Engine dies suddenly.

[saildrive2001]

I have a really puzzling problem with the engine suddenly dying. I need to give you a little bit of background information first. I rebuilt the car including the engine 10 years ago & have had little to no problems since. I installed a Petronix solid state ignition including a rev limiter. I also installed a Battery Brain which has a remote fob to disengage the battery. This system also monitors the battery voltage & if the engine isn't running it disconnects the battery at a predetermined voltage to stop the battery from being drained. To stop this whilst the engine is running I have a vibration sensor installed in the boot where the exhaust hanger is attached. My car has UK spec Stromberg carbs. The first problem was that one day when I started the engine it would sometimes almost die & occasionally did die when I released the throttle quickly. If I released the throttle slowly then it would return to idle & keep running. I decided to increase the idle speed which helped somewhat. I checked the oil level in the dashpot & everything was normal. After driving the car a couple of times the problem disappeared. One final point to note is that a month ago after the car had been unused for a couple of weeks it would not start. It would normally take a few turns to get the carbs full but always has started in the past after a few turns. This time I decided to remove a plug & rest it on the engine to check for a spark. I have a starter solenoid that you can hand energize so I pressed it & the engine immediately started on the three cylinders. ( As an added complication, I know that I have a 1 volt drop from the ignition switch to the fuses).
That's the background so now to my problem. After the problem above I let the engine warm up to normal temperature & started reversing out of my driveway, when I got to the bottom I disengaged the clutch & the engine immediately died. I tried starting it & it would go chug.......chug...... chug as though one cyl was trying to fire but it would not start running. After several attempts it finally started & ran normally. I drove it around the area for around 20 minutes with no further problem. Twice since then whilst driving it the exact same thing has happened. Each time I have been out driving for at least an hour with no problems & then suddenly when coming to a stop as soon as I depressed the clutch the engine died. Both times the same chug........chug & then suddenly it would start run & rev normally.
I don't think that the Battery brain is the problem because the starter always works when the engine dies, so power from the battery isn't cut off.
Any suggestions & diagnosis gratefully recieved.

[h20hamelan]

you have spark
do you always have spark, when it dies, what goes away?

[billwill]

I can'r read a huge block of text like that, please put blank lines between paragraphs.

[saildrive2001]

I don't know if I have a spark, both times it happened on the road I needed to try to get it started as I was in traffic.

[David1953]

Easy enough to check if the Battery brain is involved turn on the interior light, if it stay on you have 12v

I would suspect the Petronix, but maybe I am biased I like the original points

[saildrive2001]

I am going to bypass the battery brain to eliminate it & I can also remove the electronic engine rev. unit from the circuit. I have to suspect some form of electrical problem because it just dies instantly & when it does start it revs cleanly and easily. The real puzzle is why does it happen when I depress the clutch pedal, coincidence? Because it only happens very occasionally it's impossible to simulate.

[h20hamelan]

Maybe your distributor shaft has play, and when unloaded it moves?

[elans3]

Check the plastic sleeve from the Pertronix that slides over the distributor shaft. It has 4 x very slim magnets set (stuck) into the inside diameter. I had one (an Aldon Ignitor, exactly the same as a Pertronix), which I fitted in 2002, and 18 years later it failed. 2 of the magnets became unstuck, and magnetized themselves to the distrib shaft. One went first, then another soon after. I found it pretty quickly, and glued them back in, & everything back to normal. I got hold of Aldon, and bought a spare sleeve. Never needed it, but kept it in the glovebox.
It gave similar symptoms to yours. Worth a look.

[Donels]

I would suspect the rev limiter. It's probably predictive on acceleration rather than a fixed rpm. If so it may be recognising the increase in revs when you press the clutch as an overshoot of the rpm limit and cutting the ignition.

[saildrive2001]

I took the dist. cap off & all looks to be fine with the Petronix from a visual aspect. I will bypass the battery brain and the rev limiter before I next try the car. Unfortunately the weather is starting to turn here in southern Ontario so I won't have many more opportunities to do some test driving.
Could this be a fuel problem & not an electrical? The reason I am saying this, is the problem with the engine not idling when the throttle is closed, that I mentioned at the beginning of my post. What could have caused that problem & could that occur again occasionally? When it did happen originally the engine would immediately start after & idle OK.

[rgh0]

Watch what the Taqcho does when the engine dies. If it drops immediately to zero then most likely electrical. If it drops steadily with engine speed as the engine dies then most likely fuel

cheers
Rohan

[saildrive2001]

Hi Rohan,
I was hoping you were watching this subject.
The problem is that I don't know when this is going to happen. I can drive around for 1.5 hours or more with no problem.
Have you any idea why the engine wouldn't idle unless the throttle was closed slowly? As I said earlier it would always start immediately if it died.

[h20hamelan]

electric fuel pump?
if your out of fuel in the carbs, and it normally takes more than a second to get fuel back, like 10 seconds maybe?
I would guess your spark is going away

[rgh0]

My only guess is maybe a small hole in one of the Stromberg diaphrams. This would potentially allow the piston to drop fully on a rapid shut off of the the throttle leading to the engine stalling but not affecting normal running much.

Worth checking if you have not done so already

cheers
Rohan

[saildrive2001]

Mechanical fuel pump.
I haven't checked the diaphragms yet. I also wondered if the piston might have stuck. Because I have a crossover pipe you would think that both carbs would have to have the same problem.