Other 2.25 petrol (5MB) Engine runs rough when warm

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hsp

hsp

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65
Location
Arnhem, The Netherlands
Engine starts well and is running normally during warm-up period. When it reached operating temp, it is hesitating and bogs on full throttle. All the symptoms of not enough fuel, so I checked the fuel lines and fuel pump (electric), they are all new. It has a weber 32/34 carb, I cleaned it, and give it a service; did not fix the problem.

All ideas are welcome! I am thinking now of looking at the timing (although did not change that), the distributor or valves........
 
weber carb is very fussy about clean fuel, did you blow all the jets out well? also could be coil, also fuel cut off solinoids on the carb can play up if its a defender type dtml
 
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That sounds more serious. Forgot the fuel system. As you describe it it sounds like worn out valves. You are still getting power even at operating temperature but its falling away at the same time.Has the head been done? I'd get a reliable opinion from a good traditional motor repair garage with landy experience. Not a fan of weber carbs on landy engines; too pokey n stressful. If it gradually worsens it's the valves.
 
sausage said:
weber carb is very fussy about clean fuel, did you blow all the jets out well? also could be coil, also fuel cut off solinoids on the carb can play up if its a defender type dtml
Click to expand...
How can it be the coil? can the coil be working fine if engine is still cold?


John S said:
That sounds more serious. Forgot the fuel system. As you describe it it sounds like worn out valves. You are still getting power even at operating temperature but its falling away at the same time.Has the head been done? I'd get a reliable opinion from a good traditional motor repair garage with landy experience. Not a fan of weber carbs on landy engines; too pokey n stressful. If it gradually worsens it's the valves.
Click to expand...
Can I do some testing myself? measuring compression?
 
hsp said:
How can it be the coil? can the coil be working fine if engine is still cold?
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Coils can get warm if they start to break down inside - or if oil cooled and have a small crack in them.
Thus if they get too hot then they dont generate a good spark.
So a bad coil can be ok for 5 or 10 mins then need a 5 - 10 min rest to cool down.

Might not be that - but is is possible. Check if the coil feels warm after 5 mins of running.
 
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It sounds to me like it could be over-fuelling or your fuel pump is getting hot causing vapour lock

First I'd check that the choke is fully disengaging and that there are no air or fuel blockages. Then I'd adjust the carb mixture when the engine is FULLY hot, not just warm but hot. Get it up to full temperature i.e. go for a fast hard drive to get it fully hot then adjust the mixture before it has a chance to cool down. Adjusting it when the manifolds aren't up to FULL temperature will give an over-rich mixture as the fuel will be pooling in the manifolds while you're doing the adjustment. If its still out then start looking elsewhere.

In the end I ended up fitting an electric fuel pump. I tried a number of mechanical fuel pumps and all were ok until they got warm then there were problems with the valves getting locked with vapour. Modern petrols contain ethanol and or additives that vaporise at lowish temperatures and the fuel pump does tend to get hot. Since fitting the electric fuel pump its run like a good un.
 
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