Won"t hold fuel pressure?

[phantomworks]

Need a little help here. for some reason my fuel system won't hold fuel pressure.
I checked my fuel line pressure and fuel pump max pressure as per the fsm and both were well in spec (38psi and 80ish max psi), the system pressurizes also when I do the pressurizing procedure per the fsm but when shut off it immediately goes to 0psi after all tests.

Could it be the fuel pressure regulator?

[Brent]

How are you pressurizing the system? I'm not familiar with the how the FSM says to pressurize the system. I prime the system mostly by just turning the key to the on position which will cut the fuel pump on for a couple of seconds or by using the diagnostic box. How fast is the pressure dropping? Is this a stock fuel system? Mine did this when I had an injector that was stuck open. I would prime the system, and after a minute or two it would be back at 0psi

[0110-M-P]

The first thing I would do is pull out the injectors and make sure all the o-rings are good. If they are and all of the lines to and from the fuel rails look good then send the injectors off to be tested to make sure they are not sticking open like Brent said.

[David Jerome]

Sounds like a stuck injector, I have had a huge problem with this lately after I sent off 30 injectors to have cleaned and flow tested. In the last 2 1/2 months I have had 9 fail by either leaking externally out the top or getting stuck open causing the fuel to just pour into the engine once the car was shut off making it damn near impossible to restart without flooding.

Needless to say I am no longer having injectors sent off for flow testing and cleaning.

[Brent]

The procedure to test the injectors to see if they are sticking open or not is outlined in the my sticky thread in this section called "how to troubleshoot your fuel system"

[phantomworks]

I pressurized the system by taking a jumper wire to the gnd and f/p pins in the diagnostic box and turning the key to on position, primes the system to 40psi and when i remove the jumper wire it immediately drops to zero.

OK I'll check the injectors, I'm kinda leaning towards something else though Because when I did my compression check there was no fuel present on the new plugs, and
there is no visible out side leak on the fuel rail when priming system, but doesn't mean there is not a stuck injector .

btw this is only one problem I'm having, the car was running perfect and the next day it would not go WOT past 3500 rpm and would start bucking and back firing. the next day it would not start.

I replaced the TPS, spark plugs and plug wires, and still no start. I had fuel and spark at this time so I went through all my fuses, relays, grounds, and every thing checked out.

So I decided to do a compression check a few weeks later, when I pulled the plugs i noticed I had no fuel on the fresh plugs, they still looked brand new, so I checked for spark again and there was none.
Well this led me to believe that it was the CAS's I pulled and checked them and they read 1.12 and 1.15 ohms which is well within spec but I replaced them with another set anyway and they read 1.14 and 1.19ohms but still nothing. the rpm needle does bounce alittle when trying to start which tells me the injectors are receiving a signal .

The comppresion was good btw I'm pretty stumped at this point

[David Jerome]

YOu have a stuck secondary injector, just fixed a car yesterday with these exact symptoms except it was obviously getting fuel on the plugs. Car would buck like crazy at 3-3400 rpms and stumble and act an ass. Fuel system also was not holding pressure, when I would go to start the car it would about flood and shoot a nice back fire and a ploom of black smoke out the exhaust. Would constantly run rich at idle, then when at 3-3500rpms the car would just act rediculous. Changed out the secondary rail and installed another one with known good used injectors and the car now runs perfectly. First time I applied throttle after changing the injectors it still didnt act right, once the extra fuel was pushed thru the engine and the plugs cleaned themselves up the car now runs perfect.I pressurized the system by taking a jumper wire to the gnd and f/p pins in the diagnostic box and turning the key to on position, primes the system to 40psi and when i remove the jumper wire it immediately drops to zero.

OK I'll check the injectors, I'm kinda leaning towards something else though Because when I did my compression check there was no fuel present on the new plugs, and
there is no visible out side leak on the fuel rail when priming system, but doesn't mean there is not a stuck injector .

btw this is only one problem I'm having, the car was running perfect and the next day it would not go WOT past 3500 rpm and would start bucking and back firing. the next day it would not start.

I replaced the TPS, spark plugs and plug wires, and still no start. I had fuel and spark at this time so I went through all my fuses, relays, grounds, and every thing checked out.

So I decided to do a compression check a few weeks later, when I pulled the plugs i noticed I had no fuel on the fresh plugs, they still looked brand new, so I checked for spark again and there was none.
Well this led me to believe that it was the CAS's I pulled and checked them and they read 1.12 and 1.15 ohms which is well within spec but I replaced them with another set anyway and they read 1.14 and 1.19ohms but still nothing. the rpm needle does bounce alittle when trying to start which tells me the injectors are receiving a signal .

The comppresion was good btw I'm pretty stumped at this point

[David Jerome]

I replaced the TPS, spark plugs and plug wires, and still no start. I had fuel and spark at this time so I went through all my fuses, relays, grounds, and every thing checked out.

So I decided to do a compression check a few weeks later, when I pulled the plugs i noticed I had no fuel on the fresh plugs, they still looked brand new, so I checked for spark again and there was none.
Well this led me to believe that it was the CAS's I pulled and checked them and they read 1.12 and 1.15 ohms which is well within spec but I replaced them with another set anyway and they read 1.14 and 1.19ohms but still nothing. the rpm needle does bounce alittle when trying to start which tells me the injectors are receiving a signal .

The comppresion was good btw I'm pretty stumped at this point


Did you install new plugs and verify you have spark?

[Brent]

Are you running a PFC? This is similiar to what my car did when I had a burned out injector driver in my PFC. I never had fuel on my injectors and it was obvious that it wasn't getting to the engine. Doesn't really match up with the fuel pressure though. If it is dropping pressure, the fuel has to be going somewhere, either internally or externally. If it's not in the engine and the bottom of the injectors aren't wet... and the rail/orings/injectors aren't leaking that pretty much rules out the fuel losing pressure on the engine side of things. Hmmm, I'm going to be thinking about this tonight. Let me know the outcome. Maybe I'll have something to add to my fuel troubleshooting thread after this.

[Brent]

haha... David and I have def. done some fuel system troubleshooting.... and always with a fire extinguisher close by. That is a must have when you are working on these cars. Well, you should carry one in your car as well.

[phantomworks]

Thanks for the great advice, I'm not ruling out bad injectors but I'm not getting any fuel in the motor so it's not flooding out, and why don't I have spark now ( and yes the plugs and plug wires are new)?

When I try to start the car it just turns over but won't start it doesn't push fuel through the motor, no back fire doesn't catch at all?

I'm using the Pettit Racing unlimited ecu and I have swapped out that computer with my stock computer and the problems are still there.

I don't think this has anything to do with it but the engine is street ported with 3mm apex seals and full non-sequential turbos.

[scotty305]

I visited phantomworks this weekend and we got a few things figured out.

We used my AEM EMS so we could datalog the cam & crank angle sensors and fire the injectors and coils manually.
Turns out the crank angle sensors were too far away from the trigger wheel for the AEM to be happy with them. (might have been OK for the stock ECU, but the AEM is a bit more picky about signal strength). We used some washers to shim it closer and the EMS was reading both timing inputs and calculating RPM and stat sync'd correctly. The car still didn't fire, so we checked for fuel and spark. Injectors were all clicking but no spark from any of the coils. Eventually tracked that down to the ignitor not being grounded well (it grounds through the case), we cleaned it up and bolted it to the chassis and the car fired up and idled.

Fuel pressure looked OK at idle and increased when blipping the throttle in neutral, but I had to leave before we got a chance to take it around the block and make sure everything was still good during a full-throttle pull.

Just wanted to update the thread in case anyone else comes across a similar problem.

[phantomworks]

Still will not hold fuel pressure but while driving the car it seems to be ok but when shut off the car drops immediately to zero PSI.

[David Jerome]

Still will not hold fuel pressure but while driving the car it seems to be ok but when shut off the car drops immediately to zero PSI.

After it sits for an hour or so does it smoke on startup and kinda struggle to idle the first few seconds?

[phantomworks]

No, it actually idles fine and there is no smoke. It even drives like there is nothing wrong.

My only concern is that it didn't do this before, it used to hold fuel pressure for a day or two before the gauge would reach 0 psi.