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Really Confused, Out Of Ideas And Need Help

Drop_Kick

By Drop_Kick,
in Engines & Forced Induction

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Drop_Kick Apprentice

Drop_Kick

Posted
Posted

I've run into a problem while getting the car tuned and we're currently really confused and out of ideas..

The car is a r32 gtr with 2860 -5's, id1000 injectors, z32 afms, aeromotive 350lph fuel pump, power fc ect

The problem started when I swapped to e85 and had sard 700cc injectors and 044 pump, we had the injectors at 90-100% duty and it was still stupidly lean on boost so we thought they must be some how running out (should of been enough fuel for 350kw).. so I swapped to id1000's. After that the car still did the same thing, it was fine on vac but as soon as its on boost it goes real lean, no matter how much fuel we throw in (we had the 1000's at 90% duty and it made no difference).

So then we thought fuel pump,, checked the flow and it holds 40psi to start off with, goes up to 60psi then drops off back to 40psi around the 4k rpm mark.. so I changed the 044 to the aeromotive 350lph pump. It didn't make a any difference at all, even with a fuel reg and upping the pressure..

We have also checked voltage drop at the fuel pump and that's fine, timing is spot on and isnt a tooth out or anything like that.

The problem is boost dependent and does the same thing no matter how much or less boost, my afr looks like a nike tick..

MrStabby Grand Master

MrStabby

Posted
Posted

So then we thought fuel pump,, checked the flow and it holds 40psi to start off with, goes up to 60psi then drops off back to 40psi around the 4k rpm mark.. so I changed the 044 to the aeromotive 350lph pump. It didn't make a any difference at all, even with a fuel reg and upping the pressure..

We have also checked voltage drop at the fuel pump and that's fine, timing is spot on and isnt a tooth out or anything like that.

The problem is boost dependent and does the same thing no matter how much or less boost, my afr looks like a nike tick..

Sounds a lot like fuel pressure regulator. It changes the pressure in the fuel rail to compensate for pressure difference across the injectors - that is, boost and vacuum. So if its not working, you will get lean as you get boost and leaner the higher the boost is.

Check the vac signal to the FPR.

Also - you have changed the fuel filter right? E85 will clean up your fuel system and the crap it cleans up ends up in the filter. When you first run e85 you may need to change it a few extra times.

Drop_Kick Apprentice

Drop_Kick

Posted
  • Author
Posted

Sounds a lot like fuel pressure regulator. It changes the pressure in the fuel rail to compensate for pressure difference across the injectors - that is, boost and vacuum. So if its not working, you will get lean as you get boost and leaner the higher the boost is.

Check the vac signal to the FPR.

Also - you have changed the fuel filter right? E85 will clean up your fuel system and the crap it cleans up ends up in the filter. When you first run e85 you may need to change it a few extra times.

Yeah i've tried a tomei fpr and got the same results, even when we raised the fuel pressure. we where taking the vac reading for the dyno from the top of the fpr.

I've also changed the filter thinking it might of been that aswell.

Check vac line and wire the pump direct to battery if its not done already.

Yeah I might try that and wire it direct to the battery, we where seeing 11.2-11.4 volts at the resistor.

Also check that the fuel tank is able to breath.

I havn't checked that yet, but will do.

Thanks for the replys guys.

Drop_Kick Apprentice

Drop_Kick

Posted
  • Author
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there is your problem then mate. i am seeing bout 13.8 volts at the pump.

Thanks mate, you where right. I had the auto electrician look at it and he got a reading of 8-9 volts, so I had it rewired.

The car now makes a healthy 352kw @ 22psi

MrStabby Grand Master

MrStabby

Posted
Posted

how much did this cost ya?

IIRC there's a DIY, but all you need to do is run a new earth. The earth gets switched through the fuel pump control module, which can fail. But a direct earth may also be a waste of time if the module is correctly passing full earth when you are under load. Testing the voltage at the pump at idle is not a valid test, as the module only supplies a soft earth (ie via a resistor, so not full voltage) at that time.

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