My issue is pretty vague so far, but I will tell you what I know:
My wife was driving the H3 yesterday, and while going through town at about 20 mph it just stalled out. She said she just all of a sudden noticed that the car wasn't running anymore and then she pulled off the road. She tried re-starting it. The battery seems good. The engine turns over fine, just won't start. Sadly, I couldn't help her because I was unreachable at work. Once I found out 5 hours later, she had already paid to have it towed to a shop. I have not heard anything from the shop yet. They said they would call to talk to me before they made any repairs.

I just don't want to be raked over the coals on this one. Can anybody give me pointers on what things I should rule out first. (preferably the easier and more likely things first) I usually try to do a lot of work myself, but I now live quite a ways from home (and my brother's 3 car garage w/ car lift ). Should I be worried about issues with the head or head gasket?

I always take care of my vehicles, so this is a big bummer.

06 H3 ~55k miles
5-cyl 3.5L
Automatic
Adventure / Luxury package (all options available)
everything is stock including the 33" tires (285 65 16)

I don't live near a Hummer dealer. I am in Delta, PA 17314.

So pointers on what to start checking if the mechanic gets stumped or wants a ton of money?

I do have some basic tools (craftsman wrench set, compression tester, fuel pressure/vacuum tester), but I have almost no experience using them on this thing besides basic maintenance and a parking brake issue that is the unresolved subject of a different post.

 

"Should I be worried about issues with the head or head gasket? "

Only if your vin falls within the affected units. Even if you have a bad valve seat (which is the only "Head issue") that will not shut off the motor immediately, rather it would run rough for a while and should throw a CEL and code.

Same thing with a broken valve spring, retainer, rocker, and stem.

I'm guessing fuel delivery problem(s), since on the I5s you won't loose all ignition without a circuit failure (blown fuse/tripped relay) because of the individual coil on plug packs. First thing I would do is check fuses if no code shows up when scanned.

 

Good news and Bad news:

Good news: The mechanic started the car today and it ran just fine for 3 hours (zero repairs).

Bad news: There were no codes on the computer or in the history. He said all the parameters looked good.

He told me he thinks it may be the fuel pump, that might have an issue only when it gets hot and that it might be somewhat random as well. He offered to let me keep it at his shop until I figure out a solution, but I told him I would rather have it home. At least now my wife is on my AAA policy (starting 14 days from now) and I can know that I will have a free tow next time.

Fuel pump costs around $300-$400. So I would rather not replace it for no reason.

Can anybody recall any issues like this where a car suddenly stops running and then mysteriously runs fine the next day.

 

I think there's a filter on the fuel pump inside the tank. I'd make sure it was OK before replacing the entire pump module.

 

I went to pick up the H3 this afternoon. Payed $40 for the mechanics time looking into it, then went to start it up. It won't start!!!
So now we went into troubleshooting and sprayed some 2+2 (carb cleaner) into the air intake pipe. The truck started right up then, but would only stay running while the stuff was being sprayed into it. Repeated 2 or 3 times to confirm. So we are thinking the fuel pump.

Thanks for everybody's input thus far. I will make sure to check the filter out before I change the pump.

We did check both the relay and the fuse for the fuel pump. Both were good.

Any other ideas on what could be keeping me from getting fuel? He said if it was the injection system, it would be throwing a code.

How much work is the pump change-out?
I assume the tank has to be dropped to get the pump out, right?
There is no access port from the interior, right?

I do have a friend or 2 that might be willing to help out with this, so is it worth it for me to attempt this on my own?
Any special tools needed? I have a ~250 piece Craftsman set (the big black plastic toolbox with 3 drawers and a top tray).

Should I attempt to change the filter without having a new pump handy?

Well, regardless, I am sure the mechanic would love me to pay him to replace it, but I had him leave it outside his gated parking lot just in case I want to do it this weekend. Not sure where i could get the parts locally. I doubt the fuel pump is a shelf item at the local Advance Auto or Auto Zone. From a bit of research, it looks like the fuel pump should be identical to one from a Colorado, so maybe a GM dealer.

Here is one on ebay for $322
ACDelco MU1473 Fuel Pump Module Assembly | eBay

Not sure if I should just buy this or try to find one at a local dealer. I am going to call around.

Also, one other question:
We are sure it is not in "crash mode" right?
https://www.hummerforums.com/forum/h...sh-mode-20684/
Not sure if there is any validity to that reasoning (short under passenger seat, causes "crash mode"). Is there anything in the computer that could shut the fuel off. I did recently have some water on the floor. My wife told me she spilled a big jug of water. It has been about a week and still wet. We left the doors open a few days to air it out, but it didn't help. The floor still seems a bit wet and I am starting to suspect some type of roof leak. We have had a decent amount of rain recently.

Also not sure if this post is applicable:
https://www.hummerforums.com/forum/h...urn-off-21504/

Sorry this one is a bit wordy, but oh well.

 

fwiw, the scanguage 2 shows a ton of stuff including f pressure.
im just getting to know it so i dont know much.
got mine at autozone $139

oh, i hear,no filter,anywhere.

 

I have a scanning gauge. One that links to my phone via bluetooth. It only gets me the following:
Engine RPM
Engine Coolant temperature
Speed
Timing advance
Vacuum pressure

All of these are useless to me. I know that I am not getting fuel. Just need to determine what is causing it. I have been researching for the past hour and getting kind of discouraged. Nobody knows whats going on. Every time I find a scenario that looks identical to mine, the person never follows up to document how they fixed it. I promise I won't do that here. I am just hesitant to spend over $300 on a fuel pump plus an unknown amount for the install, only to have the same issue. I should specify that I am just running regular fuel from a pump. I am not making my own brew in the basement.

But for Pete's sake, These H3's have been around for 8 years and nobody has ever documented how to change a fuel pump. It must just be that easy, that nobody ever cares to document it... Maybe I am not looking hard enough on this site or the wonderful endless internet...

 

To Quote DOC,

Looks like you just replace the fuel pump. Remove skid, drain tank, remove braces, remove tank, unplug old fuel pump, remove old fuel pump and gasket(if there is one), replace pump and gasket (if there is one), then put it al back together after testing.

Depending on the year and condition of the underbody I suggest you spray some kind of penatrating oil on the skid bolts and bracket bots for a few days prior to the R&R.

 

do you know positivly that the fuel injectors are actually working, or is it actually no fuel pressure?

can you make a continuity test of the pump circuit b4 you tear it apart? could it be a intmt connection?
injector circuits,,fuel pump circuits,,,all electricity huh.

a dead injector circuit could act exactly like a dead fuel pump,,,no gas into the motor.

 

do you know positivly that the fuel injectors are actually working, or is it actually no fuel pressure?
I haven't tested the fuel pressure with a guage yet, although there looks like there are threaded pressure taps. 2 parallel lines coming up the driver side of the motor, one going to a dead end and a pressure tap. The other going towards and down into the intake area.

can you make a continuity test of the pump circuit b4 you tear it apart? could it be a intmt connection?
injector circuits,,fuel pump circuits,,,all electricity huh.
I am uncertain how I would tie in to test a circuit. I would probably have to drop the tank.

a dead injector circuit could act exactly like a dead fuel pump,,,no gas into the motor.
Anybody ever heard of a dead injector circuit one of these? not sure how to test this either
Thanks for everybody's unput thus far