hello all, I am new to the site but have spent a large amount of time over the last three weeks reviewing all the threads to solve a couple problems I am having.

I have a 94 f250 7.3 IDI with factory turbo. I have tracked my air infiltration issues down to the fuel heater o-ring from the best that I can tell. The truck starts and dies within 3 secs after it has been sitting. I used the pressurized tank method for locating the leak. I plan to fix this leak, but as there has been so much hassle and thought go into this process (eased greatly by this forum), I would like to install a push pump for the sake of priming the system.

The pump would be operated only by a push and hold button in the cab. This priming could be useful during filter changes, future diagnosis, etc. I plan on locating the pump down on the frame after the tank switching assembly and before the mech fuel pump.

I am concerned as there have been people on the forum that have done this and there have been people who have warned against it for fear of fuel in the crankcase and other possible failures. I would like any and all input on my plan. Please let me know if and how I am risking damaging my mech fuel pump, other fuel components, or contaminating the crankcase.

 

If you want an electric pump, just bypass the mechanical pump in the block and use the electric. Would be alot simpler and no fuel in block problems.

 

I think you're on the right track for using it just for priming. That way its only running when you want to prime the system. If the mechanical pump dies, the truck won't stay running, so you'll be able to find the problem (and if needed change the oil) before the crankcase becomes filled with fuel.
It would also allow you to quickly bypass the manual pump on the side of the road, and run with the electric one until you fix the manual one.

The big issue is when people just run the electric pump and leave the mechanical pump in the system. That gives no warning when the diaphragm breaks, then the crankcase fills with fuel, then the engine blows. Your system when the mechanical pump goes, the engine will just shut down do to lack of fuel.

 

This is exactly what I did to my truck, I didn't go with a fancy setup like some guys do as all I wanted was a just incase pump like you do. If you click here that post of mine has the part numbers of the stuff I used to do my setup if you like.

I got the pump & push button switch from Rock Auto and the filter one day when I was in town at Napa. Good luck man, it's an easy job and should take you less than an hour start to finish.

 

This is mostly incorrect. The mechanical pump and leak inside and still supply fuel. For running an electric you would want to simply bypass the mechanical altogether, no chance of fuel in the block, and you dont have the mech pump acting as a restriction, which would likely take out one or both of the pumps anyway. Depending on the type of pump, you may not be able to draw fuel through a non-powered electric fuel pump (most are this way in my experience). At any rate i would imagine it being quite restrictive.

 

From your knowledge if the mech pump's diaphragm were failing and the pump still worked would that not also push fuel into the crankcase?

I appreciate the thoughts on restriction problems. that is not something I had considered. What can you tell me about how the mech pump functions that would create restriction?

I currently have a call into the engineering at Facet to get me unpowered flow rates on the pump I purchased.

thank

 

yes.that is one of the many advantages of bypassing/blocking off the mechanical and running a full time electrical pump.though a rare occurrence,how much do ya trust today's China replacement parts?
if you saw oil pressure drop you could pull over and shut her down asap before major damage was done,but what if your running a crank case full of synthetic oil? there goes that hundred bucks on top of the tow bill,or down time along side the road,possibly with not only you,but another your paying by the hour,when your supposed to making money.either way its best to do it right with proven parts the first time and be done with it for good,for less than a tow bill.

https://www.ford-trucks.com/forums/1...l#post10774080

 

Yes mechanical can be failing, ie a ruptured diaphragm but the hole be slight enough to allow engine operation whilest simultaneously filling the crankcase with fuel. Thus ended my first 351M.

IMHO if youre going to go through the hassle and cost of installing an e-pump.. ditch the mechanical all-together. Build a block off plate or tear the arm out of the pump and use the pump as the block off, then simply cap the lines with some silicone or something.

As far as restriction, i dont know for certain, but if you try to push fuel through the mechanical pump without the engine at least cranking (to operate the plunger in the pump) nothing will happen, and im even more sure of the same when trying to pull fuel through the mech pump. Which is a bad idea anyway as e-pumps do not like restriction and in most cases should be mounted as close to the tank as practical. The "rule-of-thumb" here is 'never starve a pump'.

 

Does anyone have another word on the mechanical lift pump from this model and it's restriction of fuel when not in operation. This thread has been greatly helpful.

 

I've been running the system you're thinking of for over a year with good results. My e pump is a Carter made for diesel, it sits just forward of the tank selector valve, and is wired to run whenever the glow plugs are lit and any time I use the pushbutton.
I've had no restriction issues.

 

I converted from mechanical to electrical pump and I can tell you it makes starting a LOT easier especially when you change fuel filters. I did remove the mechanical pump completely so there wasn't any problems later. The electric fuel pumps I have run are the AIRTEX 8012S and a NAPA 3158 electric fuel pump. I tried a RED Holley fuel pump but it was noisy and like I was told, didn't last very long.

 

x2 on ditching the mechanical pump. ill gret around to converting mine one of these days..lol. it pays to get a good pump. Facet Duralift is one of the best. its spendy but its oem on Thermoking refers and other applications. it has 10 feet of vertical lift unlike the little pusher pumps for gasser applications. and much better quality.