Rb25 fuel & spark no start

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Zkyline
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Car: 300zx. Rb25det swap

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First off this is in a 300zx but I know you 240 guys have more experience with RBs. Now this car was running and driving for over a year, so this isn't a wiring issue. Fresh rebuild, rb26 444cc injectors with resistor box wired in, rb26 power fc ecu, no start. I have spark at all 6 coils, and all 6 injectors click when the CAS is spun. I've pulled plugs and confirmed there is fuel on piston tops. I can crack the throttle and get a few pops but nothing close to starting. This makes me think the AAC valve isn't drawing in air (has 12v, clicks when being plugged in/out) but that can be resolved later.

Some of the last things I can think of:

Hydraulic lifters dry from fresh rebuild, no oil, compressing and not lifting valves enough to draw in air?

Timing difference between rb26 ecu and rb25. (26=20*btdc 25=15*btdc) would think timing slightly advanced/retarded would still start

Timing 180* out? All timing marks have been double and triple checked, used oem Nissan belt with the "cheater" lines. Counted teeth between crank/exhaust cam, and both cams. But possibly was at tdc on EXHAUST stroke?

Any help would be appreciated. Have a basic vid, I've since gotten a few "pops" as described above by cracking the throttle. But not close to starting.

https://youtu.be/d_6Isc5LAps


ca18det_boy
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Lifters shouldn't be dry, you missed a step when you (or whoever) rebuilt the engine....but that doesn't have anything to do with a crank no start. 5 degrees shouldn't make that much of a difference in starting. Is this a S1 or S2 CAS? Also, is this a new PFC to you or was it previously installed and running? Are the 26 injectors new to the game or were they previously installed and running? Essentially what I'm getting at is you're looking at one of 2 things....

1) The timing is off depending on which series you have. I believe you can be 180 out on an S2 but not on an S1 since there's a half moon to insure that you're never 180 out.
2) The ECU simply isn't set up to run your setup. You're looking at getting a tune or if you have the cheater software then you can play with the settings to get it to fire.

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Zkyline
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Car: 300zx. Rb25det swap

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Another thought, for someone running rb26 if they can help, is the AFM voltage. I have an SAFC inline that can manipulate the readings at the ecu, since the rb26 has two AFM and in running a big single and z32 AFM. If anyone knows what their voltage is, that would help, as I can select multiple different settings to get the desired voltage, just don't know what that needs to be. Again, it should run without the AFM plugged in even, so this is all secondary to it running.

ca18det_boy
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You have a PFC AND an SAFC installed? AFM voltage is 0-5V

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Zkyline
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Joined: Tue Aug 04, 2015 10:57 pm
Car: 300zx. Rb25det swap

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This is a S2 rb25. The injectors were good used ones, and doing a basic check with spark plugs pulled they all seem to spray fine when cranking.

The PFC has been initialized and should have a decent (run-able) base tune for the stock rb26 injectors.
Last edited by Zkyline on Tue Aug 08, 2017 9:23 am, edited 1 time in total.

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Zkyline
Posts: 123
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Car: 300zx. Rb25det swap

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ca18det_boy wrote:
Tue Aug 08, 2017 9:17 am
You have a PFC AND an SAFC installed? AFM voltage is 0-5V
Yes. I'm not using it for any corrections as far as +/- fuel just because it has a setting for this exact swap (single AFM on rb26)

Now is that just with ACC on? I can do a sensor check in the PFC and with the settings I have it at now it reads 0.39v

ca18det_boy
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There isn't a need to have both installed. Remove the SAFC and take it to a tuner for the proper settings.

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Zkyline
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Car: 300zx. Rb25det swap

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This is why I'm using the SAFC

Image

The PFC just has options for types, not for single conversion

Image

Either way like I said it SHOULD start and run good enough to drive to a tuner. Unless as you said the timing is somehow off.

ca18det_boy
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IIRC the 80 means 80mm. So 4 is for the factory rb25 maf, 5 is for a z32 maf, and 1 and 2 are for R32 and R33 GTR's. You still haven't answered questions that could/would help in troubleshooting your issue.

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Zkyline
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Car: 300zx. Rb25det swap

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I got it. Figured I'd double check it didn't jump timing. Pulled radiator and timing covers checked all my index marks, they were all good, but my CAS was out 180*. Put it in and it fired up.

ca18det_boy
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:bigthumb:


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