Alright I finished my motor about a month ago, we adjusted the timing until it sounded good and the fuel pressure was ~11psi at idle, 16psi WOT. Dyno'd the car and the a/f went way lean above ~2500rpm so I replaced the stock pump with a Walbro. The only thing I had done is replaced the pump and readjusted the fuel pressure. Now the car is hard cold starting, running rough and I can't seem to smooth it out.

Setup: vAFPR w/ Topdown Solution's spring, Ultimate TBI, Open Aircleaner, LT1 cam/springs, MAC headers, Catco Cat, Edelbrock Cat back, Accell wires/cap/rotor, Rapidfire plugs, older ADS SuperChip and Walbro pump. Everything else is stock and original parts.

Current settings: timing is 8* with EST disconnected, jumps to 26-28* with EST connected, vacuum is only about 15 at idle(vacuum gauge indicates "late engine timing"), fuel pressure is about 14psi at idle and won't adjust leaner(I think due to the low vacuum)

Any ideas? No codes, going to run WinALDL tomorrow. I tried moving the timing a little but it didn't seem to help much. I assume it's running rich due to the new high volume pump but wouldn't the vAFPR just regulate the excess fuel back to tank?

Thanks

 

The timing seems OK. I am assuming you have a 305 with the stock injectors. I would try taking that vAFPR off and setting the fuel pressure to around 12 psi. I think with the fuel pressure at 14psi, the reduced vacuum and running under the stock chip you are probably running very rich at idle. How do your spark plugs look and how is car running above 3000 rpm?


PS I went to Round Rock high.

 

You're trying to run all that without a DIY PROM? Good luck...with only 15" of vacuum it's never going to run right....

 

Yeah it's a 305 with the stock injectors. I'll try the stock FPR and see what it does. I didn't think changing pumps would cause so many problems.

I went to Round Rock High as well, Class of 2000.

 

Run all of what without a DIY Prom? a mild cam, stock LO3 heads, intake, rotating assembly?? I had seen other members running the LT1 cam without a new prom. It had been running fine until I changed pumps. Strong vacuum and a decent fuel pressure sweep (11-16psi), just no fuel volume to hold higher rpms which is why I changed pumps. Maybe I'll look into DIY Prom, wasn't planning on it until new heads/intake.

Thanks

 

Ok swapped out the vAFPR for the stock one. Fuel pressure stayed about the same 15-16psi, though. Also, put a new tube on my vacuum gauge and it now reads about 17". Would a rich condition drop vacuum? I checked all vacuum lines for leaks, none.

I was thinking maybe I'm outflowing the fuel lines themselves. Creating a higher fuel pressure and thus the rich condition. This would support the fact that the fuel pressure stayed almost the same even when changing regulators or adjusting the vAFPR. Anyone else have a problem like this? Were TPI lines any bigger? Could I put some kind of voltage reducer on the pump to lower the volume some?

I'm going to try flushing the lines out tomorrow. Any tips on reading WinALDL data? I logged some data, but the only thing I recognized was a rich flag and EST code.