The car is a 1985 Z28 that I swapped a 91 305 TBI into.
fuel pump is still TPI model.
Dash/ECM wiring is a mix of 92 camaro, 85 Z28, and 91 Formula.
Dash, gauges, and dash controls are from a 92 RS

The swap has been done since around june and worked perfect until about a month ago. Now, The car starts rough about once a week whether it's parked outside in 20 below temps or parked in a 75 deg heated garage overnight. It usually only does it in the morning too. It will crank and crank and then you start to smell the gas, and then you crank and then it will slowly catch and run very rough for a min while it burns off the fuel.

Here's what I've done so far:
New plugs
New cap/rotor
New wires
Old coil was weak, so we replaced that
Tested pickup coil, well within spec
Fuel flow is great, and pressure is a constant 13 PSI
Disassembled upper TBI and cleaned/verified FPR is in good cond.
Replaced fuel filter 6 mo ago when I did engine swap
Injector spray pattern is great
Foam air filter cleaned
Engine grounds clean and solid
Timing is dead nuts 0 deg

The original plugs had carbon buildup, indicating a rich cond. (duh, it's dumping 4000 gallons of gas down the TB )

Just for kicks, I tested all the wires after I changed them. All were well within spec, and the coil wire was 225 ohms. I thought that sounded low, so I tested the new one and it was only 333 ohms. So it wasn't that far off.

I think the problem lies in the ignition system, but what is left other than the ignition module? What does the ignition module do? Could it give me this problem?

My only other idea is that a wire is corroded or broken somewhere. What wires could I start tracing?

Oh, the pump still primes even when it has the problem, so that rules out the oil pressure safety switch. (I think)

Also, when I did the dash/motor/tranny/interior/ECM swap I used a combination of alldata/chiltons and haynes manuals for schematics, testing all wires before splicing. All wires were soldered and heavily taped, and routed the harnesses in stock locations. And like I said, it was all working great since spring.

If this doesn't make sense, please ask questions. I'm pretty tired and my thoughts are jumbled from a day of no conclusive evidence that something is wrong.


What else can it be guys? Any help you can offer would be very appreciated. I'd hate to strand her somewhere

 

i'd swap fuel pumps or regulate it down. tpi puts out way more than a tbi pump. does seem strange it took this long to act up. maybe a module wouldn't hurt, however they usually fail hot. take it and have it tested.

 

The TBI regulator holds it at a constant 13 PSI, would you still recommend a change? I had her pick up a pump, but I thought she could bring it back and save herself the $$$.

Also, when the pump primes the pressure is at a constant 14.5 but as soon as I crank it the pressure drops to 13 flat. What would be optimal fuel pressure?

Thanks Ede