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Discussion Starter #1
I my bronco //78 351m// will run fine for about 15 mins and then it seems like it will cutout if I am going slow or going up a hill. All I have to do is prime the carb with a little gas and then it will start again and do fine. Is this my fuel pump going bad or maybe my idle speed adj wrong or something else? I have a Motorcraft 2150. James
 

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78rangerbronc said:
I my bronco //78 351m// will run fine for about 15 mins and then it seems like it will cutout if I am going slow or going up a hill. All I have to do is prime the carb with a little gas and then it will start again and do fine. Is this my fuel pump going bad or maybe my idle speed adj wrong or something else? I have a Motorcraft 2150. James
Nothing to do with the idle speed adjustment. Sounds more like a fuel supply problem. I'd check the float level adjustment first. It sounds like it is set too low. If that is Ok, put a pressure gauge on the pump and see if it is supplying atleast 5 to 7 lb. You can buy a cheap one to put inline with the fuel line for under 20 bucks from Advanced Auto.
 

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will run fine for about 15 mins and then it seems like it will cutout if I am going slow or going up a hill.
It has to be a weak fuel pump. At slow rpm the pump appears to have a reduced flow, and when going uphill it dosen't have enough pressure to push the fuel through the lines. Rebuilt ones are about $20.
 

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Thanks.... That is that is as close to a smoking gun as I could come up with too. I did make sure my lines were not clogged and that the filter I have is ok.
 

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I had the same problem..also would cut out at highway speeds.
Replaced mech pump with napa pump still had problem. Added holley red elec pump by fuel tank and no problems going up steep hills. I still have the mech pump on and elec pump is switched for now. Plan on removing mech when I get time.
 

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ya a clear fuel filter will really help in problems like this as well, you can watch in the filter and see if fuel is flowing through or if it is just spitting it into the filter once and a while, a few of us have had that problem, i just put on a new pump but a few of my freinds have went electric instead
 

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do you have rubber fuel line going up the front side of the motor from mech fuel pump to carb. if so it could be vapor locking. which is the fuel gets hot and turns to vapor before it gets to the carb. all i had to do for mine was run metal fuel line from the pump to carb and solved the problem.
 

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Discussion Starter #9
I have a metal line that connects to the fuel pump with a B-Nut. It runs almost all the way to the carb. It does lay on some eng areas that get really hot. Is there a way I could insulate it just to make sure? The line has got to be at least 3/8. James
 

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78rangerbronc said:
I have a metal line that connects to the fuel pump with a B-Nut. It runs almost all the way to the carb. It does lay on some eng areas that get really hot. Is there a way I could insulate it just to make sure? The line has got to be at least 3/8. James
You need to get the fuel line away from the other surface, it should not touch. If you notice in the picture above I have rubber fuel line and have had that arrangement for years with out a problem. As far as vapor locks go, you need to keep the line away from hot surfaces. Mine has a metal line from the pump to just about the top of the power steering pump bracket and from there it is rubber. In neither case is the line closer than 2 in. of the engine.

If that doesn't fix the problem some other possibilities already mentioned need to be checked.

1. Fuel pump
2. Fuel line clogged
3. Worn concentric that drives the fuel pump

A pressure gauge should tell you if you have a problem in one of these. Also as mentioned by roach57 a clear filter will let you see what is happening with the flow.

Also there are two rubber connections in the stock metal line. One from the tank to the metal line and one about 1/2 way up the chassis between two sections of metal line. Check the condition of these for cracks or holes, I had a mouse nibble thru one once causing a flow problem by sucking air, no leak just air sucked in by the flow of fuel.

Good luck,

:thumbup
 

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Discussion Starter #11
I really need to move my fuel line!!!!!!!!! Its kinda wierd thought. Its like it was routed from the pump to the carb with no support whatso ever. Definatly will move it away from mecanica caliente. Also I had carb/fuel prob before and replaced all rubber in fuel sys, from tank to carb. And will throw in a new pump for shits and giggles. Thanks James
 
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