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A very confusing starting problem
alexdj125 - 16/1/08 at 11:37 AM

Hi, all. I've got a raw striker with a 1600 Xflow running on weber 40's. It usually starts ok from cold, even if its been left standing for ages, however, when I've been for a drive and stop for fuel or something it doesn't like to start. It will hardly turn over like there is no power, yet when I check the battery its fine. This means i always have to find a petrol station on a hill. Also when this happens, after trying to start it for a few mins I find that the battery leads become warm. I have replaced the starter motor for a new one and checked the amount of power coming through the starter solenoid and it seems to be fine. Like I say, only happens occasionally, and when its hot. I'm wondering if something is expanding under the heat causing this? Any ideas would be greatly appreciated as its really getting to me! Thanks, Alex.[img]http://locostbuilders.co.uk/upload/a676915-P111207_17.11[01].JPG[/img]


britishtrident - 16/1/08 at 11:42 AM

Ignition has too much static advance.


Pdlewis - 16/1/08 at 11:43 AM

Hi,

I had this exact problem last year i found taking the negative off the chassie cleaning both contacts and re-attaching made an improvement. I also put an additional earth lead to the engine on so it had one going to the block and one to the head

hope that helps


ditchlewis - 16/1/08 at 11:43 AM

i had a very similar problem, but it was solved when i changed the starter motor to a High Torque unit, not cheap.

other things, could the fuel be vaporising in the carb float chamber? so no fuel to pump into the engine

have you got a high compression engine?

it sounds so much like the problem i had but as i say it was cured by one of these

ditch

Could be as trident says, my brother in law played with the dizzy and now i have back fireing through the carbs.

[Edited on 16/1/08 by ditchlewis]Image deleted by owner


r1_pete - 16/1/08 at 11:45 AM

Yep, I'd go with over advanced, have you a modified distributor mechanical advance to compensate for lack of vacuum, or just set the static a bit advanced? obviously dizzy is out of the question if you're running MJ or similar....


BenB - 16/1/08 at 11:46 AM

If it's fuel vaporisation the engine would still turn over..... Ditto too much advance on the timing.

I'd take off all the cables, clean the terminals and try again.
If that didn't work I'd replace the solenoid itself.... Unless the engine has been had its CR increased a standard starter motor should be sufficient....


BenB - 16/1/08 at 11:47 AM

Unless anyone can explain why too much timing advance would stop an engine from turning over.....


ditchlewis - 16/1/08 at 11:53 AM

i had the compression ratio increased a lot and the standard starters i had only turned over very slowly. it was much much worst after a run wnen the engine was hot then it would hardly turn over at all. the new starter has 200% more torque and used less amps.

the problem with starting a warm engine has not reoccured

ditch


r1_pete - 16/1/08 at 12:19 PM

quote:
Originally posted by BenB
Unless anyone can explain why too much timing advance would stop an engine from turning over.....

If ignition is too advanced, it will ignite the fresh charge of fuel/air mix too early, which tries to push the piston back down as the burn progresses, not a problem once the engine is running, but during cranking there isn't enough momentum to carry the piston over tdc against the burning charge. This happens when the engine is hot due to the better atomization of the fuel hence faster burn rate.

When advance is correct the charge ignites just before tdc, and accelerates to a full burn as the piston passes tdc, pushing the piston down the right side of tdc. As engine revs rize the ignition is advanced to ignite the fuel earlier, as there isn't as much time between ignition and TDC at higher revs.

Rgds.
Pete.

[Edited on 16/1/08 by r1_pete]


BenB - 16/1/08 at 12:21 PM

That's what I wondered- but wouldn't the pinking be obvious?


r1_pete - 16/1/08 at 12:25 PM

I'd expect some, but in a light car, the engine probably never works hard enough.

If the engine sounds ok and doesn't pink then the hi torque starter is probably the answer.

Take some tools out with you and back the ignition off a touch next time it happens, Zero cost option to find out if thats the problem.

[Edited on 16/1/08 by r1_pete]


ditchlewis - 16/1/08 at 12:31 PM

Please could you remind me of what pinking sounds like, could it be in the form of a carb back firle?

in which case i could play with the mixtures till the cows come home and will not get over the back firing and stuttering.

Ditch


UncleFista - 16/1/08 at 12:32 PM

If you're running megajolt, you can alter the map to give less advance under 500 rpm, it helped our starting no-end.


BenB - 16/1/08 at 12:33 PM

One answer to see if it is that is simple- next time it happens and it won't turn over take off the supply lead to the coil. If then it will turn over normally (obviously don't do it for too long else you'll flood the engine) it's the advance. If it still won't it something else.....

Sound reasonable?


David Jenkins - 16/1/08 at 12:38 PM

quote:
Originally posted by ditchlewis
Please could you remind me of what pinking sounds like, could it be in the form of a carb back firle


I have a recording of pinking made with a mic attached to an engine - I'll post it here once my ISP decides to make my page available again. I think they've forgotten to feed the gerbils again...


UncleFista - 16/1/08 at 12:39 PM

quote:
<snip good idea>

Sound reasonable?


Sounds eminently reasonable to me


r1_pete - 16/1/08 at 12:46 PM

quote:
Originally posted by BenB
One answer to see if it is that is simple- next time it happens and it won't turn over take off the supply lead to the coil. If then it will turn over normally (obviously don't do it for too long else you'll flood the engine) it's the advance. If it still won't it something else.....

Sound reasonable?


Good idea, it really works tossing ideas round on here.......


alexdj125 - 16/1/08 at 05:51 PM

Wow, really didnt expect this much help! Thankyou so much to everyone! It is a higher compression engine, and i'm using a lumenition and the standard distributor, will this make the problem worse? I had the timing set up by a mate with a timing light gun thingy and we did it fairly advanced I think as I've got quite a wild cam fitted. How do I set up the timing without a lightgun? The idea of the high torque starter sounds like a good idea, i'll have a search for one! Also I'll clean all the negative connections and see what happens! Again, thankyou so much for your help!


Macbeast - 16/1/08 at 07:40 PM

Ditch: pinking sounds like a metallic tinkling noise.