Misfire and lack of power

[Steve W]

My Javelin recently developed a strange mis-fire and had a distinct lack of pull. I changed the plugs, firstly to L86 but no difference. Then back to the cleaned up L10s. Same problem. Car was decidedly off colour.
Then I remembered a similar occurrence years back with my Bradford. Would start ok, run slowly but gave up on a a slight incline. Sure enough, the Jav had same cause. The flexible fuel pipe that feeds the pump from the steel pipe from tank had become soft. I think I did not use decent petrol-proof piping. Thus, when engine demanded more fuel and the pump was sucking hard, the pipe constricted thus cutting off the fuel supply. I replaced both the inlet length of pipe and the outlet length, which had also become soft. Hey presto, Javelin once more on song. I have used proper petrol piping this time too!

Incidentally, I also did a compression test, thinking that valves may be at fault, before I remembered the pipe problem. They were - 1 @ 160, 2 @ 130, 3 @ 140 and 4 @ 120psi (starting from o/s/rear cylinder and progressing forward, then to n/s bank rear to front. Could such differences cause problems. I suppose the heads need to come off and valves be re-faced. Engine has done about 20k miles since rebuild.

[Keith Clements]

Any rubber in the petrol system may be eaten by the ethanol. Use modern specification.

It is worth taking the compression readings a few times as it so depends on cranking speed and the oil seal around the bores. I would suggest about six readings, take two on each cylinder, then swap cylinders, until you have three pairs of readings for each cylinder. If the readings on the same cylinder are not all within 10psi then that shows you the possible error. Take off the lowest and highest and average the other four, should give you a better insight before taking the head off. Note it is probably a rusted valve if the car has not run a couple of hundred miles, so best to do that and take readings again. The valve should bed itself back in. The bores or rings could also cause imbalance or possibly poor balancing of the combustion chamber volume. See if plugs have any moisture on them as this may be symptom of leaking gasket.

[Steve W]

Thanks for this. The engine was cold, just driven out of garage onto drive to give me room to get jack under and lift car onto stands etc. Mind you with my back as it is, I don[t relish delving under again for a while! The state of my health and that of my wife is the reason I really need to sell the car. It will be a wrench not to have a Jowett in the garage after almost 39 years, but time is passing and we are getting older.

[Steve W]

Problem solved. Turned out it was the radiator throwing out excess coolant which was landing in the plug hole of No1 cylinder. Even with NJK water proof plug covers, it was still upsetting the electrics. Mind you the plug covers are over 15 years old, so probably their seals are shot. We have extended the overflow pipe with some rubber tubing to direct any water away from the cylinder heads.

Another potential disaster was spotted. The bottom rad hose on drivers side was nearly cut through by being in close proximity of the steering box. It has a sharp flange all around it. The new hose has been twisted away from the box as much as possible.