john rawson

I wonder if anyone is having the same problem I am having with my 1995 z 28. Lately and if the car hase been undriven for a few days it takes a long time lotsa cranking to get it started. I talked to one mechanic and he suggested that there might be a problem with a fuel pressure relief valve (?). I was thinking more fuel pump fuel filter issue. It has 110K MILES. What does the community think? Also a few times the engine episodically while run rough for a couple of seconds.
John
Well I am totally in awe of the help I have received here. Thanks fella's!!
Big time update: I replaced fuel filter, it helped a bit, but then following some posts went at the steel above the gas tank with a grinder and cut a 8X13 hole (not real pretty) , and probably aged a year while doing it. A wee bit scary shall we say . Took the car to a shop that replaced the pump, for a liitle over 350$ and the beast is amazing again. I would have done it myself but I saw some skilled dudes (on you tube)adopt some very colorful and colloquial epithets, and these fellows were 50X the wrench I am and said know your limitations.
It is like driving a new car . Actually a 95 z 28 lt1 is a very under rated toy, I wouldnt mind another 100ponies
but I am open to suggestions for 2grand that would achieve that goal. But check it out , the car would be a monster then I talked to a wrench he said $4200 for a blower. he said 25-30 psi i say that is hyperbole. ANYONES THOUGHTS? AND THANKS VERY MUCH

Injuneer

Have you checked the fuel pressure? That will tell you if there is a problem with the fuel pressure regulator.

Have you scanned it for codes? There are codes that don't turn on the SES light.

We can provide procedures for checking the fuel pressure and codes in you need them.

I'm also going to move this to "LT1 Based Engine Tech", which will provide more help on tech issues than here on "New Member Intro".

Fatdog2

Do you have any history about the car?Last maintenance performed ect.

john rawson

I installed a g force power chip but that was 6 months ago. Plugs wires 5 years ago, I will take it to a guy who will measure fuel pressure as well as replace plugs wires, It seems that more and more the momo needs gas and aint getting it. I did install a moroso intake k/n airfilter 7 years ago and recently flushed the radiator with a garden hose.

Fatdog2

I would change the gas filter first to see if that makes any difference before going to the mechanic.My02

Chimera96

you can buy a FP gauge for under 50 that just screws on the schrader valve on back of your fuel rail. Some auto part stores have loan-a-tool deals also for free.

Injuneer

First, get rid of the g-force power chip. Not likely it's the source of the problem, but its a complete scam. I isn't doing anything for your engine's performance.

Prosecutors Say GForce Performance Chip a Scam | CarComplaints.com

Have you cleaned and oiled the K&N filter recently?

When you flushed the radiator with the garden hose, did you splash water on the Optispark distributor?

Procedure for fuel pressure test:

1 - Turn key to "run" (not start). The pump will prime for 2 seconds and shut down. Observe the pressure when the pump shuts down. Should be at least 40 PSI. Observe how fast the fuel pressure drops after the pump shuts off. It should not lose more than 10 PSI in 10 minutes. Rapid loss of fuel pressure will make the engine hard to start. If it is losing pressure rapidly, cycle the key back and forth several times before turning the key to "start". If it starts faster, you have found the source of the extended cranking.

2 - Remove the vacuum compensation line from the fuel pressure regulator. Check the line for wet fuel. Should be dry. Wet fuel would indicate a torn diaphragm in the regulator, whch will cause numerous problems. Plug the end of the vacuum line to prevent a vacuum leak. Start engine and observe pressure. Correct pressure is 43.5 PSI. GM accepts anything from 41 to 47 PSI as within spec.

3 - Reattach the vacuum line to the fuel pressure regulator. Pressure should drop proportional to intake manifold vacuum. With a stock cam, pressure should drop about 8 to 10 PSI below the "no vacuum" reading. Example.... if you had 43 PSI without the vacuum line attached, pressure would be 33 - 35 PSI with the vacuum line attached.

4 - This is required only if the "not enough fuel" problem appears to occur at high RPM, ~ WOT. Tape gauge face to windshield. Take car out on road and run it up to above 5,000 RPM at WOT. Fuel pressure should not drop below 40 PSI at max engine load.

Shoebox has photos of the Schrader valve for the fuel pressure test, the location of the fuel pressure regulator, and the location of the vacuum compensation line:

john rawson

Thank You,Thank you, My dude says the gas reflect running lean. I mentioned fuel filter but the dude sez 25lbs presuure is not the requisite 41-47 lbs needed and sez replace the fuelpump which amazingly enough is in the gas tank. Bummer,so it looks like $900 to replace. is this the only avenue?
John

Injuneer

You can buy a good pump from Racetronix for ~$100-150. If you are willing to cut a "hatch" in the body sheet metal over the tank, it becomes a D-I-Y project. No need to drop the rear/exhaust or drop the tank. There are instructions for the "hatch" in a thread "stickied" at the top of the "Fuel and Ignition" forum.

Fatdog2

I gotta ask.How long ago did you flush your radiator with the hose?And did you start noticing problems after the flush?Did you flush it by sticking the hose in the radiator and opened the drain plug and just let it run and run till the water poured out of the top of the radiator for a long time?(Old school)You may have soaked your distributor and or it's connecting wires.And while everything was wet,did you start the engine or was the engine running during the flush?Here is a simple test that does not involve testing equipment right now.After letting the car sit for a day or two or three,find the schrader valve ,it's on the drivers side next to the intake looks like a valve stem and take the cap off and get a screw diver and press down on the center pin and see if gas squirts out.(Put paper towels all over the place as the gas will squirt at you and over the intake manifold.Put safety glasses on to)If this happens I would guess you got gas at least for start up immediately .Sounds like your optispark is got a bad sensor.(crank position sensor?)Got soaked?It would be like putting my cell phone in the sink while I wash my hands.It don't work that way.Sorry for the rant.Do the cheap stuff first.Hope I don't get kicked off here.My02

bw_hunter

There s no crank position sensor on a '95 and they were only used in '96 and '97 by the OBD2 system to determine where any misfires might be.That isn't the issue. If the opti did get soaked with antifreeze you can always spray wd40 on the cap and wires to see if there is an improvement. It will not be a permanent fix as the plastic cap is changed by the coolant.

Having fuel come spraying out of the Schrader valve is not a reliable method to use to estimate that fuel is available. You'll get spray out of that valve with pressure as low as 10psi and that wouldn't be enough to run the engine.

You really can't short circuit the normal troubleshooting procedures. You can reach erroneous conclusions and take actions that aren't needed or even helpful. It ends up costing more money in the long run...

Injuneer

If I read this correctly his mechanic has already determed that with only 25 PSI fuel pressure, he needs a new pump.

Fatdog2

I only thought that if there is fuel coming out of the schrader that there would be fuel in the rails enough to at least start the engine.It may not keep running,but the member said it won't start at all.Maybe the computer won't let the car start with that low fuel pressure I dunno.I believe in complete diagnostics as well and do now own a fuel pressure gauge(a good one)and a mytivac air pressure tool and some other tools,scan94-95 93 from GaryDoug.Not being a mechanic I know the first thing to do is check the fuel pressure.Just like going to the doctor,the first thing they do is check your blood pressure.But what bothers me once the car is running he can still drive it.It may need a new fuel pump.If I where john rawson I would ask to see the gauge that shows the 25lbs. or get a second opinion.but this happened after he flushed the radiator I believe.Thanks for reading.I've been wrong 5 times this year.This could be #6.

Fatdog2

Oh yes.This is old school,but before you start the car,bang on the gas tank with a rubber mallet 2 or 3 times and see if the car starts up right a way.Then it's the fuel pump.Hope this helps.

Rivas08_02

what kind of fuel pump would you recommend for 96 camaro? I've seen delphi and air tech i believe they're called???/ thanks