Is this acceptable fuel pressure for a Vortec engine

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

BOTTLEDZ28

I'm Awesome
Joined
Nov 29, 2011
Messages
894
Reaction score
43
Location
Mass
I’ve been trying to track down a multiple cylinder misfire for a while now. It appears to be getting worse and now the converter is unlocking at 2k rpm when the PCM (0411) picks up multiple misfires.

Anyway, here is a link to a video of what my fuel pressure is doing at idling as well as a few revs and sustained rpm.

The fuel pump assembly was replaced 5 years ago. The spider was replaced 3 years ago. The fuel filter, plugs, wires, cap and rotor were replaced over the last week. I still have multiple misfires. Most of them are on cylinder 4.

xc_hide_links_from_guests_guests_error_hide_media
 

pro17

I'm Awesome
Joined
May 27, 2017
Messages
113
Reaction score
40
Location
DFW
Watch this when you get a chance.
xc_hide_links_from_guests_guests_error_hide_media
 

BOTTLEDZ28

I'm Awesome
Joined
Nov 29, 2011
Messages
894
Reaction score
43
Location
Mass
I have already done a smoke test. There is no leaks at all.

The only test I have not performed yet is a compression test. I have held off on it since I am getting multiple cylinder misfires.
 

big_mike

I'm Awesome
Joined
Sep 6, 2011
Messages
857
Reaction score
162
Location
Skiatook, Ok
Pressure looks low to me honestly. Similar to what my 130k mile stock pump was doing. Should be close to this:
60-66psi key on
55 idle
55-60psi hold after shut off

At least those were the specs I found in searching. When it's unlocking the converter does it kinda feel like a buck, almost like it unlocks and the locks back up spradicly?

Could be the pump, could be the spider, if the pressure bleeds off after 30min-1hr it could be the FPR on the spider leaking or the spider itself.

Mine is still apart so I can't confirm if this fixed my issue but sounds similar.
 

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,892
Reaction score
7,542
Location
DFW, TX
Fuel pressure is low. Should be 66 psi key on engine off and 62 psi at idle with a stock spider. My MFI spider was 62 psi Key Pff Engine on and 58 psi at idle.. When my Express vans pump started going I had a pronounced stumble, lots of extra cranking to cold start and a misfire under load along with high + long term fuel trims. The fuel pump and wiring harness connectors were actually starting to melt. I ended up putting a Delphi pump and a Racetronix hotwire kit that feeds the pump straight off the alternator output stud through a secondary relay and 10 gauge wiring. It really cuts the amperage draw of the fuel pump by giving it more voltage. When I still had the OEM style MPFI spider I was running at 70 psi fuel pressure key on engine off.
 
Last edited:

BOTTLEDZ28

I'm Awesome
Joined
Nov 29, 2011
Messages
894
Reaction score
43
Location
Mass
Right now, I am trying to determine if this random misfire I have been getting for the last 3 years is from a faulty part or an engine that is getting tired. I replaced the fuel pump assembly in 2013 and I did a new spider injection in May of 2014. A year later, I did new lower intake gaskets. The truck is maintained with Ac Delco or Delphi parts. Intake gaskets were the newer Felpro design.

Right now, I am torn between replacing the fuel pump assembly, spider or distributor. I think I can rule out the spider if I can find a way to hook a pressure gauge up in place of the fuel filter. If the pressure climbs up over 66psi then I know its not the pump. But, I cant seem to locate a fitting/adapter that will allow me to connect my test gauge to the fuel line at the filter.

Ive heard about that Racetronix fuel pump wiring harness. Was it a basic install??
 

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,892
Reaction score
7,542
Location
DFW, TX
Right now, I am trying to determine if this random misfire I have been getting for the last 3 years is from a faulty part or an engine that is getting tired. I replaced the fuel pump assembly in 2013 and I did a new spider injection in May of 2014. A year later, I did new lower intake gaskets. The truck is maintained with Ac Delco or Delphi parts. Intake gaskets were the newer Felpro design.

Right now, I am torn between replacing the fuel pump assembly, spider or distributor. I think I can rule out the spider if I can find a way to hook a pressure gauge up in place of the fuel filter. If the pressure climbs up over 66psi then I know its not the pump. But, I cant seem to locate a fitting/adapter that will allow me to connect my test gauge to the fuel line at the filter.

Ive heard about that Racetronix fuel pump wiring harness. Was it a basic install??

Vortecs have a test port on top of the intake where the fuel lines feed the spider.

Racetronix kit is very basic wiring. Hardest part is routing the harness and finding a good clean ground. Just be sure to get the right harness and adapter harness if you need it. I used the SUV harness that updated from the square 4 wire connector to the flat 4 wire connector to match the replacement Delphi pump.
 

BOTTLEDZ28

I'm Awesome
Joined
Nov 29, 2011
Messages
894
Reaction score
43
Location
Mass
Vortecs have a test port on top of the intake where the fuel lines feed the spider.

Racetronix kit is very basic wiring. Hardest part is routing the harness and finding a good clean ground. Just be sure to get the right harness and adapter harness if you need it. I used the SUV harness that updated from the square 4 wire connector to the flat 4 wire connector to match the replacement Delphi pump.


I know about the test port. I used it to test the fuel pressure.

I found this kit on their site. Is this the one you used/

https://www.racetronix.biz/product.asp?ic=fpwh-001
 
Last edited:

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,892
Reaction score
7,542
Location
DFW, TX
I know about the test port. I used it to test the fuel pressure.

I found this kit on their site. Is this the one you used/

https://www.racetronix.biz/product.asp?ic=fpwh-001

Actually that one is for the older style fuel pumps with the 4 pin square connector. The harness I got from them converted my harness to the flat 4 pin style to match the newer style Delphi pump.

I forget the part number but FPWK-017A looks equivalent.
 

mistaake

Real Name: Michael
Joined
Jun 28, 2015
Messages
776
Reaction score
75
Location
SF Bay Area, CA
recently i posted about my fuel pressure, it's similar to yours, and i have determined that my next step is replacing the fuel pump. if that doesn't fix it, my recently installed fuel injection spider/pressure regulator assembly is at fault.
 
Top