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Diagnosis help, pump or???

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Old 04-20-2012, 09:55 PM   #1  
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Angry Diagnosis help, pump or???

Stepson's 94 2500 4x4 smokes white at and above 2,300-2500 rpm. He said that it also doesn't want to pull when it starts to smoke. It has over 300,000 miles and I don't know any of it's history. Last December, we installed a new lift pump, batteries, and battery cables. It has also gotten a new shut-off solonoid in the last few months. Should I be looking at something on the pump, in the pump, or the injectors? I am just guessing that it is running out of fuel. Is there a spring in the pump for the governor? Or maybe????? I own an 06, so not apples to apples, but I will be able to track it down if you fellas can send me in the right direction. Thanks in advance.

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Old 04-20-2012, 11:38 PM   #2  
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Have you guys checked the fuel pressure??
Any work done on the AFC?

White smoke could indicate slipped timing...or maybe a head gasket..

Any black smoke when he step on it?
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Old 04-21-2012, 10:55 AM   #3  
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No, we have not checked the fuel pressure. I will tell him to get some help with that. And, what the heck is the AFC and where is it? I have a few days before I head back out to work for a month, so I am trying basic parts diagnosis.
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Old 04-21-2012, 12:11 PM   #4  
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Good advice above. I would second, either slipped timing or low fuel pressure. The lift pump has been changed but there is also an overflow valve on the injector pump that controls the lift pump pressure.

You have probably changed the fuel filter, but may not be aware there is a prefilter screen in the bottom of the fuel heater that can become restricted too.
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Old 04-21-2012, 06:46 PM   #5  
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Yep, first thing I would do is clean or replace the prefilter.

Many don't even know they are there, attached to the lift pump they just replaced.

Past that, it is time to get a fuel pressure reading at idle and WOT.
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Old 04-22-2012, 08:34 AM   #6  
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OK. Lift pump pre-filter is first. Thanks
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Old 04-23-2012, 09:45 AM   #7  
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