FLUX Posted April 30, 2015 Report Share Posted April 30, 2015 OKAY, so this is whats happening. Start the truck cold (like 70 degrees F) and start to drive and it's fine. Within about a minute of driving I will loose all power and the truck will start bucking. Here are the things I have already checked. When this issue happens I view the site glass on the float bowl and it is right where it should be. I have also tried searching for vacuum leaks and found none. I have an electric fuel pump setup due to mine having a/c but I can't be that because of the mentioned fuel level thru the site glass is fine. I have checked voltage at my coil and I have about 13 volts. I have replaced my spark plugs, cap, rotor, and coil wires. I have double checked my coil wires with an ohmmeter to insure they aren't too high in resistance ( all are about 7.5 K ohms) with the coil wire ( wire leading to the coil to the cap ) being 4.7 Kohms because its shorter. I have checked compression and I have about 145psi in each cylinder. Gas is fresh. I replaced my positive cabe end (battery end) because it was questionable but I have the same issue. Timing is set to factory spec (12 degrees BTDC) and the vacuum advance has vacuum when you open up the throttle and the vacuum canister on the distributor does hold vacuum. Accelerator pump is working but I replaced it just to be sure and still nothing. ONE MORE THING... when it starts to act up you can turn the ignition off for a minute and start it up and it will run fine for about 30 seconds under load and then start acting the same way again. Truck idles fine. Quote Link to comment
Guest Rick-rat Posted April 30, 2015 Report Share Posted April 30, 2015 My truck was doing this, my problem was a loose spade connector on the coil and would lose contact once in a while, squeezed it to make it tighter and has been fine ever since Quote Link to comment
datzenmike Posted April 30, 2015 Report Share Posted April 30, 2015 When the truck is started cold the choke is in operation. A cold engine does not evaporate all the fuel on it's way to and inside the combustion chamber and it will act lean. There is lack of power and very rough running. The choke adds extra fuel to make the mixture richer and the engine will run smoother until warmed up. At this time the choke shuts off and the warmed engine motors along properly. If your primary jet is blocked or part plugged the mixture would be very lean and the engine will stutter and buck when driven. It might even lean backfire. The choke being on masks this problem until the engine warms and the choke shuts off.... then the problem is obvious. 1 Quote Link to comment
FLUX Posted May 8, 2015 Author Report Share Posted May 8, 2015 OKAY, thought id share what I found. I decided to rebuild the carb after I checked all my voltages and they seemed fine. I took the carb off and apart and found what I believe to be the jet for the accelerator pump to be loose, and by loose I mean it was one turn away from being completely out. Fixed this, cleaned the rest and replaced all the gaskets and shes running like a raped ape. Just one more problem, the float level is kicking my ass. The float valve I took out (the old one) didn't have a little clip around the bottom to support the needle valve when you took it out and the new one does. I think I have to take this out because my float level is always too high. ALSO, is the choke heating element supposed to have power all the time or is it on some kind of delay? Thanks, FLUX Quote Link to comment
datzenmike Posted May 9, 2015 Report Share Posted May 9, 2015 The choke heater is powered through a relay that only allows this when the engine is running. A charging alternator is needed. If your relay isn't working for some reason you can fix it or not Well, you can ignore the relay and just jumper the choke heater to the idle cut solenoid wire right beside it on the carb. This is a switched power source that is only on when the key is BUT engine is not necessarily running. The reason for the relay is for very cold weather start up when a choke is very much needed. Lets say you start your Datsun normally and leave it running while you go in where it's warm to finish your coffee while it warms up. Unknown to you, the engine stalls, but without the relay requiring a running (charging alternator) the choke continues to warm up and shut off even though the engine is 20 below still. You go out and try to re-start but without the choke you have extreme trouble, it won't idle and have to hold the gas down while it warms up. 1 Quote Link to comment
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