I bought the 75psi FPR Mod pre-installed in a new FPR from PTP. Car started fine once installed. I then took it out for a test drive. As soon as I got on it in 2nd gear it was like I hit a brick wall. I could hear compressor surge and chatter under the hood. The Wideband was reading 10.2-10.5 but the car was going no where! Just sputtered, no backfiring. Just getting into it a little bit I noticed several lean stumbles.
I put the stock regulator in thinking I was just flooding the car and I have the same issue. Car ran fine before I did any of this.
Then, after reading the forums, I realized that the O-ring was missing form the stock FPR (sorry, I'm a noob and have never changed the FPR, I didn't know what to look for). I dropped the tank and there the O-ring was, floating around in the cavity that the FPR sits on.
I put the 75PSI FPR back in thinking I have everything fixed. Car takes a second to crank over. I take it out for a drive and get on it. Car pulls hard at first then suddenly about 4000 RPM I go lean as hell 16-17. I take it home and swap for the stock regulator. Take it out for another test drive and now the car is still sputtering and acting like it is hitting a wall when I get on it. Wideband reads 10.2-10.5 again but I'm going no where.
Sometimes it will sputter as soon as I go WOT and then I guess recover and finally go. The car is starting but very weakly. It acts like it wants to stall and then catches.
So to recap. Now w/ the 75psi regulator in I don't get the sputtering but I start out rich and then go horribly lean around 4k. Car starts normally but cranks longer than usual. With the stock FPR in the car start very weak and wants to die then catches. At WOT the car sputters but isn't lean.
WHAT THE HELL IS GOING ON?
The car ran perfect (a little lean, hence the 75psi regulator) before this. No hard starts or hesitations.
Did my Walbro magically die on me?
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Hahn 20g (was 16g) w/ DW 650s , W/M, Custom 3" O2 Housing and some other goodies.
No returnline!
No, not yet. The stock FPR is installed right now and it's still acting weird. You think the LT and ST fuel trims are all whacked out? I will try resetting the PCM.
when going from ~58 psi to 75 psi, I would imagine that the car would have to learn it's fuel trims ... 17 psi is a big change to say the least
when having "small" problems like this, I usually try resetting the pcm first ... obviously you'd want to check your CEL's (if you have any) prior to setting the PCM, so you know what the CEL was related to
notice any leaks? is the o-ring for the FPR in tact? not torn at all? rough start seems like there might be some fuel pressure problems (i.e. leaks) ... do you have to let the pump prime when the starting the car or can you just turn the key & start it?
I can just turn the key to start it. I double checked the O-ring on the FPR. It was in tact, not torn. I have had one torn before. Anyone ever had any issues with the o-rings from PTP? I wonder if it is sitting in there all the way.
Like I said earlier, sometimes it will hesitate and then finally "catch" and go and my AFR's are 11.2 running 24 lbs on the 20g. I would imagine that if I am not getting the right fuel pressure I would be lean as hell. I will check the FPR again later but I just don't understand what is going on. I should have just left the damn thing alone.
I looked at some pics of other user's FPR and I think something is wrong with my stocker. I can fit 2 O-rings over the end of my stock FPR. Some of the pictures that I saw only looked like it had room for 1. Does the neck of the FPR move in and out? How does it work?
You definitely have a fuel supply issue. And the way it sounds, it sounds like the o-ring on the FPR isn't seating correctly and you pump may be on the way out.
If you can maybe fit 2 o-rings on your stock one then something is wrong with it and its useless. The o-ring needs to sit against the Black plastic flush and as close to the tip(without sitting on the edge) as possible. Otherwise when you install the FPR the o-ring will move back instead of seating correctly into the neck.
Basically when your car lean stumbles its sucking air.
Now, that being said. You probably also have a fuel pump issue now. Your pump was probably on the way out (i've gone through 2 walboros so far of no fault of my own) and when you put more pressure to it, it killed it, or it can't handle the increase in pressure.
You also, probably wigged the PCM out and it was trying to learn the fuel curves at part throttle but with fuel pressure unstable it couldn't do it correctly.
Your sluggish starting is because Fuel pressure is too low or bleeding off. to be sure, hook up a fuel pressure gauge (you should be able to get one from sears or the autoparts store) and monitor your fuel pressure. If it bleeds down quickly or goes straight to zero after priming then your o-ring isnt seated correctly. If your fuel pressure is low when running then you have a supply problem or the o-ring is screwed. If you tape the gauge to the windshield and go wot with the fuel pressure starting off stead then falling as rpms increase then your pump cant keep up with demand.
If you cant get a gauge then what I would do is, install the new FPR making sure the o-ring is seated correctly. Use some type of lubricant(like pb blaster) on the o-rings. Then take the car out for a drive. If it still goes lean on the top end, your pump is shot and cant keep up with the demand (probably why you were leaning out on the top end to begin with).
However, i would advise getting rid of the FPR mod all together and doing a return set-up and bottleneck fix. Running 75psi all the time never seemed, in my opinion, like a good idea in reliability terms.
Bryan
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2005 - Flame Red SRT-4 317hp/367tq
P.M. Me for details on installs, maintenance, and repair work in the North Georgia Area.
Great info, I really appreciate it. What do you suppose is causing the car to sputter when I go WOT. Once the sputtering starts it's like the car is in neutral, I'm not going anywhere. If I partially build boost, say 8-10 lbs by going partial throttle before I go WOT then it comes up to boost normally with no chattering and my AFRs are OK.
How can you tell a Walbro is going bad? It's not whining any more than I am used to.
Well, I found one problem. Something is wrong with my stock FPR. I don't know if I messed something up reinstalling it or what but the black plastic part that surrounds the stem was stuck way too far in. I bought another FPR from a member on the forums and I am going to be installing this soon.
My Idle is real bad right now and I can't get on it at all. I think the O-ring is not sealing properly because the black plastic piece is not making a snug fit up against the O-ring at the tip of the stem on the FPR. I will post some updates.
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I'm Stuck: car is running weird after FPR install
, W/M, Custom 3" O2 Housing and some other goodies.
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