87 R10 305 Random lost of spark

[Dakkar]

I have a 1987 R10 305 TBI. It keeps losing spark. power to ignition button. If i plug a spark plug into the coil wire it sparks, when plug into distributor no spark. so we double checked voltage and has voltage even when not firing. Distributor has clean post and we installed new rotor button. If we get spark and it starts after cranking it for awhile it miss fires like crazy until it finally stalls out and dies, then when we try to start it again, there is no longer any spark. We have tested everything that we could look up. Do not know what else it could be. Also there is proper mist from the injectors and pump works. Even went through the trouble and changed the timing chain and sprockets out just to be sure and it was in time. So any advice to the problems would be awesome. Do not know what else we could do, besides start spending a lot of money to find out its a simple issue.

[Captkaos]

I am confused on what you are saying.  Are you getting spark to the plug with the wire connected and the plug grounded?

[Irish_Alley]

you said you installed a new rotor but what about the cap. they can crack and get moisture and lose spark that way

[Dakkar]

Sorry. Yes while the wire is connected and is grounded I get spark. Yet when I put the wire back on the cap there is no spark while cranking. I used a spare spark plug to connect on the wire.

The cap is in good condition from what I could see after inspection.

[Irish_Alley]

spray the outside of it with wd40 see if it helps. kind of guessing and grasping at straws but its something simple to check

[Captkaos]

Still confused.  Where are you connecting the "wire" to when it works?
And by connecting to the cap you mean the HEI cap in the IGN slot right?  Are the wires in the cap ok?

[Dakkar]

Disconnected coil wire from cap, attached spark plug thats when it worked. I dont have HEI its all original distributor. The wires fine.

[87ChevyR10]

Got me.

[VileZambonie]

You did the timing chain because it intermittently loses spark?

Replace the pickup coil and module.