Looking into a possible fuel pump problem.
July 3rd 2020
Sadly the Morris has been spending most of it's time in the garage for the past few months due to this year's car events mostly being cancelled. A battery conditioner has ensured that the car always starts first time despite infrequent use, and I have been trying to give it a good run at least every couple of weeks to keep everything ticking over nicely.
One issue I have noticed lately is that one minute the fuel pump will be ticking away steadily and then all of a sudden it will go into full machine-gun mode. Clacking away at ten-to-the-dozen for no apparent reason. Even allowing the engine to drop to idle doesn't help. This can happen for 10-20 seconds before returning to its normal regular beat. An attack of car-anxiety maybe?
After doing a little research online, it appears that one cause of this could be an air leak on the inlet side of the pump causing it to suck in air. Apparently a good test is to disconnect the banjo fitting from the carburettor and drop the fuel line into a container. This allows you to see if the fuel is being delivered correctly or if any air bubbles are present. Ok, let's try that!
There have never been any signs of fuel leaking from around the inlet or outlet hoses on the pump however it's still worth checking out the possibility of an air leak. I started by removing the banjo bolt that connects the fuel line to the carburettor float bowl.
Once that had been disconnected, I placed the end into a plastic bowl and switched on the ignition to power up the fuel pump. Sure enough it fired up into a rapid (but not machine-gun like) tick and promptly started to fill the jug. Blocking off the end of the banjo fitting with my fingers resulted in the pump coming to a complete stop, as it should do. Varying the pressure with my fingers to allow small amounts of fuel through, the pump continued to perform well, dispensing only what fuel it was able to. I could also feel a good, healthy pressure with my fingers and not once did the pump attempt to go bananas. Also, even with the end of the pipe submerged in fuel there was no sign of any air bubbles. It performed flawlessly.
Well now that I know the pump seems to be working ok, I'm wondering if the fault lies in the way the carburettor is demanding that fuel. I do know that the carb on this car is in a poor state and it leaks like a sieve, so that sounds plausible. The carb is due to receive a full strip down and refurbish at my local classic car specialist once all this Covid business is over and done with. I think it might be best to wait until that job has been done to see if the pump issue cures itself or if it requires further investigation.
Not wanting to waste a drop of the amber nectar, I poured the fuel I'd collected into another container and mixed it with 2-stroke oil for use in my hedge trimmer!
While I was in my overalls and the afternoon was young, I decided to do a job that many classic car owners put off (understandably)! Time to grease my trunnions and track rod ends. I haven't done a great deal of mileage in the Morris this year but I still like to do this job every thousand miles or so....
With the fuel pump checked and the trunnions greased, the Morris can now sit a while longer and await the return of happier times with more fun car events.
Until the next instalment, dear readers...