2500S engine reluctant to start and barely runs.

[Clifford Pope]

This a Mark 1 which had a 2500S engine when I got it 2011.
I seem to have been plagued with engine problems ever since, or at least since Covid anyway.
It's always been temperamental, but was running quite well until 2019. Then came Covid, and also I was ill for some years, so the car was unused but I tried to keep things working. I started it every few months and got it up to temperature, moved it a bit inside the garage to keep the clutch free, tried the brakes, etc.
Now I have recovered my enthusiasm, and it won't start. It has new ignition parts from the Distributor Doctor, I drained the old fuel, flushed the tank, re-did the pipework with new new rubber connectors, but I flattened the newly charged battery but it didn't give even a cough or splutter. While recharging the battery again I checked the at the plugs, which spark well.
On trying again it finally almost ran, then picked up a bit, but it sounds awful, with a horrible harsh crackle in the exhaust like a boy racer, and cuts out if I try to rev it. It doesn't seem to be a weak mixture - pulling the choke out even a tiny bit causes it to stop instantly. It will rev, but misfires and bangs, and stops if I try to pull in first.

I left it for half an hour and tried again, but now it won't run at all.

Really I've run out of ideas. Can anyone suggest anything I should try (other than putting it on ebay with no reserve).

[Charles H]

Where are yo in the country? I am sure someone can help. If you have a good spark on all cylinders, I would firstly check for the correct firing order, 153624 anti clockwise as you look down at the distributor. Is the distributor loose so would have changed the timing? Then check for fuel supply to both carbs as a starting point. Good luck.

[johnnydog]

I doubt it will be a weak mixture if the car was running well before covid, but now doesn't. Unless you have done anything else to the engine, those symptoms (to me) point to a carb issue. I'd take the tops off, clean, check the rise and fall of the pistons, the balance of the linkage, the cleanliness of float valves / bowls etc. Another Register member had similar issues on his 2000 with HS4s, and checking the above and a clean of the float valves as it was flooding on the front carb, a tweak of the balance of the throttle / choke linkages, and enriching it two flats (as it was clearly running a little weak) has made the world of difference.
Not saying this could be the the sole cause of your issues, but it's where I would be looking initially.
Stale fuel can cause all sorts of of issues even after being replenished with fresh fuel.

[Clifford Pope]

Many thanks. That reinforces the thoughts I have been having after I posted my question, and also tried starting again. I'll check the carburettor items you suggest. This time it didn't bang and crackle like before, and it now does actually idle reasonably smoothly, but cuts out or misfires really badly if I try and coax it faster. If I can get past this enormous flat, or rather non, spot then it will run fast for a while, before suddenly cutting out. But if I then give it no throttle or choke it will re start instantly and idle again.

[valencia]

Hi Clifford, I've only just seen this but a few years ago my 2000 idled quite well but was reluctant to rev and lacked power. It was all down to high resistance in the plug leads and the carbon brush, I don't know if you have made any progress but maybe worth a check, the leads should be 420ohms per inch max I believe, not sure about the brush though. A tuning establishment put mine on one of those sun testers, there were six traces on the screen, all looked quite good till the throttle opened and then they all dropped as the system could not cope with the increased electrical load, this was on a rolling road so under mechanical load as well.

[Forkie]

As stupid as this may sound, i say that because i cannot even get my own 2500S to run correctly - it should be on SU HS6 carbs - have you checked the oil/oil level in the dashpots....low level /incorrect grade i believe will play havoc with starting/running issues.

[poppyman]

<t>Hi folks, i have a similar problem on my 2500S... No problem starting but after approx 8 miles it starts to misfire and will eventually stop, and refuse to start until it cools down again. Not overheating 79 degrees.... The spark at plugs becomes very weak and at the points. even happens with borrowed electronic distributor. new coils new leads, red rotors, plugs,cap,point's,condensor etc..... starting to pull out what little hair i have left. Any suggestions Please. <br/>
This started when still running ballast. Now converted to run without and bypassed in loom ballast.... Drives really well until engine is warm. Thing of note it's an automatic, only done 56k and not messed with...</t>

Thanks, Tony.... Any ideas really welcome..

[Forkie]

That to me sounds either coil or condenser. Something is not happy when it gets hot.Remember - just because it is new, does not mean it is right.

[poppyman]

I thought the the same, two different coils one new one off a running car. three condensers one off a running car and one electronic distributor to get rid of points and condenser again off a running car

[Forkie]

I assume you have tried different ht leads and dizzy cap? So as this occurred before ballast conversion, it cannot be to do with that.