Dual fuel pump
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New User
Joined: Aug 2002
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Dual fuel pump
Hi,
I've got an 89' F-150 with the 4.9L engine. I understand this year truck has 2 fuel pumps, one in the tank (low pressure) and one on the frame (high pressure). I started having problems with the motor not wanting to go. It will idle fine but once I put a load it it would start to buck and just didn't want to go. The High pressure pump had started to make a loud noise during this. While stranded, it sounded as if the fuel pump was intermitent. After some troubleshooting, I went ahead and replaced it (and the fuel filter).
Well, after about 500 miles it's started to give me that same trouble again. I had to pull over because it was bucking. Once I pulled over, it never stalled but wouldn't let me go with any type of load. After about 10 minutes, I was able to start crawling and then it eventually worked itself out.
Will the truck still run ok if the low pressure pump is bad in the tank or could this be related to the ignition module (TFI IV).
Any idea's would greatly be appreciated
Thanks
Jim
PS: I did a sarch but I didn't find anything concerning dual pumps.
I've got an 89' F-150 with the 4.9L engine. I understand this year truck has 2 fuel pumps, one in the tank (low pressure) and one on the frame (high pressure). I started having problems with the motor not wanting to go. It will idle fine but once I put a load it it would start to buck and just didn't want to go. The High pressure pump had started to make a loud noise during this. While stranded, it sounded as if the fuel pump was intermitent. After some troubleshooting, I went ahead and replaced it (and the fuel filter).
Well, after about 500 miles it's started to give me that same trouble again. I had to pull over because it was bucking. Once I pulled over, it never stalled but wouldn't let me go with any type of load. After about 10 minutes, I was able to start crawling and then it eventually worked itself out.
Will the truck still run ok if the low pressure pump is bad in the tank or could this be related to the ignition module (TFI IV).
Any idea's would greatly be appreciated
Thanks
Jim
PS: I did a sarch but I didn't find anything concerning dual pumps.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Dual fuel pump
Yes, the HP pump could pull fuel from the tank even if the LP pump dies, but it's not likely. There's a possibility that there's another filter in the bottom of the selector valve assembly, and it's hard to find but WIX still makes it. That's also the only way I was able to buy the O-ring for it, which you'll have to replace if you unscrew the bowl from it to see if it has the filter.
Another possibility is an EGR problem - next time it stalls, check the fuel pressure at the rail.
Another possibility is an EGR problem - next time it stalls, check the fuel pressure at the rail.
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New User
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Dual fuel pump
Okay. I finally got around to doing a couple things. After analyzing a couple things I decided to try an EGR restrictor plate. I also replaced the main fuel filter. I'll be getting a hold of a fuel pressure tester this weekend. I'll hook that up so I can monitor the pressure. Hopefully the EGR restrictor plate will solve the problem.
Thanks
Thanks
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
Dual fuel pump
A local Ford mechanic told me that the filter in the selector valve (pressure operated) is pointless, and if it was clogged, don't bother replacing it, just replace the o-ring and stick it back together. You already have one fuel filter, why do you need two? I haven't gotten around to that in my truck yet, but it makes sense to me. Hope this helps.
Posting Guru
Joined: Dec 2002
Posts: 1,428
Likes: 0
From: peoria, az
Dual fuel pump
You don't say if your "check engine light" ever came on during this episode.You may want to run by autozone or something and have them scan your vehicle for codes. This will point you in the right direction. Ford was prety good with their codes. If you have a bad pump it should set a code for that. (there IS a code for a bad pump on a ford and it will set)If you get something like O2 indicates lean, you may have a bad O2 sensor or you could have a weak pump. There are many other things that it could be so the first thing I would do is to see if there are any codes stored and go from there.
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