Been working on a 383 in a Tilt bed truck for exchange for a 454
Got it running really well - I am new to the 747 - man is that thing have slooooow aldl output..
Anyway 2 problems that bother me a little.. On a hot start it wants to crank about 3 seconds - But while making changes I noticed that when prom is removed and placed back in, it starts imediate on the first try? I have been making changes to the
startup a/f vs temp and choke enable to no avail.

Other problem is every once in a while cruising at 2000 maybe 40--60 kpa in will just start climing lean till it maxxes out at 192 - I had added lots of fuel and it does not change.. So for now I locked BLM to 150 max as I do not think its that lean.
Don't hear/feel any exhaust leaks and o2 seems to work fine elsewhere, stockish type cam.. Any theories.

 

With the hot start there are two items that come to mind. One is the hotstart calibration. Dependent upon the engine temp at key on the ECM can go into hot start mode. IIRC the AFR and IAC steps are changed. The other may be the amount of time between actual restarting. With a PROM change maybe it is a longer delay?

192 BLM issue: check the last byte in the bin and verify that it is $96. There was a problem a long time ago where a bunch of '747 bin's were read and the last byte wasn't correct. The issue manifested itself as a learn problem.

RBob.

 

Bad O2 sensor?