Rather strange problem!

[81_Chevy]

okay, so every once in a great while when i go to start my truck it will sit there and turn over forever and ever and wont start. my dad has always told me to take a screwdriver of something and tap the top of the distributor, as soon as i do that it fires up.

now it did this with the original engine and distributor. The engine in it now is a different engine, and every part on the distributor has been replaced, including the physical distributor itself.

I know for a fact that when this happens its not getting spark because my tach doesn't move. most of the time its not a big deal because it usually only happens once or twice a year. but its been happening alot recently, and its starting to get very annoying.

im totally lost on why this is happening, and for the fact that everything in the distributor is new. and that the fact when you tap the top of it, it fixes the problem. im totally lost, has anybody else had this problem?

-Nic

[Fairlane514]

Check your "hot" supply wire to the distributor for a loose connection.  It should be 12v in the "on" and "start" position.

[werewolfx13]

+1 on checking the supply wire to the distributor. ESPECIALLY check by the vac. advance, mine on my '83 would occasionally rub just a little right at the connector and arc to the vac. advance canister and when it would do that, it was like hitting a kill switch...engine would crank but not start. Tried a new dist, removed the aftermarket tach, checked the supply wire for loose connections..nothing..Finally found it when it pinched a chaffed point against the vac.advance and shorted out, and also made apparent, the inadvertently bypassed fusible link resulting in a solid molten mess of a wiring harness from the fuse panel to the ignition switch.

[Stewart G Griffin]

i'm just throwing this out there as another suggestion;  It sounds like it might be a grounding issue with the distributor.  Especially if you have to tap it and then it works.

[Fairlane514]

If its an aftermarket tach, try disconnecting it and see if there is a difference.   Also, look for common denominators from the old engine and new. Something that has not been changed between the two may still be the culprit with the new motor.

[81_Chevy]

okay, ill check those out. even before we put the new tach in it still did this.

[Irish_Alley]

im thinking it has to be the hot wire on the distributor. maybe loose connection this is why why you tap the distributor it will work. but its kind of hard to diagnose an intermittent problem but its worth a shot

[81_Chevy]

how would i go about checking the hot wire?

[Fairlane514]

Multimeter or test light. Should be 12v in the "on" position and "start" position.  Make sure its a tight connection when its plugged into the HEI "bat" terminal after checking.You should unplug it to check it.

[81_Chevy]

alright, so just hook the test light up to the wire then?

[Fairlane514]

You will ground the test light or multimeter, turn your ignition switch to the "on" position then touch the terminal on the wire with the test light probe or the multimeter red lead. The test light should light up and the multimeter should register 12+ volts. Do the same test in the "start"position, (may need someone to turn the key while you check the meter).

If your results are positive, then make sure its a tight fit when you plug the wire back in to your HEI.

[81_Chevy]

alrighty, i will do that next time it acts up! that way i will know if that is the problem.

[Irish_Alley]

i cant say ive done this before or if it will even work. but you could rig up a light in the cab thats grounded out and on a toggle switch then from the toggle switch run a jumper to the hot wire on the distributor. when it acts up next time just flip the toggle switch and if your light lights up then you have power to the hot wire. on a side not i made a test light with a 194 bulb and socket once when i wasnt getting spark, turned out my hot wire would "click" into place but i bent the terminal in the distributor so it wasn't touching

[81_Chevy]

Alright, I finally got around to checking into this. The hot wire has power to it in the on position, I wasn't able to check it in the start position because I was by myself.