Fuel Pressure falls off as boost builds

[Mitsu725]

i think i figured out how to solve this, i think ill just go with the bosch 044 to suck the fuel right out of the gas tank but i still need to quit being cheap and buy dsmlink so i can really check my fuel.

 

[Mitsu725]

I know this is old but the car has been sitting ever since. I drove it tonight after I re-ran the fuel lines, they aren't pinched off anymore now but I still have the crappy bulkhead slip fitting for the Fuel pump. Tonight I was only boosting 10.5 psi for safety reasons and the fuel pressure went up to about 43 or 44 and then dropped off to 25. I was wondering if my walbro has seen better days? Also what kind of voltage should my pump be pushing out during operation??

 

[Mitsu725]

Ok I was testing the car last night, and if I am driving at about 60mph and just maybe half throttle my fuel pressure rests at about 40psi. And If I stomp on it it gets into boost and the fuel pressure will go up to about 43/45 and then start falling back down. O yeah and the car is breaking up bad like it is hesitating, its popping alot... I pulled the plugs after I got into about 16lbs of boost and they were almost freaking white it looked realllly lean.

 

[dsm-onster]

I think your pump is going out.

 

[Mitsu725]

Thanks for the response, I really do appreciate it. Yeah I was thinking the same about the fuel pump maybe it was going bad. Is there a way to test the fuel pump voltage or flow or something to that matter?

 

[turboglenn]

Thanks for the response, I really do appreciate it. Yeah I was thinking the same about the fuel pump maybe it was going bad. Is there a way to test the fuel pump voltage or flow or something to that matter?

I noticed my Wally 255 that's in my car would hold pressure only for a few minutes when i first put a full time guage on it, then after another few weeks it dropped immediately. Some one had said the wally 255's didn't have teh backflow valve on them and wouldn't hold pressure. Well i have a brand new one in my hand about to go in my car tomorrow and it has a back flow prevention valve. So that's always a good thing to check. Fuel pumps have long service lives, but they do run constanly and can fail at any time Hell, i did 2 cavalier pumps this year with one having only 64k and the other only had about 27k on it.

 

[Mitsu725]

WOW thats low mileage. Well mine only has about 6k miles on it but It's not my daily. I dunno its just that the shop that sold it to me has been known for selling ppl not legitimate stuff and they closed down so I am kind of wondering if this thing is even a REAL walbro or what not. But I was looking at the pics of the walbro for my car today and even on the walbro website the pump that this shop sold me looks ok but the sock/filter that came with the pump matches the honda civic style and the nissan 200sx. When I looked at the actual pic of the 95-98 dsm style is shows a different filter setup that doesn't have the plastic 45 degree elbow. And now see that has me wondering because before I changed to a walbro my fuel pump assembly bolted down perfectly flush to the fuel tank. And since I added the walbro it is a mother to bolt that thing down because that plastic elbow off the filter assembly hits.


The one I have:

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And the supposed one for my car

 

[scottsee]

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That looks like something someone would make in jail to shank somone!!

 

[Mitsu725]

CHECK IT OUT!!! I solved something today as far as the a/c not working ::sniff:: Sniff:: DO i smell sabotage. My car has been parked in my polishing shop now for mmm about a year and a half, and all my friends have access to the car as it is usually not locked and sitting on jackstands. Well someone pulled the fuses out for the a/c on the inside fuse panel and dumbass me I didn't see they were missing. Well a/c works now so thats solved. But I was thinking about my fuel situation today. Not that this would solve anything but when I first installed the walbro, it was loud as $hite and now it just barely gets by. I am of course gonna do a rewire to it but I still think its on its way out

 

[dsm-onster]

Could someone have put something in your fuel tank?

 

[brute]

Or stuck a banana in your exhaust pipe?

 

[Mitsu725]

THATS IT A BANANA... Nahh I really think it's just the Fuel pump taking a crap. Or at least I hope...Im gonna try and test it this weekend or maybe try a new pump. I don't really know. I mean is there anything that could go wrong with the FPR maybe its "untuned" I don't know if that really is a word but maybe its wrong from the box, like something is just put together wrong. Because I have been reading that quite a bit of ppl don't get fuel accuracy like 1:1 with the aeromotive FPR.

 

[Mitsu725]

I did another test tonight, I ran 12.6 psi of boost and the fuel pressure went up to about 55lbs and then slowly died out and went down to about 38, so im almost sure that if I rewire the FP and possibly get a new pump I will be throwing more fuel to the engine.

 

[dsm-onster]

I'm not picturing that bulkhead slip fitting. . . Is it a rubber hose with or without a clamp on the pressure side of the pump? I've had loose clamps at this connection that squirted fuel and basically limited the flow of the pump to anywhere outside the tank. Fuel just released at this point and cascaded fuel in the tank.

 

[Mitsu725]

its a 90 degree bulkhead flared fitting. Then the flared part was cut off where it goes inside the gas tank and the inside was stepped so it acted like a pushtite fitting with the o-ring. And i think the biggest problem is that because it makes my fuel pump sit a little lower as well so it hits the bottom of the fuel tank. I know its hard to picture but I will post some pics tomorrow. Thanx

 

[Mitsu725]

Finally!!!!!, I got a different fuel pump assembly, like the one that has a hose barb on the inside. I figured that would work better instead of using the one that had a female end attached to the assembly and the walbro slipped into it. I went and got one from another 2g and it worked. It needed to be modded slights but it worked.

 

[boostnhard]

Are you sure that you have a fully sealed fuel system? If you have a pressure leak, it will be evident by having someone watch the pressure gauge on your AFPR from OFF, then cranking (should go to base pressure), then OFF. If it drops quickly (faster than 20-30 seconds), you more than likely have a leak.

I would FIRST make sure that the bulkhead fitting you machined to fit the inlet of the fuel pump is a SEALED connection.

This alone, will make it hard to start, and you could be losing pressure @ the pump while under load.

Next, make sure that you have a good vaccuum connection for the line that should be running between the intake manifold and your fuel pressure regulator for its boost reference. Also make sure that you are not leaking air out of the adjustment screw on the AFPR. Also as a tip, I would reccomend adding another nut onto the adjustment screw (so you have two -- locking the screw securely).

The bulkhead fitting/fuel pump and the AFPR/vaccuum connections should be looked at first.



FYI -- I had no problems running 880cc injectors on a S-AFC and a 99-ECU at stock fuel pressures. So, don't think that they are freaking huge. The S-AFC just isn't the best tuning tool for that size injector. Look into DSMLink, or AEM EMS for better tuning.

Hey thats nothing. im running 950s with the safc2, with no problems

 

[dsm-onster]

No problems that your logger shows. . . Please don't tell everyone you don't have timing issues. Prove your timing at WOT and 5K rpms. There's nothing wrong with pushing what you have to the ragged edge. There IS something terribly wrong with not telling your 'advicee' HOW after you've said it works.

. . . How soon do you reach the end of the A/F map?

 

[Car Cannibal]

Hopefully your pump will solve this issue, hit us back with the #'s.
Definitely do the hot wire while you are doing all this and test the voltage at the bat and pump to make sure it's good. Mine was only .1 volt different.