Series 3 Truck dies in idle

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85Santana3

85Santana3

Active Member
Posts
284
Location
Canada
Hello people
It looks like my engine is not getting fuel although:
1. pump is working and filter shows plenty of fuel in the hose
2. the idle screw of the carb. is turned all the way in (on max)
3. air-fuel mix screw of the carb. is open as much as possible.

Lately I did not like the odor of exhaust so yesterday I played with the two screws on the carb.
In doing so the needle/screw that adjusts the air-fuel mix came out and I put it back again. I saw the needle was sharp and pointy. The more this screw is out the more fuel is going to the engine (correct?) I have left it out as much as possible, practically I had to wrap teflon tape to keep it there to stay that open. Still the car dies if I don't press gas.
Could something be blocking the passage in the hoses after carb to the engine (I did not see any hoses, how does fuel-air mix gets from carb to engine?)
Any idea how to fix this?
thanks in advance
 
Last edited:
The air/fuel mixture screw shouldn't be out all the way. Turn it clockwise until it is full screwed in, then turn it back out again about one and a half turns to one and three quarter turns. Then adjust the idle screw to set the tickover speed. Sometimes previous owners mistakenly muck about with the air screw when the timing is out a little.

Col
 
Well let see are the plugs still okay. Do they smell heavy of fuel or thick with oil. Are the leads still good as they can fail Is the distributor cap still fresh and is the HT coil strong enough to cope. Fuel line you say it okay coming in how about returning back to the tank. Have another check at the fuel line to and from as you could air creeping in.
 
Petrols don't have a return line back to the tank, at least mine doesn't. If I suspect a fuel problem, I take the filter off the carb and pour about an eggcup full of petrol directly into the top of the carb and then try to start it. If it starts, there is a fuel problem, if it doesn't, it's usually an ignition problem

Col
 
Thanks for quick reply guys.
I don't think there is any plug issue. I know the car long enough to know if one cylinder was not firing from the sound.
Two things:
The odor is oily.
It starts always (since I changed starter a week ago) on the first try. Problem is staying on.

I will try what col suggested and see what happens. Maybe the mix is too rich and that kills the engine.
 
As Saxavordian says, check the plugs, the colour of the ceramic insulator will be a good indicator of richness of fuel. They should be a sandy tan colour. If they are white, the mixture is too weak, if they are sooty the mixture is too rich, if they are oily, there is a different problem due to engine wear, or possibles knackered valve seals.

Col
 
I changed valves and valve seals less than 4000 km ago (the moron mechanic did not change the ring while the engine was open!) I will check the plugs for color. Initially I thought he meant one cylinder not firing.
Could something be blocked between carb and engine? How do I check that?
Thanks for your help.
 
Sounds like a blocked idle jet in carb to me. Which carb is fitted?
Take air inlet hose off start engine with revs slightly raised place palm of your hand over air inlet and try and stall the engine this works on some blockages as it creates a high vacuum which sucks the crap out of the jet.
 
First of all thanks for your replies.

The carb is Zenith 36IV that was rebuilt 6 years ago.

I tried closing the needle/screw thing completely and then opening it to 1 3/4, even more. Now it does not die in idle but drives weak and makes a funny ttttttttttt sound. It is like flow of fuel is not steady. I opened the needle completely again to look at it. It is not the same thickness all along. From 6 mm to where the needle begins it gets narrower by about a millimeter. That is probably why it does not want to stay in place very open. Is this normal? Should the needle have the same thickness all they way?
I do not have a spark plug socket so I could not do the checking on plugs. It has to me done tomorrow. I will also try what was suggested by putting the hand on top of air nuzzle and letting suction clean the carb.

My own very uneducated guess is that either something is stuck in the fuel system (happens once to my motorcycle, the washer/gasket around the air box was sucked into the carb - same feeling) or my distributor is acting up.
I did a test drive of 5 km during which I stopped 3 times and each time I opened the needle more. The weakness and ttttttttttttt sound continued.
Any advice is greatly appreciated.
 
The air/fuel (volume control screw) should be tapered, the end should be pointed, if it's flat, it's damaged. There should be a spring on it as per the diagram, this stops it from turning due to engine vibration. You need to get the plugs out and examine them before we can advise much further. Does the fuel filter look clean or are there signs of debris in it. If the fuel filter is good and the air filter is good the carb should be good. Aftermarket carbs (Zenith) often have a bad joint seal and need lapping but if yours is an original carb this probably isn't the problem.

Col
 
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