Help me I'm stumped. Truck died and will no longer run.

[borahshadow]

For starters I'll just tell the short story. Long story after the break.

The other day I started up my truck and when I tried to give it throttle to accelerate the RPMs would drop and almost die. I'd let off the gas and it would come back up to a fast idle (It was mildly chilly outside at 30s). Within about .5 mile of my house it died and I could no longer restart it. Me and my uncle thought it sounded as if the motor couldn't get enough fuel. It has been a while since the fuel filter was changed so I pulled the filter and it was pretty stopped up as I couldn't blow through it easily. I replaced it with a new one which was much easier to blow through. Unfortunately I still can't get it to run. I hear the fuel pump prime when I turn the key so I think the fuel pump is ok but I don't know for sure. I'm confident that I've got spark as we tried to get it to fire with a little shot of starting fluid and it backfired so there's gotta be a spark somewhere at least.


Detailed (Long) story

I usually park my truck inside where it rarely gets much colder that 30. It usually starts nice and quick as it's not very cold. I parked it outside the other night as I knew I'd need the shop for some other things the next morning. The next morning I needed to move it out of the way so I went and started it up. It was just barely above 0 so obviouly it took a little extra cranking (maybe about 3 seconds where it normally takes about 1-2) to start up. Nothing out of the ordinary. I only had to move the truck maybe 50 yards so it really didn't get a chance to warm up. I was pondering whether or not to let it idle to get up to temp before I turned it off or to just turn it off. While I was thinking it sputtered and died. I thought that was odd so I started it up and it started up fine but within about 1 minute of idling it sputtered and died again. I didn't want to worry about it at the time so I just wrote it off as an effect of being colder than it's used to and went back to work.

It sat outside all weekend where it was probably 10-30 degrees most of the weekend. Monday I got called to do a job so had to drive. (It was about 30-40 on Monday.) It had to crank for awhile (maybe 5 seconds) then I drove away. I pulled out on the road and observed the above noted behavior where it would almost die when I would give it gas. I was close to home so I got towed back to home and put it back in the shop. I put the charger on the battery as I brought it low when I was cranking on it for a while. As I noted above I replaced the fuel filter, but I still couldn't start it. I thought that the fuel pump sounded different than I remember at it would make a bit of a pulsing lower pitched noise when the key was turned on and I'm used to it making a whine. After I replaced the fuel filter (emptying the gas lines in the process) I noticed it made the familiar whine but then made the thumping noise again so maybe that's normal when the lines are already mostly pressurized.

I should note (but I am embarrassed to) that I was low on oil through this whole deal. As I've mentioned in another thread my truck has been burning a lot of oil lately and I forgot to check the oil at the last fill up. I was probably about 1.25 - 1.5 quarts low. I brought it up to normal and it still won't start. (I don't see why bringing it full would have changed anything but it was worth a shot and obviously needed to be done anyway. The engine isn't seized and I've never seen the oil pressure lower than normal lately. Never lost oil pressure.

It's probably obvious from my explanation but the truck cranks over fine. It just won't fire at all.

I'm at a loss on this one and none of my mechanically inclined family members have any more ideas and I really don't want to take it to a mechanic if it's something that I can fix myself (which should be most things if I can just figure out what it is)


Your help will be very appreciated!

 

[ccreddell]

It has been a while since the fuel filter was changed so I pulled the filter and it was pretty stopped up as I couldn't blow through it easily. I replaced it with a new one which was much easier to blow through. Unfortunately I still can't get it to run. I hear the fuel pump prime when I turn the key so I think the fuel pump is ok but I don't know for sure./

If you have a way to check fuel pressure, thats what I would do first. Also, what year, what engine?

 

[scmsltn]

And there are no engine codes?

 

[borahshadow]

If you have a way to check fuel pressure, thats what I would do first. Also, what year, what engine?

I don't think I have any way to check fuel pressure without buying, borrowing, or renting something.

It's in my sig but it's a 1997 350 Vortec.

And there are no engine codes?

I didn't notice a check engine light right before it died and now the truck is at my house and I don't have a code scanner. I normally borrow one from the local parts store but I'm not sure they'd be ok with me taking it and running home 15 minutes away with it lol. "Yeah I'll have it back to you in 45 minutes."

 

[96twodoor]

I agree with ccredell,the fuel pump may still be making noise but that doesn't mean its puting out the appropriate pressure to run the truck. You are correct you will needa fuel pressure gauge that needs to be bought or borrowed. I would start there as that's the easiest ( albeit not the cheapest) .

Edit: ill have to look up the actual fuel pressure its suppose to have @ key on / cranking. Maybe one of these more knowledgeable guys know them off the top of his head ( draggin where you at lol )

 

[MOBS]

Tried pouring gas in intake and holding pedal to the floor while cranking? If it's fires off and revs then dies, it's a fuel issue. If not, then it's most likely your timing, as you already stated it backfired which is something a no-spark vehicle would have a hard time doing.

Also, just an fyi, but starting fluid is actually bad on your pistons and rings.

 

[borahshadow]

I agree with ccredell,the fuel pump may still be making noise but that doesn't mean its puting out the appropriate pressure to run the truck. You are correct you will needa fuel pressure gauge that needs to be bought or borrowed. I would start there as that's the easiest ( albeit not the cheapest) .

Edit: ill have to look up the actual fuel pressure its suppose to have @ key on / cranking. Maybe one of these more knowledgeable guys know them off the top of his head ( draggin where you at lol )

I think that Autozone will loan/rent tools. I've got a buddy at another parts store so I might check with him as well. If you or someone else could chime in with the correct pressure that would be great. I think I saw somewhere like in one of the towing threads where someone was discussing the appropriate fuel pressure but I'd have to try to dig it up.

Tried pouring gas in intake and holding pedal to the floor while cranking? If it's fires off and revs then dies, it's a fuel issue. If not, then it's most likely your timing, as you already stated it backfired which is something a no-spark vehicle would have a hard time doing.

Also, just an fyi, but starting fluid is actually bad on your pistons and rings.

I might have to give the gas-in-the-intake trick a try. Just take the plastics off and pour a little down through the throttle plate?

Thanks for the FYI. I've heard that starting fluid isn't the greatest if you can avoid it but I guess I didn't know that it was bad. I've also heard that it's an absolute no-no for diesels right?


Edit: I think I got the fuel pressure numbers.

This post is the one the guy mentioned it in.

http://www.gmt400.com/forum/showthread.php?3254-5.7-vs-5.3&p=95649&viewfull=1#post95649

And here's the fsc thread that he mentioned
http://www.fullsizechevy.com/forum/general-discussion/technical-maintenance/466490-1998-fuel-pump-testing-numbers-before-after-new-pump-installed.html

 

[MOBS]

I might have to give the gas-in-the-intake trick a try. Just take the plastics off and pour a little down through the throttle plate?

Thanks for the FYI. I've heard that starting fluid isn't the greatest if you can avoid it but I guess I didn't know that it was bad. I've also heard that it's an absolute no-no for diesels right?

Yeah, right on down into the intake, make sure you press the pedal to the floor, or prop the throttle plate open while cranking.

Starting fluid has a high temp flash point that scorches the ring seats in the pistons and rounds out the normally squared seating surfaces, causing the rings to rock/flex in the grooves. This causes excessive blow-by, and it's especially bad for diesels because they don't have a spark to assist proper combustion, so they need to be able to retain higher pressures on the compression stroke....more pressure loss, less likely the engine will start or remain running after it starts.

 

[DRAGGIN95]

Agreed, pour some fuel in it and see if it will start, and check fuel pressure if you can.

 

[Aloicious]

I'd almost put money on it being your fuel pump...the symptoms and events you describe point right to it. The vortec motors are very sensitive to fuel pressure changes, the poppet valve injectors are pressure operated and if the pressure gets too low they just simply don't function, and it doesn't have to be very low for them to become non-functional, even just a few psi can be the difference between a working truck and a paperweight....

you need to get a fuel pressure gauge to test what it is running at....go to autozone or orileys or somewhere, usually they rent tools like that for free....if not, they aren't expensive if you want to buy one....

check the pressure at the fuel rail port...it should read 58-60psi at key on engine off, if you're able to get it started, it should stay in the 55-60 range....if you're below that (even by just a few psi), then its your fuel pump. get that setup changed out and you should be good....also don't get a off-brand pump assembly...delco or delphi only unless you want to be changing the pump again in 8-12 months.

I bet the clogged filter burnt up your pump at least partially, but enough to limit it's output enough to make the fuel injection spider non-functional, its a very common chain of events if the fuel filter isn't changed routinely enough.....