Haven't been on here on years. Having some issues and figured I would ask for suggestions.

I recently completed a full rebuild on my 94 FD. The car was essentially stock with the usual bolt ons. It was smoking heavily, I suspected the stock twins, so me and my brother pulled the motor to upgrade to single turbo. Installed the typical GT35R, overhauled the fuel system with stock 550cc primaries and ID2000 secondaries in a KG rail, 3bar MAP, HKS Twin Power, PowerFC, all the typical single turbo upgrades.

When we pulled the motor out we saw oil- and lots of it- inside the motor through the exhaust ports. Turning the motor over by hand pushed oil out of the ports. We decided it was more likely the motor was smoking- not the turbos- so we elected to go for broke and rebuild it.

All parts spec'ed out great. My Brother ported the irons with the Pineapple street porting template and just "cleaned up" the exhaust port, nothing major. He was ported and rebuilt rotaries before.

I ordered an Atkins kit without apex seals and ran RA Classic 2mm seals per my Brother's recommendation. I clearanced the side seals myself for the first time to the recommended 0.002 gap with a long feeler. I think I did this right but I guess I could have messed it up. I used all new springs, Atkins solid corner seals, etc.

Anyways, fast-forward- we stacked the motor uneventfully, dropped it back in with a new clutch kit and ACT lightweight flywheel. Connected everything up, we adjusted the PFC. She fired right up instantly on the first try and idled like a champ.

I fixed a small oil leak but she would always fire up instantly cold, I just keep letting her run in the garage for 20 minutes at a time to heat cycle. First time I drove the FD it drove great.

Then I noticed it for the first time; I shut it down in my driveway to do a car wash, afterwards I tried to re-start her to pull her into the garage and she refused to start. At this point I'd say she had about 75-80 minutes of run time/idling and only about 40 actual miles. It just wouldn't re-start so we pushed her in the garage. My Brother suspected it was flooded so we pulled the plugs (brand new BURP9EQP leading/trailing) and they were pretty clean but it did has strong fuel smell.

Fast-forward to today, still runs great, cold starts awesome. Idle great and makes great power. I ran her for 500 miles before adding 5-psi of boost. At 1000 miles we went to 15-psi. It will spin tires into 3rd at 18-psi so I know the motor is making great power.

The hot start issue is also intermittent, but seems to happen more often than not. A few times I've been able to shut it off and it will restart fine (this has only been 2-3 times). Every other time it will refuse to start, or sound like it will just barely start and then loose it and go back to cranking.

My Brother is convinced it a tuning issue with the PFC. We've spent hours and hours dialing in the cranking map, timing, everything. Even used a known good map from another FD friend with a similar setup and it didn't work. I'm pretty sure it's the motor.

Before anyone asks about compression test- I've tried it with mixed results. I used a piston-style tester that is real cheap, I should probably get a better one. I'm also at 6100ft of elevation. First test with the valve removed and cranking showed 3 even bounces in each chamber to roughly 40psi. Max compression showed 75psi with the valve in, HOT. I know this sounds low, but another FD in the area with the same tester that runs perfectly (obviously including hot starts) only showed 68psi on the same tester. That car makes over 450rwhp. So, I'm not sure if it's the elevation or the tester, but I don't think I can rely on it.

Cliffnotes:

-Rebuilt motor with re-used housings, irons, rotors, etc
-Every seal/spring/gasket is brand new
-New fuel system, single turbo, all supporting mods
-Cold starts great, hot starts not so much

Thanks for the help, sorry for the long post.

 

Does it react differently at all if you add or remove fuel from the cranking map in the hottest couple of cells? Did you add an adjustable fpr, if so what is your base fuel pressure? What kind of vacuum are you pulling at warm idle? Make sure you didn't swap the fuel temp and water temp plugs in the harness, I think they are the same. When I had rough hot starts on my ported single turbo setup less hot cranking fuel and more cranking timing helped a ton.

 

Thanks for the reply,

We have adjusted nearly everything from the cranking map with the Datalogit. It's odd because sometimes it will help and the car will hot start fine, then the next time we drive it it's back up to the same old no-hot start routine.

I do have an adjustable FPR set to 45psi at idle with no vacuum (atmosphere). I haven't thought about adjusting that.

Vacuum for warm idle at 900rpm is -12"mm/HG. I know this sounds low, but remember I am also at over 6,000ft elevation.

I deleted the fuel temp sensor completely from the harness, the PFC reads the water temp correctly. There is no fuel temp sensor. I have zeroed out the fuel temp correction tables in the PFC with the Datalogit.

We have adjusted timing and fuel a lot during this process. More timing, less timing, more fuel, less fuel, all possible combinations I think.

My brother also says it could be a leaky primary fuel injector. We bought them used with unknown mileage. Could this be the problem?

Thank you again for the help, I will take any suggestions!

Thanks

 

absolutely.

 

Replace the primaries with known good ones or send yours out to get refreshed. Use new o-rings on reinstallation. First post explanation sounded like flooding and then you drop the bomb with questionable injectors. It's cheap to replace them or send them out.

Good luck.

 

Did you ever find out what your issue was?

 

Install a fuel kill switch,


When shutting the car off hot, try this:

Rev motor up to 3k rpms. Flip off fuel switch, floor the car as the motor begins to stumble/die. Your fuel pressure should now be nearly ZERO and you will have burned up all the fuel in the lines. If you have a leaky injector it shouldn't matter at this point.


To restart car, turn on fuel pump for a split second and turn it back off. Crank car, once it starts immediately flip fuel back on.


I have hard starting issues w my streetport motor. Sputters sputters sputters barely catches. Sometimes I just have to let it cool down first as it refuses to start unless I hook up an extra battery box for some more cranking amps.

THEN one day, my fuel pump wiring burned out (luckily at a gas station upon restarting). My car miraculously would start up with less effort but then obviously it would die immediately after. I came to the realization that the car was cranking up easier as it was running on residual pressure.