Ive just purchased a B250 conversion van (318) from a friend. He assured me all it needed was a new carb. Well, I put a 4 barrel Holley on it; it ran but when I went to start it up again it had no spark. I've changed the ignition control module and nothing.. I changed the coil and it started right up. I went to flush the coolant system and half way through went to run water through but it lost spark again. Any idea what it could be? Thanks.

 

Test for continuity between the two leads going into to the distributor. If no continuity, then the pickup coil inside of the distributor requires replacement. The job should take less than 90 minutes with the distributor completely removed from the motor.

Also fwiw I think that a 4 bbl Holley is a bit overdoing it for a 318 cu in motor. The two bbl Carter is all it needs.

 

Good chance to check if the cap and rotor contacts are in good shape too...
Another cheap and easy thing is check your battery connections are clean and secure, if in question, physically pull clean and re secure these as well as other various ground wires (battery to block, block to fire wall etc.) for good measure. I haven't personally experienced grounding issues yet... but there's plenty of threads of 70's and 80's and later model trucks and such where electrical gremlins, intermittent loss of spark or power was resolved replacing a weak battery, corroded wiring or cleaning up a bad ground connections.

just trying to be helpful in a small way

 

+++1^^^ However what I stated actually happened to me once each with two 77 Dodge Vans having a 318 motor.

And an internet search confirmed that the 2bbl carburator (Carter during the 1970s) is the standard carb for a stock 318 cu in motor

 

 

 

No it wasn't a plug like that, it was a cluster of wires that was plugged in under the hood. Had the leads to the distributor connected to it

 

Okay, understood. But fyi the proper term would be connector and not plug. 8))