Acts like a fuel pump\filter issue to me?

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Bamba

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My 1999 Yukon just died while driving down the steet. I knew it had gas but it wouldn't start, it just cranked. It's getting a strong spark and

I would like to know what's the best way to check for fuel getting to the cylinder.

I would also like to know the location where I can connect a code scanner.

Thanks in advance.

Bamba
 

Bamba

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Quick indication of fuel pump operating or not

I just realized that this topic really belongs in the 1999 Yukon technical section. If one of the moderators can move it for me I would appreciate it.

I've found some information which may be useful to someone having some of the same problems which I'm having...

Fuel pump test:

1. Get yourself a helper.

2. remove the gas cap.

3. have one person listen in the gas tank at the gas cap opening.

4. have the other person turn the ignition switch to the ON position ONLY so as the dash lights come on. Do NOT attempt to start the engine.

5. As soon as the ignition key is turned to the ON position, The person at the gas tank should hear the fuel pump run for TWO SECONDS and then it should STOP.

6. Does it ?.


If you do NOT hear it run, in most cases the fault is the fuel pump.

"B"
Thanks in advance for your comments and sggestions
 

Bamba

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Anyone??

I would also like to know the location where I can connect a code scanner\reader.
 

JKmotorsports

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I would also like to know the location where I can connect a code scanner\reader.

Look underneath the driver's side dash. There should be an OBDII plug that you can plug a scanner or programmer into.
 

Bamba

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Thanks JKmotorports, I appreciate the info. .

.. Update... I CAN hear the fuel pump turn on for a couple seconds and then turn off when listening through the gas tank while the key is turned on :)
I'll be performing a code scan, checking the fuel filter, and possibly connecting a fuel pressure gage to the manifold to check the pressure.

I'm beginning to think this may not be as bad as it looked initially. I really wasn't looking forward to forking out the $$ for a new fuel pump nor was I looking forward to removing the fuel tank just to install it.
 

Hardwarz

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Let's go back to basics. This is not specifically for you, but just anyone reading this. 3 things are needed for an engine to run.

1) Air
2) Spark
3) Fuel

As for air, I usually open up the air filter chamber and take off the filter. Putting my hand over the intake hole, lets me know that air is coming in. Flow rate is not important to me for this test.

Spark - I usually use a spark tester. It hooks inline to the spark plug and has a chamber to see spark. Note: This only test for spark, it does not check to see if the distributor has moved slightly, causing the spark to be out of time with TDC.

Fuel - Turn the ignition to on. Hear the fuel pump prime? No? Check/replace fuses/relays and fuel pump. If fuel pump is working, get a fuel pressure gauge. Test the pressure at the rails. A Haynes manual should have the pressure ratings. Low pressure? Change the fuel filter or replace the fuel pump. Pressure good? Look at timing of the spark vs. TDC.

Hope this all helps.

Hardwarz
 

marinekilz

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couldn't of said it better myself hardwarez, I would just add spark power, making sure that you don't have a weak spark as well. I would have to reasearch, if the crank sensor goes the truck would die aswell
 

Hardwarz

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couldn't of said it better myself hardwarez, I would just add spark power, making sure that you don't have a weak spark as well. I would have to reasearch, if the crank sensor goes the truck would die aswell

Camshaft position sensor will also cause a crank/no start problem. Usually, it's a HAL effect sensor and needs to be paper-thin close to the camshaft. Some vehicles require you to set the depth. Other do not. On the Tahoe, I'm not 100% sure.

Hope this helps.

Hardwarz
 

marinekilz

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for those sensors to set depth is just torqueing it to specs. over tighting and under tighting will give bad readings, atleast all the ones I have even seen or put in.
 

Bamba

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Thanks Hardwars, and marinekilz.

I appreciate the tips about putting your hand over the intake hole. Air is one of those easy to overlook things that we can wrongly assume to be there. I can see a healthy spark so I'm expecting to find a gas or timing problem? The camshaft position sensor is another thing I should keep in mind. I haven't been able to do much troubleshooting lately, by the time I get home it's usually dark and I'm tired. I have another vehicle to drive(my trusty 1991 - 5.8L Bronco) Hopefully I can check the fuel pressure, timing, and the camshaft position sensor this weekend. Those results should show & tell me a lot. Whatever the actual problem turns out to be I'll let everyong know.

"B"
 

Mike97

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Let's go back to basics. This is not specifically for you, but just anyone reading this. 3 things are needed for an engine to run.

1) Air
2) Spark
3) Fuel

Actually Hardwarz you are close, but you left out compression. Fire needs those three things in order to burn, but an internal combustion engine is a little different. It requires these three things in order to run:

1) compression
2) heat(spark)
3) fuel(air-fuel mixture).

I don't think that this is Bamba's problem, but the only reliable way to test compression is to use a compression tester. If you don't have access to one, you can use the poor man's method of removing the spark plug and putting your thumb over the hole, and have someone crank the engine for a couple of seconds. You shouldn't be able to keep air from coming out if there is good compression.
 

Hardwarz

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Well, hell, let's do this right then... (don't read anything into this.)

Let's give him a list of diagnostic tools needed for this project.

Spark tester (to check for spark)
compression and/or leak down gauge (to check for compression or leaks)
Autoranging multi-meter (to test sensors)
Fuel pressure tester (to test at fuel rails. specs avaliable in Haynes manual)

Anything else?

Hardwarz
 

Redwood

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my 2 cents

How about an faulty engine kill switch for collisions / low oil pressure switch. These modern vehicles have a lot of gizmos that make the engine die. Ignition modules also like to suddenly die if they get too hot, some will re heal themselves when they cool off. Talk about hard to troubleshoot.
Good luck.
 
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