[jrscgsr97]

I've been having this problem for a little while now, but it's lately it's been getting worse. I have a jrsc on my 97 gsr and when I give it a decent amount of gas during boost the car starts bucking or jumping, my air fuel gauge goes crazy, and boost stays constant at 6 psi. Once the car gets into vtec it stops it stops bucking and pulls normally. Another thing is after I've been driving for a while the problem completely goes away, but once I let it sit and get cold again or if I put gas in it the problem returns. I figured it had something to do with the ignition so I got colder plugs, thicker plug wires and replaced the cap and rotor. The only thing I can think of now is getting a better fuel pump. I just have the fmu that comes with the kit as a fuel set up now. Does anyone have any idea what's going on with my car? Any help is appreciated. TIA.

 

[CKidd]

I'm no expert, but I had similar problems in the past. What is your setup? My problems were all fuel related. Too much or too little. Do you have larger injectors? Describe your setup, and maybe I'll be able to help.

 

[jrscgsr97]

I only have the fmu that came with the supercharger kit. Everything else is stock. I can get a good deal on a walbro 255lph pump... will that work well with the jackson racing fmu?

 

[CKidd]

Yeah, that will work well. Did you check your plugs? Mine fouled, and my car ran like crap. However, I was/am running 310cc injectors. My car hesitated under boost before, but it was because the shop that worked on my car hooked the wrong vacuum line to the fmu, so my fuel pressures didn't raise under boost, causing a detonation problem. How about your timing, did you retard it?

 

[cspina]

I would also check the installation of the tps circuit or map controller, it sounds like you are having problems in the transition area into boost, very common with the JR kit, I would say back the timing to 10 degrees btc, then run the static fuel pressure at around 60 psi and see if the problem goes away, in the mean time check your plugs like ckidd said, then as the car smooths out, start adding timing back, at that point bring the car on a couple of runs, did it stay smooth, then it is time to knock the fuel down in increments of 2 psi (you will notice a better midrange power band), you are then roughly tuned through your means, I would not get an upgraded fuel pump at this time the car is running great on the top end so I do not believe it is leaning out due to insufficent flow capablity. Again recheck all your vaccum hose routings per JR instructions, trouble shoot your tps circuit or map mod, then set the timing and fuel to the spec above, if the car smooths out you solved the transition problem, then tune it out yourself....Good Luck

 

[jrscgsr97]

It ran great for 3 months and I never touched anything. I replaced my plugs and they seem fine, changed the wires and cap and rotor. Would the timing suddenly start causing this problem. It ran great for almost the entire summer, and the problem gradually started getting worse. Is the jackson racing fmu adjustable? Could that be going bad?

 

[CKidd]

Yes, the JR FMU is adjustable for your static fuel pressure, but your rise rate is not. Also, from what I have read about the JR FMU, it is notorious for going bad. However, I must admit mine worked fine. The Cartech FMU is a much better unit and allows you to adjust your rise rate. That is what I run now, but I only switched from the JR FMU because I needed to be able to adjust my rise rate with the larger injectors. If you don't have the JR map controller, I would strongly recommend getting one. In the mean time, if you have checked everything else, I would also check the JR enrichment relay (the map controller will replace this). Maybe it went bad, and your fuel pressures are not correct.

 

[AcidLotus]

I would highly recommend the JR Map controller as well and/or the Cartech (got mine installed, dropped 2/10ths off my time just by adjusting the rise rate!). The Cartech isn't exactly cheap, but it's worth it. I too have heard that the JR FPR can go bad, although I never had a problem with mine.

 

[jrscgsr97]

So if I pick up this 255lph fuel pump, the map controller, and a cartech fmu you guys think that should solve the problem. Where can I get the cartech fmu at and what's a good price for one?

 

[cspina]

If the car ran fine for months and something is fouled now I would say troble shoot before you just start replacing, you are going to spend money for no reason, fuel pump is for higher boost applications its a safety device, not needed for larger injectors either, it is mainly an add on to support real high fuel pressures for stock injectors (smaller flow rate you fool it by pushing more in it thus more stress on fuel system not a good thing, but a common thing), yes get the map controller it makes the transition into boost smooth as a stock FI car (it sends the car into open loop mode at boost onset, thus the computer is not tring to fuel an extremely high O2 content when the tps sensor is telling it it to stay in closed loop mode. The computer can not understand why at 35-40% of throttle position the car is seeing so much air, which in turn will display a CEL.) I first would trouble shoot the fuel enrichment relay to see whats up, it may not be the problem and to test if the jr fmu just install a fuel pressure guage on the hose going to the fuel rail (not the vacc/boost line) and push the throttle quickly does it increase or not. I believe your problem will be solved if you just investigate further into the componets you have running so far, since the car had ran great before.

 

[jrscgsr97]

the cartech fmu, the map controller, and the fuel pump are all things I should have in the future anyway if I wanted to up grade the boost so I figure if I'll get the things anyway. It seems to me like it's probably the fmu. It feels like it rapidly increases and decreases the fuel pressure until it gets to about 6k rpms and then the pressure stays increased.