Thursday, 21 August 2014

Fault finding 't Kreng

During the Border Raiders trip early this month, the car developed an engine problem. 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 over the past few weeks I have been checking various things. The first of which was the ignition system. As already mentioned there was a fair amount of corrosion on various parts of the ignition system. Also the earth wire/points from the coil and the electronic ignition module had seen better days. So I had high hopes that cleaning out the corrosion might be the solution, sadly it wasn't. Also measuring the spark plug cables didn't reveal anything strange. The measurements were the same as my (new) spare set.


Next item on the checklist was the ignition timing. At about 14° BTDC it had a little bit too much advance. But not enough to be the solution. Which turned out to be correct. Adjusting the timing to 11° BTDC (which is it's optimum setting) didn't change anything. The idle still was rather lumpy. At this point I wanted to change the spark plugs for a known good set, but I couldn't find them. So I decided to remove the spark plug caps one by one. Every time I removed one the revs would drop slightly which means all spark plugs are working, sort of ...

So I switched my attention to the carburettors. Although I knew the outcome in advance (all fuelling problems are ignition related) it had to be done just in case. Turned out to be nothing wrong there. No dirt etcetera in the float chambers, fuel level in all chambers looked to be the same, float needles were open and working as they should and the filter was almost completely clean. Check.

As a friend had dropped of his compression tester I thought it a good idea to check this to get an indication. Should have done it on a warm engine but I just wanted to rule out any issues with cylinder number 3:
# 1 - 8,0 kg/cm²     (114 psi)
# 2 - 10,0 kg/cm²   (142 psi)
# 3 - 9,7 kg/cm²     (138 psi)
# 4 - 9,4 kg/cm²     (134 psi)
Clearly nothing wrong with number three, but number one's too low. Might be caused by the fact that the engine has been running badly and it just needs to be driven properly to clean it out? I know wishful thinking!

The remaining items on the checklist;
Check condition of the ballast wire;
Clean connector from ignition module
Change spark plugs just to be sure;
Check valve clearances and cam timing (yes the engine is fitted with an adjustable cam sprocket and there is a theoretical chance it moved a bit ...)

So the search goes on although I get the feeling that if one of those doesn't solve it I'll be running out of easy options ...

2 comments:

Patrick said...

Hello.
If it could help you : I have seen that with Super 98 and not 95 (with additif) the TR7 engine reborn.
Best regards from France

Beans said...

Thanks for the suggestion, but I don't think that will be the solution, as I usually fill up the car in Germany. And they sell 100 to 102 RON fuel.
But it could be that a bad batch of fule caused the problem. That why I have emptied the fuel tank almost completely ...
Will keep you updated.