87 NA2T - Starting issues still

When you turn the key to the ON position but don't start the car, do you hear the fuel pump run for 5 secs? What's the fuel pressure at that point?

yup, the pump does its prime in the ON position like normal. I haven't checked the actual pressure at the manifold as I don't have a pressure gauge, however I am going to have my Mech do that at the shop. I was thinking maybe I need a fuel pump with higher pressure. according to Nissan parts, all the pumps for all Z31's turbo and N/A are the same. however, I know some have different PSI ratings, according to what I have seen on 300zxpartsforyou.com

something else I forgot to mention is that when I swap and plug my 87 N/A ECU in, (for ignition start testing purposes) it seems to start much better and quicker (cranks and fires faster than the two turbo ECU's) I don't know why this is. maybe because I am still using the stock n/a harness?
of course it idles like crap (to be expected with the turbo idle valve installed)

I'd try to eliminate everything else before going down the ECU rabbit hole - not that it's impossible that it's the ECU, it's just that there's lots of other stuff that's more likely and can give you a good solid diagnostic.

1) My best idea is that you might not be getting sufficient fuel pressure to cold start the car, and just enough when warm. All stock fuel pumps should be able to provide stock fuel pressure as it's the FPR that actually regulates it. For any stock-ish applications you don't need a better fuel pump, you just need a stock one that's working correctly. The test is really easy, at idle you should have 30 or a bit higher, and when you pull the vacuum line off the top of the pressure regulator it should go up to 37-40. If the pressures are lower then your fuel pump is probably screwed, which sucks because the fuel pump is a non-trivial job. It's worth disconnecting all the fuel lines and blowing high pressure air through them to see if any crud comes out before you do that lol.

2) Make sure you have the right plugs in there and while you're doing that, do a compression check. I did an NA2T on a moderately tired motor and blew the rings out on #1 and #4 in a few thousand miles at like 8PSI. I wasn't even detonating, my ring seal was just dependent on carbon and it couldn't handle boost :P. Really hard cold starts and okay warm starts can also be associated with bad compression. Where are your valve covers going to? Breathers, PCV, catch can? Got oil coming out?

yeah, I agree. I'm not chasing ECU's or anything, I just happened to have another 87T unit in addition to the 84T that I used for the swap. I thought maybe the 87T would be better since the early modules had the lean/surge issue thing at startup. and those cars evidently had a little component under the battery to help aid in that problem. my 87 does not have this as far as I know.

I was thinking that maybe my fuel pump might not be working correctly, but it was working fine before the swap. I will have to check the fuel pressure to the manifold for sure, but I do know the pump is kicking on.
when I replaced the pressure regulator (Nissan new) it seemed to start up a little better. I know the pump will need to be removed from the tank which has to come down… crap well that's the job lol.

as far as the engine goes, I had the motor rebuilt last year with new rings, pistons, valves and seals, gaskets and other associated parts. I got NGK turbo plugs (left them at the gap they came with) and performed the proper engine break-in period at a slow pace for the required miles. the motor ran like a champ after that!… and no more missing/burning oil or engine misses (this was before the NA2T conversion) and also prior to the turbo, the car never had hard starts.. I mean, ever. the ignition seemed to be the ONE system on that car that never had issues, until now.
I knew the engine had a major internal problem, so I made to sure to have it rebuilt prior to going turbo.

the valve covers are going to everything that was designed stock. no breathers or open ports. the idle hose and surge hose coming from the intake charge pipe and the PCV, all there where they should be. no catch can. I did remove the AIV, charcoal canister, and EGR systems (when it was N/A) except the charcoal was done after turbo. all open vacuum pipes have been blocked off and un-needed hoses removed.
I wanted to ensure a vacuum leak free system. I just installed a boost/vac gauge in the cockpit and when the car does start, it shows 10 PSI of vacuum at idle.

can I ask, when your engine blew, were you running an intercooler or anything? mine is completely stock, no cooler. just a new 2-core radiator. I'm worried about mine going due to the hot climate that is now at my location.

You REALLY need to do a compression test but If you have 10in/Hg at idle and you've eliminated vac leak possibilities, you may as well make a date to pull the motor. Your rings are shot unless you have a big vac leak somewhere. Vac at idle on a VG3x should be 18-22 I think, for reference I have a freshly rebuilt block and my vac at idle is juuuust under 21. Even my totally hosed motor that had ~90 compression in two cylinders and ~120 in another was still pulling 14 at idle.

(For reference, I just blew crappy old ring seal with new boost, I wasn't detonating.)

hey Frozen,

I really appreciate your replies. thanks for that. I am going to have the compression checked, but I don't think my rings are shot. when the engine does eventually start and finally warms up, it runs good. sounds good. no misses or hesitations or smoke or anything. and when I drove the car the last time out on the freeway, it ran well. so it seemed, nothing abnormal anyways. and she stayed cool. anyways, I will post the compression results. I do know that my idle control valve makes a hissing, vacuum-like noise when connected. if I disconnect the electrical connector, that noise goes away. don't know if its vacuum related or not. oh, this car of mine.... sometimes I wished I would have never messed with it. used to drive like a champ… just not very fast. haha

Bonny