Help!! Fuel Pressure Nightmare
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
Help!! Fuel Pressure Nightmare
I recently did an intake swap to an Accel SuperRam.
It runs rich, sounds like a tractor, and threw code 33 & 43.
Busted out fuel pressure gauge, and hooked it up. Turn ignition to start position, fuel pressure goes to 40 psi and has a very slow but steady drop, right away. Within 2 minutes, the pressure is back at zero.
When i start the car, the needle bounces between 40-50 psi very rapidly.
Any thing else i should do to further diagnose this? I think I have leaking injectors, but could it also be a bad fuel pump? The fuel filter itself is less than 2000 miles old, but it may have gone bad from running the main line and the return line together with a rubber hose from when I did the intake swap.
Any help is appreciated!
It runs rich, sounds like a tractor, and threw code 33 & 43.
Busted out fuel pressure gauge, and hooked it up. Turn ignition to start position, fuel pressure goes to 40 psi and has a very slow but steady drop, right away. Within 2 minutes, the pressure is back at zero.
When i start the car, the needle bounces between 40-50 psi very rapidly.
Any thing else i should do to further diagnose this? I think I have leaking injectors, but could it also be a bad fuel pump? The fuel filter itself is less than 2000 miles old, but it may have gone bad from running the main line and the return line together with a rubber hose from when I did the intake swap.
Any help is appreciated!
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Wow, a lot of people are having fuel problems lately...
Here is what I got for ya (taken from a thread I recently posted in)
Here is my expierence: My Vette stopped starting on the first crank and would have to turn over a few times before she started. I did some tests and it ended up being the fuel pump that went bad (leaking check valve)...
The first test I would do is a fuel pressure test.
If it bleeds down then now you need to go and remove the fuel filler door and clamp off the fuel line, that goes to the fuel rail, right after the pump is primed (this is a 2 person job)...
Now if the pressure stays up, you know its something with the fuel pump. If it bleeds off, it could be injectors, the fuel pressure regulator, etc...
If you have any questions feel free to ask, I know the process so it I might not have been so clear to you...
--------------------------------------------------------------------------------------------------------------------
If its the fuel pump here are some instructions for the fuel pump replacement...
Its pretty straight forward. The hardest part was getting the hoses off the part the runs into the tank.
Steps (from memory)
1.) Disconnect battery (make sure you dont take chances around gasoline)
2.) Take off the rear gas filler door with 4 star-head shaped screws
3.) Take out the rubber around the filler tube and now the gas tank and the fuel filter assembly top will be visible (be careful to not rip the rubber boot)
4.) Take off all of the hoses that connect to the top of the assembly (maybe hit the hoses with some wd40 the night before)
5.) Unscrew the bolts that hold the assembly to the tank and be careful because there is a gasket that would break up and fall into the tank
6.) There should also be an electrical connector that you need to disconnect too
7.) pull out the whole fuel pump assembly and get it on a workbench
8.) change out the fuel pump and fuel sock (the original sock was really tough to get off so I just ripped it up and tore it off)
9.) Thats pretty much it, take a pic of the fuel pump assembly so if you are a little confused putting the new pump in you have something to reference!
I think that is all, good luck!
Here is what I got for ya (taken from a thread I recently posted in)
Here is my expierence: My Vette stopped starting on the first crank and would have to turn over a few times before she started. I did some tests and it ended up being the fuel pump that went bad (leaking check valve)...
The first test I would do is a fuel pressure test.
If it bleeds down then now you need to go and remove the fuel filler door and clamp off the fuel line, that goes to the fuel rail, right after the pump is primed (this is a 2 person job)...
Now if the pressure stays up, you know its something with the fuel pump. If it bleeds off, it could be injectors, the fuel pressure regulator, etc...
If you have any questions feel free to ask, I know the process so it I might not have been so clear to you...
--------------------------------------------------------------------------------------------------------------------
If its the fuel pump here are some instructions for the fuel pump replacement...
Its pretty straight forward. The hardest part was getting the hoses off the part the runs into the tank.
Steps (from memory)
1.) Disconnect battery (make sure you dont take chances around gasoline)
2.) Take off the rear gas filler door with 4 star-head shaped screws
3.) Take out the rubber around the filler tube and now the gas tank and the fuel filter assembly top will be visible (be careful to not rip the rubber boot)
4.) Take off all of the hoses that connect to the top of the assembly (maybe hit the hoses with some wd40 the night before)
5.) Unscrew the bolts that hold the assembly to the tank and be careful because there is a gasket that would break up and fall into the tank
6.) There should also be an electrical connector that you need to disconnect too
7.) pull out the whole fuel pump assembly and get it on a workbench
8.) change out the fuel pump and fuel sock (the original sock was really tough to get off so I just ripped it up and tore it off)
9.) Thats pretty much it, take a pic of the fuel pump assembly so if you are a little confused putting the new pump in you have something to reference!
I think that is all, good luck!
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
I recently did an intake swap to an Accel SuperRam.
It runs rich, sounds like a tractor, and threw code 33 & 43.
Busted out fuel pressure gauge, and hooked it up. Turn ignition to start position, fuel pressure goes to 40 psi and has a very slow but steady drop, right away. Within 2 minutes, the pressure is back at zero.
When i start the car, the needle bounces between 40-50 psi very rapidly.
Any thing else i should do to further diagnose this? I think I have leaking injectors, but could it also be a bad fuel pump? The fuel filter itself is less than 2000 miles old, but it may have gone bad from running the main line and the return line together with a rubber hose from when I did the intake swap.
Any help is appreciated!
It runs rich, sounds like a tractor, and threw code 33 & 43.
Busted out fuel pressure gauge, and hooked it up. Turn ignition to start position, fuel pressure goes to 40 psi and has a very slow but steady drop, right away. Within 2 minutes, the pressure is back at zero.
When i start the car, the needle bounces between 40-50 psi very rapidly.
Any thing else i should do to further diagnose this? I think I have leaking injectors, but could it also be a bad fuel pump? The fuel filter itself is less than 2000 miles old, but it may have gone bad from running the main line and the return line together with a rubber hose from when I did the intake swap.
Any help is appreciated!
Melting Slicks
Joined: Dec 2009
Posts: 2,233
Likes: 285
The fuel pressure should hold psi for a while, you shouldn't see the needle drop, in fact it should rise alittle as the fpr is no longer getting vacuum. Pull the vacuum hose on the f. press. regulator(after running it so it has psi), no fuel should come out of the regulator port. Yeah you may have a leaky injector, a leaking hose in the tank right above the pump, or a bad pump. You can cycle the pump to build pressure, then pinch off rubber hoses to isolate the area thats leaking down.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Code 33 (1985-1990) Inspect intake system for leaks, Inspect for vacuum leaks, Check MAF connector and wiring, Check MAF for open using digital Ohm meter. Possible ECM failure.
Code 43 Check ECM wiring. Replace knock sensor.
I would check wiring like mentioned above, then maybe give the ECM some thought since they both refer to that as a possible cause..WW
Code 43 Check ECM wiring. Replace knock sensor.
I would check wiring like mentioned above, then maybe give the ECM some thought since they both refer to that as a possible cause..WW
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Eliminate the codes first and then see how the car runs. The fuel pressure bleeding down in 2 minutes is not a big deal in itself but it could point to bad injectors. Once the code 33 is eliminated I would suppect the car will run much better.
I did a little checking and code 33 is MAS signal voltage is high. That means the MAS is recording a grams per second reading higher then what the computer expects for the RPM and throttle position. A modified engine can set this code since it may be moving more air at a preset throttle position and RPM then what the stock tables are expecting to see. You may have to have a custom chip programmed that raises your stock values for the above mentioned table. Make sure the MAS sensor circuit is working correctly, and if it is, have a custom chip made. The easiest way to determine if the MAS is working correctly is to scan the car and see if the MAS is reading in a linear fashion as RPM and load values change.
I did a little checking and code 33 is MAS signal voltage is high. That means the MAS is recording a grams per second reading higher then what the computer expects for the RPM and throttle position. A modified engine can set this code since it may be moving more air at a preset throttle position and RPM then what the stock tables are expecting to see. You may have to have a custom chip programmed that raises your stock values for the above mentioned table. Make sure the MAS sensor circuit is working correctly, and if it is, have a custom chip made. The easiest way to determine if the MAS is working correctly is to scan the car and see if the MAS is reading in a linear fashion as RPM and load values change.
Last edited by bjankuski; Jun 18, 2010 at 08:29 AM.
