Twenty Minutes Then Nothing...

[RedS4]

Hi All
My Elan has suddenly developed an interesting and extremely annoying issue.
The car will start and run happily, then after about 20 minutes (give or take) it starts to run rougher and rougher and stops. I will not run after that.
Not low on fuel (3/4 full right now).
Not overheating.
I have had the carbs fully overhauled. Still happens.
I have rebuilt the fuel pump.
I have replaced the coil, the HT leads, the suppressor and the rotor. ( No points as the car has luminition).
The plugs are relatively new (slighty hotter spec than normal) - I will try another set.

Does the above sound familiar to anyone? Please help!!

[rgh0]

Have you confirmed you have no spark when it fails to run but still have power to the coil and to the electronic ignition module?

Try putting the points back in to see if its in the electronics versus the high voltage side of the system


cheers
Rohan

[69S4]

Fuel tank vacuum developing?

They're classic symptoms of carb icing in a Stromberg Elan but five or ten minutes and you can restart from that.

[rgh0]

They're classic symptoms of carb icing in a Stromberg Elan but five or ten minutes and you can restart from that.

Not much icing going on in Toongabbie in January

cheers
Rohan

[PeterK]

Is it 20 minutes only when driven or also when at idle ?
As a repeatable time based failure, I would be looking for an electrical item failing due to heat build up, such as coil or a ballast resistor, fuel vaporisation, or a partial fuel blockage, including
- crud in tank blocking outlet (blow back down fuel pipe)
- fuel filter
- pipe partially crushed
- tank breather blocked (leave fuel cap open)

Maybe try a clean/direct 12v supply to the coil and a temporary gravity fuel feed directly to the carbs

Peter

[Geoffers71]

I had exactly these symptoms on a Europa. Traced eventually to crud in the tank (actually over enthusiastic use of Silicone by a PO that had been used to seal the sender unit). It was floating about freely in the tank and would eventually block the pipe. Leave the car for a while and the crud would float away from the pipe entrance and car would start and run fine until it happened again a bit later. Worth checking that there is fuel being delivered as soon as you can after the engine first stops

[Dave_Newcastle]

Does it run again if you let it all cool off for an hour or two? I had similar helping a friend all day with his MGA. We knew it was ignition but could not find the problem for a long while.

It turned out it was a faulty rotor arm and the new replacement one(s) was also faulty because it came from the same supplier and stock.

Eventually we tried an old scabby rotor arm out of an adjacent Sprite and it ran perfectly.

There is quite a few posts in MG and Triumph circles about this and it relates to a huge batch of faulty arms that conduct when they reach a certain temperature and go to earth.

The recommendation from those forums is to source a red coloured rotor arm because the faulty ones are black.

[ericbushby]

I had two similar faults like that.
It would leave home home happily but did not like going back. Once recovered and back home it would start immediately.
One fault was a black rotor arm going short circuit to the shaft. Only under a lens could I see a bubble in the inside surface. A red rotor fixed that.
The other fault was random and intermittent. It would run rough and stop but then eventually start and run OK all day.
Once, I took the jet cover off the Webers and looked inside with a torch to find the float chamber empty.
A new petrol pump sorted that one.
I tested the old pump with water and could find nothing wrong.
I see that you have already done these but you cannot trust anything until you find the definite cause of the fault.
I have just had three faulty new indicator flasher units. Different story, still ongoing but don't trust anything.
Eric in Burnley
1967 S3SE DHC

[RedS4]

Thankyou everyone!

In reply:
Rohan - The Luminition has been installed for over 20 years without issue. I doubt that is the issue.

69S4 - interesting... I will check the breather. That said, The bowl on the fuel pump was always full - certainly above the gauze.

PeterK - Both running and (today) idling (with the occasional rev). I have just replaced the coil (a GT40R with in-built resistor as was the previous one) and the HT leads as well as the rotor with apparently no effect.

Geoffers71 - The "crud" theory has merit, as I have seen soft "orange gunk" come through and deposit on the gauze a few years ago, but not since. So none since this issue arose, but maybe it's blocking rather than passing through. So what to do with 40 litres of fuel... As mentioned above, however, the bulb is full so the fuel is apparently getting through - this was checked also the previous time it stopped.

Dave - I have replaced the rotor (different manufacturer) but apparently has made no difference.

Eric - Thanks for your advice, I know where you are coming from! i might source another (3rd) rotor if only to eliminate that possibility!

[rgh0]

Hi Evan
Have you done the basic checks to determine if its fuel or spark that is causing the failure to run after 20 minutes? Does the car restart and run once its cooled down?

You say you believe you have fuel up to the pump but have you checked in the carbs by lifting a cover and looking in the fuel bowl.

Have you pulled a plug lead to see if its sparking and pulled a plug to see it its wet? If no spark at plugs have you tracked back through the system to see if spark at coil and / or if low voltage current through the coil is switching when the engine is turned over.

Without the basics checks to try to narrow down the location of the problem everyone is just guessing at one of many many possible causes

cheers
Rohan

[RedS4]

Rohan
Have you done the basic checks to determine if its fuel or spark that is causing the failure to run after 20 minutes? Does the car restart and run once its cooled down?
An NRMA serviceman (RACV to you I think - I needed someone to help me get the thing home after all...) did this and was convinced it was electric, hence my wholesale replacement of so many components, plus the professional servicing of the carbs and the serviced pump.

You say you believe you have fuel up to the pump but have you checked in the carbs by lifting a cover and looking in the fuel bowl.
I have to concede no. I will check this.

Have you pulled a plug lead to see if its sparking and pulled a plug to see it its wet?
The NRMA bloke did and it appeared #2 was suss. I did today pull all of them and found #3 was wet, with the others indicating a rich mixture (probably from the carbs service). I will replace all the plugs.
If no spark at plugs have you tracked back through the system to see if spark at coil and / or if low voltage current through the coil is switching when the engine is turned over.
How does this change after 20 minutes or so of running?

[AHM]

Crud in the fuel filter / tank or a blocked or damaged pipe.

Yes the pump may have fuel in it but the carbs are higher and may not!

[69S4]

They're classic symptoms of carb icing in a Stromberg Elan but five or ten minutes and you can restart from that.

Not much icing going on in Toongabbie in January

cheers
Rohan

Sadly plenty going on round here - first snow of the winter this morning.

[ensign42]

I would eco the ful problem- had an alfa did the same thing. Took the tank out- flushed it. I also rebuilt the fuel pump, and installed a new filter, also adding a canister style in line filter under the chassis. Solved the problem.

I would also not discount your coil- newish doesn't always mean good- and heat build up will cause them to conk out.

Best of luck in your troubleshooting!

[promotor]

In reply:
Rohan - The Luminition has been installed for over 20 years without issue. I doubt that is the issue.

Sounds like that's really only one of the key things left that it actually could be, and 20 years is a good time for it to pack up - that's not bad going really! It's likely to fail at some point!

Which Lumenition is it? Optronic is less likely to fail as there aren't any parts that are likely to be affected by engine vibrations (ie optical sensor), whereas a Magnetronic unit is a little more fragile. I would try points back in the car to see if it makes a difference. It's a cheap test!