1998 Tahoe 5.7 Usually wont start, but sometimes does

[MT-2500]

Guide lines for hard to start.
First check for spark to spark plugs at 2 or more plugs.
Then check for proper fuel pressure.
If spark and good fuel pressure then move on to injector pulse check.
Also if you have spark feed it a little carb cleaner not starting fluid and see if it will run.
On the fuel pressure check.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Most Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Even 1 or 2 lbs low will give a no start.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
MT

[MT-2500]

Originally Posted by Tagahoe

happend again. i now know its electrical. my pump sometimes doesnt get power. im going to be going over the electrical stuff tmrw. im tired of this sh*t! i want to fix it once and for all. i almost got the dealership to do it, but damn, they are crazy as joe rogan.

First check for spark to spark plugs.
If you have spark to plugs then jumper the fuel pump prime conection or see if it has 12 volts on it when no start.
If jumpered or it has 12 volts on it the fuel pump should run.
Mt

[teknology]

where's the fuel pump prime connection?

[Tagahoe]

just saw this old post. i'll try to find the fuel prime connection and try jumping it and check voltage.
thanks MT-2500

[Tagahoe]

well i was gonna check the voltage, but when i went to start my tahoe, it started, so i turned it off, unplugged what i thought was the prime connector, to make sure that was it, i checked if it would start (which it shouldnt), but it did. so i guess i dont know where the prime connector is. but my tahoe started over and over again with no problems. fuel pump kicked on everytime. i dont wanna drive it, till i find out whats going on.

[primal1]

mine was doing something similar. i found out it was the battery connection. gm used 2 connectors on the battery terminal. the conct area between the 2 becomes corroded. i cleaned mine, put on some anti-corrosion gel, and put it back together. have not had a problem since. when i was reseaching for mine i found that it could also be the anti-theft device. if you need to bypass it, you can find out how on this site. do a search for "passlock bypass". good luck.

[tahoe53]

Originally Posted by txgearhead

Your issue defintely sounds like the Passlock has gone bad, which they have been known to do. I've got a 98 and I have been lucky that the Passlock system has only shut the fuel pump off about 5 times and I know what not to do....tu8rn the ignition so ast it dioesn't have time to recognize the key!

This post is old and you may have already fixed the issue, if not reply I've got schems, etc.

I have a 99 tahoe with the same security problem, i have changed the passlock, key cylinder, pretty much everything in the security system except for the wiring itself. I am stumped completely, it turns over then shuts itself off and blinks security, i also have recently changed the fuel pump in the gas tank. Please help!!!

[erstadmr]

Originally Posted by Acclude91

I have a 98 Tahoe in my shop now with similar issues. The entire fuel system is new and has all new wires for the pump, sending unit, and pressure sensor. It has just under 60 PSI at the fuel rail and my scan tool says everything is working fine. The only reason it won't start is because of the security feature prohibiting it (VTD). The injectors are getting the +12V they need, but the ECU just won't pulse the ground needed to operate them. I've been trying to find info on this security feature and how to "reset" it. GM says to put the key in the ignition and turn it on and let it sit for 10 minutes. That didn't work. I re-programmed the keyless entry remote and that didn't work either. Another GM dealership said that there is no way to reset it and that there is probably something wrong with the Passlock security feature. You guys might be having a different issue because fuel issues are common on Suburbans/Yukons/Tahoes, but the 98 Tahoe in my shop won't start because of the security feature. If anyone has any info or diagrams of the VTD system please PM or email me with the info. Thanks in advance for any help.

I've had a similar problem: Put the key in, crank it, it starts and with in a second it shuts off. Dealership replaced the sensor in the steering column and this fixed the problem. This sensor reads the key and matches it. The only way to get around this (untill you actually fix it) is to put your key in, crank it, let it start and die, now....without touching the key leave the key in the on position 3 minutes, then....turn it off for 1 minute, then....turn it back on for 3 minutes (without cranking the engine) then off for 1 minute and back on for 3 more (without cranking the engine)....This came from a friend that works at a GM dealership. Somewhere within those last 3 minutes the "Security" light in the dash should go out, and if it does it will start.http://www.automotiveforums.com/vbul...lies/chair.gif

[wafrederick]

Check the fuel pressure and it might be a fuel pump agian and did you replace the fuel filter when you replaced the fuel pump?That is part of the warrenty of a fuel pump,replacing the fuel filter.The old fuel filter is full of dirt and trash that will ruin the fuel pump right awayThe fuel pressure specs are 60-66 psi and will not run under those specs.