Misfiring Sprint Engine
Posted: 10 Oct 2014 13:07
During the Border Raiders in August the car developed an engine problem (Sprint engine on DCOE Webers and optical ignition module from Newtronic). Symptoms were lack of power especially at higher revs, running rather lumpy at idle. But running fairly well in higher gears at about 3000 rpm. So since then I have been checking various things;
• The contacts inside the distributor cap were showing signs of corrosion as were some earth wires;
• The spark plugs from cylinder 1, 2 and 4 looked OK, but number 3 was literally washed clean;
• Removing spark plug caps one by one reveals that number 3 is not working on idle;
• Measured the spark plug leads but the measurements were the same as a (new) spare set.
• Ignition timing is spot on (in this case 11° BTDC, checked both static and dynamic);
• Changed dizzy cap, spark plugs, spark plug leads and coil, no success;
• Checked the compression to see if there was anything wrong with number 3.
Should have done it on a warm engine but I just wanted to rule out any issues with cylinder number 3:
o # 1 - 8,0 kg/cm² (114 psi)
o # 2 - 10,0 kg/cm² (142 psi)
o # 3 - 9,7 kg/cm² (138 psi)
o # 4 - 9,4 kg/cm² (134 psi)
Clearly nothing wrong with number three, but number one's too low.
But I don't think that's causing the problem
• Checked the carburettors but nothing visibly wrong there.
• Same applies for the in line filters and the electric fuel pump;
• With the ignition switched on and the dizzy's chopper disc in the correct position
I got a reading of approximately 6 Volts. So the ballast wire is OK;
• Checked valve clearances, though not spot on, they didn't need immediate adjustment.
Al the above have had no effect whatsoever, so has anyone suggestions as to a solution for this problem?
<center>
<font color="blue"><i>1976 TR7 FHC (needs some TLC ...)
1980 TR7 DHC (my first car, a.k.a. Kermette)
1981 TR7 FHC (Sprint engined a.k.a. 't Kreng
</font id="blue"><b>[url="http://www.tr7beans.blogspot.com/"]<u><b><font size="3"><font color="red">My full Blog</font id="red"></font id="size3"></b></u>[/url]</b></i></center>
• The contacts inside the distributor cap were showing signs of corrosion as were some earth wires;
• The spark plugs from cylinder 1, 2 and 4 looked OK, but number 3 was literally washed clean;
• Removing spark plug caps one by one reveals that number 3 is not working on idle;
• Measured the spark plug leads but the measurements were the same as a (new) spare set.
• Ignition timing is spot on (in this case 11° BTDC, checked both static and dynamic);
• Changed dizzy cap, spark plugs, spark plug leads and coil, no success;
• Checked the compression to see if there was anything wrong with number 3.
Should have done it on a warm engine but I just wanted to rule out any issues with cylinder number 3:
o # 1 - 8,0 kg/cm² (114 psi)
o # 2 - 10,0 kg/cm² (142 psi)
o # 3 - 9,7 kg/cm² (138 psi)
o # 4 - 9,4 kg/cm² (134 psi)
Clearly nothing wrong with number three, but number one's too low.
But I don't think that's causing the problem
• Checked the carburettors but nothing visibly wrong there.
• Same applies for the in line filters and the electric fuel pump;
• With the ignition switched on and the dizzy's chopper disc in the correct position
I got a reading of approximately 6 Volts. So the ballast wire is OK;
• Checked valve clearances, though not spot on, they didn't need immediate adjustment.
Al the above have had no effect whatsoever, so has anyone suggestions as to a solution for this problem?
<center>
<font color="blue"><i>1976 TR7 FHC (needs some TLC ...)
1980 TR7 DHC (my first car, a.k.a. Kermette)
1981 TR7 FHC (Sprint engined a.k.a. 't Kreng
</font id="blue"><b>[url="http://www.tr7beans.blogspot.com/"]<u><b><font size="3"><font color="red">My full Blog</font id="red"></font id="size3"></b></u>[/url]</b></i></center>
