Petrol starvation, or not petrol starvation that is the question

[Chris A]

Hi all

I think the problem I am going to describe is fuel related but don't let that influence you.

Yesterday the car started as usual, first turn of key, ran as usual did 10 Kms to a meeting and left car for about 1 ½ hours. After meeting I and a couple of others decided to go to the local aero club open day. Car started as usual etc. Got to the air strip and we had to wait until there was someone to let us through into the VIP parking. After a couple of minutes at tick over I switched off the engine. There was a further few minutes before we could move on. The car refused to start, not a cough or splutter – turned over without any problem but not a singe attempt to fire.

After several repeated attempts to start we pushed the car to the parking area, again no joy after a few tries, not even the smell of petrol as if the carb had flooded. Left the car for about 10 minutes and it then started on the button. Drove home (didn’t want to risk stopping the engine) no problems at low revs, high revs, under load or on overrun. Once home stopped engine and immediately restarted without a problem.

This morning the car started as usual, went for a short drive to try and reproduce yesterday’s problem. Did exactly the same thing.

Petrol filter fitted just before pump looed empty, it is usually about ¼ full. Took out the filter and the connected pipe work blew through it, not blocked, but didn’t seem to have petrol in.

Took the filler cap off the petrol tank, full of petrol so not short of fuel, blew though the petrol line and could hear bubbles in the tank, no blockage then.

Reconnected everything started car and repeated the run. No improvement. Car left to stand for 10 to 15 minutes and presto! Life. Did another run but this time instead of letting the engine idle for a few minutes switched off straight away. The car needed to be left for a good ¼ hour before it would again start. First turn of key.

Could it be petrol is evaporating? Haven’t noticed a problem all through the summer when it has been far hotter than yesterday and today.

Carb flooding? Why and how?

Petrol pump problem? The car runs fine, I would have thought that any problem would show up during a run.

Spark problem? The coil isn’t getting hot, Accuspark system fitted – if it was the electronics why would it behave like this, Distributor isn’t hot or showing signs of burning etc.

I think the fault must be recent as earlier in the week I filled with petrol and stopped off to see someone for a few minutes as well and there was no problem.

I am sure the car is running rich, is this a clue?

Sorry this is a ‘bit’ on the long side but wanted to give as much detail as possible.

I would certainy welcome any/all help possible.

In the meantime I will:-

1.     Take the jerry can and modern next time I need petrol for it.

2.     Make sure when I go out and park up I will be staying for 30 minutes at least.

3.     Cross my fingers.

 

[Roger]

Hi Chris! What kind of petrol pump do you have? Original or electric?

[Chris A]

sorry, should have said - the pump is the original AC item

[Dick Twitchen]

Chris, 

Had similar symptoms a couple of years ago immediately after filling up, and went through the same logic process as yourself.  In the end took the sender out of the tank and found a piece of neutrally buoyant debris about the size of a 50 p piece like a plasticised price label.  This was getting sucked over the outlet pipe, then if left would 'float' away....repeat; blowing through pump to tank produced bubbles.  The other one to check is if you are starting to get flexible fuel line degradtion that is acting like a one way valve, sometimes.

Dick 

[dougbgt6]

I've had the same as Dick, to add insult to injury the obstruction was a fibre washer that had come off a fuel can I employed when I ran out of fuel. Took weeks to find it. 

The other possible cause is the dread rubber slivers which come off the rubber tubing and lodge in the reservoir valves either flooding or blocking the carbs.

Doug

[Chris A]

1 hour ago, Dick Twitchen said:

Chris, 

Had similar symptoms a couple of years ago immediately after filling up, and went through the same logic process as yourself.  In the end took the sender out of the tank and found a piece of neutrally buoyant debris about the size of a 50 p piece like a plasticised price label.  This was getting sucked over the outlet pipe, then if left would 'float' away....repeat; blowing through pump to tank produced bubbles.  The other one to check is if you are starting to get flexible fuel line degradtion that is acting like a one way valve, sometimes.

Dick 

If somethng was getting sucked onto the outlet pipe I would expect fuel starvation when driving not after the car has stopped and the engine switched off. Interesting point though

[Chris A]

26 minutes ago, dougbgt6 said:

 

The other possible cause is the dread rubber slivers which come off the rubber tubing and lodge in the reservoir valves either flooding or blocking the carbs.

Doug

I had started to wonder if the problem might be at the carb end of the supply. I will think this over and look into it.

I don't want to start dismantling a carb though, yet. Maybe a sticking needle?

 

[Chris A]

Thanks for he replies so far.

Tomorow I am going to start the car and do stop starts at home until the problem occurs again. I will then check that I am getting a spark, just in case there is some weird electrical snag. Again I don't see what as the car performes fine until switched off and left for a few minutes.

I will also blow through the pipe between pump and carb to see if this is clear.

Another thing I will try is having a botle handy and as soon as I stop the engine put the connected to the intake of he pump in it to see if he pump drains, i.e. the valve in the pump isn't working.

The flexible pipes in the engine bay to filter, pump and carb are Gates R9 and were replaced last year, although the one from tank to petrol filter is old red stuff.

[Nick Jones]

Couple more checks to try.  After attempting to start it and failing, try sniffing the exhaust tail-pipe.  If it smells of raw fuel, either you have a temporary absence of ignition or it's flooding due to the fuel in the float chamber expanding/boiling and pushing out into the carb throat up the jet.  This could be further confirmed by whipping a plug out and seeing if it's wet.

I struggle to see how the non-start after switching off intentionally could be due to the fuel pump or fuel draining back as there is an air-gap in the float chamber that will prevent syphoning and the engine should start and run for a while on what is in the float chamber.  In any case, the fuel level in a Herald is usually above  the fuel pump unless the tank is very empty.

If the engine had spluttered to a stop after a period idling then I would be more inclined to blame fuel vaporisation, most probably in the pump valves, preventing the pump from operating.  Pouring cool water over the pump is fastest fix for that.

Ignition wise - if you have a spare rotor arm, try swapping it over.

Nick

[Chris A]

Thanks Nick, I will try as you say - I will make sure no neighbours are about to see me sniffing the exhaust ?

I also like your reasoning about temporary ignition fault or flooding

Thanks for the leads

[Anglefire]

Another thing to try, is taking off the fuel line from the pump to a jam jar and crank the engine - obviously fuel should come out.

[StuartO]

When you have switched off the engine normally the carburettor(s) should be full of fuel, so you should not suffer a subsequent failure to start due to fuel shortage.  I had an intermittent and puzzling failure to start which turned out to be an intermittent failure of the ignition coil - it took ages to discover the cause but at least it was simple to remedy by substituting a new one.

[Chris A]

StuartO : As I have a spare that I know works I had thought of swapping them over just in case, as you say easy and quick to do.

The coil isn't getting hot but I suppose an internal fault might not cause it heat up.

Thanks

[NonMember]

An off-the-wall thought - after a bit of a heat soak like that, your distributor will get hot. Perhaps the condenser's on the way out and shorting when hot?

[poppyman]

24 minutes ago, NonMember said:

An off-the-wall thought - after a bit of a heat soak like that, your distributor will get hot. Perhaps the condenser's on the way out and shorting when hot?

I have had that a couple of times, but not on a Triumph........ I ended up mounting the condensor on the bulkhead and had no more trouble after that.

Tony.

[Chris A]

41 minutes ago, poppyman said:

I have had that a couple of times, but not on a Triumph........ I ended up mounting the condensor on the bulkhead and had no more trouble after that.

Tony.

 

1 hour ago, NonMember said:

An off-the-wall thought - after a bit of a heat soak like that, your distributor will get hot. Perhaps the condenser's on the way out and shorting when hot?

Hi both, neither coil nor distributor felt hot, not even warm. Ignition is Accuspark electronic so no condenser.

I am going to do a coil swap and check for spark as recommended above.

Thanks guys

[dougbgt6]

I've had an electronic ignition go intermittent, easy to reinstall points and condenser, just to check. I keep mine in a plastic bag in the glove compartment, just in case it happens again.

Doug

[Chris A]

 Thanks Doug: if it is intermittent it is always at the same moment in the cycle, which I thought would be unlikely.

As the fault clears after a while I am more inclined to petrol delivery system to be honest.

 

[Anglefire]

2 hours ago, StuartO said:

When you have switched off the engine normally the carburettor(s) should be full of fuel, so you should not suffer a subsequent failure to start due to fuel shortage.  I had an intermittent and puzzling failure to start which turned out to be an intermittent failure of the ignition coil - it took ages to discover the cause but at least it was simple to remedy by substituting a new one.

That is actually a very good call.

Accuspark have been known to fail and cause problems - its certainly does sound like electric - once going is fine, but perhaps the heat causes extra resistance in a joint somewhere along the line and is enough to stop spark creation ion startup when its hot - but not enough to cause it to fail when running - possibly due to the lower starting volts - possibly that could be proven by jump starting from a running car.

[poppyman]

Another thing i forgot.... Earth wire in distributor, they can make or break even inside insulation.

Tony.

[Chris A]

 

" possibly that could be proven by jump starting from a running car."

Interesting thought, I'll add it to my list of things to try when the car has been running and refuses to start. Worth a try as it is easy to do. Thanks

 

[Chris A]

1 hour ago, poppyman said:

Another thing i forgot.... Earth wire in distributor, they can make or break even inside insulation.

Tony.

To be honest I doubt this is the cause as it is always under the same conditions that it fails to start, I would have thought a problem like this would occur at random.

[poppyman]

26 minutes ago, Chris A said:

 

" possibly that could be proven by jump starting from a running car."

Interesting thought, I'll add it to my list of things to try when the car has been running and refuses to start. Worth a try as it is easy to do. Thanks

 

Sorry, i should have said its the wire in the dizzy that earths the base plate... So would not make any difference in a jump start.

Tony.

[Pete Lewis]

This stop , give it a kick it starts , runs stops , has the tell tale of the coil polarity being reversed

So check the dizzy wire is the same as the battery earth and the coil feed polarity is the same as the battery feed ign feed 

Dont want pos and negs mixed up

PETE

 

[Chris A]

17 minutes ago, Pete Lewis said:

This stop , give it a kick it starts , runs stops , has the tell tale of the coil polarity being reversed

So check the dizzy wire is the same as the battery earth and the coil feed polarity is the same as the battery feed ign feed 

Dont want pos and negs mixed up

PETE

 

Why would the polarity suddenly change on its own? I haven't changed any of this part of the car for months and it has been running fine, several times per week, until Sunday. It doesn't stop itself it is always me who choses when to stop it after a run of 10 minutes or 45 minutes without a single missed beat. Failed/failing coil is to be checked tomorrow (I hope)