Fuel Pressure Very Low

Hey guys so I've been trying to diagnose this intermittent miss my 1994 Z28 has been having that's become worse since I bought it. I daily drove it for over a week with no issues until it started losing power across the powerband then became too unreliable to continue driving. I thought it was an ignition coil and wire problem (that turned out to be just one issue) and I fixed that. But after a bunch of troubleshooting and little issues fixed here and there, the car idled well enough again and I test drove it around my neighborhood (maybe a 15 mile drive) and it did good enough that I wanted to drive it to town yesterday.

Well it drove fine on the way, but when I tried driving home from the restaurant my fiancée and I went to, it barely cranked, stumbled, and missed badly until it finally wouldn't crank anymore and we had to have it towed home. (Second time it's left me stranded. First time was the coil lol).

So tonight I found my old fuel pressure tester and hooked it up. When I turned the key, nothing happened on the gauge but I did hear the fuel pump prime. So I turned the key off and on 5 more times and the needle reached 5psi but that was it. Wouldn't fire when I tried cranking it. So I sprayed starting fluid in the throttle body and it fired right up, but ran terribly, and the FP tester needle never reached past 5psi before I shut the engine off after running for 20 seconds or so.

Therefore I guess I have a fuel problem. I've read about people removing some vacuum line to get a different reading but I'm not sure exactly what they're referring to. So what I would like to know, is there another way I need to test the pressure before assuming it's the fuel pump? Also, how would I be able to tell if it's the fuel pressure regulator that's causing my problems? I do plan on changing the fuel filter to see if that helps anything before diving into a pump replacement.

Any advice would greatly be appreciated. I hate that I can't even enjoy driving this car right after buying it from someone that used it as a daily driver and never had a problem out of it. Thanks for reading

You should have between 41-47 with KOEO. If you pull the vaccum line and there's fuel in the line your reg is bad. But if your at 5psi, I'm thinking its a bad pump more so than a bad regulator.

The vacuum line is the one going to the fuel pressure regulator on the rear of the fuel rail where the schrader valve is. There is a "L" shaped rubber nipple. You pull it off and plug it to check fuel pressure with the engine running. KOEO method you don't need to pull it off

...but in your case given your gauge, assume it is accurate, shows 5 psi your fuel pump likely died. You can take a rubber mallet and pound the bottom of your fuel tank under the area where the pump is to see if it comes back alive...and if it does it will only be temporary but some have done this to get home if it craps out on the road somewhere. It does not work all the time though

http://shbox.com/1/fp_reg.jpg

So apparently someone has already done the trapdoor mod and replaced the pump at least once.
https://c5.staticflickr.com/1/763/31...664e18ba_c.jpgUntitled by Josh McClure, on Flickr

Now I wonder why it would go through two pumps with 150,000 miles. Maybe they used a cheap one the second time around. I tried beating on the bottom of the fuel tank with a rubber mallet and the fuel pressure tester hooked up, but it made no effect on the pressure.

So I guess I'll be ordering a pump. I've read Racetronix 255 pumps are basically reboxed Walbros. Are those still good, reliable pumps today? Or would you guys suggest a different brand fuel pump

Quote:

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Originally Posted by FastLT1

So I guess I'll be ordering a pump. I've read Racetronix 255 pumps are basically reboxed Walbros. Are those still good, reliable pumps today? Or would you guys suggest a different brand fuel pump

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Racetronix here.

Quote:

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Originally Posted by FastLT1

So apparently someone has already done the trapdoor mod and replaced the pump at least once.
https://c5.staticflickr.com/1/763/31...664e18ba_c.jpgUntitled by Josh McClure, on Flickr

Now I wonder why it would go through two pumps with 150,000 miles. Maybe they used a cheap one the second time around. I tried beating on the bottom of the fuel tank with a rubber mallet and the fuel pressure tester hooked up, but it made no effect on the pressure.

So I guess I'll be ordering a pump. I've read Racetronix 255 pumps are basically reboxed Walbros. Are those still good, reliable pumps today? Or would you guys suggest a different brand fuel pump

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There is a place online to get legit walbro 255's for 117 shipped, I'm trying to find the link.


Found it: http://autoperformanceengineering.com/html/lt1_kit.html

I have personally used this pump and it worked well, so well that it was sold to another member and I think he is still using it


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there have been reports of counterfeit "Walbro" fuel pumps so confirm your source for purchase.

I believe Racetronix no longer uses Walbro. Last pic I saw of their pump was red. Of two threads I did follow about Racetronix's latest offering.....both had fail in short time. Both had a very hard time getting Racetronix to even respond and/or replace the pump so thy both went elsewhere. From my understanding if you buy something from them you need to join their forum to contact tech support...

I put in my 255 in the stock housing about 15 years ago...all still good

Quote:

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Originally Posted by BALLSS

there have been reports of counterfeit "Walbro" fuel pumps so confirm your source for purchase.

I believe Racetronix no longer uses Walbro. Last pic I saw of their pump was red. Of two threads I did follow about Racetronix's latest offering.....both had fail in short time. Both had a very hard time getting Racetronix to even respond and/or replace the pump so thy both went elsewhere. From my understanding if you buy something from them you need to join their forum to contact tech support...

I put in my 255 in the stock housing about 15 years ago...all still good

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Walbro I posted IS legit, link was given to me by one of this site's owners.

Also, one of the Racetronix pumps in @Ltconvert lpp dual pumper died 3 months after purchase....the thing never even ran Cuz the car wasn't tuned for boost yet. Not happy

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Aeromotive also makes a drop in, 340lph pump.