New carburettors - take four

Since fitting the new carburettors things have not exactly been going to plan! I left this bit of TR7 ownership a week ago and with a few hours to spare today I had another go at tuning the carburettors. At least the previous actions did have an effect, as there were no more fuel leaks. But she still refused to idle at a proper engine speed. This time the engine didn't react at all on winding up the idle screws, and kept running at over 2000 rpm! Time to go for a short test drive. Overall the engine runs nicely but when slowing down for low speed corners there was a distinctive petrol smell. But on returning home there were again no visible leaks, which prompted me to have a proper look at the old carburettors. The throttle discs were almost completely closed!

As the reconditioned carburettors have been checked and double checked, I think it is by now safe to rule them out. Though the symptoms could be caused by a faulty float needle valve. Time for a rethink and a browse through my personal notebook, this blog! And that was when I was reminded of a slight problem that reared its head when I fitted this fuel pump only days  before the 2014 edition of Club Triumph's Taith o Amgylch Cymru (or Tour of Wales):

I did have some problems while fitting the pump to the engine. At the time I thought this was purely caused by the lobe on the idler shaft being in the wrong position. And this seemed to be confirmed by the fact that after rotating the crank shaft half a turn the pump slipped in place without any problems. I also checked the new pump's lever arm length against the original pump. The last one was of the long arm variety, fitted with a half inch thick spacer. Well actually two quarter inch ones:

As the new pump had a significant shorter lever I fitted it without the spacer, and headed for Wales. At the time I didn't think much about the fact that the idle speed had risen somewhat to around 1500 rpm. I simply adjusted it till the idle speed was around 1000 rpm and carried on with touring Wales.

Fast forward four years and bearing the above in mind I thought it a good idea to compare the pump fitted to the car with two original TR7/Dolomite 1850 fuel pumps. One with a long and one with a short lever arm, and with the current fuel pump in the middle:

At first glance the two pumps on the right look more or less the same. But after some measurements I found the following dimensions between the pump's mounting flange and the end of the lever arm where the cam lobe touches (from left to right): 57mm - 48mm - 44mm. So it seems like a safe bet that the fuel pressure might be too high, but how high? As I don't have a fuel pressure gauge I think I'll start with a 3 or 4 mm spacer. And hopefully that will get the car driveable enough to my friendly workshop to check fuel pressure and carburettor settings.

At least a scan of a fuel pump gasket enabled me to produce a file for machining the spacer. To be continued ...