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33gtst Fuel Pump Upgrade, Now Running Rich, Fark!

admS15

By admS15,
in Engines & Forced Induction

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admS15 Grand Master

admS15

Posted
Posted

Hey guys. Decided to upgrade my fuel pump for e85. Was running a walbro 255 on stock wiring and working fpcm. Was feeding 250rwkw with AFR in the low 11's top end no problems.

I upgraded to dw340 lph e85 pump. Installed in same configuration as walbro and went for test drive. Ran well but was leaning out, top end AFR of 13+ was occurring. Was thinking this pump requires more voltage.

I went back home and rewired the pump with a 30 amp relay and wiring to the battery. Went for test drive again and ran well cruising around but extremely rich when on boost, I saw AFR of low 9's. Ran like shit, WTF.

Not sure what's going on.

I was assuming that my stock fpr would cope. Is it not able to?

Is it because I had the car tuned with the fpcm and now running without?

Maybe the walbro was weak and the car was tuned on low fuel pressure?

Any ideas and advice or explanation of what's occuring appreciated.

dr phil Collaborator

dr phil

Posted
Posted

Remember the check your rubber fuel return line in the engine bay for a restrictor, it feels like a hard bump, mine was down near the damper that turns 90deg. My rail pressure was out of control with a walbro 460 because of the restrictor.

admS15 Grand Master

admS15

Posted
  • Author
Posted

Remember the check your rubber fuel return line in the engine bay for a restrictor, it feels like a hard bump, mine was down near the damper that turns 90deg. My rail pressure was out of control with a walbro 460 because of the restrictor.

Thanks for that, I'll have a look tomorrow.
admS15 Grand Master

admS15

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Had another play around this morning. Couldn't find any restrictor in the return line. I went back to stock wiring, same lean result. I then grounded the pump -ve to take out the fpcm circuit and back to extremely rich again. At this point I'm thinking about putting the walbro back in, checking AFR again and seeing if the wiring changes have the same effect.

If the same thing happens I'm thinking possibly the fpcm is stuck in low voltage mode and was tuned like that. Thoughts please.

Moving forward, to correct the rich conditions with direct power, retuning will be required. Correct?

Ryno Experienced

Ryno

Posted
Posted

I had the same issue when I swapped out a Walbro pump for a Nismo. Even though both pumps are quoted as a similar flow rate, the Walbro flowed significantly less - I had to take around 10% of fuel out of the tune to correct the Air/Fuel ratio change.

admS15 Grand Master

admS15

Posted
  • Author
Posted

I had the same issue when I swapped out a Walbro pump for a Nismo. Even though both pumps are quoted as a similar flow rate, the Walbro flowed significantly less - I had to take around 10% of fuel out of the tune to correct the Air/Fuel ratio change.

Where your idle and cruise AFR OK or rich. Mine are fine, its only when on boost. I'm pretty hesitant on playing with the map myself at this stage. Did you take fuel out of the whole map or just parts of it?
Trex Grand Master

Trex

Posted
Posted

I had the same issue when I swapped out a Walbro pump for a Nismo. Even though both pumps are quoted as a similar flow rate, the Walbro flowed significantly less - I had to take around 10% of fuel out of the tune to correct the Air/Fuel ratio change.

the std fpr should adjust for this. sounds like your walbro was lazy.

admS15 Grand Master

admS15

Posted
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Stupid question maybe, but can't you just adjust you base fuel pressure off your fuel regulator.

Yep stock reg isn't adjustable but my idle and cruise are fine so even if I could adjust fpr it probably would lean out the idle too much.
Ryno Experienced

Ryno

Posted
Posted

Where your idle and cruise AFR OK or rich. Mine are fine, its only when on boost. I'm pretty hesitant on playing with the map myself at this stage. Did you take fuel out of the whole map or just parts of it?

Yeah the idle and light cruise wasn't too far off, the on boost part of the map required the largest change

admS15 Grand Master

admS15

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  • Author
Posted

Thanks for all the replies guys[emoji106] . I had a quick play with the master fuel trim and took out 20% fuel and it was still pig rich on boost. Time for professional help as I don't feel like losing a perfectly good engine due to me stuffing around with it, I also need the maps to be spot on as it will be the base for my flex tune. I'll update when I get it sorted.

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  • 2 weeks later...
admS15 Grand Master

admS15

Posted
  • Author
Posted

Just had the car retuned properly and it appears the old walbro was indeed on the way out. Now the shape of the map is a lot flatter, idle is better than ever, throttle response feels sharper and more importantly the car made an extra 12rwkw bringing it up to 260[emoji3], not bad for a HG 21u h/flow turbo. AFR is rock solid now across all gears and plenty of extra fuel available for e85 goodness.

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