Fuel tank issue and engine problems
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Fuel tank issue and engine problems
I bought a 96' F150 with 4.9L i6 automatic. Has 189k on it. I filled up both tanks when I got it and drove until front tank was about 1/4 full then switched to the rear tank. When that was 1/4 full I went to fill up and the front tank wouldn't take any gas. It would start and stop, eventually spilling out so I filled the rear tank and kept driving. I tried again a couple days later and had the same results. I did a lot of reading and figured it's probably a venting problem, but it's strange since I was able to fill up the week before.
Anyways, a couple days later I'm driving on the rear tank and the engine dies when I come to a stop. It cranked up again fine but did it again a couple miles down the road. I switched back to the almost empty front tank and it still would die when I came to a stop. Not every stop, but maybe every 2-3 stops. It also hesitates and "jumps" a little when going about 20-30 mph.
I was checking underneath the truck for anything unusual but couldn't find anything. Lines look clean and the fuel filter looks rather new. I had the front engine cap off and cranked the truck and gas started coming out of the front filler hole. Doesn't do it on the rear tank when it's off. I plan on getting a gauge to check fuel pressure to rule that out, but I'm hoping someone can give me a few ideas on what to check.
Anyways, a couple days later I'm driving on the rear tank and the engine dies when I come to a stop. It cranked up again fine but did it again a couple miles down the road. I switched back to the almost empty front tank and it still would die when I came to a stop. Not every stop, but maybe every 2-3 stops. It also hesitates and "jumps" a little when going about 20-30 mph.
I was checking underneath the truck for anything unusual but couldn't find anything. Lines look clean and the fuel filter looks rather new. I had the front engine cap off and cranked the truck and gas started coming out of the front filler hole. Doesn't do it on the rear tank when it's off. I plan on getting a gauge to check fuel pressure to rule that out, but I'm hoping someone can give me a few ideas on what to check.
Tuned
Joined: Dec 2005
Posts: 400
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From: Saskatchewan
Sounds like another fuel transfer issue. The front tank won't take any fuel because the the rear tank fuel is returning to the front tank instead of the rear. Research the dual tanks and the switching system.
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I checked the pressure and wasn't getting anything with key in the ignition. I'm guessing it's an electrical thing now. Aside from checking relays, what should I check before having to take the tanks off and get to the pumps?
Fleet Owner
Joined: Oct 2005
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From: Kentucky
The front tank has bad check valves in the Fuel Delivery Module. As the rear tank pump is running the fuel is returning to front since the check valve is open. Very common issue. Most likely the open check valve is bleeding off enough pressure to cause the engine to starve for fuel.
As far as your statement of "I checked the pressure and wasn't getting anything with key in the ignition" is concerned did you turn the key from the Off to Run position a few times before/while checking the fuel pressure? FYI..the fuel pump relay is energized for 1-2 seconds when cycling the key. The relay will not fully energize until the engine is running.
As far as your statement of "I checked the pressure and wasn't getting anything with key in the ignition" is concerned did you turn the key from the Off to Run position a few times before/while checking the fuel pressure? FYI..the fuel pump relay is energized for 1-2 seconds when cycling the key. The relay will not fully energize until the engine is running.
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The front tank has bad check valves in the Fuel Delivery Module. As the rear tank pump is running the fuel is returning to front since the check valve is open. Very common issue. Most likely the open check valve is bleeding off enough pressure to cause the engine to starve for fuel.
As far as your statement of "I checked the pressure and wasn't getting anything with key in the ignition" is concerned did you turn the key from the Off to Run position a few times before/while checking the fuel pressure? FYI..the fuel pump relay is energized for 1-2 seconds when cycling the key. The relay will not fully energize until the engine is running.
As far as your statement of "I checked the pressure and wasn't getting anything with key in the ignition" is concerned did you turn the key from the Off to Run position a few times before/while checking the fuel pressure? FYI..the fuel pump relay is energized for 1-2 seconds when cycling the key. The relay will not fully energize until the engine is running.
Question: do both pumps turn on when the engine starts or just the one selected?
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Only the selected tank's pump is activated via one set of contacts of the switch located on the dash. The other contacts are for the fuel level circuit.
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I rechecked the fuel pressure today and was getting between 40-50 on both tanks with just key turned and when cranked. I let it idle for about 5 minutes and it stayed right at or just under 50 psi. I was hoping it would start to die out and I could check it but I didn't. There's also a pretty noticeable gas smell that's been around since it started doing this. I'm guessing that's consistent with bad valves or venting issues?
Sorry if I'm missing something obvious, I'm just not used to diagnosing truck problems yet. I appreciate all the help so far. After reading other people's problems with fuel pumps on these trucks I'm planning on just replacing the pump/module in the rear tank. Is there anything electrical I should check before trying to deal with the tanks?
Sorry if I'm missing something obvious, I'm just not used to diagnosing truck problems yet. I appreciate all the help so far. After reading other people's problems with fuel pumps on these trucks I'm planning on just replacing the pump/module in the rear tank. Is there anything electrical I should check before trying to deal with the tanks?
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FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Based on your description you should be changing the FDM in the front tank since that is the one that is receiving fuel and potentially overflowing.
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That is consistent with the fuel transfer problem, fuel overflows one of both tanks out the fill tube and the gas tank vent system will often get flooded with gas as well.
Based on your description you should be changing the FDM in the front tank since that is the one that is receiving fuel and potentially overflowing.
Based on your description you should be changing the FDM in the front tank since that is the one that is receiving fuel and potentially overflowing.
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Not sure if this is relevant to the diagnosis, but when the engine does start to die, the battery gauge dips as well. It actually starts flickering before it sputters and then it dies. Cranks right back up again though. Also I remember the guys at the dealership having to change the OBD1 to OBD2 for emissions testing. The problem with the engine dying didn't start until a few days after that. However the fuel coming out of the front tank fil tube did happen before then.
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If it's a real '96, it should have come from the factory with obd2, per Federal regs(link).
The issue you describe sounds like a loose/bad ground?
The issue you describe sounds like a loose/bad ground?
The ground from engine block to firewall was resting against this line and was melting.
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Update
i replaced the fuel pump in the front tank with the Spectra pump (I’m aware that everyone hates Spectra, but I’m cheap) and it’s been running great for about 2 weeks. Was having some engine misfires before so I had the spark plugs changed as well. I’m now getting a p0171 code running too lean. The only thing I’ve noticed is that after maybe 10 miles of driving the engine temp will start to rise when idle. As soon as I start driving again it goes back down to or below normal. I’ve also noticed when I have my heat on, it will get cool when idleing and then blow hot again when I start driving.
The battery meter has always been funny since I got the truck and will dip down or tick with the blinker when I’m idleing. It still does this.
I changed the oil yesterday and checked the fuel pressure and I was sitting right at 50 psi on the fthe not tank. Haven’t used the rear tank since I got the front one working. Could I be looking at a vacuum leak somewhere in the air intake? Or possibly fuel pressure stuff?
The battery meter has always been funny since I got the truck and will dip down or tick with the blinker when I’m idleing. It still does this.
I changed the oil yesterday and checked the fuel pressure and I was sitting right at 50 psi on the fthe not tank. Haven’t used the rear tank since I got the front one working. Could I be looking at a vacuum leak somewhere in the air intake? Or possibly fuel pressure stuff?
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