

Without a coil the engine won't run, the coil provides the high voltage energy for the spark at the plugs.
The points/electronic module in the distributor is just a low voltage switch that collapses the high tension circuit in the coil, and the rotor arm directs the high voltage from the coil king lead to the relevant cylinder's ht lead and onto the spark plug.

 

[owent2005]

Ok, thanks for the info I learn a little more each day! If the coil was the fault would it still be able to start and run for a while? it also ran continually with the oversized idle jet I put in?

 

[sparkywig]

Yes, could run fine until the coil heats up and the insulation breaks down.

 

[owent2005]

Ok thanks, I’ll try that when I get home.

 

[owent2005]

Ok, another update, I have now changed the carb and coil for known good ones and still no change. I can’t think of any other reason why it’ll run when I’m pressing the accelerator but not at idle.
Any further thoughts would be welcome!

 

[owent2005]

Evening all, so this afternoon I have changed the points, the rotor arm and dizzy cap. It still won't idle, after changing the rotor arm it idled for a minute or two then cut out. Is it possible there's a problem with it getting air, as I've changed/checked everything to do with the fuel and spark? Really am stumped and looking for inspiration.

 

[pom2ter]

air intake with the brake assistance ?

 

[thejinx]

Have u looked at your fuel filter and fuel lines. I am clutching at straws here but could the be partially blocked? when you swapped the dizzy is TDC in the same place. My original had no 1 lead at 5 o'clock. When I changed it the new dizzy had no1 at 2 o'clock. Did you set your idle and mixture screws to the default of 2.5 turns out as a start point.

 

[owent2005]

Good morning,

I've now managed to get it to idle and it turned out to be the fuel filter. Thanks everyone for your help.