Hi everyone, I'm really looking for help and inspiration to solve a fuel related misfire now that all logical fault finding paths seem to be exhausted!
Am running a 1975 CR which has been getting progressively richer during the past few years, so finally, after many attempts at tuning, the exhaust smell prompted me to exchange the metering unit. Then things got a little crazy!
I chose the correct MU for the CR engine and had to modify the fuel return as this version of the MU only has the screw fitting, but the car had been built at some time in the past with a push fitting pipe connection.
No big issue, and the replacement went really well, respecting the 'special' injection timing position ATDC of the CR engine. The car started easily and was soon running smoothly, at least for the first cautious test run of 30 miles. Then, a few miles into a higher speed run, a misfire developed :-(
After limping home and checking / replacing all the usual suspects (new plugs, leads, KMI injectors, fuel pressure at 100psi....) the problem would not go away, and by cracking the injector pipes, I eventually found very little fuel at Number 5.
Swapping the injectors confirmed that whatever injector was taken from a running cylinder and attached to Number 5 pipe, it would not spray in that position. The original Nr 5 injector worked well on another cylinder.
So suspicion fell on the none return valves in the Banjo unions, and two new Banjos were purchased (KMI) and installed. The Nr 5 pipe was also checked for blockages and this appeared okay. The misfire still persisted!
So phone call through the Metering Unit supply chain resulted in the MU being exchanged for a newly refurbished one, which was fitted with due care a couple of days ago. PERFECT :-) .... for a few miles, then the misfire returned :-(
Again, fault finding proved that whatever injector (now new ones) was fitted onto Nr 5. it would not spray! But the one taken from Nr 5 works on other cylinders! Swapping the Banjo's was also tried to see whether the problem moved to Number 2 - it stayed on Number 5!!!
So any gems of inspiration, or preferably someone saying they know exactly what the problem is, would be appreciated.
Living in hope