got a question from a new member.have a '95 z28 6 speed,stock,128k miles,almost mint condition,black,t-tops,gutted cat,k&n.had for a few years (2nd '95 lt1 by the way)now.never had a problem till new years weekend.went camping down a long,dirt washboard road.went three places.third place went to start it and didnt want to start.seemed to be starving on gas.feathered it a couple times.start/die/start/die,then seemed flooded.finally started and ran fine for two weeks.wouldnt start on the coldest day of year(here in sunny florida)same symptoms.had spark,but plugs were worn.installed new ac delco platinums,fuel filter,pcv and noticed catalytic converter stuffing coming out exhaust.gutted cat and exhaust.still no start.same symptoms and no ses light.cleaned maf sensor,map,fixed a couple broken grounds near coil,replaced couple broken vacuum lines.found cracked tps sensor and replaced.eventually started after alot of cranking,assumed it may be flooded.last week been turning key on/off 4 times to check for difference in starting.put it in shop one friday(friends shop)2 weeks ago,had to push it in after shutting it off.they found broken black wire to back of pcm.said "ah ha"!still wouldnt start.hour later it started.fuel pressure gauge hooked up and scanner.no codes,injectors balanced,adequate pressure 44lbs.said nothing was wrong.shut it down and would not restart.replaced pcm with new.wouldnt start.put old pcm back in and eventually started.no ses or codes.didnt get charged for the pcm by the way.ran fine 2 weeks.wouldnt start this morning.noid lights showed signal to injectors and fuel pressure.did notice first turn of keyapprox.45 psi pressure till pump quit(2seconds)pressure dropped to 40 but then slowly climbed back.after 30 minutes pressure drops to 35 or so.first turn of key and climbs back.finally started 45 mins. later.left pressure gauge attached and drove to work city driving.stayed about 41-45.couldnt wot in city.started fine after work and two other attempts.left guage hooked up at work still had pressure after.just checked now and guage was at20 psi.turned key on,pressure instantly up.car started instantly.sorry for the long post,just trying to give info.should fuelpressure remain indefinately?will move on to icm,coil,regulator next .opti seems to be fine but dunno for sure.never a problem getting wet.go to auto car wash every week.any help would be appreciated.thanks.vo dave

 

got to be a fuel issue right?

 

sounds like its the fuel pump, its bad or is getting weak.

with the pump on and the car not running it should be 41-47 psi and running it should drop 3-10 psi and at wot it should be a steady 41-47

also check the fuel pressure regulator

 

thanks guys
car not running and key on is about 45 psi.with car running is about 37-40.as close as i can get to w.o.t in city jumps it to about 43 then back down to 37-40.increases as i hit throttle but stableizes at 37-40.so is the fuel pressure supposed to die away overnight?it does.been running fine last 3 days.have left my fuel pressure gauge hooked up and sticking in front of windshield for 3 days now to observe.also reset iac and replaced ect on water pump(lil stuff first).would be easier if it was consistant.but so random it makes it hard to be prepared.and always happens when least expecting it like before work or when out of town lol.always eventually starts but........just waiting for the next time.will change coil and iac sensor as i already have them.and maybe some seafoam this weekend.then move onto icm and opti if it does it again,but have to replace radiator first as i noticed a hairline crack in plastic tank.if i find anything that totally cures it i will post it.thanks for the input and great job to everyone.been reading posts everyday.will add pics soon.

 

If it's truly this random you may want to make sure it's not a connection issue, whether it's a wire or sensor etc. I'm sure Z28Pete could give you a list of all the stuff that goes into determining fuel pressure off the top of his head, unfortunately I can't do that for you...

 

thanks again all.been waiting for pete to jump in as well.

 

My 3.8L was having some trouble starting and it turned out to be the fuel pressure regulator. Even though the pressure was good while running when it shut off it would go down to almost nothing the mechanic said.

 

Random hard starts are hard to pin down because they come & go. However; there are several things to consider.
Starting procedure- These cars are designed to start with the foot off the gas pedal, so if you step on the pedal when starting the car, the computer gets confused and commands the wrong amount of fuel. Thiscan causea flooded condition that will hinder starting. To clear a flood condition, press the gas pedal to the floor and crank the engine over. The PCM sees this as an attempt to clear a flooded condition and shuts off the injectors until the car starts.

Fuel Pressure Problems- No or low pressure when first attempting to start. Usually due to an internal fuel leak, caused by bad fuel pump check valve, bad pressure regulator, or leaky injector. Verify pressure with a pressure gage and follow test procedures for testing the fuel pump and regulator. A leaky injector requires more work as the fuel rack and injectors are removed as a unit, the fuel pump forced on with the key off (use the test connector to power up the pump). The injectors should all be closed and not leak any fuel. A leaky injector should be replaced.

Weak Ignition- Because of the random problem, the whole ignition system needs to be looked over and tested when possible. This includes all low voltage (primary)ignition wiring and connectors, ignition coil module, ignition coil, spark plug wires, spark plugs, and distributor.
Unplug all connections & check for corrosion.

Sensor Problems- At start up the computer uses data from the MAP, IAT, and ECT to calculate the proper fuel mixture. Look at the output of these sensors at start time using a scannerto see if they make senses (silly things like the ECT sensor showing 200 deg, when you know the engine is cold).
MAP sensor should read between 20 to 48 kPa depending on altitude. High elevation = lower absolute pressure.
ECTsensor, temperature from ECT should track with temp gage reading
IAT sensor, temperature from IAT should be the same as under hood temperature, check with thermometer placed under the hood.

VATS Problems- The VATS system is known for causing intermittent problem especially on older cars where the key contacs in either the key and the lock get worn, or where the pellet in the key gets damaged. A VATS problem will prevent starter engagement, shuts down the fuel injection, and light the Security lite