Fuel pump not working
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Trailering
Joined: Jun 2025
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Fuel pump not working
so today my truck shutoff in town and wouldn't start back up, lucked out as a mobile mechanic stopped by on the road to help me, he found that the mechanical fuel pump wasn't creating any suction so i put a new fuel pump on and it also doesn't create any suction, is there a special thing I need to do when I install a new pump, that if I don't do it wont work?
any ideas. hand tested new pump and it works fine, the old one shot fuel out when I worked it by hand.
any ideas. hand tested new pump and it works fine, the old one shot fuel out when I worked it by hand.
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Trailering
Joined: Jun 2025
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I got just over have a tank, the new pump like the old one wont pull suction at all at the inlet when turning over the engine. thinking of converting to an electric pump instead, but I just got a new fuel pump, and it pulls suction when I work it by hand, so it seems the engine isn't actuating the pump.
Lead Driver
Joined: Apr 2002
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I'm wondering if you lost your fuel pump cam? If the new and old pumps work by hand then that leads me to wonder about the cam?
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Trailering
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Lead Driver
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You can view the cam by removing the fuel pump. You may need to use an inspection mirror to see the lobe for the fuel pump.
Take a look at this thread. Make sure your replacement pump is installed properly, with the arm on the correct side of the cam:
https://www.ford-trucks.com/forums/1...on-300-i6.html
Look at the wear marks on the lever of the old pump. Looks like the lever goes on top of the cam. It would appear possible to get the lever underneath.
Moderator
Joined: Jan 2001
Posts: 56,984
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From: Virginia
Many things to go wrong. You need to inspect the fuel line along the frame underneath, looking for heavy rust and pinholes. If you are using the side tank, you can usually stick your head up inbetween the driveshaft and the tank and see the sending unit. Look for rust. The lines going into the tank like to rust and it will suck air instead of fuel. And if all that looks good, your sending unit may have broke off inside the tank, or the sock on the end is clogged.
If you have dual tanks with a selector valve on the frame, I would bypass the valve for now to help get it running.
If you have dual tanks with a selector valve on the frame, I would bypass the valve for now to help get it running.
Last edited by Franklin2; Apr 29, 2026 at 02:45 PM.
Thread Starter
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Trailering
Joined: Jun 2025
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as of right now the tank and lines are not the problem as the feed line to the pump is not connected, the pump doesn't create suction when I crank the engine, so it wouldn't matter as of now if the lines and tank selector are compromised at this point. trying to focus on getting the pump to work first, then work my way through the lines and what not. though i do get fuel coming out of the feed line when its disconnected.
Last edited by Bunta3209; Apr 29, 2026 at 03:33 PM.
Moderator
Joined: Jan 2001
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From: Virginia
I do not know of a reliable way to test the pump suction except sticking a piece of hose on the suction side and putting the other end in a gas can sitting on the ground. I do not know if just putting your finger over the suction pipe is a good enough test.
Thread Starter
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Trailering
Joined: Jun 2025
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when I put my finger over it and work the pump by hand there is an audible suction when I remove my finger, figured it should be doing similar when on the engine. that's the test the mobile mechanic did when he saw me on side of the road. but yeah I'm not sure if that's right. got some fuel line arriving tomorrow so ill try just a can going to the pump and test again.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
You can view the cam by removing the fuel pump. You may need to use an inspection mirror to see the lobe for the fuel pump.
Take a look at this thread. Make sure your replacement pump is installed properly, with the arm on the correct side of the cam:
https://www.ford-trucks.com/forums/1...on-300-i6.html
Look at the wear marks on the lever of the old pump. Looks like the lever goes on top of the cam. It would appear possible to get the lever underneath.
Take a look at this thread. Make sure your replacement pump is installed properly, with the arm on the correct side of the cam:
https://www.ford-trucks.com/forums/1...on-300-i6.html
Look at the wear marks on the lever of the old pump. Looks like the lever goes on top of the cam. It would appear possible to get the lever underneath.
The 300 the pump works off a cam lobe unlike the v8's that use a drive on the front of the cam shaft that can fail.
Now can that lobe go flat? Guess anything can happen but I would not think so.
I thought it was a bad pump as it had not been used in a long time so replaced it and got the same thing, no fuel pumping? I even used 2 clamps and still no fuel pumping.
I went with 5/16" hose and it pulled fuel. I have never seen anything like that before even with the 2 clamps.
So make sure you are using the right size hose, 5/16"
Dave ----