TKR 88 GTA

Ok guys first ill list the setup
HSR, XFI268 cam, and AFR 195 heads, 30# svo injectors
Now the symptoms...
Sometimes while starting it starts up just fine no problems runs perfect. Other times rough starts. As in excessive cranking and when it does start it idles real rough and misfires bad when I give it gas to try and keep the engine from dying, half throttle barely keeps the engine staying on and its only jumps up to 1500rpm maybe.
Sometimes it idles right at 700 in park and others it'll idle at 1000 rpms
But when it does finally turn over its fine no problems just a little bit of a bog when the engine is cold and hasn't been turned on for a while but after maybe a minute of letting it idle its fine
What I've done...
I've tried to reset the fuel pressure because it was at 38 its up to 44 ish now. Fuel pressure holds up there fine when it is idling smooth. When I find ignition on engine off fuel pressure jumps to about 55-60 psi and then starts falling and will go all the way down in less than 30 seconds.
TPS was acting up so I replaced it and reset the voltage to .54v still acts up.
All the spark plug wires seem fine, the IAC is adjusting idle so I assume its working (correct me if that is not true)

What else is there to check? I know MAF could be checked but idk how I tried to look it up and no real tests came up.

Thanks for any info...

watajob

iTrader: (29)

To me, it sounds like 1 or more leaking injectors.

TKR 88 GTA

Ok so how can you test to know for sure if its a leaking injector(s)? They are probly about 2 and a half years old. Never thought of that though. Now makes me wonder lol

ASE doc

To test for leaking injectors, you need to isolate the injectors from the supply and return lines by using pinch off pliers. Activate the pump by turning on the key or better yet by using the fuel pump test connector which is close to the FP relay. You can also activate the fuel pump by applying 12 volts to terminal G of the ALDL connector. Then, pinch off the return line first, then the supply line, and quickly turn off the pump. You don't want to dead head the pump for longer than 20 seconds. With the supply and return lines pinched shut, the only place the fuel can go is through the injectors. Be sure of course that the fuel pressure regulator diaphram isn't leaking by removing the vacuum hose and looking for fuel at the port.

If there is no leak at the regulator and you still lose pressure with the lines pinched shut, you have a leaky injector. I assume that you've verified no drop in fuel pressure when the problem is occurring.

To test the MAF sensor, monitor voltage on the signal circuit of the sensor. It's pin C, dark green wire. It should read about .5 volts with the key on, engine off, 1.6 at idle, and 4.5 at WOT.

TKR 88 GTA

Dang good info thanks a lot. Only a couple questions where is the fuel pump test connection at or the relay? I have replaced the regulator once already because it only holding 28 psi applied vacuum to it and didn't hold. As far as I can see when I was adjusting the fuel pressure no fuel was coming out of it. So i assume its all ok as far as regulator. Fuel pressure drops as soon as the pump primes and then with in minute drops to 10 or below.

ASE doc

The OE fuel pump contains a check valve and should hold pressure for at least several minutes after shut down. The fuel pump test connector would be a single wire break out from the harness close to the fuel pump relay which is located above the brake booster. The fan relays are also located there. To identify the fuel pump relay, look for one large orange wire, a small green and white wire, a small black and white wire, and a small orange wire and one tan and white wire. Your car may not have the test connector but you can still activate the pump by applying 12 volts to terminal G of the ALDL. or, just jump the large orange wire of the relay connector to the tan and white wire.

TKR 88 GTA

Dang wish I had my ALLDATA still lol well I got out of work early today so ill get to testing here in about an hour or 2 hopefully. How common is it for that check valve you mentioned to go out?

TKR 88 GTA

Ok so I did the test the results...
During all test I primed the pump and let it build pressure to 50...
Both lines pinched = 12+ minutes to drop from 50psi to 40psi.
Feed line pinched off as soon as it primed less then a minute to drop from 50-0 psi
Return line pinched = 12+ minutes to drop from 50psi to 40psi
So that leads me to think something on the return line isn't allowing pressure to build. What else after the return line allows the pressure to hold?

watajob

iTrader: (29)

All your pressure is on the feed side. Your return line does just that; return fuel. Your pressure is determined by the FPR. I've heard of pumps back bleeding but not often. My money is still on a bum injector.

TKR 88 GTA

Well that's what I had though too but going based of the results from the test the feed line is holding pressure, the injectors aren't leaking and if they are its very minimal, and my FPR is holding pressure. As soon as I took that clamp off the hose it was immediate drop in the fuel pressure. It's gotta be something down the return line but idk if there is I've seen just lines going all the way down the car and once it goes up to the tank I can't see anything else.

ASE doc

As watajob has stated, the only fuel passing through the return line is what is bypassing the regulator. Your results confirm that your regulator is not holding pressure. You need to D&I the regulator and figure out what went wrong there.

TKR 88 GTA

Ok idk if its just bad luck or what but this is the 2nd FPR that I've needed to replace. So is there another regulator that will work with my Holley stealth ram fuel rails? Idk when I can D&I the regulator cuz this is my daily right now.

watajob

iTrader: (29)

Make sure the diaphragm in the FPR isn't damaged/leaking.

TKR 88 GTA

That's exactly what happened to the first one. I applied vacuum to it and it didn't hold lol I'll bebmad if its that again lol what would cause the diaphragm to go bad like that then?

ASE doc

It may not be that the diaphram is ruptured. When you installed it, you may have not gotten the seat aligned correctly. When you disassemble it, look for anything that doesn't fit right. Remember, the vacuum diaphram is only part of the regulator. The spring is what sets actual fuel pressure and the seat is what holds the pressure in.

TKR 88 GTA

So if I can open up the regulator what will the seat look like? And how will I know it messed up or installed incorrectly?

TKR 88 GTA

Well I can't open up the regulator I just took it off and no screws or anyrhing that allow you to take it off. But before I did this, I ran a different test. I took off the end of.the return line and put it into a bottle. When I did that it gushed fuel into the bottle for that one second I primed the pump. So ya tells me the regulator isn't holding the pressure.

What can I do now?

TKR 88 GTA

Ok guys so I called Holley to see if they really stand behind their products for the regulator. All they said was "hmmm that's weird" then he came up with "maybe its your pump, its not the regulators job to hold line pressure at the fuel rails the pump is suppose to take care of that. The regulator should bleed off the fuel as the pump primes." I was just sitting there listening thinking is this guy really serious lol

So do you guys think I should stick with the same style regulator but different brand? Or should I try to find a way to rig up a remote mounted one some how to the fuel rails?

ASE doc

The stock style regulator is perfectly suitable for a stock style fuel system. Only if you redesign the fuel system in some way should you need a different pressure regulator.

The stock regulator is built in to the fuel rails and when you replace it, you only replace the diaphram and cover. Is it possible that the seat, which is part of the rails, is damaged. The crossover tube that includes the regulator base can be removed from the rails and replaced. You could look for a used rail set. I would certainly D & I the regulator before I settle on any conclusion.

TKR 88 GTA

When I took off the regulator I looked at the seat where the regulator pops in to it and it all seemed fine but all that I seen was just a hole nothing else in it, is there suppose to be something in there? Im not quite sure what you mean by the cross over tube? How would I disassemble the regulator then?

ASE doc

The regulator sits between the two rails. It's installed in a tube that crosses between the rails. If you look at each end of the tube where it meets the rails, you'll see a small torx head screw that attaches the tube to the rail. There is also the return tube fastened to the inside of one rail. The fuel rails are built from seperate pieces and held together with these little torx head screws. Each joint has an o-ring that seals it. The rails can be taken apart and reassembled pretty easily. I've had to do a few to address leaky o-rings.

The regulator base has a hole in it. The return hole is bored in the center of the valve seat. Make sure that the seat isn't damaged. Even a small nick will make it drop pressure. A larger nick will make it drop pressure bad. Look at the underside of the diaphram, look at the valve where it would seal against the seat. Does it look okay?

TKR 88 GTA

I figured the cross over tube was that. How ever in my stealth ram set up the regulator sits under the driver side fuel rail it gets fastened to the bottom of the fuel rail. So your saying taking the fitting where the return line comes out of the regulator should show me if that seal is messed up?

ASE doc

I'm sorry. I forgot that you are running the Stealth ram. The SR borrows its regulator from the LT1. It is a one piece design and is not servicible except as a unit. You have a faulty regulator.