Very weird but runs perfectly for 40 minutes then motor stops and wont restart.
once stopped have found following problems
- no fuel coming up to carby
- fuel control relay feels very hot

After calling RACQ we have replaced the Ignition control module as they suggested. Still no change.
Have replaced fuel pump relay under glovebox but no change.
Fuel pump was replaced with new one a few years ago.
Carby was completely overhauled about a month ago.

Any ideas would be greatly appreciated because we seem to be spending money on parts that are not needing to be replaced.
What seems odd is that in the last 3 days I have made the exact same trip via the same route and each day it stops after about 40 minutes within a km or 2 of the same spot. If it is left sit for 30 minutes or more then it will restart and I can drive on with no problem. It seems like something is getting over heated and once it cools it works again.

Can a fuel pump suddenly stop working after the exact same amount of time each trip?

Please help!

fuel filter may need changing or the needle and seat may have some crap in there

No fuel filter is new and carby has just been reconditioned.......it appears to be heat related somewhere. The fuel is not getting to the fuel filter or the carby so the problem is somewhere before that in the system.

Possible fuel pump related issue as these were electric pumps.

That is a guess however.

The fuel is not getting to the fuel filter or the carby so the problem is somewhere before that in the system.

I don't think you should put too much faith in that assumption. If the line is shut off or blocked further up, fuel still won't go anywhere.

If the problem IS before the filter, then it almost has to be the fuel pump since you've already replaced the relay. However I can't see how that could be time-related.

When it stops, does it cough and splutter a bit first or just die instantly?

Next time it happens, try loosening the fuel cap temporarily to see whether that allows you to restart it straight away. It is supposed to be a closed system, so I was thinking a vacuum might build up in the tank and cause a flow problem after a certain amount of time.

Other things to check would be the carburetor vent valve and the fuel cut-off solenoid (in the carby). I can't see how the latter could have a time-related fault. However, if it did the engine would stop instantly.

The carby fuel pump puts out a whimpy 3.5 psi of pressure (or thereabouts).
Worthwhile blowing out the fuel lines and checking for constrictions.
I'd be tempted to pull the pump out and check for blockage of the sock filter and deposits in the tank. If that is clear, fill the tank right up and see if that makes a difference.

Needs some on the spot intelligent faultfinding though.

I don't think you should put too much faith in that assumption. If the line is shut off or blocked further up, fuel still won't go anywhere.
The reason we are thinking it is back from the filter is that when it stops and we remove the fuel line from the filter on the fuel tank side there is no fuel pumped through when the engine is turned over.

I will certainly try the fuel cap idea as we have blown the lines out on a few occasions and when we did we removed the fuel cap at the same time. The car did start after doing it so it could possibly be a vacuum build up rather than as a result of the lines being blown out.


Other things to check would be the carburetor vent valve and the fuel cut-off solenoid (in the carby).
These items have already been cleared of fault when the carby was reconditioned a month ago.


I'd be tempted to pull the pump out and check for blockage of the sock filter and deposits in the tank. If that is clear, fill the tank right up and see if that makes a difference.
The fuel pump has been removed and checked it is working and clean. The fuel tank was full the first time this occurred and is still over half now.


Needs some on the spot intelligent faultfinding though
I agree totally Madmax. Any suggestions?

Well did the same trip this morning and it ran for exactly 40 minutes before stopping. Got out and opened fuel cap as suggested but no go. We removed the fuel line from the fuel pump side of the fuel filter and no fuel was coming through when turning motor over. Changed fuel relay but still no fuel coming through. Blew air down that fuel line with fuel cap off and there was no blockages but still no fuel coming through. We will remove fuel tank yet again today and recheck lines and pump for blockages. Most likely we will replace the fuel pump also. Still cannot work out why it will only run for 40 minutes before stopping. I would have thought a fuel pump problem would be irregular and happen at any time.

next time it stops have a test light or multimeter with you and check for power at the pump connection when you crank the motor.
If you have power then connect the pump to it and see if it operates you will hear it . You can remove the pump to do this if you wish.
Does it stop on a hill??

I would have thought a fuel pump problem would be irregular and happen at any time.
Might take that long to get hot enough if it is the pump at fault. Vee

I really appreciate all your ideas. We are kind of stumped and willing to try anything reasonable. We will try the power test at the pump next time, I am sure it will do the same thing again tomorrow. What makes it more difficult is that it takes a 40 minute drive to get the problem to occur so until we fix it we have one chance a day to problem solve.

Well last night we powered up the fuel pump from an external source and it ran quite happily for over 50 minutes with no problems. So now what?

For anyone having similar problems we have found where the problem lies. When the car stopped we unplugged the connector that goes into the regulator that is mounted on the alternator.......car started again immediately. Now to work out if it is just the regulator or the complete alternator that is causng the issue.......starting to breathe again now :)

So you recon the alternator has a problem and that is what makes your car cut out after 40 minutes of driving?

Might be worthwhile checking battery condition and alternator output by putting a voltmeter across the battery. Check battery voltage with the car off and the engine running, and let us know.

Normally, the regulator (if it does) go stupid, you get no charge and the battery goes flat and the car stops.
If there is an internal short in the alternator dropping voltage to the car to such an extent that it cuts out, there is a large fuse (60A?) that should blow.

Possibly the alternator is undercharging and the fuel pump relay quits when the voltage drops too low?

Not sure about the magnas but alot of cars have a safety feature that after starting the pump switchs to alternator output from start circuit power so in the event of an accident the motor stops and alternator nolonger providing power thus the fuel pump is switched off.
Having a direct wired fuel pump spraying the fuel everywhere until the battery goes flat or tank drains is not good in that sort of situation. Unless someone is able to turn ignition off!!!
So somewhere in that circuit there is a problem it seems. Either alternator or fuel relay. Not looked into the fuel relay system at all as never had a problem but that would be what controls it all.Vee

I had a similar problem with a carby TP. Relay for the fuel pump got hot, so I swapped it for one from the wreckers. Fixed the problem.

Another time it turned out to be the ignition coil and power transistor though.

Maybe my exhuberation was short lived. We have tested the battery power and it is 12.4V with it off. With it running and revs between 1500 and 2000 the voltage sat around 13.9.

As for the fuel relay...(if you mean the one that resembles a circuit board)...we got another one a few days ago and it made no difference. When the car stopped we even swapped relays and it didnt start. Both seem to heat up at times.

Intermittent short circuit in the wiring between fuel relay and the pump?

MadMax is the relay supposed to get hot at all?? We have the actual circuit board out of the black case to be able to check for heat and at times it is cool and other times gets quite hot. The one we just got from the wreckers does the same but there is no consistency to hot or cold and the car working or not.

The fuel relay I swapped was on a TS fuel injected, not the carby TP. (faulty memory on my part lol)
It was a silver box hiding behind the glovebox lower supporting rail.
If your relay is the same, check the contacts on it, if they are pitted or burnt, that may be the problem. They can get warmish in normal use though.

No our relay is a circuitboard inside a black plastic case.....there is a pic on another thread in her that shows it. It gets too hot to touch and we can only assume it is supposed to because there is a heatsink on the transistor(??) on the circuitboard indicating the need to remove excess heat.
Any autoelectricians around in here or anyone know of one that is good with magnas in Brisbane?

Fuel Pump Control Unit
Carburettor Models:
The control unit is a transistorised unit which supplies power to the fuel pump under the following conditions only:
#With the ignition switch in the START position i.e engine cranking.
#With the ignition switch in the ON position with the engine running.
This ensures that should the engine stall, e.g. in the event of an accident, the pump will stop operating.

Download the manual here:
http://www.aussiemagna.com/forums/showthread.php?t=95825&highlight=manual+download
http://depositfiles.com/files/cen9su9k9
Page 187 onwards how to test pump and control unit. Diagram also shows which wires are which on the unit.
Also a chance the one you got at the wreckers is suspect as well............
Might be an idea to bridge the approriate wires on the loom and bypass the unit for a while and see if the pump is ok when you drive your 40k etc.
It has to be one of the two or the alternator stoppping charge sometimes does your charge light work??
Thing is though once you go to start and crank the engine it will pump fuel until you stop cranking and ignition switch comes back to the on position so probably rule out the alt. Vee