Air in the fuel system
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Air in the fuel system
Hi my name is Chris and I have a 1993 f250 with the 7.3 idi. The truck starts good and runs good at idle but if I drive it down the road at all the fuel filter light will come on and loose all power but if I let it idle it goes back off because it is getting air in the line and I can’t seem to find the leak anywhere. I have put a new lift pump on and new injector return line as well and it has not help at all. At this time I only have the front take on the truck so I have bypassed the selector value. This is the only diesel truck I have worked on so I don’t know much and I would really appreciate the help. Thanks
Scope Wizard
Joined: May 2019
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that Filter light means the filter is Clogged and the IP is making Negative pressure on the Housing.
I would check your Supply Line to the tank and make sure it is not restricted.
Also make sure that the return line is not restricted, this however would not cause the Clogged filter to turn on.
I would check your Supply Line to the tank and make sure it is not restricted.
Also make sure that the return line is not restricted, this however would not cause the Clogged filter to turn on.
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Okay when the light comes on tho I can go to the bleeder on top of the housing and air comes out is that still because of the vacuum?
Scope Wizard
Joined: May 2019
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you get air in the system when the fuel supply line has leaks .. then the Mechanical Lift Pump sucks air with fuel and that ends up in the filter.... also if the check valve on the return side of the filter is leaking it can cause fuel to drain back to the tank causing Air in the filter housing.
this doesn't seem to be your Issue else the clogged filter light would not come on.
this doesn't seem to be your Issue else the clogged filter light would not come on.
Scope Wizard
Joined: May 2019
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I have changed the filter twice, could a bad lift pump also cause that the one I put on was a carquest
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Scope Wizard
Joined: May 2019
Posts: 6,530
Likes: 25
yes a bad lift pump can cause this issue.
The reason the Light comes on is because the IP has a Transfer pump inside it and it sucks fuel from the filter .... IF the filter doesn't have enough supply then a Vacuum is created causing that Pressure sensor on the Filter housing to switch on (Negative Pressure) which turns on the Filter Light on the Dash.
IF the lift pump is not installed properly then it could be failed......
This is why I asked about fuel supply restrictions too, as this can cause Negative pressure in the Filter.
The reason the Light comes on is because the IP has a Transfer pump inside it and it sucks fuel from the filter .... IF the filter doesn't have enough supply then a Vacuum is created causing that Pressure sensor on the Filter housing to switch on (Negative Pressure) which turns on the Filter Light on the Dash.
IF the lift pump is not installed properly then it could be failed......
This is why I asked about fuel supply restrictions too, as this can cause Negative pressure in the Filter.
Scope Wizard
Joined: May 2019
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when you have negative Pressure on the filter and you Press the schrader then the first thing that happens is Air Goes in.
Scope Wizard
Joined: May 2019
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to Install the Lift Pump... the easiest way is to turn the engine over so that it is on TDC number 1 Cylinder... this way the Cam Lobe that operates the pump in in the Lowest position (putting the least amount of pressure on the Pump Lever)
Scope Wizard
Joined: May 2019
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the easiest way is connect a fuel Pressure Gauge to that schrader Valve on the filter housing ... you should see Positive pressure at all engine speeds.