NotARobit

So we're swapping a crate L31 vortec into a 91 305 RS. We tested the new engine with the original throttle body and it started and idled for a few minutes. Then we took the throttle body off and upgraded the spring and injectors, and replaced the gaskets and diaphragm. When we put it back on, the injectors dribbled instead of misted and the engine wouldn't fire.

We took it apart and double checked our work and it still wouldn't fire. So we swapped back to all the original parts to test and now the original parts are dribbling just like the new parts were. (see video)

The injectors on both sides dribble the same. Any ideas what is going on? During the couple of weeks in between tests, we only connected some vacuum lines.

I'm not a mechanic and appreciate any help. Thanks.

RFmaster

Some dribling during cranking is normal - I suspect that your fuel pump is not delivering enough fuel pressure. Do a fuel pressure check first.

//RF

static80

I think pressure is likely the cause but if you didn't do anything with the fuel pump, I'd double check the regulator. You changed the spring/diaphragm so I'd suspect something there not allowing you to build enough pressure to get a good spray.

NotARobit

Thanks guys. It looks like it's going to be too cold to work on the car for at least a week. I've taken it off to clean it real good and if it doesn't work when I put it on, I'll look into acquiring some equipment to test the fuel pressure.

NotARobit

Well Dad and I had to mess with it. We tore it down, cleaned everything, and put it back together with old spring and new injectors. It worked! Sometimes, you're just happy to be back to where you started.