95s10 cpi wont start

[mylows10]

i have a 95 s10 cpi that wont start.last week it would start but only after priming and getting the engine warm.was told to change the fuel pump.so i did,didn't work any better.ten i was told to try the fuel pressure regulator,so i replaced that it idled great for about 30 min but when i test drove it it would sputter and finally die,i pulled the plenum back off to see if the nut kit was leaking but couldn't tell, didn't seem so.so now i'm stuck cuz i don't have a fuel pressure gauge to check.was just wondering what to look at next , also does anyone know the correct fuel pressure

[MT-2500]

Originally Posted by mylows10

i have a 95 s10 cpi that wont start.last week it would start but only after priming and getting the engine warm.was told to change the fuel pump.so i did,didn't work any better.ten i was told to try the fuel pressure regulator,so i replaced that it idled great for about 30 min but when i test drove it it would sputter and finally die,i pulled the plenum back off to see if the nut kit was leaking but couldn't tell, didn't seem so.so now i'm stuck cuz i don't have a fuel pressure gauge to check.was just wondering what to look at next , also does anyone know the correct fuel pressure

You need a fuel pressure gauge.
Rent borrow or buy on at your local parts place.
Most AZ parts places have loaners or renters.

Fuel pressure depends on what engine and engine code you have.
If single injector under intake or Trottle body 2 injectors?
What is your engine code?

Do you still have upper intake off?

95 - 4.3 W code eng 55/61 fuel pressure specs.
95 - 4.3 Z code is 9-13 lbs.

Do you still have to prime to start cold or hot?
Got good hot blue spark to all plugs?
Any check engine lights or codes?
Post back your fuel pressure readings.

[mylows10]

vin w no codes wont start at all next i will check fuel pressure it looks to be low but not sure thats why i was asking what the pressure should be

[mylows10]

ok got the test gauge when fuel pump is on pressure goes up to 60 psi.when pump shuts off it goes down to 50 psi then starts to loose pressure very slowly.i'm thinking the nut kit and or the whole cpi

[MT-2500]

Originally Posted by mylows10

ok got the test gauge when fuel pump is on pressure goes up to 60 psi.when pump shuts off it goes down to 50 psi then starts to loose pressure very slowly.i'm thinking the nut kit and or the whole cpi

60 lbs should start it.

Make sure it has 60 lbs with engine cranking.
Make sure you have good spark to all plugs.
Will it start with a shot of carb cleaner into intake?
If so and it has 60 lbs of pressure cranking engine you may be losing injector pulse.
Check for injector pulse at the wire going into intake.
Also pull a few plugs and see if they are dry or wet on ends.
If dist turning and sparking spark to all plugs and fuel pressure at 60 lbs and injector pulse it should start.

If it starts on carb cleaner and it has injector pulse to intake.
I would be checking the wiring that gooes into intake to injector.
I have saw the break or have bad conection to injector.
Let us know how it goes.
And if you pull intake prime up fuel pressure and watch the injector unit ad nut kit line for fuel leakage.

[mylows10]

starts if primed but will only run on whats in the plenum doesn't seem to be getting gas to the spark.also checked the electrical current going to the injector on the outside of the plenum and thats 11.7 volts ,would need to repull the plenum to check voltage at injector but problem seems to be in there

[MT-2500]

Originally Posted by mylows10

starts if primed but will only run on whats in the plenum doesn't seem to be getting gas to the spark.also checked the electrical current going to the injector on the outside of the plenum and thats 11.7 volts ,would need to repull the plenum to check voltage at injector but problem seems to be in there

Starts if primes points to fuel deliver problem.

The 12 volts on injector wire is not the injector pulse.
It is only the positive feed to injector.
you need to test for injector pulse.

The other wire going to injector is pulse wire or injector ground circuit.
It pulses the ground threw the 12 volts feed going threw the injector to make it squirt.

A injector tester node light is the best way to test for injector pulse.

A good injector pulse will make the noise light blink good when cranking with injector pulse.
No blink = no injector pulse.

Check for injector pulse on the outside before pulling intake.
Let us know what you find there.

[mylows10]

pulled plenum again after work,messed with the 2 wires going into the injector.moved them around and checked with multimeter,also pulled a couple of the poppets to see if leaking no leaks,also cranked the engine to see if they where working.guess what the engine tried to start , so i put it back together and it fired right up.so it looks like its the wire for the injector going bad again[just changed a little over a year ago],thanks for all the help ,was very helpful

[mylows10]

how do i take that wire apart to replace on the cpi

[MT-2500]

You are welcome.
If just replace yrear ago with a good GM wire harnessit should not be bad yet.
Does the wire show signs of shorting out or burnt or broken wire?
If the wiring is bad get a new wiring harness.
I have found several of the wire inside wiring harness bad.
Also plugin lose and burnt from arching.
Broben inside wire or bad injector plug on plugs.
Replace it and be done with that problem.
If injector unit leaking or bad replace it.
Also good time check or replace the nut kit plastic lines are bad about leaking.
The wire should just plug on to injector but has plastic clip to hold it on there.
The other end goes threw a rubber gromet on front of intake and plugs into wiring from computer.

[mylows10]

been driving it for a couple of days n ow ,and it runs perfect.harness is still good just was a little loose from the fuel leaking in the plenum

[MT-2500]

Originally Posted by mylows10

been driving it for a couple of days n ow ,and it runs perfect.harness is still good just was a little loose from the fuel leaking in the plenum

Thanks for posting back hoe it is doing.
Sounds like a winner.

On the harness loose what part or where is it lose?
Fuel should not bother/loosen up the metal plug-in part of harness.
But does work on the rubber plug.
Good luck

[mylows10]

not sure what was loose ,i checked for electrical signal at injector wit my multimeter ,at first there wasn't any signal so i moved the probes around a little then got a signal,which was less than what i had gotten at the outside plug[11.7 outside and 4.7 at the injector]i found this to be a little strange but the current was staying steady.then i tried to bump the engine over with the plenum off and it wanted to start,so i think poking around at the injector fittings gave me a better connection by possibly scraping a corroded end or crimping the fitting for the wire.all i know is it runs better than it has in a while.thanks again. what i can say is that before pulling the plenum check fuel pressure and electrical current going into the plenum first

[MT-2500]

Originally Posted by mylows10

not sure what was loose ,i checked for electrical signal at injector wit my multimeter ,at first there wasn't any signal so i moved the probes around a little then got a signal,which was less than what i had gotten at the outside plug[11.7 outside and 4.7 at the injector]i found this to be a little strange but the current was staying steady.then i tried to bump the engine over with the plenum off and it wanted to start,so i think poking around at the injector fittings gave me a better connection by possibly scraping a corroded end or crimping the fitting for the wire.all i know is it runs better than it has in a while.thanks again. what i can say is that before pulling the plenum check fuel pressure and electrical current going into the plenum first

You are welcome and thanks for posting back.

I have had several of them with bad wire on the wiring under intake going to injector and aso lose plugin terminals at injector.
If it gives you any more problems replace it.