'99 Tahoe Engine/Starting Problems

Have a 99 Tahoe 2wd, approximately 140,000 miles. Bought it at around 80,000 miles. Since I've had it, had intermittant problems where it would not start in the morning. The issue seemed random, the only potential common thread was it seemed to happen most often on rainy/humid days. After it sat for 20-30 minutes, it would start up like nothing ever happened. Over time, I've replaced the mass air flow sensor, ignition module, distributor cap/rotor, plugs, and wires. Recently, I discovered that during these no-start periods, if I removed the fuel pump relay and cranked it for a bit, it would start up immediately. By the way, I've also experienced the #5 cylinder misfire issue that I've seen in several forums.

About a week ago, we had a pretty significant ice storm, and the Tahoe sat in the driveway while we drove the 4wd truck. Yesterday, I went to start it, and had zero luck. Turns over, but will not start. In addition, it's wanting to ignite cylinders out of sequence - it will crank ok for a bit, then hesitate or stop due to what seems like ignition occurring before TDC. I pulled the distributor cap off and dried it out, but it didn't help. Fuel pump hits 60 psi immediately after the key is turned on, but it does drop down to almost zero shortly thereafter (with the key still on; not sure if this is what it's supposed to do). By the way, I also have replaced the fuel pressure regulator.

I'm thinking at this point it may be the crankshaft or cam position sensor. I would like to pinpoint the problem so I don't waste any more time or money on problem. Any ideas would be greatly appreciated.

it sounds more like an injector or injectors leaking or bleeding down.when you turn the key on you said it had 60psi.that pressure is within spec,but when you leave the key on it drops down.fuel pressure is only suppost to drop (with key on)5psi every 20minutes.if an injector or injectors are hung open fuel pressure will drop steady and fast.that could explain why it starts with fuel pump relay removed.check the oil for gas.if the crank case is full of gas that is a sign of fuel being dumped into crankcase.the popit valves get stuck open.very common.or check fuel filter,could be restricted.i would at least start there.and other info would help.post back if any other problems,or fix.

Replaced the fuel pump today, truck started up. Not 100 percent sure that was the sole cause, but at least it's running, and it probably needed to be done anyway. If anyone's contemplating this repair, it is not too bad, especially when everything starts to go back together. Before I started, I took the spare tire and driveshaft off to have more working room. Biggest key is the back of the truck must be raised at least 8" so the tank will slide out. I didn't find this out until I had wrestled with the tank for a significant amount of time. Also, the special tools they sell to release the two fuel lines are pretty worthless. I ended up using a micro flat blade screwdriver to release the four spring clips inside the housing. Other than that, pretty straightforward job.

your problem usually leads to defective fuel pump, if pressure drops rapidly after fuel pump stops running. to reduce early pump failure keep gas tank above 1/4 tank , replace fuel filter every 30-40,000mi . if fuel pressure bleeds down slowly usually injector but since after start it ran good and your pump produced 60psi it was the pump check valve that was defective. when you changed your plugs you would have noticed the wet plug if injector was bad. because your vehicle has high mileage i would replace the fuel pump relay as i have found my relay in need of replacement due to voltage drop as contacts were worn.........