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Author Topic: Universal electric pump for priming.  (Read 2737 times)
rampeyboy
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« on: November 22, 2010, 12:28:30 PM »

Hello guys, My bus has lost prime, and I was thinking of using an electric pump to prime the engine. Should I be concerned about the electric pump damaging the gear driven pump? Why do some of the cheapo electric pumps specify to not use with diesel? I would think it would pick up any liquid provided it wasn't too thick??

Boyce
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Boyce Rampey
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« Reply #1 on: November 22, 2010, 01:17:41 PM »

Hello guys, My bus has lost prime, and I was thinking of using an electric pump to prime the engine. Should I be concerned about the electric pump damaging the gear driven pump? Why do some of the cheapo electric pumps specify to not use with diesel? I would think it would pick up any liquid provided it wasn't too thick??

Boyce

Boyce,
I can not say 100% that the reason for certain pumps saying not to use with diesel. But my guess would be because diesels usually require high pressure and many of the elcheapo's can not do the required pressure. Thus they tell you not to use them with diesel so they don't have to honor returns for the retards that try it anyway!
For what you are talking about it is fine to do. as your not planning to run the engine off this pump, but rather just provide fuel to the existing pump for priming situations!

Of course there are simpler ways to do it with out an installed pump as well! Some use garden sprayers and I personally like the dish soap bottle method!
Grin  BK  Grin
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« Reply #2 on: November 22, 2010, 01:32:39 PM »

Boyce, Auto Zone sells the inline flo through diesel electric pump for around 70 bucks buy the 3/8 pipe size and don't use the mickey rat filter that comes with install it in the line and forget about it no need to do all the bypass valves has worked good for me over the years 


good luck
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gus
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« Reply #3 on: November 22, 2010, 03:17:42 PM »

I can't think of any way a simple generic fuel pump can harm the mechanical fuel pump. I used one the last time (Only time) I lost prime and it worked fine.
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« Reply #4 on: November 22, 2010, 08:02:50 PM »

When I inadvertently introduced air into my fuel system and lost prime (Doh!), I put in a $50 Facet-Purolator pump that's plumbed and wired in parallel between the Racor and the fuel pump.   Flip a switch and close a valve, and in less than a minute you're on your way.   Once the engine's running, close the valve and turn it off.   Easy.   (The valve and fittings ended up costing more than the pump!)

John   
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« Reply #5 on: November 23, 2010, 04:26:20 AM »

Here's how I did mine, inexpensive generic fuel pump.
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« Reply #6 on: November 23, 2010, 08:31:15 AM »

Here is a diagram for a fuel priming system.
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« Reply #7 on: November 23, 2010, 08:43:14 AM »

You don't need to do all the plumbing Pat a flo thru inline pump works without all the valves and fittings

good luck
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« Reply #8 on: November 23, 2010, 02:40:12 PM »

Clifford, you forgot to mention the built in check valve.  Wink Grin Grin I'm gonna put a couple of valves on mine, just cause they look cool! Grin Grin
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« Reply #9 on: November 23, 2010, 08:29:31 PM »

I was thinking about plumbing one in parallel also but have to agree that series with flow through valves will work just as well and much easier to plumb.

My guess is that all electric pumps will allow flow through, anyone think otherwise?
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« Reply #10 on: November 23, 2010, 10:57:41 PM »

Gus, if you check the pressure required to open the DD check valve, you will see that the pressure drop across it is very low. I discovered this when I was trying to run down why I wasn't getting the fuel pressure delivery the engine book calls for.

We changed the filter, replaced the fuel line, the fuel pump and the pressure was still low. Then, we found that the check valve had a faint crack in the side of it.

We changed that out (it was around the price of a new fuel pump) and the pressure was just shy of the spec. in the manual. When we started out, the pressure was about half of spec.

I finally concluded that the long run in the bus, compared to other applications was leading to a pressure drop at the engine. We left it at that and we have had good fuel economy and power and no fuel delivery problems since.

I would not put an in line fuel pump without being sure that there was enough delivered pressure.

For what it's worth.

Tom Caffrey
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Tom Caffrey PD4106-2576
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rampeyboy
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« Reply #11 on: November 24, 2010, 02:25:57 AM »

Thanks for all the tips guys. I think I will look into that flo through pump. Putting it inline in a permanent manner may be best. I'm thinking that may be a good back up in case the mechanical pump quits. It looks to be tough to change, particularly on the side of the road.
Boyce
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Boyce Rampey
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« Reply #12 on: November 24, 2010, 04:02:40 AM »

Just so we don't get to far off here Boyce the in line flo thru will not supply enough fuel or pressure alone to run the Detroit above idle it is only to prime and does not affect the gpm and pressure of the gear driven pump and you are right the fuel pump is a bear to change,I can post the parts number for the Airtex flo thru pump with the check valve if you like fwiw the pump cost less the than check valve from DD

good luck
« Last Edit: November 24, 2010, 04:49:32 AM by luvrbus » Logged

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rampeyboy
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« Reply #13 on: November 24, 2010, 10:13:36 AM »

Does the check valve come with the pump or separate? I would appreciate the part number if you have it handy, that'll save a little leg work!

Boyce
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Boyce Rampey
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gus
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« Reply #14 on: November 25, 2010, 08:38:34 PM »

Tom,

You and luvrbus have me going now, he says it works fine for him and you have doubts!!

I can understand that the check valve in a series pump could restrict the flow somewhat but if the pump inlet/outlet is larger than the fuel feed line wouldn't that compensate for it?

Also, why not eliminate the check valve at the primary filter and use the series pump check valve instead - no need for two check valves.

The stock DD check valve is suction operated. If you have a leak between the tank and check valve or in the check valve you will take in air and lose suction. This could explain your original  low  pressure drop across the check valve.

This is a really long supply line for a suction system.

The good part is if you have a supply line leak you don't pump out fuel.

The bad part is if you have a big leak you will fill your engine fuel system with air!!
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« Reply #15 on: November 26, 2010, 10:48:50 AM »

I think they are saying the same thing - that an in-line electric pump won't actually run the engine, but that if you select a "flow-through" in line pump, when it is off it will let the regular gear pump work properly and run the engine just fine.  The idea being that a flow through pump can be simply in-line and not have a bunch of valves.  sounds like a great idea!

Brian
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« Reply #16 on: November 26, 2010, 08:08:00 PM »

I own a 1976 MCI8 with an 8v71. My mechanical fuel pump quit and I installed an electric pump off the shelf. There were two types, a low pressure and a "regular" pressure. (bought at an auto parts place) I put the pump inline at the tank. It's still there, I haven't fixed the mechanical pump yet. Bus runs like a dream.

In my opinion, put an electric pump inline, hook it to a toggle switch, it's there if you ever need it.

Greg
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« Reply #17 on: November 26, 2010, 11:14:06 PM »

Greg,

Sounds very good.

Even better is to fix the mechanical pump and use the electric pump both as a backup and a primer  now that you know it works - peace of mind.

What size inlet and outlet tubes are on your pump and what is the brand & model?   
« Last Edit: November 26, 2010, 11:19:25 PM by gus » Logged

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« Reply #18 on: November 27, 2010, 05:45:49 AM »

Guys pressure is one thing they will run on 10 lbs but the pump needs to supply 65 gph at 50 lbs and above on a 8v to keep the injectors cool,I would repair the gear driven and do as Gus recommends me I always replace the old style DD pump with the newer DDEC pump 95 gph just my way because I don't like stuck injectors plus those little filters in each injector are a pain to change and they are going to plug without the correct flow and pressure.  



good luck
« Last Edit: November 27, 2010, 06:06:33 AM by luvrbus » Logged

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