1999 Chevrolet Silverado, WONT START

rmweber · 10-19-2006, 06:47 PM

1999 Chevrolet Silverado 5.7 L 4x4
150k miles

Problem: Wont Start, truck is broken down in a parking lot 5 miles from my house in jeporady of being towed.

Symptoms:

As I turn the key, it sounds like it might start for a 1/4 second, but then just cranks and cranks.

Supporting Information:

I can hear the fuel pump comming on as I turn the key on. If I bypass the fuel pump relay, It comes on and stays on and I can hear fuel in the injection tubes, but it still will not start.

It has a full tank of gas.

I have already replaced the fuel pump once, not sure how long ago, but it seems to be working.

Battery is good.

The idiot lights show a battery symbol and check engine soon is lit.

Next Move:

1.) I am going to check fuel pressure if I can get a guage.

2.) I am going to check for spark.

3.) I am going to try to get the trouble codes read out if i can get my hands on a meter.

Question:

Anyone have any other ideas of what I can do short of the items that require a special meter/guage that I listed above?

Should I replace the fuel filter just incase?

Thanks!

rhandwor · 10-19-2006, 07:01 PM

If you purchased bad gas or have over 30,000 mile on it change the filter or if you can blow through the filter it will run the truck. A bad pressure regulator the pressure will come up and go down. Try using a hose clamp on the return line on a section of rubber hose. If it starts drive home and change the pressure regulator.
If you belong to AAA have it towed home where you have tools and ect.

rmweber · 10-19-2006, 09:24 PM

Could you elaborate on clamping the return line? Im not sure I know what line to clamp. I thought the lines were metal...

I think I may just put a new filter and regulator on and hope for the best, but I am willing to try this test you mentioned.

Thanks much, really.

2000CAYukon · 10-20-2006, 12:04 AM

Quote:

Originally Posted by rmweber

Could you elaborate on clamping the return line? Im not sure I know what line to clamp. I thought the lines were metal...

I think I may just put a new filter and regulator on and hope for the best, but I am willing to try this test you mentioned.

Thanks much, really.

Please read MT-2500's post in this thread http://www.automotiveforums.com/vbul...d.php?t=633914

Since you have a no start condition, first thing is to find out if you are at the necessary 60-65 PSI to start and go from there.

//2000CAYukon

sc_customs · 10-20-2006, 01:45 AM

Mine has done a similiar thing. I'll turn the key and it will sound like it's going to start...I actually hear my exhaust fire up. Then dies. It has something to do with my Security. When this happens my security light flashes. I know I should fix it, but opening my door, closing it, then turning the key again fixes it. I'd rather do this than pay the dealer an arm and a leg just to look at it.

rmweber · 10-25-2006, 02:19 PM

Ok Folks, Here is whats going on with the beast,

I checked the fuel pressure. When I turn the key on and the pump comes on it reads 55-57 PSI.

From other posts, and the shop manual, this appears to be too low. SO, I replaced the fuel filter and nothing changed.

What next? Fuel pressure regulator?

Fuel pump?

I read the computer and there were no codes. However, I had the computer unplugged at some point during all this so it may have reset.

Thanks for any pointers you can give.

rhandwor · 10-25-2006, 03:50 PM

The spec for fuel pressure is 55 to 65 so you appear good. Does the pressure drop after the initial pressure. If the regulator is bad it will come up then drop when vacuum gets to it. Is their gas in the vacuum line to the regulator.

rmweber · 10-25-2006, 04:30 PM

No, there is not gas in the vac line. I am not sure about the pressure drop. I did not test the pressure with the fuel pump forced on. I only watched it when I turned the key and the pump ran for 5 seconds. It appears to be steady for the 5 seconds, and then when it stops, it does drop down several psi, not sure how much.

Is there a way to test the regulator?

Thanks for the help!

MT-2500 · 10-25-2006, 05:25 PM

Quote:

Originally Posted by rmweber

Ok Folks, Here is whats going on with the beast,

I checked the fuel pressure. When I turn the key on and the pump comes on it reads 55-57 PSI.

From other posts, and the shop manual, this appears to be too low. SO, I replaced the fuel filter and nothing changed.

What next? Fuel pressure regulator?

Fuel pump?

I read the computer and there were no codes. However, I had the computer unplugged at some point during all this so it may have reset.

Thanks for any pointers you can give.

55/57 will not fire a injector on a cold start.
You need at least 63/64 or more.

If you have good fire try a little carb cleaner in the intake or pinch off furl return line and see if pressure will come up some.

Here is guide lines on fuel pressure.
With a no start check as much as you can on it.
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.
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.
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.

rhandwor · 10-25-2006, 06:26 PM

MT-2500 is correct about the specs.but unless his gage is dead weight pressure tested every 10 days it is probably off + or - 5 psi. I used to do nuclear shop inspection and every new pressure gage was dead weight tested before use. I bought a new set of MAC gages,hoses and every one was bad and leaked.
While you are cranking the pressure should stay up or the regulator is bad.
If the pump shuts off while cranking you are losing reference pulse. After you replace a regulator they should be adjusted by using a torx screwdriver in the end to the proper pressure. Either buy a gage or borrow one. You have been over a week on this. You also could have a bad o-ring leaking on the regulator bleeding off pressure.

rmweber · 10-25-2006, 07:07 PM

Ok, now were gettin somewhere. The manual did say that the reading should be around 66, so since it is only 55 or so, maybe that is it. But if the guage is off, it could be at 60 or so, still less than the manual says it should be.

I will do a pressure test while cranking and get back to you.

THANK YOU!

rmweber · 10-27-2006, 05:55 PM

All,

I tested the fuel pressure while I was cranking and it held steady at 55psi. After I stopped cranking it did gradually go down. Over about 15 minutes it dropped to about 30psi or so. Should it stay steady at 55psi after I stop cranking?

The first time I tried to start it it actually ran for a split second. I could hear the exhaust, etc.

I may still replace the fuel pressure regulator if it is fairly cheap. It seems I definitely have a fuel problem.

If that does not work then I guess it is the Pump? Or maybe just the sender?

I could not figure out how to pinch off the return fuel line. The lines are all hard sleeve.

Would you recommend somehow attaching a temporary rubber hose to the return line and dumping it in a can or something and pinching it off?

If so, what would that tell me?

On another note, related to the post about guage accuracy, Even if my guage was off 5 psi, my pressure would still be low. Maybe it is off 10 though? Maybe I should get a new guage.

Hmmmmmm

Thanks.

MT-2500 · 10-27-2006, 06:13 PM

55 is to low you need a good 63-65 lbs cold cranking.
The leak down is not bad. Just watch for a real fast leak down.
like 10-20 lbs a minute
If you can not pinch return line off either take off and plug the end of it or just go to the fuel filter line from the pump and hook onto it and check direct full fuel pump pressure.
Should be 75-85 lbs.
And also make sure the pump is getting good voltage and ground.
On the gauge you could try it on another car/truck or try another gauge.
Good luck
MT

rhandwor · 10-27-2006, 08:34 PM

My 2000 silverado has two disconnects at the fuel rail by the regulator. I use a k-d tool to disconnect these type fittings. My wifes malibu uses this type of fitting on one end of the filter. These would readidly available at a yard. You could cut off a section and put a bolt in the end and make a test tool. The filter end looks to be almost exactly 5/16 inch you could buy a 6 inch piece of fuel injection hose put a bolt in it and use two clamps to block the line for a test. I was going to check on a filter but I only had spares for my truck as I recently changed it. Check a piece of hose on a filter before purchasing it.
Your gage may be 5 psi low so judge according to at least MT-2500 test pressure. The tool looks like two bars with a piece of tubing for 5/16 and 3/8 fittings. They used to be around $6.00 although they make plastic ones also.
Mine is a 5.3L but yours surely has flexible with disconnects. One line is metallic cable and the other is gasline material with a plastic cover.If the truck starts during the test you are sure you have low pressure.

rmweber · 10-28-2006, 10:31 AM

All,

Ok, I went ahead and replaced the fuel pressure regulator. It did not help. Waste of 50 bucks. Oh well.

I called the dealer and they said that 55psi is fine for the fuel pressure. They said that they think it is related to the security system and that there may have been a technical service bullitin on it a while back....

I think I may be barking up the wrong tree with this fuel pressure thing.

more later

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