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TR4A running/fuel problem


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Car starts from cold but after some miles, can be little as 12 will stall at a junction or when stopped will not restart. Endless churning on the starter motor to get started. Then on one occasion had a push and it bump started with no problem. The fuel pump looks original and has the glass bowl and fuel looks clear. Has the prime lever and pumping that that makes no difference. The pump filter has been removed. There is an inline filter before the pump. When it wont start when hot the filter appears to be empty. But when the car cools down still empty and starts straight away. Informed that the amount of fuel in the filter means nothing providing fuel is flowing. So even if fuel stops flowing and pump glass bowl is full why will it not start. 

I'm stumped on what to look for. Carb float chambers cleaned.   

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Since this appears to be temperature related, it may be ignition rather than fuel. If everything is adjusted correctly, try changing the condenser ( if you have points).  Also the coil may be failing as it warms up.

If the ignition is electronic that may also become intermittent as it heats up. I had a Pertronix unit that stopped working when hot . 

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As RobH it could be ignition related when it happens again take a float chamber top off and check for fuel if present then start checking ignition items condenser to start with points ,coil ,rotor arm distributor cap coil lead its a process of elimination

Chris

 

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The fact it started easily with a bump, but not when starter being used could be relevant. If a very weak fuel mixture is present, then the spark at the plugs may be insufficient when starter is operating, causing a voltage drop to the ignition circuit.. When cold presumably the choke is used so starts readily.  If this problem has just developed on a car that was otherwise running OK up to this point it is more likely to be electrics, coil, condenser, cap, leads, plugs etc, but I wouldn`t rule out the carbs if the car has been unused over winter, so check for sticking pistons in carbs or punctured diaphragms if Strombergs, and gunk in float bowls.

Ralph

Edited by Ralph Whitaker
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Not been used over the winter but the problem was there before that so cleaned the float bowls and that made no difference.

What I have done when stalled is to take the fuel pipe of the bowl of the front carb and no fuel comes out but not taken the bowl off. Hand priming gets the fuel flowing but not sure how many pumps needed to fill the bowl. Then cranking a lot still would not start. Kind person then pushed me and it started in 2nd gear on letting the clutch out. So as said there must be a clue there. Had to drive 25 miles to get back home and towards the end I felt it would not idle so kept it running at 2000 rpm at junctions.

Got home and it just stalled and would not restart. Left for two hours then it started straight away but the engine was still hot as it was the hottest day of the year 29.  

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I'd concur with Rob, and suspect the coil failing when it gets hot. We have the same symptoms on vintage Sunbeam motorcycles, which place the coil out-of-the-weather in 'an electrical box' ..which in turn prevent air flow over it.  On these bike it typically runs for about 6 miles from cold and then stops, until allowed to cool ..and then it will restart easily enough, run for another few miles and then stop again.  Over the years, some owners had replaced the original with a (cheaper) smaller coil off the diminutive BSA Bantam and that fails even sooner.  Possibly, the easiest way to check this on your own car is to temporarily move the coil to somewhere cooler / in clearer-airflow perhaps behind the cooling fan.  Run the car and see if the same symptoms occur.  If they do then replace the coil for new and again place it somewhere cooler.

Pete. 

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I moved the coil on my 4A off the side of the engine and onto the wheel arch on passenger side where it is a bit cooler. Has worked ok there ok for years. Previous to that the original coil was getting too hot I think. 

Keith

 

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I think the general consensus over coil/condenser is probably right, but a couple of your comments indicate the possibility of a fuel issue.

If you use the priming lever but the supply pipe and float chambers are already full, then the pump wont pump any more fuel if the system is sealed - if you then take off the supply pipe to the carb fuel bowl, it should produce a flow when priming - if it doesn't then it sounds like a pump issue - you say the filter has already been taken out of the pump - do you mean the very fine filter gauze in the top of the glass bowl bit? If so, why has it been removed  - they can be easily cleaned with thinners and a toothbrush if it was blocked.

Have you checked the condition of your fuel tank, because if it's rusty inside, this could be causing temporary blockages which get released when engine and hence suction stops, and then restarting happens till the debris get sucked over the outlet again.

You also mention a inline filter has been installed before the pump - I'm sure I read somewhere that a lot of fuel filters need to be fitted on the pressure side of the system, not the sucking side as the collapse internally in the latter case.

Just a few thoughts

Cheers Rich

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+1   
I had exactly this issue recently and traced it to the fuel tank exit pipe which had debris blocking the normal fuel flow.  Combined with a poorly fitted fuel pipe it just starved the pump and the engine coughed and died. Wait a while and it starts again!  Worth a look. Tank is easily removed. 
David

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If I undo the supply pipe to carb and prime sometimes fuel does not come out straight away and when it does it spurts out with each prime. On putting the pipe back it still will not start except for the one bump start. The pump glass bowl is always full.

If I undo the inlet pipe to the in line filter (before the pump) fuel pours out. There must be debri in the tank because there are bits in the filter, it is a glass one that can be cleaned. So could that debri starve the pump. Above 2000 rpm it runs fine it is when coasting to a stop when there is less fuel needed that gives the problem.

The pump filter gauze is missing. Note the point regarding where to fit an inline filter but have had several classics with filter fitted before the pump and no problem.

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6 minutes ago, eng622 said:

If I undo the supply pipe to carb and prime sometimes fuel does not come out straight away and when it does it spurts out with each prime.

That is how it is supposed to work.  Lifting the priming lever lowers the diaphragm and sucks fuel into the pump. Releasing the lever allows the spring to drive the diaphragm up which pushes fuel to the carbs. 

7 minutes ago, eng622 said:

On putting the pipe back it still will not start except for the one bump start.

Which means this may not be a fuel problem. If there was no fuel then a  bump-start wouldn't work.

The debris is not good but it doesn't sound as though this is the cause of the problem, as it would affect high speed running rather than at idle,  unless there was a complete blockage as Rich and David describe above  - but then there would be no spurt of fuel when you prime and the glass bowl would be empty. 

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Tried in the drive today. Fuel pipe off carb, cranked with coil lead off and fuel spurted out. Started ok ran until hot, no problems. Stopped and restarted straight away and tried several times all ok. So cannot repeat the on road issue. Thinking could be blockage as David had but why did it bump start so easily after churning on the starter for a long time and several attempts  without success. 

Have measured the coil V positive to earth which looks ok just dipping to 10V on starting

Do not want to do another road test as the problem is getting worse but like David said if left long enough, maybe over one hour, would probably start but do not want to risk it.

Where is the access point for the tank outlet.

 

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Sounds like an electrical fault to me. Obvious candidates are the coil and/or condenser in the distributor. Also check that the carbon rod in the distributor cap is free to move up and down (might it stick when hot). Another possibility is a dodgy connection. I once had a BMW that had 2 faults when hot. One was a hairline crack on the circuit board n the fuel pump relay and the other was a dry solder joint at the back of the fuel gauge. Took ages to find. Check the connections on the wiring to the distributor and the coil. If the low voltage wiring on the distributor is disconnected then the engine will not fire up. When the car engine bay gets hot that may be enough to cause a slightly loose crimp to open up enough to stop the car. When you check the car on the drive do it with the bonnet closed so the distributor wiring etc get hot. A friend of mine had an intermittent misfire but only when the bonnet was closed - one of the plug leads was touching the bonnet and arcing to earth. Opening the bonnet meant the problem disappeared. Operating the starter and nothing from the engine sounds like no spark from plug leads. That in turn suggests wiring fault on low tension side or faulty coil. A slightly loose crimp joint could be enough. I tend to crimp and solder joints now especially in bullet connectors.

Good luck

Keith

 

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Just a thought, have you got SU HIF carburettors fitted - the bi-metallic strip can cause over-weakening. I went down the electrical route and that may have helped but did not fix the hot starting problem I had. I removed them for other reasons and then found out about the known issue with them.

Chris

 

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The rear access point for the fuel supply pipe is at the front of the tank, passenger side.
Removing the wheel gives good access to the compression fitting. 
I siphoned fuel from the tank but there was still a few cupfulls remaining. 
When I disconnected the compression fitting nothing came out of the tank, until I poked up into it with a piece of wire when the aforementioned cupfulls drained out very quickly into a catch tray. 
BTW your engine failure symptoms all sound pretty much the same as mine. I managed to get home with the fault still in place and was very relieved to eventually find the fuel blockage.  
I followed up with an air line connected to the flexi pipe at the fuel pump end to give a v careful blow through in case there’s any debris in the pipe. New filter fitted, remains clear with good flow through the pump. Good luck. 
David
 

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I'm fairly sure it is a fuel problem after reading several earlier posts. At speed the fuel flow is highest which disturbs any debris but the flow is enough to keep going. As you slow down the debris settles and blocks the fuel pipe so when you come to stop it stalls and wont restart. I have been purging the fuel line at the filter which I guess disturbs any debris and has improved flow so can start. That worked until the last time when only the bump start got me going.

This is what I'm looking at doing. Remove most of the fuel from the tank, tried an electric pump but not enough lift so will try siphoning. Then Iift the rear end a little, undo the pipe to the filter (before the pump), make up a rubber seal to fit the tank  filler neck and a hole to fit the compressor gun. Some fuel will come out due to gravity and then hoping compressed air will clean the pipe work out.   

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Hi - do you have a name ?

I have sent you a personal message ( a PM) which you will find in your forum mailbox - this is the envelope in the top RH corner of a forum page - if you have an unread message, there will be a small red flag next to it - click on the envelope and it will open your mailbox and you can then see any messages and reply from there

Cheers Rich

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9 hours ago, eng622 said:

I'm fairly sure it is a fuel problem after reading several earlier posts.

You may have convinced yourself and I  hope you do manage to clear the fault but that really does not fit the symptoms you have told us about.

If the glass bowl of the pump is full of fuel but the engine will not start, that is not a fuel flow problem.

If you get fuel by operating the priming lever it is not a fuel-flow problem. 

If you can bump start the car it is not a fuel flow problem.  

If the car won't idle without dying but will run if you keep the revs up, that is not a fuel flow problem. 

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Perhaps it is the pump. The glass bowl is always full and fuel clean but it is on the inlet side. When it has stalled using the priming lever does not give an instant squirt of fuel, takes several primes. It is an AC pump are these serviceable. What is there to check.

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16 minutes ago, eng622 said:

It is an AC pump are these serviceable. What is there to check.

The diaphragm and the two non-return valves.  However, if those are faulty they are probably not going to 'recover' if you wait a bit so again it doesn't fit the symptoms really.  

You don't get an instant squirt as you operate the lever, the lever lowers the diaphragm and makes the pump suck in fuel from the glass bowl. It pumps when you release the lever and the spring pushes the diaphragm upwards again.   ( that way fuel pressure is determined by the strength of the return spring - not by how hard you push the lever)

 

 

Edited by RobH
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I simply attached a normal size tyre inflator to the rubber pipe before the pump (it fits perfectly and avoids any interaction with the fuel pump or filter), with the fuel tank end disconnected and fired up my small tyre compressor.  That cleaned out the pipe.  
I wanted to avoid forcing any debris into the pipe from the tank, that’s why I chose to blow through as described. 
David

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I will relate this problem that occurred on my dad's Vitesse in the 1960's. A garage mechanic had disconnected and then reconnected a fuel line. As they pushed the rubber tube onto the metal a thin flap of rubber peeled off inside the rubber tube creating a one way valve that caused the car to lose power and cut out. The garage blew out the fuel pipe as you have decided to do and discovered that when they blew it from the tank end the flap of rubber closed the pipe but not the other way round. Under the 4A are 2 rubber connectors so check those are ok. I have changed my fuel line so it is one length without connectors. Saves me crawling under the car to check they are ok and removes 4 potential leak connections. 

For info the pipe to the filter just before the mechanical pump is approx at level of bottom of fuel tank so you can jack up the rear end and drain most of the fuel from the tank using the pipe in the engine bay. Easier than trying to siphon it out. Again I have installed a fuel shut off tap just before the filter so I can shut off the tank and work on the engine bay fuel system without risk of getting fuel everywhere.

Make sure you have the garage well ventilated when you are messing about with fuel.

Keith

p.s. I still think it may be an electrical issue.

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Interesting, I still have what looks to be two small lengths of rubber hose, one at the tank end the other at the front. But in front of that is a third rubber hose. There appears to be a small length of copper pipe from the front hose to the third one. The third one connects to the filter and then there is a fourth rubber one from the filter outlet to the pump.   

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There were cases of inline fuel filter failing and blocking fuel, you may also replace the filter, they are cheap.  Also, my car did sit for almost a year without running and i had a couple of strong hiccups after climbing the ramp exiting the garage.  I probably disturbed dirt in fuel either in the carb bowls or at the pump or in the tank.  This disappeared as i drive the car every week now, but we had to clean the bowl near the pump.  So that ca be fuel related as it does not take much to block the flow, but i'm also more convinced it is an electrical issue.  If it was my car i would make sure the battery is fully charged, replace the coil, plugs, rotor and wires and check all electrical connections including ground and retest.

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