Head scratcher

[spiral]

Hello everyone..New member!
Thought I would post here and see if anyone has any ideas because I'm stumped..This is the problem..
A friends 03 trailblazer came in to the shop ..Cranking but no start..He replaced fuel pump and pressure regulator on fuel rail before it was brought to me..He also mentioned he put ignition switch in, but it still would not start so he took it back and got a refund..
So I started my normal troubleshooting..Checked all fuses..Fuel pressure is at 65lb or so on check valve on fuel filter..Pressure is 85lb at the line at fuel rail..Have fuel pressure when cranking..I have spark..I sprayed fuel into throttle body and it will fire and run..
So my thoughts was injectors not firing..So I got a wiring diagram offline..I have 12v on pink wire at injectors with switch on and cranking..I hooked an LED light to the injector grounds from PCM and I'm getting the signal to all injector grounds from the PCM when cranking (LED flashes)..I unplugged injector harness and injectors OHM good..11.5 K.. So harness should be good from plug to injectors..
No security light blinking , no codes..I just can't find a problem anywhere..Checked grounds and voltages everywhere I can think of..The engine has everything it needs to start as far as I can tell, but it just won't..Usually with a multi-meter and scan tool, I can figure out where the problem is, but this one has me confused..Any ideas or help would be greatly appreciated because I'm running out of things to check..It's probably something simple and stupid that I'm overlooking, but I just can't find a problem that would keep it from running...Thanks in advance..

 

[budwich]

well... you did lots of good stuff, but your "history" is lacking...
what miles and why did your friend do what he did?

Next, you need to verify the mechanical "sanity" of the engine with a compression test. Further, since you are there, you will be pulling the plugs, what is their state?

 

[spiral]

well... you did lots of good stuff, but your "history" is lacking...
what miles and why did your friend do what he did?

Next, you need to verify the mechanical "sanity" of the engine with a compression test. Further, since you are there, you will be pulling the plugs, what is their state?

Miles are around 190,000..Truck was running and sputtered a little and just died..The friend thought it was fuel pump and just replaced it without any testing along with regulator..After cranking on it for awhile, I pulled plugs and all look good, chocolate color and bone dry..Not wet with gas.. It runs fine as long as I keep spraying gas into throttle body..The fuel from the rail is not reaching the engine for some reason..I know what the problem is, I just don't know why it has the problem..I can't find anything wrong that should keep it from starting..

 

[Sparky]

So basically not getting fuel injected despite the voltage and signal being there.

If you apply voltage to an injector directly, can you hear it click?

Would seem odd that all of them would fail, but, hey, worth checking.

Another thing then is to pull the fuel rail from the injectors and make sure they aren't somehow clogged or something preventing fuel from actually hitting the injector.

 

[AWD V8]

If you throw fuel in it and it fires and dies, you know it at least has spark. If you have fuel pressure in the rail, and you have a flashing LED or NOID then either all injectors are dead ( like really!), or the fuel in the system is not what the engine needs. Test the injectors by adding a battery + and ground, see if they click. You could also pressurize the system with the engine off and do the injector thing, pressure should drop if the injector is opening.

Compression or valve timing is a moot point at this point as it WILL fire when you add fuel.

 

[AtlWrk]

85psi at the fuel rail is very high (should be in the 50s) and it doesn't make physical sense to have more pressure at the rail than the filter port--was that supposed to be 58 at the rail?

Agreeing with Budwich: were the pump and regulator replaced because of the no-start condition or did the no-start condition occur after the replacement?

(EDIT: D'oh, didn't get notified that others had responded while typing this)

 

[budwich]

thanks for the "history update". Did you do any "sensor connector" checks?

hmmm... what's the 11.5K ohm reading again?

 

[spiral]

No, at the big line at the rail is, pressure is 85 and at test valve at filter it reads around 65..Maintains that pressure in both places while cranking..I thought that was a little odd that it would be higher at the rail, But that's the readings..Actually, now that i think about it, I have never seen pressure that high..Hmm..
I think I will test this again and do the procedure AWD V8 mentioned on injectors..

 

[budwich]

not sure if you missed my question... what's the 11.5K ohm measurement? surely this is wrong either as typing or "test procedure".

 

[spiral]

That's from pink power wire to signal grounds on injector harness..I checked that just to insure harness is intact and didn't have an open circuit on injectors..

 

[budwich]

well, IF its not a "testing problem", you have found your issue. There's no way you will get 11.5K as in Kilo OHMS on that path. Your issue is likely a bad splice on the power "line".

 

[spiral]

The 11.5K is thru each injector..From pink to each of the grounds on each injector, with injector harness unplugged(at top of valve cover).I have some other injectors laying around and they measure 10.2K..

 

[budwich]

???.... there is no way an injector coil is going to measure "anything K".... 12 ohms maybe.

 

[spiral]

Ha,ha you are right..I went back out and checked just now, but this time I took my glasses..11.5 ohms..NOT K..My bad..

 

[budwich]

OK.... now that you got your glasses on... how about checking the fuse...

Further, what kind of "led light" were you using?

 

[spiral]

LOL..It was recommended on some other forum for checking injector pulse some years ago..I think I got it at Radio Shack..

 

[Mooseman]

I think that pressure is way too high. Maybe the injectors can't handle that much? On 03's, they had a pressure regulator. Maybe that's the problem because everything else seems to be there.

I also found a post with a very similar issue to yours, which would up being the fuel rail/injectors. He didn't say what the problem was but I think something just clogged up all the injectors. He also indicated he had high pressure.
http://gmtnation.com/forums/threads/03-trailblazer-cranks-but-wont-start.16619/#post-527640

 

[Reprise]

Once the OP gets his issue resolved, I'm going to ask about the FPR in the '03s vs the later MY. Learned something new today...

But for now - I did a search on the part - it looks like it's sub-$20 USD and fairly easy to get to - I might try that, before going for the rail (or worse, the injectors).

At the very least, it would be worth removing to check it - there's a screen that can get clogged (which can be cleaned, but if the FPR is 'contaminated', then it's recommended to 'replace' it).

 

[Sparky]

Said he replaced the FPR on the fuel rail already...

I'd still want to yank the rail/injectors to check for blockages at this point.

 

[spiral]

I think that pressure is way too high. Maybe the injectors can't handle that much? On 03's, they had a pressure regulator. Maybe that's the problem because everything else seems to be there.

I also found a post with a very similar issue to yours, which would up being the fuel rail/injectors. He didn't say what the problem was but I think something just clogged up all the injectors. He also indicated he had high pressure.
http://gmtnation.com/forums/threads/03-trailblazer-cranks-but-wont-start.16619/#post-527640

Thanks for the post..Where I'm getting the high pressure is at the big fuel line where it attaches to the rail..That eliminates the regulator because its at the other end of the rail with the return line..Plus, its been replaced..I am curious why the pressure is that high and at the valve at fuel filter (where you are supposed to check it) is around 65lbs..

Said he replaced the FPR on the fuel rail already...

I'd still want to yank the rail/injectors to check for blockages at this point.

Yes, that's my plan as of now..Pull the rail..May be Wed before I can get to it..Will be busy tomorrow..Thanks for all the replies every one and I will update as soon as I know more..

Mod Edit: Please use the +Quote button instead of posting consecutively. Posts have been merged.

 

[Tiggerr]

Said he replaced the FPR on the fuel rail already...

I'd still want to yank the rail/injectors to check for blockages at this point.

The FPR origin is unknown though... it was replaced by the owner....could it be faulty CCC regulator?....lord knows these trucks are very temperamental when it comes to aftermarket parts....

 

[Mooseman]

Unlike fuel pumps, I don't think there are any CCC regulators as there isn't that big a market for them.

I have a feeling the injectors are clogged or the pressure is too high for some reason. Other slim possibility is that the fuel system is badly contaminated with water and injectors are just spraying water. If you get the fuel rail out, you could reconnect everything and see if they spray while cranking.

Another thing to do is find someone or a shop with a Tech 2 and have an injector balance test done. You could also do a lot of diagnostics with it, including injector pulses and voltages.

 

[Reprise]

Other slim possibility is that the fuel system is badly contaminated with water and injectors are just spraying water.

I was thinking this same thing earlier, but when he said his plugs were dry, discounted it. Wonder if the OP had recently filled up?

 

[spiral]

Problem solved..Sorry for the delay on the update, but just got around to changing the fuel rail and injectors out today with a used unit..It fired right up and ran great..I have no idea what was wrong with original fuel rail..All injectors checked good, but none would spray fuel..