1997 7.3l Losing Power. - Ford Powerstroke Diesel Forum
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Old 10-06-2013, 05:52 PM
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1997 7.3l Losing Power.

Posting for my not so internet savvy dad.

He has a 1997 Ford F250 7.3.

Has 135,000 or so miles on it. He bought it with 55k miles on it. He had the tranny rebuilt at 60k miles or so. Other than that the only maintenance he has done to it is basic stuff. Brakes, Oil Change, Fuel filter change, tires, etc. Nothing complex. Not sure what was done to the truck before he bought it.

Anyways he was driving tonight (This is the second time this has happened) and he just lost all power. It just bogs down like it's starving for gas. When it happened last time he switch gas tanks and that fixed the problem. (or so he says - i wasn't there.) Tonight that did not work. It just stayed bogged down (but did not stall) for about 5 minutes and then it just picked back up to full RPMs like nothing happened.

Any ideas? Fuel Pump going bad?

Oh, and first post.
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Old 10-07-2013, 08:05 AM
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welcome to the .org

it sound like you father's truck is running out of fuel. the first time he switched tanks soon enough that the motor didn't ingest any air and the second time the motor got some air in the fuel lines and needed to purge it.

how much fuel was in the tank when this happened? was it the same tank both time? the pick up tubes in the tanks can break or the "foot" can fall off not allowing you to get all the way to E on the gauge before the engine stops getting fuel

you can check fuel pressure at the schrader valve on the side of the Fuel Pressure Regulator (FPR) on the fuel bowl. FP should be >50 at all time 65 is optimal. that will tell you the health of you fuel pump
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Old 10-07-2013, 08:30 AM
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Since you are poking around also pull off the intake system and reach into the turbo. Grab the shaft and pull/push it in all directions. If it moves side to side you might need to rebuild it, if it moves in and out you do need to rebuild it. The blades should be clean and straight and should never be able to contact the side of the compressor housing.

How cold outside was it when it happened?

The Cam Position Sensor is typically only good for two years. Normally the CPS fails and the engine cuts off not to restart again till a new CPS is installed. They can intermittently fail putting the PCM into limp mode till the CPS signal becomes reliable again (usually by turning the truck off and back on).

I too feel this is going in the Fuel pump/pickup issue, just giving you some other things to think about. Please check fuel pressure and turbo for hanging/binding and let us know.

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Old 10-07-2013, 05:13 PM
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Quote:
Originally Posted by terryknight View Post
welcome to the .org

it sound like you father's truck is running out of fuel. the first time he switched tanks soon enough that the motor didn't ingest any air and the second time the motor got some air in the fuel lines and needed to purge it.

how much fuel was in the tank when this happened? was it the same tank both time? the pick up tubes in the tanks can break or the "foot" can fall off not allowing you to get all the way to E on the gauge before the engine stops getting fuel

you can check fuel pressure at the schrader valve on the side of the Fuel Pressure Regulator (FPR) on the fuel bowl. FP should be >50 at all time 65 is optimal. that will tell you the health of you fuel pump
3/4 Full in the tank he was using. The tank he switched to was totally full. Yes, both times it was the front tank he was using when it acted up.

I don't think that should affect him if he had 3/4 in the tank.

I'll go look for the shrader valve and put my fuel pressure gauge on it when i get a minute and report that number back here.

Quote:
Originally Posted by BigFuel View Post
Since you are poking around also pull off the intake system and reach into the turbo. Grab the shaft and pull/push it in all directions. If it moves side to side you might need to rebuild it, if it moves in and out you do need to rebuild it. The blades should be clean and straight and should never be able to contact the side of the compressor housing.

How cold outside was it when it happened?

The Cam Position Sensor is typically only good for two years. Normally the CPS fails and the engine cuts off not to restart again till a new CPS is installed. They can intermittently fail putting the PCM into limp mode till the CPS signal becomes reliable again (usually by turning the truck off and back on).

I too feel this is going in the Fuel pump/pickup issue, just giving you some other things to think about. Please check fuel pressure and turbo for hanging/binding and let us know.

I'll pull the intake off and feel the propellers on the turbo when i check the fuel pressure.

It was ~60-70F when it happened.

I don't think it's a sensor issue but i'm not sure. I won't rule it out yet.

Are the fuel pumps in the tank on these trucks? I'd assume since he has two tanks he'd have one full pump that sits before the tanks so you don't need to have two separate fuel pumps for each tank, but i could be wrong.
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Old 10-07-2013, 05:24 PM
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there is a 2 stage mechanical pump that sits in the valley. first stage is a low pressure to pull from the tanks to the filter the second stage pressurizes the fuel from the filter to the rails
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Old 10-07-2013, 05:27 PM
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Never assume it costs too much, on your dads 7.3 there is one pump and it is located behind the fuel bowl in the valley
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Old 10-07-2013, 05:34 PM
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Another thing to consider is the tank selector is gumming up. Switching tanks while your hand is on the valve you should feel it cleanly "click" from tank to tank. Is the issue still happening? Tap on the selector while he switches tanks a couple times. Then go for a ride.
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Old 10-07-2013, 05:40 PM
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Alright. Uploading a video of the fuel pressure test at the moment so you can actually see me doing it. Figure it's easier that way so you don't assume i did/didn't do something correct.

At idle the fuel pressure goes from ~54-60PSI. Can't test it under load because i don't have someone else to help me.

I check the turbo on the intake side and not the exhaust side correct?

The issue just happens at random. There isn't something he's doing that causes it. I personally haven't been with him yet when it has happened. The problem doesn't occur when he's switching tanks, the problem just happens randomly. He attempts to switch tanks though thinking that there is water in the gas or something.
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Old 10-07-2013, 05:46 PM
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Video.

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  #10  
Old 10-07-2013, 06:10 PM
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Quote:
Originally Posted by HudsonN View Post
Alright. Uploading a video of the fuel pressure test at the moment so you can actually see me doing it. Figure it's easier that way so you don't assume i did/didn't do something correct.

At idle the fuel pressure goes from ~54-60PSI. Can't test it under load because i don't have someone else to help me.

good pressure there

I check the turbo on the intake side and not the exhaust side correct?

intake side, yes

The issue just happens at random. There isn't something he's doing that causes it. I personally haven't been with him yet when it has happened. The problem doesn't occur when he's switching tanks, yep, you did say that sorry the problem just happens randomly. He attempts to switch tanks though thinking that there is water in the gas or something.
Please see above. Between the down pipe and the exhaust turbine on the turbo there is what is commonly called the Exhaust Back Pressure Valve ( Ford calls it the extension tube). Find it? Under it should be a narrow metal arm that goes back to the turbo pedestal. Pull the arm straight down and it'll pop off the butterfly actuator. With it off does the actuator swing freely? Wire it open (toward the turbo) and have your dad drive it for a while. If you want to be sure it is open unclamp the down pipe and look in. Wire up the arm so that it hangs unattached to the actuator but inline as if it were. Without wiring up the arm it will put a side load on the wiper seal under/behind the pedestal.
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