Strange hot start problem!
Discussion
Hello, if I run my car for more than a hand full of miles, switch off and let it heat soak it will not restart. I have spark at the HT lead if I put a spark plug on it, but I don't have a spark on any of the plug leads!?!?!?
If I let it cool down, it's fine again and never gives any trouble when running.
What do you think???
If I let it cool down, it's fine again and never gives any trouble when running.
What do you think???
It's called the hot start issue, and it is due to a number of factors, including weak main cable wiring, a wrongly wired immobiliser and therefore immobiliser failure when hot.
Edited - it's NOT the hot start problem, having read subsequent posts.
Edited - it's NOT the hot start problem, having read subsequent posts.
Edited by QBee on Saturday 26th August 09:04
If you have a spark on the HT lead (presumably you mean coil to distributor cap HT lead) but none on any of the plug leads, that seems to point to distributor cap or rotor arm. There have been some poor quality replacement rotor arms about in recent years. The chances of all plug leads/extenders failing together is slim.
What's the internal contact like in the centre of the cap?
Coil is another possibility, but doesn't really seem to fit symptoms. Are all leads making good contact?
What's the internal contact like in the centre of the cap?
Coil is another possibility, but doesn't really seem to fit symptoms. Are all leads making good contact?
Yes I've got a spark going down the HT lead from the coil to the distributor, but no electricity going down any of the plug leads individually.
The engine is cranking perfectly as I've got a brand new Power-Lite starter, 500 amp earth lead direct from starter to negative terminal (it's big!), new plugs, leads & good battery. Fuel pump is doing the business as well.
It's looking like it might be the ignition amplifier on the distributor body. I've read that when they heat soak, they breakdown, then when cooled they work again helping to produce the spark circuit.
The engine is cranking perfectly as I've got a brand new Power-Lite starter, 500 amp earth lead direct from starter to negative terminal (it's big!), new plugs, leads & good battery. Fuel pump is doing the business as well.
It's looking like it might be the ignition amplifier on the distributor body. I've read that when they heat soak, they breakdown, then when cooled they work again helping to produce the spark circuit.
If you have a good strong spark at the end of the HT lead from the coil then the next place the electricity goes is through the small carbon brush in the centre of the distributor cap. From there it travels along the rotor arm - the bit that goes round and round - and as the tip passes each segment (8 of them, one for each cylinder) the spark jumps from the rotor arm to the segment, then along the HT lead and finally to the spark plug.
So, if you have a spark from the coil to the distributor on the centre lead (called the king lead) then the coil is providing a spark. So, first you must check the condition of the brush inside the distributor cap and the rotor arm.
If the spark was weak and not able to make the jump from the the rotor arm to a segment this would suggest the coil is not providing a strong enough spark. When you crank the engine with the king lead off, holding the tip about 1/4" from the engine block, do you get a succession of good strong sparks?
So, if you have a spark from the coil to the distributor on the centre lead (called the king lead) then the coil is providing a spark. So, first you must check the condition of the brush inside the distributor cap and the rotor arm.
If the spark was weak and not able to make the jump from the the rotor arm to a segment this would suggest the coil is not providing a strong enough spark. When you crank the engine with the king lead off, holding the tip about 1/4" from the engine block, do you get a succession of good strong sparks?
N7GTX said:
If you have a good strong spark at the end of the HT lead from the coil then the next place the electricity goes is through the small carbon brush in the centre of the distributor cap. From there it travels along the rotor arm - the bit that goes round and round - and as the tip passes each segment (8 of them, one for each cylinder) the spark jumps from the rotor arm to the segment, then along the HT lead and finally to the spark plug.
So, if you have a spark from the coil to the distributor on the centre lead (called the king lead) then the coil is providing a spark. So, first you must check the condition of the brush inside the distributor cap and the rotor arm.
If the spark was weak and not able to make the jump from the the rotor arm to a segment this would suggest the coil is not providing a strong enough spark. When you crank the engine with the king lead off, holding the tip about 1/4" from the engine block, do you get a succession of good strong sparks?
While I agree with your post, how do you think heat is causing the problem ?, I would go with the amplifier or coil as being the problem.So, if you have a spark from the coil to the distributor on the centre lead (called the king lead) then the coil is providing a spark. So, first you must check the condition of the brush inside the distributor cap and the rotor arm.
If the spark was weak and not able to make the jump from the the rotor arm to a segment this would suggest the coil is not providing a strong enough spark. When you crank the engine with the king lead off, holding the tip about 1/4" from the engine block, do you get a succession of good strong sparks?
PRTVR said:
N7GTX said:
If you have a good strong spark at the end of the HT lead from the coil then the next place the electricity goes is through the small carbon brush in the centre of the distributor cap. From there it travels along the rotor arm - the bit that goes round and round - and as the tip passes each segment (8 of them, one for each cylinder) the spark jumps from the rotor arm to the segment, then along the HT lead and finally to the spark plug.
So, if you have a spark from the coil to the distributor on the centre lead (called the king lead) then the coil is providing a spark. So, first you must check the condition of the brush inside the distributor cap and the rotor arm.
If the spark was weak and not able to make the jump from the the rotor arm to a segment this would suggest the coil is not providing a strong enough spark. When you crank the engine with the king lead off, holding the tip about 1/4" from the engine block, do you get a succession of good strong sparks?
While I agree with your post, how do you think heat is causing the problem ?, I would go with the amplifier or coil as being the problem.So, if you have a spark from the coil to the distributor on the centre lead (called the king lead) then the coil is providing a spark. So, first you must check the condition of the brush inside the distributor cap and the rotor arm.
If the spark was weak and not able to make the jump from the the rotor arm to a segment this would suggest the coil is not providing a strong enough spark. When you crank the engine with the king lead off, holding the tip about 1/4" from the engine block, do you get a succession of good strong sparks?
In this case the coil is making good spark so both coil and amp should be good.
Contact in cap and rotor arm would be my prime suspects. I've seen a rotor where there was not enough plastic below the brass contact bar and the spark was shorting to the top of the dizzy drive shaft so a careful inspect of the arm for cracks or burnt areas.
I think the cap would be giving singular misfires rather than all sparks missing.
Steve
Right! I *think* I've cured it. I removed the ignition amplifier, made up some remote wires so it's not bolted to the side of the distributor, earthed the metal underside to the distributor wire connector that wasn't doing anything, flowed some denture acrylic down the amps electric connector holes so my wires don't short one another out, put an on 486 cooling tower on it to disperse the heat and cable tide it to another cable sleeve to hold it in place. It seems to work as it's dropped the temperature by over 20 degrees! She starts with some heat in her now. A bit more testing yet but it's gone very well so far.
Just a warning shot if you have removed the amp from the side of the dizzy body- I assume you have therefore extended the wires from the trigger head to reach the new amp position? Id recommend you use 2 core screened audio cable, and ground the sheath to the dizzy ground at one end. The signals are tiny from the reluctor trigger head, and the V8 HT system is something Dr Frankenstein would have been proud of, so there is enough stray interference to cause false triggering of the amp if the wires are not shielded.
An update!
Went for a really good drive this evening and all is well with the engine. Even when I let it idle for a long time and built some good temperature it started instantly. It never restarted before, even if you went straight back and tried, it would turn no problem but it wouldn't catch.
Now I can leave it 5, 10, 15 minutes and it just starts. Really pleased. Thanks for all the input chaps, most appreciated and I will look to get some screened wire so that stray signals don't interfere with the amp/dizzy/coil.
Went for a really good drive this evening and all is well with the engine. Even when I let it idle for a long time and built some good temperature it started instantly. It never restarted before, even if you went straight back and tried, it would turn no problem but it wouldn't catch.
Now I can leave it 5, 10, 15 minutes and it just starts. Really pleased. Thanks for all the input chaps, most appreciated and I will look to get some screened wire so that stray signals don't interfere with the amp/dizzy/coil.
At what point (possibly serp) did the amp move from the dizzy to the coil mounting bracket?
OP have you used heat transfer paste when you mounted it on the heatsink? The fact you have a heatsink to hand I assume you have.
Agree with Blitz on the screened wire + only earth the screen at one end.
Steve
OP have you used heat transfer paste when you mounted it on the heatsink? The fact you have a heatsink to hand I assume you have.
Agree with Blitz on the screened wire + only earth the screen at one end.
Steve
Years ago I had a hell of a game with uncontrolled idle on my 4.3 precat Griff - no one could sort it until someone came up with the idea of relocating the ignition amp from dizzy to chassis rail. I reckon that why the later (serp?) cars have the amp relocated away from the dizzy.
No dental cement on mine... but it sounds almost as useful as cable ties...
No dental cement on mine... but it sounds almost as useful as cable ties...
Steve_D said:
At what point (possibly serp) did the amp move from the dizzy to the coil mounting bracket?
OP have you used heat transfer paste when you mounted it on the heatsink? The fact you have a heatsink to hand I assume you have.
Agree with Blitz on the screened wire + only earth the screen at one end.
Steve
Hello Steve, I haven't used any heat transfer paste because I don't have any. The heat sink is new old stock from many years ago and as such already has a coating on it to conduct the heat from the processor. It's pre cooling fan tech. Used to run a computer shop and dental lab from one shop many years ago. OP have you used heat transfer paste when you mounted it on the heatsink? The fact you have a heatsink to hand I assume you have.
Agree with Blitz on the screened wire + only earth the screen at one end.
Steve
Anyway, it's definitely running now as opposed to large green plastic garden ornament. Might get an upgrade unit from R.P.I. In Norwich.
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