2.8 CFI - stalls after starting up...

[Kevin Evans]

I'm having an issue with my project 1984 Ford Ranger 2.8L. Swapped out the carb for CFI from a 3.8 Cougar.

After starting up, the engine stalls after a few seconds. I've adjusted the timing to get max manifold vacuum (need to borrow a timing light) and it's holding steady around 19 inHg.

Here's a video of the issue: https://youtu.be/5PsgbxbdrvM



Pardon the mess in the engine bay, still need to clean it up...


Does anybody know what could cause this, or is there anything that I should be checking? Any leads would be helpful.

 

[RonD]

A Cold Engine needs to be "Choked", carb or CFI.
Choked = richer fuel mix, advanced spark timing, and higher idle RPM.

FI uses computer and a Temperature sensor(ECT sensor) to set "choke mode"
You can't use a Choke plate with FI, no jets to suck extra fuel from, so computer must "told" to add the extra fuel based on engine/coolant temp

Gasoline vapor will ignite with a spark, liquid gasoline will not.
Cold engine/cold gasoline will have little vapor to ignite, which is why engine needs to be "choked.
You need 30% vapor to start engine, cold you get about 10%, from carb or FI, so if you increase the amount of gasoline you get 30% and engine starts

Other causes could be a drop in fuel pressure after startup

 

[Kevin Evans]

Just tested the fuel pressure last night and it's dropping way too much after starting :/

Will need to dive deeper into it but I'm thinking one of the pumps has gone bad... probably the high pressure one...

 

[RonD]

Could be pump or pump is losing power after start up.

Not sure how you wired electric fuel pumps or what computer you are using to run the CFI system.

One thing you DO NOT want to have happen is electric fuel pumps to have power if there is an accident, i.e. fuel being pumped out of the tank feeding a fire.

So systems that use electric pumps usually have two shutoffs
Inertia switch passes 12volts to fuel pump(s), it has a weight inside, if there is a sudden stop or roll over the weight movement trips the switch cutting off the 12volts.
RPM switch, computer uses RPM to meter fuel flow thru the injectors, if RPMs stop the computer opens "Fuel Pump Relay" cutting power to fuel pump.

On older carb systems with electric pump(s), they used an oil pressure switch with Fuel Pump Relay, carb had fuel for starting in float bowl, when engine starts oil pressure causes switch and then relay to close and fuel pump(s) get 12volts to refill the bowl and continue filling it as needed .