So car ha been working fine for a few months no issue. Then started bucking at 7k in boost. So I had a tune scheduled for IFO evenet anyway so I took it in and low and behold the car is leaning out at around 7k under boost. So of course we track down the obvious first. Checked both pumps and even hard wire the second pump to be sure and ut still is lean. IDC is going way up too seeing around 130%. So next we look at the injectors and swapped in new ones and same thing. Then notice then when the second pump is on the car goes lean wich is weird. The car had a stock FPR so now I am woundering if the stock FPR goes out will the extra flow of the pump just push the fuel pass the injectors to the return. That would explain why it was lean out at high rpm under a load with the second pump switching on. Anyone have any ideas. Remmber it was all fine for a few months so it has to be a failure some where. Maybe even fuel pump relay I dont know im stuck now after 2 days of trouble shooting plaeas someone.

 

Is the hobbs switch working as it should and providing the full voltage to the second pump? What PSI is the hobbs set to?

 

We eliminated the switch all together and hard wired the pump, just to make sure it was coming on. It goes lean with both pumps on and IDC shoots up. We are thinking the stock FPR has taken a crap and is allowing fuel to bypas injectors when the second pump comes on because of the increased volume. Does that make since or am I overthinking it.

 

In that case it may have crapped the OEM FPR out... I know when I hardwired both my pumps it overran the regulator at idle anyway even with a drilled siphon, which is why I went with a hobbs kicking in at 15 psi... an OEM FPR should be quick and easy to swap over if someone in your area has one you can borrow for a bit...

What pumps? walbro 255s or something else?

Inline fuel filter?

 

It's a buschur double pump setup and not exactly sure about the inline filter. My tuner is going to do a gauge setup so he can check FP. He has an after market FPR and if it checks bad then he will swap. Yeah my car leans out at idle with hardware also.

 

One of the pumps might be crapping out... mine DIY DP which has been on the car for 3 + years now started leaning out after about 6 pulls and I determined that one of the pumps was on its way out... swapped in new walbro 340 pumps but have been deployed so much haven't had time to see if it fixed the issues...

 

Both pumps are pretty new maybe 1k miles on them. The car runs perfect until the second pump comes on. Even at idle. Car still pulls over 600hp but just goes lean with 2 pumps on