Ok, So this is a strange fuel issue. Changed fuel pump and filter and main computer from 2 separate issues last summer there not even a year old keep that in mind. When I turn my key to the On position my fuel pump primes, My pressure gauge on my pillar gos to 42psi ( keep in mind this issue doesn't have any problem with me starting the car after a couple primes ) So my pressure gos to 42 PSI but instead of holding at 42 Psi it bleeds back down. So I heard could be a fuel pressure regulator most likely and I said well its only fuel thing I have not changed except for the injectors. So I spent a couple days changing that out and I still have the issue. After I prime the pump a couple times she starts and holds pressure and runs fine. But it shouldn't bleed down when I turn my key to the on position. Whos got ideas I am stumped. :dunno:
How fast does it bleed down? My bird is doing the exact same thing now. I have changed injectors and the pump is about a year and a half old. My pressure bleeds off as soon as the pump cuts off its back to zero. Check the fuel pressure regulator for fuel in the vacuum line to see if its bad. Mine has no fuel in it, so i suspect the issue is the check valve in the fuel pump itself. Thats where im at with my issue that seems to be the same.
Really ? So last May I changed my fuel pump, and found it kinda odd cause It was my 3rd pump I changed it for the very first time In Jan 2013 and said man I cant believe it died just in 3 years it was a factory Ac delco pump to. So I changed it and the filter in May last year and I was good for a couple months Drove to florida to go to Univeral studios on the 4th of July got to the parking garage and my car started spuddering and was like (what the hell ) and my fuel pressure was boucing around and then went to normal and later than night My car wouldn't crank no pressure. I waited a second and it cranked and I got down to the road and it cut off again and it kept cutting off over n over unitl I made it to a hotel across the street. So spent a couple days there changing the pump lucky I did the trap door method 2 months before when I put my 3rd pump in and then I found out with my power probe on the pumps power wire that it wasn't getting power and it was my main computer not sending power to the pump. So being 4 hours from home. I rigged the pump to a switch just to get me home and orderd a new computer and bam fixed my issue. Then since Novemeber I have been having this issue with the pressure bleeding down only when I turn the key. I can cycle the key a couple times and it starts and runs fine. I can hear the pump and all. Im wondering if its the PCM again. Since you said you changed your fuel injectors cant be them. One thing I might do is the pump I changed in Orlando was autozone pump and since it wasn't my pump that was bad ( was the pcm ) I might change my pump back to my Ac delco that I changed in May I Trust Ac Delco over Autozone crap. Hopefully that might be it, Only thing I can think of trying. It runs fine while driving which makes it weird, I have no clue ! Hope someone can come up with a answer !
well last may I did put in a new Ac delco pump but 2 months after I broke down in florida and thought it was the pump and put a autozone pump in there only choice I had at the time, after that my car still wouldn't crank and turned out the pump wasn't getting power so I wired in a switch off the battery to get me home. ( like I said in the previous post ) So I think to fix my current issue I need to put the Delco pump back or get a walbro pump. gonna try that and see what happens
I'm thinking check valve. Make sure when you change it that there isn't a bunch of sediment in there or rust. You've got a 98 so it has a metal tank. Might need to treat the tank with some STA-BIL once in awhile.
Although my bird doesn't need it, im considering a walbro like the one i put in my z28. Im thinking like 94ta said that it is a failed check valve in mine. Also, mine stutters randomly and i haven't had a chance to check fuel pressure while its running rough. Im going to change my fuel filter again and see if its clogged, and probably put a new pump in mine.
Every pump I've dealt with that has had a failed check valve the main symptoms are hesitation at higher rpm, and hard starts. If you spring for a performance pump like a walboro you need to Hotwire it. Performance pumps don't like the varying voltage the PCM supplies, they need a constant 12 if you want it to last.
oh really, thanks for the tip 94 T/A. yeah I do beleive its the check valve gonna swap back to my new Delco pump for the time being that was only a month old when I thought that was my problem when it was my PCM. Just put a cheap autozone pump in it ( no choice ) being stranded in florida last summer even though I discovered that wasnt the problem. thanks guys Good luck with yours 94z28
Hope I am not to late to hop on the band wagon of this thread. I see this problem at my garage a lot with older and some aftermarket fuel pumps. The valve in the pump fails and traditionally needs a new fuel pump. Also, you should be around 47-50 psi on initial prime, if you have to prime it a few times, either the filter is plugged or that pump is having an internal issue.
Yeah, its a cheap pump that I only put there cause I had no choice when I was broken down in Florida,, Changing to a new high quality Pump in a few days when it warms up ! To cold to work outside right now lol ! Thanks for all the info guys !
Here, here! Had this issue with my original Delco pump so I swapped it out with an Airtex unit. Pressure came up quite a bit but the bleed down still occurred. Did the same as most of you, six new injectors and a new FPR... pressure still bled down. I finally got sick of it and installed one of these:
That finally took care of it and my car starts with just the slightest flick of the key and has done so for about three years since putting it in. I installed mine just AFTER the filter on the hard line. It's best to install before the filter if possible but it works just fine for me after.
If bleed off is indeed your issue they will work. The one I posted is the one I'm using and have been for quite a while. It works without any issues whatsoever but is pretty pricey as far as they go. There's a bunch of others you could find for cheaper but at least it's a complete kit for nylon, steel or rubber. I'd gladly pay $35 for one if I needed another in the future though. I just got tired of playing with the fuel system, every component was brand new and still bleeding off. I also didn't feel like having the car down while I sent the pump back and waited for a replacement especially since pressure output was very, very good. This was the easiest option that I knew would work.:rock:
Interesting man ! I will look into that if my New Delco doesn't do the trick, gonna change it this weekend. thanks for the tip like that !
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