Mongoose

iTrader: (2)

I did a search but didn't find what I needed. I started my Formula after swapping from TBI to TPI. The problem is that it stalls out after about 10-15 seconds. The first start lasted about 4-5 minutes while I checked for leaks (no fluid or vacuum leaks to be found) and then stalled and since that no more than a few seconds. I pulled the distributor and set the engine to #1 TDC just to be sure and this helped some but still the same stalling. The fuel pump is priming and running as well. Here's the parts I used:
'89 350 TPI with 22# injectors
Adapter from TPIParts to correct for 22# inj. on a 305 and disable AIR
'91 ECM, PROM and harness
Timing is at somewhere between 8-12 BTDC I think
Fuel pressure is at 44psi according to the gauge
All sensors are for a speed density application
Using a Holley adjustable regulator and airfoil
I thought that maybe the minimum air was high with it being from a 350 so I tried to adjust it down but it didn't help.
I also have a K&N valve cover breather where the normal breather tube would be to the TB.
There's also an MSD6AL and a Blaster 2 coil but they worked before the swap.
Hopefully someone here can help with this.

AtomicTruck

Something doesn't seem right. Did you change the fuel pump? Is the ECM the exact one out of the donor vehicle for the intake and all other TPI parts? If the ecm is for a 350 and you have a 305 you'll need to burn a new chip. What are the GM numbers on the ecm?

Mongoose

iTrader: (2)

Fuel pump was changed. The TPI itself came from a different vehicle than the ecm,harness and prom. The TPI came from an '89 350 IROC while the ecm,harness and prom came from a '91 305 auto Formula. The car is running as of yesterday but still not to my satisfaction. The initial problem was improper routing of vacuum lines. The MAP needs it's own dedicated line and I had it sharing with the accumulator and the hvac. Problem now is surging and I'm unsure if the O2 sensor is working as I'm getting no readings from the A/F ratio gauge. I intend to plug the car into a scan tool by this weekend and see just what's going on now that it runs.

AtomicTruck

So did you find the exact cause of the short run time? These trouble shooting stories are great info.

Thanks

PS. I also made a mistake on the MAP sensor. I had hooked it up to a "timed" vac port, which works as inverted vac... Had me scratching my head for a bit.

Mongoose

iTrader: (2)

I had the MAP sensor hooked up to a shared vacuum source instead of it's own line. Much better after I switched it. The problem now is surging after it goes into closed loop. I'm going to replace the TPS and IAC valve which are the last sensors and such that came with the TPI. I'm also suspecting an O2 sensor/ A/F ratio gauge problem as I'm getting no reading on the gauge. I'll get a scan tool on it either today or tomorrow and see for sure.

superchevy72

iTrader: (1)

since your using the ecm/wiring from a 90 car, you might wanna look into the passkey/vats being a problem. vats was the problem with short run time being the symptom in an LT1 swap i did.

techno101

I had similar problems when I did my TBI to TPI swap. My main problem was timing though. I had to set mine to 6 degrees base. If you can use a timing light and make sure you unplug the necessary wires for setting the intial timing.

Mongoose

iTrader: (2)

Sorry for the delay in replying. Problems turned out to be a bad O2 sensor and a faulty ignition module. Once those were corrected had to readjust the timing and the minimum air (idle) and get the correct TV cable. Got to break the car in last Saturday and it runs great. Smooth idle and great throttle response. I'm using the stock '91 PROM with TPIParts adapter and everything is good. Looking at having a PROM burned for it soon to fine tune everything for this specific car but for right now I'm very pleased with the results.