350TPI69Bird

Hi all, I am new to the board and have an interesting problem I hope you all can help with. I am building a 69 Bird with an 86 TPI (305) bolted to a 350 roller. This system ran fine on the 305 but now that I have it on the 350 it cranks but will not start with out squirting a little fuel into the plenum, then it starts and runs fine with good throttle response. (Note: I have not been able to drive or test it under load as I have no drive shaft yet). Fuel pump (280Z) seems ok I hear it run for a few seconds when I turn on the key, I have even hard wired it to run constantly with no change, I have 60 PSI on the return line. I have tried 350 injectors and the ones from the 305 with same issue. Computer seems ok, code 12 and an O2 sensor code 44 after it warms up. Any ideas? Thanks

Air_Adam

60psi sounds pretty high, should be around 40-45psi or so IIRC. Have you checked if all the pressure is bleeding out when its not running? The fuel system should hold pressure for awhile after its been shut off.

350TPI69Bird

I have watched it and It seems to holds fuel pressure at least for a few minutes. Thanks for the idea, I will check the pressue at the schrader valve and see if it bleeds down.

350TPI69Bird

Hello all, did some more trouble shooting, fuel pressure at the schrader valve 45 PSI key on, 40-42 running, minimal bleed down after shut down, appears to have a minor seepage at one line fitting. Still have to prime to start. Checked injector wiring with noid light, no pulse when cranking, good pulse once running. What would cause the no insector pulse while cranking?
Thanks

Air_Adam

Does your TPI system have the cold-start injector (sometimes called the 9th injector)? Some years had it, others did not. What ECM are you using (whats the number)?

350TPI69Bird

Yes it has the cold start (ninth) injector, ecm number 1227165. The entire TPI system came from a running 86 IROC 305 I had it in the 69 and running before I found the 350 and swapped it out.

350TPI69Bird

What do you all think about an internal distributor problem or ignition module? Could either be the culprit?
Thanks

Air_Adam

If it starts when you manually shoot some fuel into the intake, then its likely not a spark issue, its a fuel problem.

Have you still got the stock oil pressure switch? I know some TPI engines had an oil pressure switch that would not allow the injectors to start firing untill a certain level of oil pressure was present (from cranking). Maybe something to check?

350TPI69Bird

This one uses the oil pressure switch to turn the fuel pump off if it looses oil pressure and I have bypassed it with no change. I know it is not a spark issue but I do not think the ecm is getting the distributor reference pulse while cranking. Is there a way to test the ignition module? I have tested the circuit from the dizzy plug to the ecm and it seems to work.

350TPI69Bird

Morning All. I went through all the trouble shooting guides in the Chevy TPI swappers guide (again) and it points to the ECM.... But It runs ok once primed, how could the ECM be bad, can this be correct? Any other ideas?

Theking

iTrader: (1)

ECMs can go bad for no reason, or just because they are old.. So it COULD be a bad ECM it also could be bad injectors or due to high fuelpressure...

So if youre able to test another ECM that would be good, then lower your pressure to ~48 PSI instead. and then go from there..

350TPI69Bird

Fuel pressure is at 45, injectors are working, tried another ignition module, no change. Tried swapping the fuel pump relay, and then the ESC, no change. Put everything back together and it will not run at all, so it must be the ecm. I do not have a spare one, so unless there is disagreement from you all, I will try a trip to the bone yard. Thanks.

350TPI69Bird

Found the problem, it was none of the above, my wiring harness shorted so my cold start injector circuit was not complete and the power to the ECU was lost while cranking. Don't quite understand why it would start at all. Glad I did not by that new computer. Thank you all.