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1994 Ford F 350 problem fuel or electric?


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I'm having trouble with my 1994 Ford F 350, 351 EFI gas engine, 2 fuel tanks.

The engine will not start on it's own, I have to spray engine starting fluid in the air intake hose to start it. After it starts it will run fine, if I shut it off I have to go through the same procedure to restart it. We have run fuel pressure checks on both in tank fuel pumps, the rear pump was OK the front side tank pump showed low pressure. There has not been a check engine light coming on but we did a trouble code check anyway, no codes showed up. We just replaced the side tank pump but it has not cleared the problem. We have tried starting the engine using suggestions from the Haynes manual but nothing has worked. We also ran a test on the pressure regulator and it passed. The problem is the same no matter which tank we use when trying to start it. 

My brother thinks crud from the gas is clogging the injectors because it sits so long without being used. When I turn the key on the sound the engine makes is like an engine that is not trying to fire, it just spins until I release the key. I have swapped the fuse for the pump system but that did not work either.     My friend who has the diagnostic tools lives in Tomball and I live in Channelview, he's been down here twice to help me, he's not a professional mechanic but he is pretty good at finding a solution. This has all of us stumped. Any help or suggestions will be appreciated.  

Thanks;  Byron

PS, I am retired and the truck doesn't get used much anymore, but I do still need it.

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On 10/20/2019 at 2:15 PM, byron said:

 Thanks Nathan, my diagnostic buddy mentioned a leaking vacuum line could be the problem but we weren't able to test any of them. I will get on this this week and report the outcome.

Thanks; Byron 

I take it runs good once you start it .,. start motor and lightly spray starting fluid around small spots on the motor . if you have a big enough leak to keep that motor from starting with out using stating fluid . it should run at high rpm once it is started . . makes me wonder if you have weak spark . bad  or rusted grounds .. low amped battery . .. battery can still turn the motor over and draw down  enough amps to hurt the starting / 

Edited by HiTech
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OK I need to get back on this, I was going to use the truck this past weekend, gassed it up Thursday, parked it, loaded it up and it would not start. It would fire with the spray but would not catch. If the rain lets up in the morning I will hook up the battery charger and then try to start it, If it starts with or without the spray I will do the spray technique and see what happens. I am my wife's driver and It's difficult to just concentrate on the truck, she has another doctors appointment tomorrow afternoon. I am also going to contact a friend of my sons who works near me, he is a fleet truck mechanic and has helped me before, I can't pin down a day which I can ask him to stop by after work right now. 

Thanks for the advice ,  eager to let ya'll know what the problem is and the solution.  Byron.

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I'm wondering if the computer just isn't turning the fuel pump on while cranking?

When you checked the fuel pressure, was that while running, or not running with just the key on? Check it with just the key on and while cranking. When you turn the key on, the fuel pump should run about 2 seconds to build pressure. And it should start running again while cranking the engine.

Alternatively, pull the fuel pump relay and jump the fuel pump terminals to make it run continuously, and see if it starts. 

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Time for an update.

Yesterday (Thursday) The weather allowed me to go out and hook the battery charger up. This is the kind of charger you would find in an auto repair shop about forty years ago, it's stout. After about five minutes I put the key in the ignition and the engine fired right away without any spray. I did this a couple of times and it was the same result. Then I unhooked the charger and tried to start it, the starter would spin but the engine would not even try to fire even with the spray. So it looks like battery time(My son had to replace his battery in August, His wife a new battery about a month ago, my wifes car 2 weekends ago) so it's my turn now. Before I finished my work I noticed the belt tensioner was at odd angle, the bolt that holds it in place had snapped off. I spent most of today removing the support bracket and then drilling and easy outing the rest of the broken fastener, it had seized in the tensioner arm. In 25 years of owning this truck I have replaced several batteries but It was always obvious that the battery was going dead. This problem started in July, it was an odd problem but I didn't think much of it until we weren't able to solve it.  I hope I've learned my lesson, I should have come here first. Thanks for taking time to help, all suggestions will be noted and added to my Haynes manual. I won't be able to get the new battery until sometime next week, after I install it I will report back. 

Thanks;  Byron     Oh I did spray around the intake and connections, everything seams OK.

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