Pre-Power Stroke Diesel (7.3L IDI & 6.9L) Diesel Topics Only

fuel pump losing prime

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Old 09-20-2015, 01:38 PM
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fuel pump losing prime

I have a 94 f350 with dual tanks. Neither of the fuel guages work. I have a mr gasket low pressure elecrtic diesel pump on it. Im having an issue with the truck losing prime. First it started off as after driving, it would not restart until i let the pump run and depess the schrader until fuel came out, then it would start. Now its starting to do it while im driving. Itll shut off and ill pull over with the pump on and depress the schrader until i get fuel and off i go. Im new to the idi fuel system. What all is involved and what do you all think is my issue here?
 
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Old 09-20-2015, 03:18 PM
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Where is the electric pump mounted? Sounds like the electric pump is sucking air. If the leak was after the electric pump - it ought to show up as a fuel leak somewhere. The Fuel injection pump has its own rotary-vane fuel-delivery pump inside the housing. If it is trying to suck more fuel then is being delivered by your electric fuel pump - it will make the injection pump get air-bound. I assume you realize that most cheap electric pumps are designed to push fuel, not suck fuel. There are a few exceptions though - like the reciprocating Walbro FRB pumps. In theory . . the Stanadyne injection pump can work with no fuel pump at all since it has its own. But then you'd have no way to bleed the filters unless some sort of extra hand-pump was added. That's how a few odd-ball diesels left the factory like Isuzus, Chevy Chevette diesels, etc.
 
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Old 09-20-2015, 03:37 PM
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Its mounted on the fender on the passenger side.
 
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Old 09-20-2015, 03:46 PM
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Electric fuel pump would be of greater benefit if mounted near the tank.
 
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Old 09-20-2015, 09:18 PM
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Originally Posted by tankguy
Electric fuel pump would be of greater benefit if mounted near the tank.
And also lower than the tank. siphon effect. I have dealt with this issue before on a carbed v8 ranger i used to have. Had the pump, also a mr. gasket oddly enough, mounted on the fender. It would work but i would have to pull the fuel line and suck on the line to get gas up to the carb. It was terrible. moved the pump to the back and nearly below the tank and no further issues, unless i ran it out of fuel.
 
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Old 09-21-2015, 05:59 PM
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<p>the mr gasket electric low pressure diesel pump is not very good. they will work for a while, but not very long.</p><p>the preferred and better pump is the facet duralift 40285 pump. they can be mounted in the engine bay with no problem, and are designed to lift fuel from 10 foot above the fuel source and work.</p><p>they were originally designed for use in diesel refer units.</p><p>&nbsp;</p><p>you can buy one here: http://www.aircraftspruce.com/catalo...ump2.php&nbsp; for $88.75</p>
 
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Old 09-21-2015, 07:48 PM
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Originally Posted by tjc transport
<p>the mr gasket electric low pressure diesel pump is not very good. they will work for a while, but not very long.</p><p>the preferred and better pump is the facet duralift 40285 pump. they can be mounted in the engine bay with no problem, and are designed to lift fuel from 10 foot above the fuel source and work.</p><p>they were originally designed for use in diesel refer units.</p><p>&nbsp;</p><p>you can buy one here: http://www.aircraftspruce.com/catalo...ump2.php&nbsp; for $88.75</p>
Thank you. I was looking into these, but i wasnt sure what psi this engine ran at. I found some info on 4-7 psi.
 
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Old 09-21-2015, 08:37 PM
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+1 on facet. I think I actually have the 9psi version.
 
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Old 09-21-2015, 10:40 PM
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I have a mr gasket diesel pump mounted on a plate, i use it as a fuel transfer pump for draining old tanks, gas, diesel, it will prime a 25' hose no problem.

It also has a check valve in it, so if your valve is working then your leak more than likely after the pump. I know it can catch air before then put it in your system, and it sounds like your air is coming when your running too, maybe pickups in tanks. Fill em up and report back

Just having that check valve helped mine when i had air leaks, the most annoying air leaks are the ones that don't leak diesel!!!

I would check everything after it, replace schrader valve just because, they use the same ones ac's do, least both the seals are white haha

Fuel line olives could be at fault too. When my olives started sucking air it would die if you suddenly let off the throttle while not in gear. Also lost prime 20 minutes after shutdown.

Check in the valley for diesel, had an ip throw the rear seal one time, would just barely drip diesel, gave me priming issues from hell if you left it sit.
 
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Old 09-22-2015, 07:19 AM
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Originally Posted by BRay09
Thank you. I was looking into these, but i wasnt sure what psi this engine ran at. I found some info on 4-7 psi.
Anything less then 8 PSI delivered to the injection pump is fine. So is 0 PSI. Main issue is not to get too high or it can interfere with the automatic injection timing advance inside the injection pump. It runs at pressures from 10 to sometimes 80 PSI internally. The Walbro FRB-11 is one of the most rugged electric fuel pumps on the market and if used a lot on big rigs and boats. A big pricey for a pickup but if you want one of the most reliable pumps made - it is a good choice.

FRB11 Series Fuel Pump
 
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