Installed a new Fuel Pump today..

[hamish_18]

Hi All,

I think I have a couple ideas on this, but wanted to pass it through you all to get your thoughts. I did some searching, but couldn't really find any threads really sounding like they were having the same issue as my friend..

Over the last year or so he has been running a Toyota 2rz-fe engine in his old 84 toyota pickup. It is running a garrett gt35r turbo with 550 cc injectors, running around a bar of boost. Well he has pretty much self tuned his diypnp ecu. He has continued to use his stock fuel pump as well. Well he had the ecu professionally tuned, and didn't even think about the fuel pump. Shortly after getting it tuned, say a couple weeks later, the pump went out. He replaced it with a walbro 255. The AFR's are now extremely rich. low 9's at idle, and afr's don't get much past 10.x...

He didn't think it would make that much of a difference while not even making boost. It definitely makes sense that a new pump will flow more than a stock fuel pump naturally, but that is a pretty big difference..

What are your thoughts one possible fixes?? Is it a terrible idea to change the req. fuel number? Or could we just scale all the maps by the same percentage? Would the numbers match like that from how the tune was prior to the pump failure? Or is he screwed, and just lost out on all that money he spent to have it tuned and dyno'd.

Thanks for and suggestions!!!!!

-Chris

[Blown88GT]

You didn't say what the fuel pressure was before & what it is now.
Fuel pressure is too high because return line is too small. AFPR might help.

[billr]

Has fuel pressure been logged; before the pump was changed, after the pump was changed, or during the dyno tuning? Having the tune change so much with the new pump hints that the old pump wasn't maintaining a steady FP, so the injector flow was continually varying and the req_fuel value was continually varying. Yeah, the dyno tune is probably of dubious value now.

I urge you to flow the injectors, get the present correct rate and req_fuel numbers, and go from there. Using req_fuel as a scaling factor can be made to work, but will result in a VE table and other parameters that are also fake, not like a real engine, and be harder for anybody to make sense of if you want help. And, playing with the req_fuel won't save the dyno tune if FP was varying before. The dyno tune VE table would have been based on that "variable req_fuel" and there is no practical way you can account for that now.

[Yves]

You didn't say what the fuel pressure was before & what it is now.
Fuel pressure is too high because return line is too small. AFPR might help.

Sounds like it.