Bad MPG
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New User
Joined: Aug 2010
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Bad MPG
Hey guys i just purchased a 1990 F-250 with a 351w. im new to fords. when i got the truck it had a miss so i replaced the plugs, wires, cap, and rotor. The miss is gone now but my MPG are really bad. i filled my main tank and only got 98 miles out of it. if i figured it right im only getting 5 MPG. do any of you know what i can do to help this? the guy had deleted the smog system and cut off the cats and put two cherry bombs in their place. now i know that you need to have back pressure for any motor. so do you think adding an exhaust with cats will fix the MPG problem? I use this as my DD for work and this is really killing me if its not fixed 
thank you.
thank you.
Fleet Mechanic
Joined: May 2005
Posts: 1,575
Likes: 11
From: Puyallup, WA
I would approach this like this -
#1 Could it be that you have FDM (fuel delivery modual) problem and the fuel is not being burned but transfered to the other tank (if you have two)
#2 Check for codes
#3 Ignition timing?
#4 Sit down and see if the previous owner removed more than just the cats, or in other words removed items/bypasssed from the computer controlled engine managment system.
#5 Compression test, miles on the engine? Badly worn timing chain?
#6 TPS voltage, O2 Sensor? MAP sensor?
At least that is the direction that I would take, but that is over the internet and I am not sitting next to the truck and listening to it run, which might make me go in a slightly different direction / order of items to check.
David
#1 Could it be that you have FDM (fuel delivery modual) problem and the fuel is not being burned but transfered to the other tank (if you have two)
#2 Check for codes
#3 Ignition timing?
#4 Sit down and see if the previous owner removed more than just the cats, or in other words removed items/bypasssed from the computer controlled engine managment system.
#5 Compression test, miles on the engine? Badly worn timing chain?
#6 TPS voltage, O2 Sensor? MAP sensor?
At least that is the direction that I would take, but that is over the internet and I am not sitting next to the truck and listening to it run, which might make me go in a slightly different direction / order of items to check.
David
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
You could have the dual tank crossflow problem. That would pump gas into the other tank.
Having no cats is not going to hurt fuel economy. If anything that will help it.
Check to make sure the O2 sensor is there. Maybe it needs to be replaced.
Having no cats is not going to hurt fuel economy. If anything that will help it.
Check to make sure the O2 sensor is there. Maybe it needs to be replaced.
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New User
Joined: Aug 2010
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I would approach this like this -
#1 Could it be that you have FDM (fuel delivery modual) problem and the fuel is not being burned but transfered to the other tank (if you have two)
#2 Check for codes
#3 Ignition timing?
#4 Sit down and see if the previous owner removed more than just the cats, or in other words removed items/bypasssed from the computer controlled engine managment system.
#5 Compression test, miles on the engine? Badly worn timing chain?
#6 TPS voltage, O2 Sensor? MAP sensor?
At least that is the direction that I would take, but that is over the internet and I am not sitting next to the truck and listening to it run, which might make me go in a slightly different direction / order of items to check.
David
#1 Could it be that you have FDM (fuel delivery modual) problem and the fuel is not being burned but transfered to the other tank (if you have two)
#2 Check for codes
#3 Ignition timing?
#4 Sit down and see if the previous owner removed more than just the cats, or in other words removed items/bypasssed from the computer controlled engine managment system.
#5 Compression test, miles on the engine? Badly worn timing chain?
#6 TPS voltage, O2 Sensor? MAP sensor?
At least that is the direction that I would take, but that is over the internet and I am not sitting next to the truck and listening to it run, which might make me go in a slightly different direction / order of items to check.
David
. im going to look into the whole it transfering into the other tank thing but i dont think its doing that when the other tank is full. the motor only has 101k
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Ha ha ha!!. . silly newbe, codes can be set without triggering the check engine light. The FIRST step when troubleshooting any engine problem on these trucks is.... PULL THE CODES. It's easy to do with nothing but a paper clip and a notepad by following the selftest procedure at www.fordfuelinjection.com. Or you could buy an Equus 3145 and avoid any confusion.
The fuel transfer problem is probably responsible for half the bad milage reports with these truck, the tank that's not in use simply gets overfilled and fuel is dumped out the filler tube vent onto the ground as you drive so you may never notice unless you happen to catch a strong fuel smell just after parking the vehicle
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New User
Joined: Aug 2010
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If the ignition module was gone the engine wouldn't run at all... so you can politely ignore the guy in question.. because he knows less than you about Ford trucks.
Ha ha ha!!. . silly newbe, codes can be set without triggering the check engine light. The FIRST step when troubleshooting any engine problem on these trucks is.... PULL THE CODES. It's easy to do with nothing but a paper clip and a notepad by following the selftest procedure at www.fordfuelinjection.com. Or you could buy an Equus 3145 and avoid any confusion.
The fuel transfer problem is probably responsible for half the bad milage reports with these truck, the tank that's not in use simply gets overfilled and fuel is dumped out the filler tube vent onto the ground as you drive so you may never notice unless you happen to catch a strong fuel smell just after parking the vehicle
Ha ha ha!!. . silly newbe, codes can be set without triggering the check engine light. The FIRST step when troubleshooting any engine problem on these trucks is.... PULL THE CODES. It's easy to do with nothing but a paper clip and a notepad by following the selftest procedure at www.fordfuelinjection.com. Or you could buy an Equus 3145 and avoid any confusion.
The fuel transfer problem is probably responsible for half the bad milage reports with these truck, the tank that's not in use simply gets overfilled and fuel is dumped out the filler tube vent onto the ground as you drive so you may never notice unless you happen to catch a strong fuel smell just after parking the vehicle
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Your truck doesn't have a switching valve there are check valves integrated into the fuel delivery modules. Ford did add some check valves in the lines as a bandaid fix on a recall for this problem, you could do the same or disconnect and plug the lines to the unused tank, I made some plugs from old engine fasteners one time to do this, worked great and didn't leak.
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New User
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Your truck doesn't have a switching valve there are check valves integrated into the fuel delivery modules. Ford did add some check valves in the lines as a bandaid fix on a recall for this problem, you could do the same or disconnect and plug the lines to the unused tank, I made some plugs from old engine fasteners one time to do this, worked great and didn't leak.
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so here is an update. im filling my front tank for now and seeing if fuel is getting into the back. so if fuel it transfering to the back then the back pump needs to be replaced right? im going to try and check my timing tomorrw and see what the deal in there.
also about my 62 code. from what ive looked at on here people say they have hard shifting of suttering. i dont have these problems. but i was two qts low on trans fluid. so im assuming that might be why my code set. i reset the codes and will take a drive on the highway and get over 55 and see if the code comes back. now if the code comes back that means i need to replace the converter?
also about my 62 code. from what ive looked at on here people say they have hard shifting of suttering. i dont have these problems. but i was two qts low on trans fluid. so im assuming that might be why my code set. i reset the codes and will take a drive on the highway and get over 55 and see if the code comes back. now if the code comes back that means i need to replace the converter?
Senior User
Joined: Jul 2010
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lol. yes if fuel is getting into the back tank via the front tank, you will need to replace that pump.(the rear pump) im currently in the same situation i have fuel going from the back to the front. and am getting about 5mpg, (theres a hole in the front tank, so if i dont switch tanks in time, there goes my fuel)
Senior User
Joined: Sep 2007
Posts: 144
Likes: 0
From: Garage Floor
I just bought an 88 with dual tanks that was sendin fuel to the front tank. Bit the bullet and paid Ford $125 and got a new fuel tank selector valve and all is well!!! Good luck with it, keep at it and itll all come together soon enough.
Matt
Matt
Postmaster
Joined: Aug 2005
Posts: 4,728
Likes: 8
From: Cleveland, TN
so here is an update. im filling my front tank for now and seeing if fuel is getting into the back. so if fuel it transfering to the back then the back pump needs to be replaced right? im going to try and check my timing tomorrw and see what the deal in there.
also about my 62 code. from what ive looked at on here people say they have hard shifting of suttering. i dont have these problems. but i was two qts low on trans fluid. so im assuming that might be why my code set. i reset the codes and will take a drive on the highway and get over 55 and see if the code comes back. now if the code comes back that means i need to replace the converter?
also about my 62 code. from what ive looked at on here people say they have hard shifting of suttering. i dont have these problems. but i was two qts low on trans fluid. so im assuming that might be why my code set. i reset the codes and will take a drive on the highway and get over 55 and see if the code comes back. now if the code comes back that means i need to replace the converter?
Good grief, it's not like everyone has absolutely nothing to do but watch for your post and get you an answer immediately!!
Sorry for the rant, but these guys here have a life too...
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New User
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Yeah, it's really bad, check the post time on the quoted posts, 13 minutes, someone sure should have been more on the ball...
Good grief, it's not like everyone has absolutely nothing to do but watch for your post and get you an answer immediately!!
Sorry for the rant, but these guys here have a life too...
Good grief, it's not like everyone has absolutely nothing to do but watch for your post and get you an answer immediately!!
Sorry for the rant, but these guys here have a life too...
im leaving now to get a gun and see if my timing is off.