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MG MG Y Type - Overheating - part 2
|Although I recently had a heat shield professionally fitted, I am still having problems with an overheating fuel pump. In fact the car broke down on the way home from having the heat shield fitted! The helpful breakdown man informs me that there is a blockage on the inlet side of the fuel pump. It seems that at some point I have been supplied with some contaminated fuel as, prior to that, I had driven the car without any problems, no matter how hot it was, or how long the journey was. The thing is, the blockage only seems to occur when the engine is hot. If I leave it to cool down it runs okay (for a couple of miles until the same thing happens). So, I'm thinking of draining off the fuel, cleaning the tank and fuel pipes and then getting a filter fitted in the fuel line. (I know the pump should have one, but mine doesn't.) The question is, is there an easy way to clean out a tank and fuel pipes? Also, how does one dispose of the contaminated fuel? I was going to take the car to my local garage this morning (which doesn't normally deal with old cars), but the car started spluttering when I got to the main road, so I drove it back home, to avoid clogging up the contra flow! Any suggestions would be gratefully received to prevent me turning into Basil Fawlty!|
|I'd book it in for an afternnon service, wait until the rush hour has subsided drive it further than 5 miles from home, stop, call the AA/RAC say to them "well actually I am on the way to have it serviced funnily enough, can I have a tow?".|
|Andrew - Before you go to a lot of fussing around with cleaning the tank and the lines, etc., try one more thing. Drive the car until the problem occures and then remove the fuel filler cap and see if the car will start. It is not uncommon for the tank vents to get clogged up and then a vacuum is formed in the tank, stopping the fuel from being pulled out by the pump. The length of time it takes for this vacuum to form is dependent on how much fuel is in the tank. If you have a full tank, it will stop the pump much sooner than when the tank is down to, say a quarter, since there is a much larger head of air n the tank when is closer to empty. Since a fuel tank is seldom 100% sealed to air, letting the car sit for a period of time will allow the vacuum to bleed off and you can start up again.|
I would not recommend a filter between the tank and the pump for the reason that if the filter clogs, it will stop the pump in a current on condition. If the power is left on for any length of time in this condition, it will burn out the swamping resistor inside the coil housing (where it can't be seen). The swamping resistor in the early pumps is the only thing that there is in the way of arc suppression, so when it burns out, the points will arc much worse than usual and have a greatly shortened life. The pump has a filter in the inlet side that will stop large particles, but allow smaller ones to pass, which doesn't hurt anything. The paper filter will stop the much smaller particles and are prone to clog up much faster. If there is an issue with rust particles getting into the pump or the carburetor float bowls, then the tank should be cleaned and sealed rather than installing a filter. Good luck - Dave
|Good point the tank not breathing You would hear it suck the air in when you open the fuel cap too.But it's a long shot|
|Andrew - A PS to my above post, you could also have a flakey fuel pump that is just quiting when it gets hot. This would not necessarily be overheating, just when the pump warms up is quits. If the removal of the filler cap doesn't get the pump going, then try disconnecting the input line at the pump and see if it will run. If it does, reconnect the line to the pump and disconnect it at the tank and try again. If the pump fails with the fuel line disconnected from the tank, then the line is clogged. If it run with the line disconnected from the tank but not when it is connected to the tank, then the filter inside the tank is clogged. Good luck - Dave|
|Not such a long shot after all John, I had it happen to us in our MGB and have heard of it happening on TDs (never on ours). It is real exciting to have just passed a large simi truck at about 70 mph, only to have the engine start sputtering and have to cut in front of the truck while diving for the shoulder. Cheers - Dave|
|Yes I have remembered I have had the problem with the tank breather before on my Riley 1.5 I drilled a small hole at the top of the filler neck near the filler cap.|
|Many thanks for those tips. I must admit I wasn't very keen on having the fuel pipes cut to insert a filter. I tend to believe if it's worked okay for 55 years it should be possible to fix it without changing too much. I may have to switch to the correct type of fuel pump with inbuilt filter. Being a non-mechanical person I didn't even know there was a filter in the tank, but this could well be the source of the problem. I suppose it could just be that any debris in the fuel tank settles when the car is stationary, but then clogs things up when the car has been run for a while, giving the impression that the problem just occurs when the engine heats up. Then again, it also happens in traffic jams. Incidentally my petrol cap just clicks on, but is very loose, so I'd be very surprised if it's causing a vacuum, but I will take a look at it. I desperately want to get the car ready for Clotherhome Farm in a couple of weeks, so I may have to make another (expensive) trip to a specialist. If that fails the car may well feature in the classified section of this website! Thanks again for your much valued advice.|
|We had one not a MG but it would go for a random amount of time and stop it was a leaf in getting sucked on to the pipe inside the tank.Try bypassing the petrol pipe by getting a length of pipe putting it from the pump to a can of petrol in the car throw the windscreen it would tell you if it was before or after the pump.|
|Not only do you need to fit a heat-shield and insulation block to the carburetter, between it and the inlet manifold, the fuel pipe that runs behind the engine needs insulating as well. This is the feed pipe to the fuel pump, and it gets very, very hot as it is situated in a tight space between the battery box, and the rear of the head. The close-ness of the exhaust manifold also passes a lot of heat to this pipe. As the pipe is copper, it soaks up the heat. Hot fuel feeding into the pump heats up the pump, and cuaes a vapour-lock. On modern fuel injections systems, fuel is pumped from the tank, to the injectors, then back to the tank, thereby having a flow of cool fuel at all times. In our cars the fuel can sit for some time when we a stationary, or moving slowly, so it get very hot, and can simply turn to vapour. Also, the fuel feed pipe from the fuel pump must be routed away from the exhaust manifold. The normal run is right over the exhaust manifold then down to the float chamber. Run a new copper pipe from the pump, up the radiator supprot tube, then via a flexible braided hose to the float chamber. This helps to keep the fuel cooler.|
|I would not recommend drilling a hole in the filler cap for two reasons:|
a)it spoils the cap, and more importantly
b) the fuel cap should effectively seal the fuel in the pipe in the event of the car being rolled. This IS an MoT requirement and failure may result if you tamper with this.
I would strongly suggest that if you find that it is a vaccum related problem (by releasing the cap and you hear the inrush) that you find another solution. I think the leaf in the tank has possibilities - how it got there would be an interesting one!!
Hope you find a solution, but I dont think you'll regret fitting the heat shield.
|I didn't say drill the cap I did say drill the neck near the filler cap and morris minors etc. have a hole in the cap anyway and the tester must be wrong as we no the engine will not run if the tank can't breath (let air in)|
|I had a similar problem with a Sunbeam Alpine many years ago caused by a piece of cellophane in the tank sucking against the outlet pipe, cutting off the fuel and then floating away when the suction stopped because the engimne stopped (mechanical pump. In the Y Type switching off the S.U pump (ignition) would have the same effect. This is similar to the record of the leaf by John Arkley. Incidentally I thought all the S.U. pumps had a built in filter and have not heard of one without. On the other hand that is a fairly hefty size and I would have thought would take some blocking. Phil Waltham.|
This thread was discussed between 01/07/2004 and 26/07/2004
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