1999 Chevrolet Silverado, WONT START

[rmweber]

Ok,

Now I understand what you are trying to tell me. I sat down and actually read the shop manual more carefully.

I was reading the wrong fuel system diagnosis page. I was reading the page for the 4.3 L engine. The fuel pressure there said it should be 60 to 66psi, while the page for the 4.8, 5.3 and 6.0L engines said it should be 55 to 62psi.

SO! Maybe I never told you guys what engine I had. Sorry. I have a 5.3 L.

Therefore, the 55psi I have is fine. The test with the Tahoe confirms that.

However, the manual also said that the pressure should not leak down more than 5psi in 10 minutes. I am not exactly sure, I will test again, but I think it did leak down faster.

Therefore, my problem should be one of a few things,

1.) I have a bad fuel pump check valve

2.) I hae a bad fuel pump flex pipe

3.) The fuel pressure regulator is bad

Or

4.) I have a bad or leaking fuel injector.

SO, What do you think about THAT.

I plan to do the following,

The book describes putting a fuel pipe shut off adapter inline between the fuel rail and the return line and feed line. Then, they walk through pressureizing the system and then turning off one valve then the other, effectively what you guys were trying to get me to do.

If the pressure remains constant on either test it points you to a leak in the regulator or injectors or in the fuel pump/line.

I may try to get some of these shut off valves, but first I will do the return block test and see if the pressure holds.

My problem is adapting to these screwy connections they use nowadays. It used to be all rubber hoses...

So my theory is that it is pumping up to the required 55psi, but may be immediately leaking down causing the split second start and then stall condition.

I dont suspect an injector though, it seems like that is unlikely.

Whew...

[GMMerlin]

You told us it was a 5.7

Have you taken a fuel sample? You could have contaminated gas causing this...you didn't fill the tank with E85 did you?

Fuel pressure should not leak down..with all the work you have done, just pull up the fuel rail and see if you have any injectors leaking when you turn the key on and pressurize the rail.

[rmweber]

Originally Posted by GMMerlin

You told us it was a 5.7

Have you taken a fuel sample? You could have contaminated gas causing this...you didn't fill the tank with E85 did you?

Fuel pressure should not leak down..with all the work you have done, just pull up the fuel rail and see if you have any injectors leaking when you turn the key on and pressurize the rail.

Sorry to all for the misinfo on the engine size. I did say 5.7, but it is a 5.3. My bad.

This did happen right after I got a full tank of gas. I tried putting gas dry stuff in the tank to see if that would help.

What is E85?

The gas smells really weird....

Sorry again.

[MT-2500]

Originally Posted by rmweber

Sorry to all for the misinfo on the engine size. I did say 5.7, but it is a 5.3. My bad.

This did happen right after I got a full tank of gas. I tried putting gas dry stuff in the tank to see if that would help.

What is E85?

The gas smells really weird....

Sorry again.

Well we all do things like that.
Fuel specs for it is 55/62 and should hold at least 26 lbs after one minute of shut off.
55 is still a little low but a 5.3 should start.
Does it have 55 when cranking or just key on?
I would still do the pinch off return line fuel pressure check.
If pressure comes up with return line pinched try to start it with pressure up.
Is your security light going out or staying on?
Have you got a theft alarm or remote start on it.
If you have fuel pressure and good spark to all plugs then check for injector pulse.
All gas smells strange to me anymore.
If the gas smells strange get a second opinion like have someone else smell it that knows what gas should smell like.
Good luck
MT

[rmweber]

Originally Posted by MT-2500

Well we all do things like that.
Fuel specs for it is 55/62 and should hold at least 26 lbs after one minute of shut off.
55 is still a little low but a 5.3 should start.
Does it have 55 when cranking or just key on?
I would still do the pinch off return line fuel pressure check.
If pressure comes up with return line pinched try to start it with pressure up.
Is your security light going out or staying on?
Have you got a theft alarm or remote start on it.
If you have fuel pressure and good spark to all plugs then check for injector pulse.
Good luck
MT

It has 55psi key on or cranking or with the return pinched off.

So I will do the return pinch thing again, but I did already do it. Even if I did not get it completely closed, it seems like it would have raised the pressure a bit.

My security light is not on, except when the door is open.
I have a battery light and service engine light on.
No codes readout on the code reader.
I have no theft or remote starter type devices on it.

I only checked one plug for spark, I will check all.

Thx

[rhandwor]

He said he did this test and had 55psi. He is checking pump pressure and said he had 90psi. He clamped the return line at the rail and still had 55psi. The question is what happened to the pressure.

[MT-2500]

Originally Posted by rhandwor

He said he did this test and had 55psi. He is checking pump pressure and said he had 90psi. He clamped the return line at the rail and still had 55psi. The question is what happened to the pressure.

Very good question.
It is going to give me nightmares thinking about it.
If the return line is pinched good and fuel pump is stiill puting out 90 lbs.
It should have 90 lbs at fuel rail.
Are you sure you are clamping the return line?
Double check your fuel pump out put.
Any gas in the vacume line to fuel pressure regulator or leaks at fuel rail?
Check more than one plug for good fire.
And get a noid light and check for injector pulse while cranking.

[rhandwor]

I looked over the posts again and since your engine has adequate pressure to start. As it wasn't a 5.7L but a 5.3L and it ran on starting fluid and your friend has a Tahoe. I would ask him if he would let you swap his pcm relay for a test also check the two 15amp injector fuses. The fuses are in the relay center. A print is on top of the cover. The relays are around $55.00 so this would be a big help.
Hopefully you are already running.

[rmweber]

Thanks to all for the help. The truck is being towed to the dealer today. I really need it and cannot wait any longer.

I went ahead and put a new fuel pump in it, but it did not help.

If I turned on the key and let the fuel pressure build up to 55psi, and then clamped the fuel supply line, the pressure would hold. However, if I did not clamp anything the pressure dropped ~20psi in 10 min. The book said if it drops 5psi in 10 min you have a problem. The book recommended replacing the pump if it held with the supply pinched.

Anyway, I am going to cut my losses.

Again Thanks for the help. I will post the results of the dealers work.

Best regards.

[silverado122775]

Good luck to you.. hopefully they will not screw you too bad at the stealership

[MT-2500]

Originally Posted by rmweber

Thanks to all for the help. The truck is being towed to the dealer today. I really need it and cannot wait any longer.

I went ahead and put a new fuel pump in it, but it did not help.

If I turned on the key and let the fuel pressure build up to 55psi, and then clamped the fuel supply line, the pressure would hold. However, if I did not clamp anything the pressure dropped ~20psi in 10 min. The book said if it drops 5psi in 10 min you have a problem. The book recommended replacing the pump if it held with the supply pinched.

Anyway, I am going to cut my losses.

Again Thanks for the help. I will post the results of the dealers work.

Best regards.

You are welcome And.
Thanks for letting us know how it is going.
That fuel pressure is kinda of a brain tester.
Did the pressure ever go over 55 lbs.
Good Luck.
Let us know what the dealer finds.
MT

[rhandwor]

Hopefully the dealer will be able to fix it for a reasonable price. Do you live in a high salt area where you could have a pinhole in the gas line? I never was able to figure out your tests and this could explain the reason why.

[rmweber]

I inspected the whole line and did not see any wet areas ever. I do not live in a high salt area really, the lines looked good from the outside except in one place where they transition to flex line as it goes up from the frame to the engine. However, no wetness there.

The tow truck guy was convinced it was the mass air flow sensor..but I disconnected that and it still would not start....

You cannot believe the number of opinions I have gotten while it has been sitting in the parking lot for the last several weeks.....

Anyway...I will let you know how big a loan I have to take out...I have already bought a new jar of vaseline....

[rhandwor]

Is the dealer still working on your truck. I was curious as to what they replaced?

[rmweber]

There was a snafu with the dealer and the tow truck. The tow truck driver forgot to tell them that he dropped the truck off and where he put it. I had called to let them know it was comming, but they did not get the hint. Therefore, from a friday to the next monday I thought they were working on it and they did not even know it was there!

In addition, they were so busy, they did not even look at it until today.

They dont know what is wrong with it. They said it might be a PCM problem.

They said that the tech was on with the "techline help" or something like that.

This sounds like it is going to be expensive. If it is the PCM that is simple to replace, they better not charge me much for labor on that. I am sure the part is going to be expensive though.

I will let you know.

Thanks for keeping in touch.