Okay, I have been having an AFR consistency problem under boost for a long time now and at first I think it was tune related but now I feel like I'm getting close to solving the problem. You can see my thread where I think it was tune-related here:

https://www.evolutionm.net/forums/ev...onsistent.html

So, I tried everything, switched maf, spark plugs, boost leak tests, tuned, etc. Finally, I ghetto-rigged a camera and flashlight underneath my hood and recorded my fuel pressure gauge to see what fuel pressure was doing under boost/load. It wasn't holding fuel pressure under boost, it was dropping off even though boost was rising/staying consistent. So I went and bought a Aeromotive A1000-6 fuel pressure regulator, hooked everything up, triple-checked the boost line from intake manifold to regulator, and did the same test again. It seems this time, it was holding it SOMETIMES but not all the time. It would drop off sometimes like it did before, causing my AFR's to go lean.

So my fuel pressure isn't consistent under boost/load. I have the new blue relay from mitsu, could that be failing? Has anyone experienced them failing? I find it weird it would work sometimes and not work other times. I really can't think what else it could be. I have a walbro 255 fuel pump, ultimate racing fuel filter/pump kit, and my fuel pressure is about 40 PSI at idle. It's only under boost and load that the fuel pressure messes up at seemingly random times. Sometimes it holds fuel pressure, other times it doesn't, making it very difficult to properly tune my air/fuel ratios.

I was thinking about just making the fuel pump run 12V all the time, but I don't know if this will cause any major problems or not. Does anyone else have any other suggestions/ideas on what I could do? If I should do 12V all the time or not? Any input is greatly appreciated.

Thanks!

 

why dont you get a DMM and see if the voltage to the fuel pump drops?

or just hard wire it temporarily and see if your problems go away...

maybe the pump is on the way out?

 

or there is a leak between the fuel pump and the fp housing withinth fuel tank....

 

I will try the DMM route soon and see if that works....as for the possibility of a leak, it's of course POSSIBLE but wouldn't you think the problem would always be present and not just happen part of the time? Sometimes it holds fuel pressure, sometimes it doesn't. The only thing I could think it would be is the relay isn't always switching over (unlikely because I got the new blue relay) OR the fuel pump is going out? Also unlikely as I havent heard of many Walbro 255's going bad.

Perhaps there is something I'm overlooking?

 

i had what sounds like the same issue for a while, finally got it figured out, it was the relay. if you want to read more about it check here

https://www.evolutionm.net/forums/ev...der-boost.html

check post 15, my relay came in before i could try this but there seem to be several relays in the fuse box that can be switched around. may want to try a different one to see if it is the relay.

also, i havent heard of one of the blue relays failing yet but i am sure it is only a matter of time.

 

Yeah, just because the blue relay is good in general, doesn't mean that one of the thousands couldn't be bad.

Edit, maybe just try swapping it with one of the random black or green relays and see if you get different results.

 

So you guys think the relay is at fault for the fuel pressure inconsistency? Haven't seen a blue one fail yet, but I guess there's a first time for everything. Only other thing I can think of is fuel pump dying, or there's like a pinch in the fuel line or something, but I havent been able to find any.

 

dont know...

hot wire it and retest...

 

Yeah that. We are just trying to rule things out.

 

Update:

So today I connected a DMM to the fuel pump to monitor the voltage. One thing I noticed was that in lower gears (1st, 2nd, and sometimes 3rd) the voltage switches from 9 to 12 at around 3000 RPM's no matter what throttle I'm giving it. So if I'm at 10% or 100% throttle, the voltage always switches to 12V at that RPM level and when it does, the AFR's momentarily go extremely lean. like high 16's, 17's, and even pegged the UEGO out sometimes. it's like the car stutters, almost like it hits a brick wall, but then the AFR's come back.

So under WOT, the car was all over the place throughout the day/test. The voltage was stable and the AFR's were still oscillating a lot, so it's not the relay. at one point, it was like low 10's under WOT. Voltage still kicking over to 12. I turned the car off for about 10 seconds, turned it back on, and then the AFR's went lean this time. Voltage still kicked over to 12v, but the AFR's went into the 12's. What the hell?

What could possibly be the problem? I'm really running out of ideas. It's seriously to the point where I feel like I need to sell my car, which I really don't wanna do because I really like it...



Thanks Tephra, Golden, and everyone else who has tried to help me.

Kenny

 

ok so its NOT the relay

I am thinking your fuel pump install is dodgey..

I dont know about the X, but on the IX if you didn't put the sock on properly you would get the symptoms you are getting now...

Good testing so far thou!

 

Or the pump has a bad coil on it and is not working properly. If you give it voltage and it doesn't pump fuel, seems like something is wrong.

Try putting the stock one back on if you have a Walbro. Just be careful to not rev too high and run out of fuel that way.

 

Ok, I will check the install tomorrow, and take the whole housing out and see if anything catches my eye. It's seeing the proper voltage, and sometimes it does pump enough fuel, too much even, but then OTHER times it doesn't pump enough. So the walbro definitely isn't running out of flow or anything. I'm gonna try and find my stock fuel pump. If I can't I guess I'll just buy another walbro and then cross another thing off the possible causes list :-\

 

swap back to stock pump... just keep it under 5000rpm... you will be fine

 

bad fuel pump or or faulty FPR