So iI found out last week that my fuel pump was heading south, so I replaced it with the Racetronix unit on Saturday. The car runs soooooo much better now I can't believe I managed to drive it for over a year with a weak pump(I had no clue it was bad because the car semed to run fine to me). Well, now that I have the proper supply of fuel my nitrous system isn't working. I have a ZEX dry kit jetted for 100 HP.

When it's activated the car flat out DIES. No popping or anything. It feels like someone slammed on the brakes, but as soon as you let off everything is fine. My only thought is that now that I have the proper fuel system, the stock injectors are locking up under the increased fuel pressure. Does this sound reasonable? I've head people talk about the stoock injectors doing this, but I never thought a 100 shot would be enough. What is the FP limit on stock injectors, and do you guys think I'm on the right track? Thanks!!!!!!

Izzy

 

First, I'd pull the solenoid lines and make sure it's spraying both fuel and nitrous. If you're just getting fuel, it'll fall on it's face like you describe. You might want to move this to the N2O section.

What pressures are you running? I ran my stock injectors over 80psi with no sign of lockup...

 

Stock injectors don't lock up at stock fuel pressure. Unless your fuel pressure regulator is shot, the system should be running at stock pressure. The stock RP injectors may "lock up" if you subject them to the 80-90psi required for the NOS dry kit, but its not a problem with a wet kit and stock pressure.

Have you checked your fuel pressure before and after the fuel pump install?

Oe thing to consider - if you selected the fuel jet with the low pressure produced by your weak/failing pump, now that the pressure has been corrected to stock, it may be flowing too much fuel.

 

I am running the ZEX DRY kit, which does indeed jack up the fuel pressure to compensate for the n2o. I am running stock fuel pressure, and I am using the jetting recommendations supplied by ZEX. These are the same jets I used with the failing pump and I had no problems with the setup, besides trap speeds declining as my pump got weaker. I don't know what my WOT fuel pressure on spray was before the pump, because I was afraid of damaging my engine to find out. I'll probably go out today and hook up the gauge and see what it goes to when I squeeze it. I'm still leaning towards injectors. With this kit there is only one solenoid, and if it's open it's spraying n2o and boosting fuel pressure. I checked the line going to the intake and it's clear, so something else is going on.

 

I just went outside and taped a FP gauge to my windshield and went for a drive. Pressure is normal (~40-46 psi) when N/A, so the pump is working as expected. I let the bottle cool a little so I would have more time to watch the gauge, and this is what I found: Upon n2o activation the pressure very quickly climbs to a maximum of ~90 psi. The car pulls hard up until the gauge reads ~80 psi, and then it starts breaking up or missing. By 90 psi the engine completely lays down like the key was turned off. I believe this supports my theory of the injectors "locking up". Yay or nay guys?

 

Sure sounds like it..... sorry - I missed the "dry kit" in your original post.

 

Thanks Injuneer! Will 32 lb Bosch injectors work well, or should I go with a different design such as the Delphi injectors?

 

LOL...as did I! People are still running dry kits around here??

 

Its the "ball and seat" type injectors (stock Rochester Products) that do no like high pressures. The "pintle" style, like Bosch, SVO/FMS, Denso, etc. will live happily at higher pressures. I don't know how the disc type injectors (Lucas) respond to pressure. Ask whoever sells the Delphi's because I think since Delphi was "spun off" from General Motors, they might make/sell a variety of injector types. Doesn't Racetronix sell Delphi?

I bought my NOS dry kit in early 1995, and at that point, no one was aware the stock injectors could have problems with the high pressures. Eventually, I toasted a couple sets of plugs, burning the ground electrodes completely off them. I switched to the Ford/Denso pintle injectors and never had a problem.

 

Thanks Injuneer! Racetronix does indeed sell the Delphi injectors. However, I think I'm going to go with a set of Bosch injectors since I work there and can get them for a very good price through one of my colleagues. I was originally going to go with the 32 lb injectors, but now I'm leaning towards 24 pounders because at the moment I really don't feel like having the PCM reprogrammed again. I also don't plan on modifying the car in the near future, so as long as the Bosch injectors will handle the higher pressures I'll be good to go!