97 Blazer 4.3 cranks but won't start


jeff1367
04-03-2009, 03:01 PM
I was driving my Blazer, parked it, and tried starting it a few hours later. It would crank all day but wouldn't even stumble a little. I've replaced the fuel pump and filter, cam sensor, crank sensor, coil, and ignition control module and it still won't start. Cap and rotor were new last year and still look good so I just cleaned off the contacts. I have good fuel pressure at the schrader valve checked with a guage. I pulled two spark plugs and they have a good blue spark. I believe something is stopping the injectors from spraying. What could do this and what should I check next?

MT-2500
04-03-2009, 04:16 PM
I was driving my Blazer, parked it, and tried starting it a few hours later. It would crank all day but wouldn't even stumble a little. I've replaced the fuel pump and filter, cam sensor, crank sensor, coil, and ignition control module and it still won't start. Cap and rotor were new last year and still look good so I just cleaned off the contacts. I have good fuel pressure at the schrader valve checked with a guage. I pulled two spark plugs and they have a good blue spark. I believe something is stopping the injectors from spraying. What could do this and what should I check next?

What is fuel pressure reading?

Are plugs wet or dry on end.
Always check all plugs for good spark.
Any codes or check engine lights?
Check all fuses.
97 is a bad year on ign switches.
are injectors getting 12 volts to pos side.
Have you got injector pulse?

jeff1367
04-04-2009, 02:11 AM
What is fuel pressure reading?

Are plugs wet or dry on end.
Always check all plugs for good spark.
Any codes or check engine lights?
Check all fuses.
97 is a bad year on ign switches.
are injectors getting 12 volts to pos side.
Have you got injector pulse?


Fuel pressure was around 62 when I turn the key on or crank. Plugs are dry. Not sure if there were any codes. There are no stored codes, but I disconnected the battery while working on it and no new codes pop up while cranking or with the key on. Fuses are good and I replaced the ignition switch a few months ago. Did not check voltage to the injectors yet.

MT-2500
04-04-2009, 09:38 AM
Make sure you have all power at fuse box key on.
Check for 12 volts to injector pos side.
To check for fuel delivery problem.
Give it a squirt of carb cleaner and see if it will fie up.

jeff1367
04-04-2009, 01:45 PM
I will try these things when I get a chance and report back. Is it common for the fuel meter body to fail? A friend of mine has an S10 and had to replace that whole piece that controls the injectors. He thinks that's my problem but I want to be sure before I buy it because it's an expensive part.

MT-2500
04-04-2009, 04:26 PM
I will try these things when I get a chance and report back. Is it common for the fuel meter body to fail? A friend of mine has an S10 and had to replace that whole piece that controls the injectors. He thinks that's my problem but I want to be sure before I buy it because it's an expensive part.

No it is not a common problem.
Each injector is seperate.
The VCM controls injectors not the fuel body.
Remember proper testing before throwing parts at it.

jeff1367
04-04-2009, 07:44 PM
Make sure you have all power at fuse box key on.
Check for 12 volts to injector pos side.
To check for fuel delivery problem.
Give it a squirt of carb cleaner and see if it will fie up.


I do have power at all fuses with the key on. I pulled the connector for the injectors and every positive had about 13 volts. I don't have any carb cleaner but I did try dumping some gas past the throttle body and the car did not even try to start or sputter. When I was checking the fuses, the only one that did not have voltage was crank, which makes sense. I checked the voltage while cranking and it was only 6.5-7. Is this normal? I also touched both leads of the voltmeter to each wire for one of the injectors to see what number would come up while cranking and it was also about 7 volts.

By the way, I REALLY appreciate your help!

manicmechanix
04-04-2009, 08:23 PM
OK it sounds like you have a spark problem or really a system voltage problem. I don't think 6.5-7V is normal. I think you should see over 9.5V when the engine's cranking.

jeff1367
04-04-2009, 08:58 PM
It may be low because I was jumping it from another car. I'm going to get a battery charger and give it a full charge and try again.

MT-2500
04-04-2009, 10:38 PM
It may be low because I was jumping it from another car. I'm going to get a battery charger and give it a full charge and try again.

You need a noid light to check for injector pulse.
Or watch for injector pul;se on a good engine scannner.
If it is getting spark and fuel it should fire.

Pull spark plug and see if any wet or dry on end.

Josh Smith
04-05-2009, 12:59 AM
+1 on the noid light, though I kinda' think the fuel pressure regulator will end up being your problem. That, or a stuck open EGR valve.

I'll also bet your spark plugs will be dry.

Sounds like a lean condition as you've not mentioned gasoline smell.

Josh <><

jeff1367
04-05-2009, 10:32 PM
+1 on the noid light, though I kinda' think the fuel pressure regulator will end up being your problem. That, or a stuck open EGR valve.

I'll also bet your spark plugs will be dry.

Sounds like a lean condition as you've not mentioned gasoline smell.

Josh <><

My plugs are dry. I took off the EGR valve to take a look at it and that plunger is in the right place and I can push it in and it will spring back. I'm assuming that means it is alright. Is there any way to diagnose the fuel pressure regulator?

Josh Smith
04-05-2009, 10:41 PM
What is your fuel pressure at the injectors, or after the regulator? I can't remember how the shrader valve is set up on that one.

What is your fuel pressure, same location, while cranking?

What happens if you turn the key on, off, on, off, on, start? (This is priming the pump).

Right now I'm thinking priming circuit or injector circuit.

Did you try the noid light?

Josh <><

manicmechanix
04-05-2009, 10:57 PM
My plugs are dry. I took off the EGR valve to take a look at it and that plunger is in the right place and I can push it in and it will spring back. I'm assuming that means it is alright. Is there any way to diagnose the fuel pressure regulator?

You could pinch off the return line and see if that helps. Earlier you said you put gas in the throttle body and it still wouldn't fire up. That would indicate you weren't getting good spark and maybe because your battery voltage is too low. If the voltage is below about 9Vs the PCM won't cycle the injector. This serves as a safety feature for the engine and cat.

MT-2500
04-06-2009, 09:12 AM
Recheck for good hot blue spark to all spark plugs.
Make sur engine is cranking good.
Remember 97 is a bad year on ign switches.
Double check all 12 volt ign on voltages.
Does security light work right?
Any aftermarket anit theft or remote stat stuff?
A quick test for fuel delivery problem is to give it a shot of carb cleaner while cranking.
If it fires up with carb cleaner you have a fuel delivery problem.
For fuel pressure check you will need a fuel pressure gauge.

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 or hot and fuel pressure testing guide lines.
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.

jeff1367
04-06-2009, 08:59 PM
Well I went and bought myself a fuel pressure gauge and some starting fluid. It fired right up on the starting fluid so that eliminates spark. Fuel pressure jumped right to 62 with the key on and after the fuel pump shut off, it dropped to 54. I left the key on for awhile and the pressure started to slowly drop. After about five minutes it was down to 45. Is this normal or is it leaking pressure somewhere? I'm going to pull off the plenum in the morning and poke around in there.

manicmechanix
04-06-2009, 09:36 PM
So it will fire up with starter fluid? I don't think fuel pressure should drop that much but I haven't worked on CPI's much. I don't think this is keeping it from starting. It sounds like your injector isn't cycling. Were you able to get battery voltage over 9Vs? Apply +battery with a test light to the harness side of the injector ground to see if the computer is pulsing the injector during cranking.

jeff1367
04-06-2009, 10:21 PM
So it will fire up with starter fluid? I don't think fuel pressure should drop that much but I haven't worked on CPI's much. I don't think this is keeping it from starting. It sounds like your injector isn't cycling. Were you able to get battery voltage over 9Vs? Apply +battery with a test light to the harness side of the injector ground to see if the computer is pulsing the injector during cranking.


Yeah, it runs for a few seconds with starting fluid. Battery voltage is fine, what I was talking about earlier was the fuse that was labeled crank. It showed 6-7 volts while cranking. I did stick a test light in the injector harness and it was flashing while the engine was cranking.

Josh Smith
04-07-2009, 02:12 AM
Yeah, it runs for a few seconds with starting fluid. Battery voltage is fine, what I was talking about earlier was the fuse that was labeled crank. It showed 6-7 volts while cranking. I did stick a test light in the injector harness and it was flashing while the engine was cranking.

Take that battery to Autozone and have it tested. A good battery should pull down no more than 11v when cranking.

Have them charge it then ARBST test it.

I've seen a bad battery cause your condition exactly ONCE in 15 years. It is not common, but worth checking.

Having worked at Autozone for a bit in my early 20s, I can tell you that most of their stuff is junk, with the exception of the batteries. IMNSHO, among all the lead-acid automotive batteries out there today, the Duralast Gold is the best. I will only run that, or the Optima gel-cell.

Josh <><

manicmechanix
04-07-2009, 02:33 AM
Yeah, it runs for a few seconds with starting fluid. Battery voltage is fine, what I was talking about earlier was the fuse that was labeled crank. It showed 6-7 volts while cranking. I did stick a test light in the injector harness and it was flashing while the engine was cranking.


Well you shouldn't see 6-7V while cranking, but if you are getting power to the injector and injector pulsing, fuel pressure is good and the engine starts with starting fluid, then you pretty much narrowed it down the injector not delivering fuel. Have you checked the injector's resistance?

jeff1367
04-07-2009, 02:51 AM
Well you shouldn't see 6-7V while cranking, but if you are getting power to the injector and injector pulsing, fuel pressure is good and the engine starts with starting fluid, then you pretty much narrowed it down the injector not delivering fuel. Have you checked the injector's resistance?

No, what is the resistance I should look for?

MT-2500
04-07-2009, 09:16 AM
Well I went and bought myself a fuel pressure gauge and some starting fluid. It fired right up on the starting fluid so that eliminates spark. Fuel pressure jumped right to 62 with the key on and after the fuel pump shut off, it dropped to 54. I left the key on for awhile and the pressure started to slowly drop. After about five minutes it was down to 45. Is this normal or is it leaking pressure somewhere? I'm going to pull off the plenum in the morning and poke around in there.

Should not have a fast leak down.
But check pump pressure before taking it apart.
You need 65 lbs of pressure with good fuel volumn on a cold start.



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 or hot and fuel pressure testing guide lines.
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.

manicmechanix
04-07-2009, 12:59 PM
No, what is the resistance I should look for?


I don't know, I think the earlier models should have at least 1.5 ohms and later models which I think yours is should have around 12 ohms.

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