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Old 12-11-2008, 04:31 PM   #1
lookout
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Default 99 thoe wont start has new fuel pump what can it be ??


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trouble starting my 99 tahoe i put a new fuel pump in 2 weeks ago ran fine. sounds like no fire, cranks just fine, when i stop cranking it bumps like its firing, weird!
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Old 12-11-2008, 05:02 PM   #2
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Try spraying some carb cleaner through the thottle body and see if it pops off and starts. If it does, it would seem to me that the 2 week old fuel pump died on you or there is a problem with the fuel pump circuit.

You can also try whacking on the fuel tank and try to start the truck too.
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Old 12-11-2008, 05:11 PM   #3
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dump question,but did you change the fuel filter with the new pump?
Alot of times the pump is incorrectly diagnosed when the fuel filter is restricted.
A restricted filter will cause a pump of these design to wear quickly when they try to pump through a restriction.
Check to make sure your fuel filter is good-if you didn't replace it with the pump then go ahead and replace.
Here at the Ford dealer I never replace a pump without replacing the filter,I don't care if they just put a new one on or not.

Easy way to diagnose a no-start due to clogged filter is to cycle the key on for a few seconds,off,then on again-do that several times and it should charge the line enough to fire off.

Check voltage at the pump if that isn't the issue,make sure to check it while the pump is plugged into the circuit. Fuel pumps can have a short internally and show voltage to the circuit when unplugged but when backprobed will show no voltage due to the short.

Don't forget to check fuses,and see if the theft light is flashing signaling a VATS issue.
If spraying fuel in the TB doesn't make it start then you might have an ignition problem.
Also try to start it with your foot halfway down on the throttle,this will allow air into the intake in case it is the IAC controls not allowing it to start.

Just some suggestions off the the top of my head,hope one of them helps.
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Old 12-12-2008, 12:39 PM   #4
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i tried all you suggested it flared fire out of the trottle bdy but no ignition. i checked plugs they have spark. but it wont start with either gas or starter fluid
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Old 12-12-2008, 03:11 PM   #5
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Also check the fuel pressure. I forgot if the 5.7 had a test port. If so, then it's real easy...
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Old 12-13-2008, 01:28 PM   #6
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contaminated fuel or clogged exhaust.
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Old 12-14-2008, 11:49 AM   #7
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hey defeddie it trys to start and then blows back thru the trottle body when you cut the key off. filter is clear and pump is working what electronic could it be with the ignition??? thanks mike.
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Old 12-14-2008, 02:31 PM   #8
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pop off the distributor cap and check it for moisture if its wet soak it down with crc and see if it starts. or replace it.
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Old 12-15-2008, 11:38 PM   #9
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for combustion all you need is FAST
Fuel was taken care of by spraying the fluid in there
Air-i'm assuming their is airflow through the intake and out the exhaust
Spark-you said you have spark
Timing- Is it incorrect?

If you have a timing chain issue that would throw off timing,so would moisture or a problem with your cap. How did you check spark? If it was at the coil then check it at the spark plug.
From the noises your talking about it sounds like either plugged exhaust and the air is still escaping after you kill it or the timing is off and it's backfiring through the intake.
Might be an idea to turn the motor so #1 cyl is at top dead center and pull the cap off and make sure the rotor bug corresponds with the electrode for the #1 plug wire.
That should verify the integrity(or lack of) of the timing-it would need to be more than 1 tooth off to not start,and that might be obvious i'm thinking by checking TDC.
If it looks good,then you might try having someone try starting it while you look at the rotor bug and verify it is actually turning.
I'm sure there's someone here with some better ideas than that,but it's something to check.
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Old 12-16-2008, 06:05 AM   #10
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thanks fast eddie i have no spark the problem is dist. module i think i will also change cap and button
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