97 TAHOE 5.7L VORTEC WON'T START...GM Merlin ideas?

[tempfixit]

I recommend that when you change the plugs check the compression while the plugs are out. Then you know if compression is good or not.

[motobtn]

Will do! Thanks!

[777stickman]

In response to a question on the ECT needing to re-learn or be "flashed" the answer is NO.

As to the Crank Sensor (CKP) being replaced, this will need the "CKP variation learn procedure" accomplished. This requires a high end scan tool in the hands of competent technician.

[motobtn]

Well, it started up again today, and I checked the IAT and it was close to the CTS, which matched spec. I also checked fuel pressure for 15min with key on engine off, and it help 60psi. Hopefully this is fixed, just a little gunshy after thinking I have fixed it a few times now. Just need some real cold weather to verify.
That being said, and it has been a while since I haven't owned a diesel or newer gas vehicle, should I NEED to put HEET in when it is cold, or is that just covering something up?
I know a lot of people here in MN will just throw in some HEET when their cars won't start, but I feel that shouldn't need to be done unless something isn't right...is this correct thinking? thanks!

[j cAT]

Originally Posted by motobtn

Well, it started up again today, and I checked the IAT and it was close to the CTS, which matched spec. I also checked fuel pressure for 15min with key on engine off, and it help 60psi. Hopefully this is fixed, just a little gunshy after thinking I have fixed it a few times now. Just need some real cold weather to verify.
That being said, and it has been a while since I haven't owned a diesel or newer gas vehicle, should I NEED to put HEET in when it is cold, or is that just covering something up?
I know a lot of people here in MN will just throw in some HEET when their cars won't start, but I feel that shouldn't need to be done unless something isn't right...is this correct thinking? thanks!

most times the fuel supplier causes water to be in your tank. keep tank around 1/-3/4 full..

if you have problems with fuel contamination go to another station and use some dry gas. this is done when you get below 10 deg f or the fuel purchased is bad.

[motobtn]

Originally Posted by j cAT

most times the fuel supplier causes water to be in your tank. keep tank around 1/-3/4 full..

if you have problems with fuel contamination go to another station and use some dry gas. this is done when you get below 10 deg f or the fuel purchased is bad.

Thanks! My question is moreso, because it doesn't happen to me on new vehicles, is the HEET just covering up a deeper issue, or did older vehicles just need HEET sometimes, even when they were relatively new. basically, I have no problem using HEET when it is cold, but would rather just fix the issue if there is one to be fixed, assuming gas is good and temps are no lower than -30F.
Thanks!

[j cAT]

Originally Posted by motobtn

Thanks! My question is moreso, because it doesn't happen to me on new vehicles, is the HEET just covering up a deeper issue, or did older vehicles just need HEET sometimes, even when they were relatively new. basically, I have no problem using HEET when it is cold, but would rather just fix the issue if there is one to be fixed, assuming gas is good and temps are no lower than -30F.
Thanks!

the problem this year is the weather is changing rapidly from cold to warm and lots of mositure. with alcohol fuels we use the water gets created all the more. the fuel filter will freeze. using heet/dry gas these products breakup the water so it mixes better with the fuel better and reduces the freezing. new vehicles do have less of an issue because the fuel tank has a great vapor sealing pressure controlling system. still this can not help when you buy bad fuel. some stations have been caught adding water. or the storage tank has a leak and water enters.

[mikedlox]

I believe it is an electrical wiring problem.
I am having the same problem, Buy listening to yall have already done and the diagnosis that I performed on my truck im getting some of the same symptoms but with some extra ones. I found a melted wire and not to far from the underhood fuse box. This is a red wire with a white strip on it (not sure were it is going it is bundled with 3 or 4 other wires near the firewall on the drivers side it also runs behind the engine this wire was stuck to the ground wire) pulled it apart and fixed the shorted wire But still have the crank and no start problem. ALso for the extras, Im only getting +-10psi fuel pressure at the rail. so I disconnected the fuel filter and tested there still only 10psi with key on and engine off. Next I cut a hatch in the bed to gain access to fuel pump (YOUTUBE BABY) tested the connection with key on and get 12v for 2 seconds then have about 5 volts steady. Im also getting an evap code that comes and goes on its own but for the past year or two it has been there keeping my check engine light on but it never caused me to not be able to start and truck was runs good once started but havent been able to start it for about a week now. Any help will be greatly appreciated maybe some of the symptoms im having someone else might also

[j cAT]

obviously having melted shorted wiring is a bad situation which needs attention. wires will need to be insulated and covered with a loom material as the vehicle was equipt or similar.

the fuel pump with the vehicle you have requires 60-65psi. therefore with 12volts for 2 sec and 10 psi you will never get it to start.

the fuel pump is shot and you will need a delphi fuel pump. if you use someother type wires/connectors may need be cut spliced to connect to the vehicle wire harness. also aftermarket pumps like airtex are short lived.

[mikedlox]

so did anyone figure out anything...im going to get my truck scanned cause someone told me it could be a burnt out fusable link Have anyone ever heard of this or would anyone have a schematic of a 98 silverado pickup fuel pump wiring any help is appreciated

[777stickman]

For less than $30 you can get all the schematics you want, and more, for 1 year.

http://alldatadiy.com/

Also, did you not read this from j cAT?

the fuel pump with the vehicle you have requires 60-65psi. therefore with 12volts for 2 sec and 10 psi you will never get it to start.

[j cAT]

Originally Posted by mikedlox

so did anyone figure out anything...im going to get my truck scanned cause someone told me it could be a burnt out fusable link Have anyone ever heard of this or would anyone have a schematic of a 98 silverado pickup fuel pump wiring any help is appreciated

first off there is no fuseable link. second with a bad fuel pump you will have no codes. there is no code for a failed pump.

bring the vehicle to a recommended repair shop and have them replace the pump. make sure it is a delphi or gm pump. no airtex pumps or it will not last more than a year if your lucky.

after its fixed keep fuel above 1/3 tank . this will keep pump from damage. you run out of gas a few times good bye pump............

[mikedlox]

thanks a lot guys it was the pump, after extensive trouble shooting and reading thread after thread It was the pump not holding the pressure. After fixing the pump it fired right up. I couldint believe it was the pump because the pump was only 2 years old (maybe cause i dont drive that much)

[j cAT]

Originally Posted by mikedlox

thanks a lot guys it was the pump, after extensive trouble shooting and reading thread after thread It was the pump not holding the pressure. After fixing the pump it fired right up. I couldint believe it was the pump because the pump was only 2 years old (maybe cause i dont drive that much)

not using the vehicle creates fuel debris from the alcohol in it . things start growing. also water with condesation reacting with the fuel tank. fuel filters get pluged, pumps gets stressed.

low fuel levels destroy pumps. with a vehicle this old replace the fuel pump relay. if the pump does not get a strong 12 volts the pump will get damaged.

so what pump was installed today ? 2 years ago ? AIRTEX ? IF this is the pump used , no surprise to most that are experienced in this stuff...

if you know what to do and use these forums , this is a very easy problem to diagnose.

[mikedlox]

well the pump was repaired due to empty pockets. I found out that the low psi was due to a leaking connection where the actual pump pushes into the plastic housing, to finally flow through that seethrough hose. found out the hard way that the pump is not actually held on by the plastic hose and clamp that is around the bottom of the seethrough hose but is pushed into a sort of rubber compression fitting that shrinks and wears out over time. I just rapped about 3 inches of duct tape around the plastic output on the actual pump then slid it into the rubber compression fitting in the housing. Next I put the pump back into the housing and put the pump back in the tank (after testing it in a bucket of water with a fuel tester attached to the (F)connecter on the top of the pump housing). Once back in the tank the truck took about 2 starts to fire up. Drove the truck for about an hour and shut it of about an half hour later I started it back up it started after the second try again but for the most part I can drive again. If your expeirienceing low fuel pressure its probably this connection were the pump is leaking internally and not allowing the fuel lines to build pressure. I will post my results as for how the truck is performing after this fix/repair