Need help please! Fuel or electrical?
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Need help please! Fuel or electrical?
Hi new to forum and Ford truck ownership. 1985 F 150 302 FI 4x4 short bed. Drove from Dallas to KC. Truck only worked off front tank. Hard to fill on last gas stop (acted full but was only half). Truck idle really rough but smoothed out after highway speed. Now truck will start, run for a few minutes (seems to get shorter each time) and die suddenly, no hesitation, just dead, cranks but won't start. Let sit for several hours (doesn't seem to be any pattern 1 hour one time, 1 day the next) and will start and do same thing. 6 port selector valve does not seem to be working (leading to problem using rear tank). Both tank fuel pumps will energize individually according to switch position. Hi pressure pump works. Manual says it would have the 6 port resevoir but it has the electrical 6 port selector switch (manual says that was for carbs). Doesn't lookd to have been modified, looks factory. Also, no fuel filter in line as described in manual.
Ignition (TFI) module was replaced with no effect. Need to get back to Texas, please help if you have any thoughts. Thanks!
Ignition (TFI) module was replaced with no effect. Need to get back to Texas, please help if you have any thoughts. Thanks!
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do you have the means to check fuel pressure at the engine ?
F/P should be around 40 psi, there has to be a fuel filter somewhere on that vehicle, follow your f/lines until you find it, pull the output side and see if fuel flows out w/key off and then w/key on, I would say your problem is definely fuel related, just really hard to diagnose w/out to have it in front of me.
Just the same I will help if I can.
F/P should be around 40 psi, there has to be a fuel filter somewhere on that vehicle, follow your f/lines until you find it, pull the output side and see if fuel flows out w/key off and then w/key on, I would say your problem is definely fuel related, just really hard to diagnose w/out to have it in front of me.
Just the same I will help if I can.
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I'm on the road and have pretty limited tools. Another very odd thing on this truck is there is no schrader valve on either fuel rail, I have looked at both from end to end, so I'm not sure how I'd check the pressure?
I have looked at the lines all the way from the engine compartment to the tanks, no external filter. It does have a single function reservoir forward the selector valve before the high pressure pump. I haven't dropped the tanks, but I assume they have the little sock filters.
I will check fuel flow as best I can tomorrow and post again.
Thanks for the reply! Let me know if you can think of anything else.
I have looked at the lines all the way from the engine compartment to the tanks, no external filter. It does have a single function reservoir forward the selector valve before the high pressure pump. I haven't dropped the tanks, but I assume they have the little sock filters.
I will check fuel flow as best I can tomorrow and post again.
Thanks for the reply! Let me know if you can think of anything else.
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From: Virginia
I just thought of something. Before you do the test below, you do need to check for spark. If the ignition module gets hot and you lose the signal from it, the computer for the efi will think the engine is not running, and will not energize the fuel pump relay. So check for spark first. You could also get the store to check for any engine codes you might have. If you have any ignition codes, I would start there.
Go to the store and get a can of ether. When it refuses to start, spray it into the engine and see if it will start and run on the ether. If it does, then it probably is a fuel problem. I haven't ever worked on one of those 6 port valves, but is it obvious what line does what? If so, could you bypass the valve and run on one tank to get home? The parts store might have a splice kit you can buy if you have those plastic fuel lines.
Go to the store and get a can of ether. When it refuses to start, spray it into the engine and see if it will start and run on the ether. If it does, then it probably is a fuel problem. I haven't ever worked on one of those 6 port valves, but is it obvious what line does what? If so, could you bypass the valve and run on one tank to get home? The parts store might have a splice kit you can buy if you have those plastic fuel lines.
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Several people said the module was probably bad. Seemed likely to me with the symptoms (I had an old harley do something similar and new module fixed it). Replaced module today with no joy. It is starting now. Will run tomorrow and see if it dies. If it does, I'll check spark and do your test.
Yes the lines are clear as far which tank they go to and I was thinking about the bypass route myself. I will have to get some kind of line as they are the horseshoe type clip fittings going into the valve.
Thanks!
Yes the lines are clear as far which tank they go to and I was thinking about the bypass route myself. I will have to get some kind of line as they are the horseshoe type clip fittings going into the valve.
Thanks!
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You can purchase a splice kit for those lines in the help section of just about auto parts retailer.
The dual tank thing is really kinda new to me, I never owned a truck w/twins until this 150 that I just bought this past weekend. But, I am thinking all the same rules and theries still apply as far as running, IE- compression, fuel, spark. We just need to do a process of elimination to figure out wich one is causing your given dilema.
The dual tank thing is really kinda new to me, I never owned a truck w/twins until this 150 that I just bought this past weekend. But, I am thinking all the same rules and theries still apply as far as running, IE- compression, fuel, spark. We just need to do a process of elimination to figure out wich one is causing your given dilema.
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Update
Appears to have been ignition related. As my first post said I had replaced the TFI module. Talked with a mechanic here who said he always replaces the internals in the distributor at the same time. Just did that and took a fairly long drive, much further than I could go before and the truck worked good. Hopefully that's it and I can get it back to TX. Still have an issue with tank selector but I'll run off one tank if I can. Now I'm dealing with the weather. Thanks to those who replied. Merry Christmas all!
