Rough Running - What Next?

amcdonald

amcdonald

Active Member
Hello

Apologies as this is pretty basic level stuff. Without much skill in the tune-up department, I am struggling to get my NADA3500S going. Well, it goes but badly. The power is really poor, but it is smooth at idle - especially compared to the 2000TC I am more used to. The symptom is a sort of fluttering hesitation under load, with seemingly continuous and very rapid change from power to no power or surge and slow many times per second. It gets there in the end, but going up a steep hill for instance it would struggle.

I thought it may be an air leak and so I redid the hoses, and strangely it then seemed to disappear and I had power. Then later in the day it was back! Then I richened up the mixture, and that makes it a little better but its still there ( I went from nice blue to definite orange -and smelly exhaust- on colourtune). The linkage was tinkered with so its all in order and the carbs air flow is matched. I replaced the fuel filter, checked the flow of fuel back through the return line and it is steady. The spark seems to be strong enough.

Unfortunately the timing marks are in the wrong place. Not sure but it must have been reassembled incorrectly (possible?) but it will never run at the indicated 6deg BTDC. There is a tippex mark at around the "right" timing based on smoothness etc and I just set it based on what appeared to be the "right" seeming position. Close to the tippex.

I thought I would do the carb piston lift check - mistaking myself for someone with skills, and lifting one immediately stalls the motor. Lifting the other does nothing; it would eventually stall at about1/2" lift or more. What does this mean?

This had a bunch of emission control junk on that I removed.

What should I check next?

Thanks
Adrian
 
well from that the 2 carbs are set differently at the very least, and the timing sounds suspect. forget figures and turn the dizzy till its just retarded off the highest idle point.

hows the points/condenser?
 
As has been said, first you MUST get the timing right, but an important point to note is that the vacuum to the distributor must be disconnected before you optimize the timing by turning the distributor to best idle rpm and then back it off a degree or two. The vac can then be reconnected. The yellow on the colortune indicates definite richness somewhere . Start by taking both carb bellchambers and pistons out , adjusting the jets up until they are level with the bridge , and then turn the adjuster screws 2.5 turns down . Have a look down the jets to see that the fuel levels are below the jet level and approximately equal with each other . Now check to see that the throttles are equalised. Now you can use your colortune , adjusting each carb mixture by the same amount, to get a good even colour.

Good luck
 
Thanks for the comments. Today I will determine tdc with a tool so that I have that for reference. As its a US car, I understand the vacuum retard system is on there. I will take this out of the equation and plug it up for now, although as I understand it - which is not very much - that is likely not a major miscreant.
 
Hi . Just tape up the vacuum advance ( not retard ) while you make adjustments . Then connect the pipe back up after , you only need to take the vacuum advance out of the equasion while you make the adjustments , but not loose it all together , fuel economy will drop even more .
I would seriously consider a fuel pump overhaul if it has a mechanical pump , for the few quid and an hours work you can rule it out , then see how it goes , if your still having problems consider a carb overhaul , less than a hundred quid , and a nice Saturday project . :D
 
Well I managed to:
- Dremel-scrape new timing marks.
- Set timing properly (was close enough)
- Drain gas and put nice fresh 100 octane juice in there
- Inspect carb floats and fuel flow (electric pump and regulator just fine)
- Fix the linkage slop and......
- Set the carb air flow so they now open somewhat simultaneously
- verify that the vacuum unit does indeed retard the timing as it "should" for this emissions vehicle (and disconnect that mysterious nonsense altogether)

.....and then discover it was the ignition coil. Great result as it is the only component in the entire system that I have a spare and I got all that other stuff done. Now to replace the vacuum "retard" unit with an advance unit or rather replacing the distributor entirely. More research required on that topic
 
Hi Adrian,

The vacuum units available from Land Rover for the RV8 have both advance and retard built in. The advance take off is on the front of the module whilst the retard take off is on the reverse side. They come with plastic covers over each take off, so which ever you don't use, the cover remains in place.

Ron.
 
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