[ktrim]

F,I.L. has a 99 yukon 5.7 vortec. It will crank but will not start, Fuel pressure is 63lbs with key on and 68 while cranking. It has a strong spark on all cylinders. cant figure out whats going on. Hooked up an obdII scanner it has no codes. Please help , I need this thing out of my driveway.

Thanks

 

[NOTHINBUT69s]

Did you check fuses in dash and under hood?

 

[ktrim]

checked them all with a meter, all good. also checked to make sure timing chain wasn't broken. still at a loss here

 

[136679ss]

checked them all with a meter, all good. also checked to make sure timing chain wasn't broken. still at a loss here

What kind of wires does he have under the hood?

 

[ktrim]

autozone wires, I have spark at all 8 cylinders, also hooked up a scan tool, it has no codes

 

[Steve340]

Lack of compression? Did you get it hot? I spent forever trying to get a car to start once, when it turns out my buddy had borrowed it and baked it, had no compression.

if you got spark, and fuel, and air, something should go boom boom

 

[ktrim]

compression is good, He drove the car home at midnight, got up at 7:00am to go back to work and it wouldnt start. I cant tell if the injectors are firing because they are inside the intake. Im starting to think the injectors are bad/sticking. I just dont know for sure and dont want him to spend $350 on a maybe

 

[Steve340]

the pop the induction hose off, and spray starting fluid down the throttle body tube while your cranking, it if tries to start you know its lacking fuel, dont do to much, I had a can light on me once, had to throw it QUICK lololol

 

[turbo]

What does the fuel press. do if you turn the key on and wait for the pump to shut off? does it hold or bleed down rapidly? If it has the goofy ces injection or whatever they call it, it may have a plastic hose in the "spider" leaking or a leaking regulator. Have seen them just leak into the plenum and real hard to start if at all. If pressure is bleeding off you will have to pull the plenum and see what is going on. Let us know what you find.

 

[ktrim]

What does the fuel press. do if you turn the key on and wait for the pump to shut off? does it hold or bleed down rapidly? If it has the goofy ces injection or whatever they call it, it may have a plastic hose in the "spider" leaking or a leaking regulator. Have seen them just leak into the plenum and real hard to start if at all. If pressure is bleeding off you will have to pull the plenum and see what is going on. Let us know what you find.

checked this last night, the pressure held for 15 minutes with out dropping..

I think it may be something simple im just overlooking, but am so frustrated with the p.o.s. that I cant think straight enough to figure it out

 

[136679ss]

autozone wires, I have spark at all 8 cylinders, also hooked up a scan tool, it has no codes

Theres your problem, trust me on this one. Those wires carry a lifetime warranty, go replace them at your local autozone, I guarantee she fires right up. Ask me how I know. If you've replaced the cap with autozone stuff, now would also be a good time to get a new one of those as well. I experienced the same exact symptoms with my 99 burban, went through all the usual suspects and changed my AUTOZONE wires cap, and plugs and the truck ran perfect afterwards. Absolutely no symptoms the day before, ran FINE. It didnt' happen to rain the day of or before the truck wouldn't start did it?

 

[136679ss]

What does the fuel press. do if you turn the key on and wait for the pump to shut off? does it hold or bleed down rapidly? If it has the goofy ces injection or whatever they call it, it may have a plastic hose in the "spider" leaking or a leaking regulator. Have seen them just leak into the plenum and real hard to start if at all. If pressure is bleeding off you will have to pull the plenum and see what is going on. Let us know what you find.

If you get the momentary "prime" buzz with key on from the tank with that truck, the fuel pumps fine. My experience with tahoes and burbans, is that it's an all or nothing phenomenon

 

[Chris R]

If your getting good fuel pressure at the gage. There may be problems after the gage then. These have a similiar port injection system to the 4.3, a sort of spider like assembly that has tubes running to each cylinder. It is located in the upper intake plenum. It is all part of the fuel pressure regulator assembly. Perhaps the nozzles are plugged up.

 

[136679ss]

If your getting good fuel pressure at the gage. There may be problems after the gage then. These have a similiar port injection system to the 4.3, a sort of spider like assembly that has tubes running to each cylinder. It is located in the upper intake plenum. It is all part of the fuel pressure regulator assembly. Perhaps the nozzles are plugged up.

chris, if the fuel injection branches were clogged the engine would throw 2 conditions:1 single, or multiple cylinder misfires, or 2 Lean condition.
I know you said you had spark at all 8, and plug wires sounds very trivial. I had the same issue, and spark at all 8. change your wires, that's your problem

 

[turbo]

8 plug wires didn't go bad overnight. You must not be getting any injector pulse. You will need to start checking the harness. Get a subscription to Alldata so you can have the wiring diagrams. I know you said that you checked all the fuses, but double check them again( I have missed a blown fuse before, swore that I checked them all) I believe the ECM fuses are in the underhood dist. box. I don't really know much about this system, but if you get in on alldata there should be enough troubleshooting info there for you to figure it out. Good Luck

 

[NOTHINBUT69s]

Do you have a ground problem? Some guys might disagree with these but i've taken a screw driver handle to the ecm and just tapped on it and hit the key and the old van fired right up, replaced the ecm with no problems afterwards. Also ck the crank sensor and wire.

I dont know were you live but if its possible your buddy put some bad gas in it or you have water in the lines/tank. Take starting fluid like stated above and spray it in the air cleaner tube and see if it fires. How old are the plugs?

 

[ktrim]

changed plugs and wires, still will not start. I did get a backfire out the throttle body and exhaust. Ill start checkeing the harness and fuses again

 

[Steve340]

You can also, cheaply, get a noid,l a clear plastic thing that you plug the injector harness end into, it will flash when it gets the pulse.
So no flash, no pulse, flashes, its working

Easier to simply spray starting fliud down the throttle body, it it starts to start, you KNOW its fuel related

Otherwise your doing a lot of looking and research on the fuel system for possibly nothing

 

[ktrim]

You can also, cheaply, get a noid,l a clear plastic thing that you plug the injector harness end into, it will flash when it gets the pulse.
So no flash, no pulse, flashes, its working

Easier to simply spray starting fliud down the throttle body, it it starts to start, you KNOW its fuel related


Otherwise your doing a lot of looking and research on the fuel system for possibly nothing

tried starting fluid, thats when I got the back fire. I dont think the injectors are firing. I think im going to pull it to a friends garge and have them scope it

 

[72silver4u]

I have a theory, it has spark, it has a good chance of getting fuel, you should be getting some kind of firing. Also when you tried the starting fluid it backfired through the TB, which sounds like it's not sparking at the correct timing. How about the crankshaft position sensor? I've heard quite a few guys that have had troubles with them, and it would make more sense to me. One sensor went down, engine doesnt know where the crankshaft is and when to fire the plugs so no firing. That idea sounds more plausible to me, but I'm no expert. Might want to try this over at www.ls1tech.com , they will have you figured out in no time!