1999 Blazer 4.3 no spark

I was driving down the road and truck just died. Tried to restart and it just clicked. Found that battery was dead so I took it and the alternator off and went o the parts store and had them checked. Both tested bad but both under warranty still. Went back to truck put new ones on tried to start it and it would just crank but not start. Pulled number 1 spark plug wire held it close to exhaust manifold and got an orange spark. Put a little gas in intake and it started and ran until fuel ran out. Checked all fuses and relays, good. Tested fuel pump pressure and it was 52psi. Kept messing with stuff and every now and then it would start for a few seconds and then die again. came back next day and now truck isnt getting spark, but seems to be getting fuel as the spark plugs were wet. Changed plugs,wires,cam position sensor,distributor cap,rotor button. Still no spark. Ohm tested ignition coil good. got my sisters 98 blazer and switched vcms out still no spark. But hers wouldnt run on my vcm either. switched them back. not sure what to do next. Do the 99 models have the ignition switch problems as other models?

Make sure your fuel pressure gauge is good.

Check it on sister's truck.
You need 60/66 lbs of fuel pressure.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold and fuel pressure testing guide line.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

already tested sisters truck and it was 60psi. cant test pressure on mine while running cause it wont run. but right now my biggest problem is no spark. cant figure out why. i am going now to switch out the crank sensors, and ignition control modules to see what happens.

already tested sisters truck and it was 60psi. cant test pressure on mine while running cause it wont run. but right now my biggest problem is no spark. cant figure out why. i am going now to switch out the crank sensors, and ignition control modules to see what happens. also truck is holding steady pressure around 52 even after key off a while.

ok, i just tried switching icm and crankshaft position sensor and still have no spark. I pinched off fuel ruturn line and pressure went to about 69 or 70 psi

Your fuel pressure is to low.
But you need spark to.
Where or how are you checking for spark?
Does coil have 12 volt ign voltage to it?
Does the coil spark at the coil tower?
Does secuirty light come on key on bulb check and go off?

not sure on the security light. but yes i do have batt voltage at coil. checked for spark at 1256 plug wires.

not sure on the security light. but yes i do have batt voltage at coil. checked for spark at 1256 plug wires.

Check for spark out of coil tower.
If spark there check cap and rotor and wires and for dist turning while cranking.

no spark out of coil and distributor is turning while cranking

Does fuel pump prime up key on?
Doe fuel pump run on engine cranking?

yes it runs key on and during cranking. I took it to a shop to have them look at it and so far they have told me fuel pump is bad again, and they still havent figured out why it has no spark. they told me the fuel pressure sensor controls spark. Is this true? If so why would u want spark to quit if fuel pressure became too low? It has no advantage that I can think of.

There is no fuel presure sensor on it.
If no spark go threw the no spark repair flow chart.

For spark you need crank shaft sensor rpm readings to start with.
Does it have that?

how do i check that?

A good scanner.\
Read out data for rpm signal.

how do i check that?

It sounds like what happened to me while travelling last year.

I had the best GMC guy in Washington state looking at it and he was baffled.

Turned out to be a wire to a sensor had broken inside the insulation and would not allow the truck to start. 99SE.

They spent a full day screwing with that truck - $400.00. For that I lost 2 days travel time, cause it was the weekend. Good party though. People in Washington are great.

Good luck

sorry i havent came back sooner, but i took it to a shop. they replaced the computer and truck runs perfect now. thanks for all the help

sorry i havent came back sooner, but i took it to a shop. they replaced the computer and truck runs perfect now. thanks for all the help

Glad to hear it. If yours is anything like mine you have a good truck there. Good luck and take care.