Silvertop Rb20det Lean/cut issue

[Empire087]

Ok so ive been troubleshooting My car for the last 6-7 months, Basically ive had an issue that over a short period of driving:Generally 5-10 minutes my car will start a lean cut out and slowly get worse until its a 2500 rpm cut and it will sometimes climb over that. It happens at around 4k rpm, but it comes on after some spirited driving sometimes faster than others but always comes. Essentially I will get on the throttle for a few times and do a few good pulls then the car will start just going max lean all the time when throttle is applied. The first bit of it is at 3700-4000 rpm, and its it will lean bog Max at 18 afr ---. Then it will get to the point where you can barely give in any throttle without it cutting out Like 1/16 of the pedal. It will always happen, sometimes it takes longer than others. So far ive tried/replaced: ecu(Mine is blitz access with custom rom R32mt, One i have is a rom tuned for an r32 a/t)No difference, Another cas NO difference, Brand new plugs, Clean/taped coil boots, Different Ignitor NO difference, Another Maf NO difference, 98 sentra cts, 98 ka cts both no difference, New 255 fuel pump(2), Different Fpr(both tested good), multiple fuel filters, checked injectors all 14ohm, checked tps at .46 idle/around 5.0 wfo, and deleted my cold idle valve. The weird thing is if i restart my engine(Key all the way off) and turn back on the problem goes away for a little while but comes back as before. The car also starts like s***, not quite sure why, im pretty sure i wired the start signal in right.


Ive been struggling with this for the last 6 or so months i really need some help guys!!

[Yellow4g63]

Check your voltage.

[Empire087]

tps voltage? Car running it tagged at .46/.47 at idle and went up with throttle.

[Yellow4g63]

Battery voltage make sure your not running @ 12.8v

[Empire087]

Ok so upon cold start my battery while running was 14.12v
once the problem set in i was at 13.7
Did a on the vehicle alternator diagnostic at autozone and it said everything was ok.

[Yellow4g63]

It wouldn't hurt to rewire the fuel pump if you haven't done that. Put a relay on it and use the OEM power wire to trigger the relay and run a new power to the batter with a bigger gauge power wire.

[Empire087]

I forgot to mention that, its already done.

[Empire087]

Another thing i left out is that if i shut the car off while driving and turn it back on it will boost and drive just fine. It also cruises rich. Like 13.0 afr.

[xracerx972]

I'm willing to bet it's your wiring. Something between the fuel pump plastic connector/your aftermarket wired in relay and the pump itself is probably not making a good connection, or a dodgy one at best. A pressurized line takes a minute for the engine to die when the fuel pump stops working, it's not instantaneous. I'd use a multimeter and check for continuity / resistance and jiggle the connections or tap on the metal fuel pump cover to find the problem. After that, I'd check the grounds for the pumps wiring.

[Empire087]

Roger that, will take a look at it when i get home.

[Empire087]

Well i put a new 12v wire to my direct battery relay and it madr no difference. Heres a video of the problem. The fuel gauge may be way off. Ive been having problems with the ones ive been renting.

[xracerx972]

When I had a similar problem, it was the connectors inside the tank that spliced in my new pump. The pump can get 12v all day long but the second the ground starts losing continuity, the pump wont be working as hard. The system builds pressure when you first turn the car on as the pump briefly primes. Try recreating your problem parked with a multimeter attached to the pump, watch it get battery power when it first primes and after you start the car, watch the voltage to see it receives 12v or whatever your alternator is putting out. If your FPR is good and your pump is new, the only thing it could be is youre losing voltage to the pump. If your 12v is good, then it only leaves the ground connections in question. Youll see the voltage start faultering as the car starts running lean and then dies. Hope this helps.

** I put small jumper wires into the plastic fuel pump connector on the pump 12v and ground and plugged the connector back in so i could connect the multimeter and still have an operational pump.

[Empire087]

That may be it! When i did the battery direct mod for the pump i didnt change the ground at all. Fingers crossed, as i moved the ground to where im grounding the relay on the pump access port cover.

[Empire087]

Ok so i went out and drove the 240 again, still does it but takes longer? Restarting the engine still temporarily fixes the problem :/

I couldnt have wired the swap in wrong causing this could i?

[Yellow4g63]

It's crazy, The rewire of the pump should eliminate and flow problems the pump has because it's getting 12v and comes on with the stock power wire. Your fuel filter is new, so I'm at a loss as to why your car is leaning out. Did you use the right relay for the ecu? The two green relays near the ecu?

[Empire087]

Is this the only thing that could cause whats happening with my car? And yeah, should be a green relay. I will go double check here in a few minutes.

[Empire087]

Ok definetly green relays, today while i was out for a drive after it started breaking up a little that it wanted to die when i came to stops. And it came really close one time and then the problem again temporarily went away. I didnt have to restart the engine anything the rpm just got really really low. Thoughts?

[Empire087]

Ok so i did clamp off the return line and the pressure does increase to about 90 psi. However if i rev it, then the fuel pressure drops off incredibly fast and falls well below 20 psi. So this would point at the pump correct?

[Yellow4g63]

Anyway you can monitor your pump voltage? hook up some test leads to a volt meter and take a drive. It sounds like your pump is not doing it's job.

[Empire087]

I did check the voltage when it was acting up, and what i found was that it was about .5volts off from when the motor started. I dont think id lose like 225 lph for .5 volts though. Cold i was at 13.7 and warm i was at 13.2 at the pump.

[xracerx972]

That may be it! When i did the battery direct mod for the pump i didnt change the ground at all. Fingers crossed, as i moved the ground to where im grounding the relay on the pump access port cover.

I would suggest not using the OEM harness ground. Use this image as a guide http://www.enginebasics.com/Advanced%20 ... 0Relay.gif Except ground the relay and the pump both directly to the negative terminal of the battery. This is how I have mine essentially and this is what worked for me. You dont have to use a fuse, but for me, i like to play it safe, so I have one.