78 280z Severe Driving Problems

[kinser86]

We were able to perform the test tonight. I am going through the videos/data to do a formal post, I haven't given up yet.?

[kinser86]

Alright here are the results. I had to assume 188cc/min at 12VDC so a 30 second flow should yield 94mL. We ran a couple of test, not much deviation between then data groups. The second video shows what the PSI at the rail was during the test as well as the quality of the return from the rail. I even mention it in the first video. The gas is not bad, it has some 102 octane in the tank, that is why it is orange.

[jonathanrussell]

Once you solve this, I think that this thread should be a sticky or pinned or something. If nothing else, it shows how to go about diagnosing EFI really well.

Great work!

[Zed Head]

The work is well done.  Bummer though that nothing dramatic is showing up.  Could be that the injector functions aren't right, that they aren't opening rapidly, maybe sticking at low frequency/RPM.  That would be the benefit of a dynamic test.  I showed my results from a set of injectors that actually worked well on the engine and they were much more unbalanced  than those.  So even though the volumes aren't balanced for yours the engine still shouldn't have the problems it does if it's just a clogging problem.

Seems like a new set of injectors would be in order since those aren't flowing evenly.  But, considering all, it might not fix the problem.  But, it might.  Or it might not.  Who knows.  For the record, the fuel pressure on the gauge is still too high, which partially explains why most of the injectors flowed over 94 cc.  I have another set of injectors from a 1978 280Z that are old and rusty and sat on a non-running engine for 10 years.  They flowed perfectly even at full flow, for all 6.

Sorry you're not finding that smoking gun.  If I had been there when you did that test drive in the video I would have cranked the potentiometer to high resistance to make sure that it wasn't a lean problem.  Sometimes you just have to try stuff.  Anyway, I don't think I'd put those injectors back on for a permanent fix.  They're not right.  Maybe for more testing though.

[Zed Head]

One more thing - the Nissan injectors just spray a thin stream, no cloud of vapor.  So, your injectors might not be stock Nissan anyway.  Have you checked resistance on them?  Maybe somebody installed 16 ohm injectors.  I looked back at your first page and I see voltage but not resistance.

p.s. I have a set of OReilly Auto BWD injectors that I bought and ran for about a year. I also have the set of 78 Nissan injectors, old and rusty.  I actually like them better.  I could ship them out to you for not much.  They're just sitting in my garage.  I ran them on the engine and tested them, but switched to a different system when I was fighting hot-start issues.

Edited September 12, 2018 by Zed Head

[kinser86]

7 hours ago, jonathanrussell said:

Once you solve this, I think that this thread should be a sticky or pinned or something. If nothing else, it shows how to go about diagnosing EFI really well.

Great work!

I hope others can learn from this too. ?

6 hours ago, Zed Head said:

Seems like a new set of injectors would be in order since those aren't flowing evenly.  But, considering all, it might not fix the problem.  But, it might.  Or it might not.  Who knows.  For the record, the fuel pressure on the gauge is still too high, which partially explains why most of the injectors flowed over 94 cc.  I have another set of injectors from a 1978 280Z that are old and rusty and sat on a non-running engine for 10 years.  They flowed perfectly even at full flow, for all 6.

Sorry you're not finding that smoking gun.  If I had been there when you did that test drive in the video I would have cranked the potentiometer to high resistance to make sure that it wasn't a lean problem.  Sometimes you just have to try stuff.  Anyway, I don't think I'd put those injectors back on for a permanent fix.  They're not right.  Maybe for more testing though.

The statement in bold summarizes how I approached everything with respect to this car. ?? Regarding the fuel pressure, really the only solution here is to replace the regulator on the rail or change the fuel pump back from the walbro. Considering they are about the same price, I would go with a regulator first to see if that helps.

6 hours ago, Zed Head said:

One more thing - the Nissan injectors just spray a thin stream, no cloud of vapor.  So, your injectors might not be stock Nissan anyway.  Have you checked resistance on them?  Maybe somebody installed 16 ohm injectors.  I looked back at your first page and I see voltage but not resistance.

p.s. I have a set of OReilly Auto BWD injectors that I bought and ran for about a year. I also have the set of 78 Nissan injectors, old and rusty.  I actually like them better.  I could ship them out to you for not much.  They're just sitting in my garage.  I ran them on the engine and tested them, but switched to a different system when I was fighting hot-start issues.

The injectors were at 2.4Ω and 2.3Ω, so they were definitely not 16Ω. Sorry those were not included originally, I need to update that data sheet. We had the injectors serviced with Fuel Injection Specialties and the nozzles were replaced as part of the service(they used to not be black tipped). That may explain the mist/vapor appearance versus the stream appearance.

I would definitely be interested in a set of injectors that have a known past. PM will be on it's way shortly! Thanks for the input everyone, this is a journey ? 

[Zed Head]

I saw your PM.  Let me go take a look at what I have.  The 78 injectors are still on a rail, sealed, so might still have some wet fuel inside.  I'm sure I could fit them in a flat rate USPS envelope.

[kinser86]

22 hours ago, Zed Head said:

I saw your PM.  Let me go take a look at what I have.  The 78 injectors are still on a rail, sealed, so might still have some wet fuel inside.  I'm sure I could fit them in a flat rate USPS envelope.

Thanks! Just let me know. 

I have been thinking if I am going to replace the FPR, that I should go with a Pallnet rail with an adjustable FPR. This was going to be a modification down the road but given the circumstances and cost associated with a stock replacement, the Pallnet rail would be closer. I would still use the factory barb style injectors. Just a thought.

[Zed Head]

Wow, injector prices have really gone up.  BWD even changed the color of theirs, they're not green anymore.  Give me time to ponder.

I wonder if you shouldn't get back to Fuel Injection Services in the meantime.  Your test shows the reconditioning was not effective, they are unbalanced.  They didn't replace the nozzle, that part is called the pintle cap.  It doesn't affect the spray pattern unless it's the wrong one.  The only replaceable parts on these fuel injectors are the filter screen in the inlet and the plastic pintle cap.  They are permanently swaged together during assembly.  Can't be disassembled.  Reconditioning really just means cleaning.  They should have checked the flow balance on their own equipment.  Usually those places give some documentation showing what they got.

[kinser86]

I have been weighing some options here.. going back and forth between switching rails to a Pallnet style with an adjustable FPR or sticking stock. Right now a replacement fuel pressure regulator (Bosch 64018), is available from rockauto and Amazon Prime (believe it or not). If I can't overcome the fuel pressure, then a lower flowing pump would be in order, yanking out the walbro 255 to something less. This would only leave me with the injectors as the variable in the fuel world.

Rockauto has a few injectors available, but I would not go re-manufactured if I'm trying to eliminate some variables of 'what ifs'. Granted I intend on running the same test as before prior to installing the rail. That will provide a degree of confidence.

We have found some good symptoms with the high fuel pressure, unbalanced injectors, and vacuum advance routing. But what if after this next round of parts, the car is still rough. Is it then time to look for an ECU/AFM pair and try then? I'm trying to find the smoking gun between the lines, again going in circles as I do. 

Thoughts?

[Zed Head]

Take the FPR out of the picture.  Connect the fuel rail supply line to the fuel return line, with the gauge plumbed in.  Run the pump.  If you don't have pressure then it's not the pump.  It might be the FPR.  Or a restriction in the rail.  Bypass the FPR on the rail and run another test.  Break the system down in to its parts and something will show up.

Hopefully, eventually, as you're working on the individual sub-systems you'll have a realization about something that's not right.  You've kind of gone past the original finding that swapping injector connectors had no affect.  Which might have been a clue that you had some injectors not opening completely.  Which might be supported by the varying flow rates at wide open.  One or two might be gummed up.

I have my old BWD injectors from OReilly Auto with 10,000 miles on them.  Kind of waiting to see what your plan is.  Did you contact the rebuild guys?  Seems like they owe you something.  Maybe they have a couple of injectors that they can give you to make up for the bad ones they said were reconditioned.

 

[Zed Head]

On 9/11/2018 at 8:39 PM, kinser86 said:

 

On 9/11/2018 at 8:39 PM, kinser86 said:

Alright here are the results. I had to assume 188cc/min at 12VDC so a 30 second flow should yield 94mL. We ran a couple of test, not much deviation between then data groups. The second video shows what the PSI at the rail was during the test as well as the quality of the return from the rail. I even mention it in the first video. The gas is not bad, it has some 102 octane in the tank, that is why it is orange.

 

 

 

In post #42 you said that swapping 2 and 3 had no effect.