Good Day All!

I've got a goofy problem with my money pit, err.. I mean truck, that I'm hoping some of you will share your knowledge & experiences to help me figure this out:

Every once in a great while, the truck (2000 Sierra 6.0l 4Wd ca 122,000 miles) would not start. It would crank and fire for about 1 second & die. If I pulled the battery negative, then re-install it- the truck would start. Someone told me that, by dong this I reset the PCM.

It hasn't done this for a few months & a few thousand miles.
Now, it is doing its no-start thing a lot (5 times today). Pulling the negative didn't help these times. Neither did pulling any ignition fuses. I checked the fuel pump relay. It was OK on a meter & test bench. (I also switched it with the horn relay just in case.)

Here are all the clues I can offer with my limited knowledge:
1) If I squirt starting fluid in the intake, it will run for a second or two- I guess until the ether runs out. It still wouldn't start without the fluid being shot in.
2) The fuel filter is relatively new. I changed it as a PM job a few hundred miles ago.
3) I think the gas is OK. Once running, it runs & idles fine. I've got 62 miles on this batch of fuel without rough running. The last time(s) it pulled the no-start trick was many tanks ago (and the old fuel filter was still on).
4) Prior to today, after not starting; by the time I was done pulling fuses, it would start & run OK. Starting today, a very long time elapsed before it would start. Then it would start & run several times in a row. I ran it for half an hour or so to warm everything up. It re-started fine. After an hour, it was back to no start. No real pattern is revealing itself to help figure this out.
5) I just had the transfer case rebuilt. I don't see how this could be related, but I never can tell what effects what, so I added it to the list.
6) The battery is new- a few months old.
7) It used to do this stubborn mule trick more often if I have not driven the truck for a couple of days. This time, I have not driven it for 4 days, but have started it to move it around several times. (Been replacing rusted rockers & more rusted parts.)
8) A bunch of water is dripping (more accurate = steadily streaming) out of the muffler drain. If I raise the idle quickly, a cup or more launches out of the tail pipe. I never noticed this before, but it may have been there all along. I checked the dip stick to see if it looked like coolant in the oil. Oil is clean amber colored. Coolant level has not dropped for many months & the muffler water does not smell like coolant.
9) The fuel sending unit reads Empty when the fuel tank is full. It works fine after the level drops a few gallons. It's done this since I bought the truck 2 1/2 years ago. Is this a clue that the fuel pump may be dying?
10) Weather doesn't seem to be the cause. The last time it did this, it was still winter. Today it is 80 or so & the truck was in the sun all day.
11) On just one of the starting fluid start tries, it blew a bunch of grey smoke out of the exhaust. A bunch! (But, I may have sent too much in while someone else cranked the engine. The engine knocked scary loud for the 3-4 seconds it ran. I think I'll quit trying starting fluid before I destroy the engine.)

Are there any diagnostic checks I can make? I have tools, but no special fuel pressure gauges (read about that test here today!) or equipment to read diagnostic codes. I remember as a kid, being able to pull the fuel line & measuring how much gas the pump put out in a certain number of seconds to see it if was going bad. Can you do this on these trucks, or is it more complex than that? ( I also remember NOT having to drop the tank to change a pump!)

Do any of you have any guesses what the heck is going on?

I sure appreciate any ideas offered!
Thanks,
Paul

 

I now you say you don't have a pressure gauge, but you might be able to do the tool rental deal at an auto parts store to get a fuel pressure reading. You can also pull the vacuum line on the fuel pressure regulator which is right on the drivers side of the intake. If there is gas in the vacuum line or coming out of the port on the FPR than you know that is your culprit - it should be dry.

 

Thanks Mr Shamrock!

I never even thought such things could be rented. (Guess where I'm going Monday morning?)

Is the test port the tee with a capped fitting which, I'd guess, has a Schrader type stem in it?

What is a good pressure to have? Is it tested while cranking or just key on?

I just read something about hitting the tank with a mallet while cranking. if it starts while hitting the tank, the pump is bad. Is this a legitimate test? How does banging make the fuel 'pump' to the engine? Just curious.

Thanks,
Paul

 

I think you might be looking at the evap fitting on the drivers side. It's been a while but I think it is on the passenger side right near the fuel rail. I will double check tomorrow if you need me to. There are a couple things to check - first turn the key on without starting to prime the system and check the pressure. Then start the truck and check the pressure. Lastly turn the truck off and check to see how far it leaks down. I think anything from 58-65 is acceptable and it shouldn't leak down more than 5 PSI in 5 minutes. Again I am going by memory here and will have to double check those numbers, but I am sure they are very close.
There is also a little debate over what exactly is acceptable b/c pressure vs. volume comes into play. I had a truck with 55 PSI that ran perfect and most would say it shouldn't, but I drove it everyday.
As far as hitting the tank, I have seen that work and can only assume it jars the pump a little to get it to work a few more times, but I wouldn't take that test as an indication of a good or bad pump b/c it doesn't always work. It is more of a last ditch "get me home" effort if you are stranded. I had a pump go out right in front of gas station before. I was able to coast into the station and even though I was showing just under 1/4 tank I figured let me put some gas in it in case my gauge is wrong. The truck fired right up and ran all day (enough for me to make all my appointments) and on my way home it completely went out so you never know when they are going to completely quit on you.

Good luck!

 

your pump should make a humming noise when running properly i know it is hard to hear but it should hum you may have to put your ear on the tank itself it your truck has loud exsaust
have a trusted freind start your truck for you and leave it in park
and you go under the tank and listen
i hope that helps a little

 

A running pump doesn't mean it is a good pump. A pressure test needs to be done. There is also a volume test, but usually a pressure test will let you know if it is good or not.

 

Good Morning!

I tried to rent a pressure tester, but all of them were out on rent from the local auto stores. So, I made a Franken-Tester from an old (tested accurate) CO-2 regulator & an old refrigeration hose. Here's what I found-

Before Doing Anything- Truck would not start

I traced the fuel pump wires as far as I could. I think I found the ground connection (Frame just behind fromt wheel near body mount.) For kicks, I pulled the two ring terminals, sanded everything to super bright condition, put anti-oxydation paste & re-installed.

Also, I pulled the regulator's vacuum line & didn't smell or see fuel. The smell test might be invalid, as I don't smell too good. (That came out wrong! I can't smell things very well)

Gauge Tests:
Off, But Key On- The pressure was zero (This is after several failed starting attempts)
Key On Not Cranking: Zero
Running- (It Started For me) 49 PSI
Off: 40 PSI Immediately Upon Turning The Engine Off
5 Minutes later: Still 40 PSI
10 Minutes Later: Would not start. Gauge was still at 40. It stayed at 40 while I cranked.

Current status: Not Starting.

Do these test results give you any clues?

Thanks Very Much! I appreciate the great ideas & knowledge!
Paul

 

With the key on and the engine off it should have close to 60 PSI of pressure. I think the pump may be waiving the white flag. When you turn the key on do you hear the pump running for about 3 seconds?

 

your ground for your fuel pump may also be on your filler neck and cool idea for testing the psi i would never thaught of that lol

 

Holy Cow!
I got a good laugh when I read the phrase 'waving the white flag'. I think it's waving directly at my checkbook. I guess, just like me, the pump likes to take a siesta once in a while. On the plus side, the flag waved before the pump decided to retire totally, stranding my wife (or me) somewhere.

This week has gone haywire, so I'll dig in deeper as soon as I can. I'll certainly focus on the fuel pump being the culprit. Hopefully, it will fail to pump while have a meter on the terminals right at the pump. If I see 12 volts, that would proof enough for me.

I did look at the filler neck grounding strap. On my truck, it goes from the neck to the frame directly. Static dissipating, I'd imagine. Glad you mentioned it. Mine was corroded and making poor electrical contact.

When I worked industrial (electrician), you would not believe how we grounded petroleum distribution systems. Gasoline, due to its molecular structure, readily builds static electricity while moving through a tube or pipe. So, when at the gas station, be sure to always, always, always keep the dispenser's nozzle firmly in contact with the fill port on the vehicle. No mid-air top offs! Put portable gas cans (even plastic ones) on the ground-concrete or dirt preferred (out of the truck bed) and keep the nozzle 100% in contact with the container. When filling the (cold engine) lawn mower, same thing- Nozzle in contact, safety glasses on.

Thank you both for your ideas & help. I'll post the final results, hoping all of your advice will help someone in the future. (Someone like me when it happens again & I can't remember what the heck you guys told me!)

Paul