Cranks but won't start

[catmandude]

2000 Bravada. Recently, I have been getting Code P0300 multiple engine misfires detected, she would hesitate erratically when driving only at 2000 RPM. If I let the vehicle sit for a couple days without starting it, she would sputter when cranking and eventually start, but running it everyday she would start immediately. Well, she sat and I cranked the engine today and I heard one sputter/pop and that was it, no attempt to start after that. Here's what I checked/did... Fuel pump is priming for a couple seconds upon turning ignition switch on. I checked for spark at No.1 cylinder plug wire and good spark there. All fuses good. I dumped some gas down intake plenum and cranked...nothing, then spayed some starting fluid down it, cranked and got maybe one cylinder attempting to fire then nothing. I don't have fuel pressure tester but would think if there is spark and injectors are not spraying due to low fuel pressure, the engine should of at least made a attempt to fire once highly flammable starting fluid was directly injected. OK, additional info I'm adding that I think is the problem but there is no fix I can find for this one...The security light in the dash stays blinking when a door is opened (key in or out doesn't matter), then goes out when a door is closed! Totally backwards right? I remember normally the light only would blink after close door and lock the vehicle with the key fob and go out after I unlock with it. Now the second the door is opened the light blinks. The frustrating part is I can't reset the security system because when I put key in the "on" position the light goes out! It doesn't stay on! like there is nothing wrong with it. I did try PassKey III reset sequence- it did not work, Also I tried to disconnect the battery for 30 minutes and now every possible idiot light on the dash lights up when I turn the key to the ON position, and security light still blinking.

[maxwedge]

First verify proper fuel pressure using a gage on the rail port. Post back results.

[catmandude]

No pressure. The passkey anti-theft "security" light is flashing and cutting off the fuel. Engine cranks though. I tried the re-learn reset procedure and it doesn't work. What and how to test next?

[maxwedge]

You said the fp primes, no? So there should be some fuel press. , also pk sec system disables the starter, sounds like something else is going on.

[catmandude]

I do have good spark at coil, cap, and plug!. Pulled plug and it is dry after lots of cranking, injectors not firing?

[Chris Stewart]

The 2 second fuel system "prime" is enough to raise the fuel pressure to 60-62psi necessary to start the engine.
Are there any trouble codes present?

[catmandude]

No P codes present.

[catmandude]

I noticed that while cranking the engine, the RPM gauge does NOT move at all. It should on this vehicle, correct?

[catmandude]

Update, there is RPM while cranking using a scan tool. Also, there is battery voltage on HALF of the pink injector wires. I read somewhere that all these pink wires should have battery voltage in run position?

[catmandude]

Read pins incorrectly...All 6 wires to the injector connector are getting battery voltage with key on, fuel pressure primes at 61 psi, cranking at 55 psi, good spark, I sprayed start fluid down intake and one cylinder while I had plug out to check spark and plug was dry. Crank engine and not even a hint of it trying to start, I am stumped...and stranded.

[Blue Bowtie]

Originally Posted by catmandude

...Fuel pressure primes at 61 psi, cranking at 55 psi, good spark, I sprayed start fluid down intake and one cylinder while I had plug out to check spark and plug was dry. Crank engine and not even a hint of it trying to start, I am stumped...and stranded.

Your 61 PSIG reading KOEO is sufficient, but 55 PSIG may be insufficient to operate the injector poppets during cranking. According to the factory manual 55 PSIG is the minimum regulated pressure for the system while the engine is running, or in other words, when vacuum is applied to the pressure regulator in the intake pod. My own experience with CPFI systems from pickups to Blazers to Astros is that 58 PSIG is the minimum for reliable starting.

It may help to connect a second battery (jump) or large charger/starting unit to maintain battery voltage during cranking so the pump can develop the required 58 PSIG.

Considering that you report a "good spark" and the fact that you applied starting fluid (presumably ether) and got no response is not a complete surprise. Ether evaporates quickly, and unless the throttle body was open it is questionable whether any ether actually made it into any cylinder(s) to allow the engine to fire. It may be more effective to prime the engine with a small amount of fresh liquid fuel instead. This has proven more effective for me but must be done carefully, especially considering the plastic intake which could be less tolerant of backfire. Perform this at your discretion.

Originally Posted by catmandude

No pressure. The passkey anti-theft "security" light is flashing and cutting off the fuel. Engine cranks though. I tried the re-learn reset procedure and it doesn't work. What and how to test next?

If the SECURITY warning is flashing the VTD may be in tamper mode. If you have a scanner available you should be able to read a DTC B3031.

[catmandude]

Check this out.....I got an injector noid tester, plugged it in the "disconnected" FI connector, cranked engine and light flashed, great we got switching, tried next pins, light flashed again! tried 3rd injector pin, light flashed again and the frikkin' engine started this time!!!! It ran for a few seconds then quit. How the heck did the engine start when the FI electrical connector was unplugged?? I quit testing, plugged the connector back in and engine fired right up and purred! I'm thinking perhaps the whole problem started with a weak/going bad battery? It is approximately 6 years old when I checked it and figured that's about the time they start to crap out. I had it on 15 amp charge for 2 days straight, then started to T-shoot again. Ultimately though- did connecting the noid tester somehow reset the system? OR simply was this episode a result from not enough voltage when cranking that threw everything out of whack? Feedback please anyone.

[Chris Stewart]

On older GM vehicles, 7.5vdc was the minimum to fire the ignition. A check of your system voltage while you're cranking the engine over might offer some useful info.