Plantoil/diesel conversion basics
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danalinscott

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Reply with quote  #16 
This is just a version of #14 with a FPHE replacing the tube in tube type heat exchenger.



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danalinscott

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Reply with quote  #17 
A version of #16 that incorporates a "limited loop" VO return. (Only shown in the uppermost image)



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roverhybrids

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Reply with quote  #18 
You have the looped return T'd into the wrong place on all these examples.
The return needs to be T'd into the suction side of the pump, for mechanical and electric pumps.
danalinscott

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Reply with quote  #19 

Quote:
Originally Posted by roverhybrids
You have the looped return T'd into the wrong place on all these examples.
The return needs to be T'd into the suction side of the pump, for mechanical and electric pumps.

That is a pretty strong statement.
Why do you think that?


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kkelly

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Reply with quote  #20 
In the schematics for example 16:  I see that there are two pumps being used- one from the VO tank and one from the diesel tank.  However, there's only one 3 port valve and it's dedicated to the diesel.  What determines the tank to be drawn from?  In other words, how is the switchover accomplished?  Is the switch for the valve wired to turn on the VO pump when switched off of diesel?

If I use my stock pollak and have the VO line t'd to the supply line (to the engine) with the pump after it, will this accomplish the same thing?

Thanks, Kevin
danalinscott

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Reply with quote  #21 
Quote:
In the schematics for example 16:  I see that there are two pumps being used- one from the VO tank and one from the diesel tank.  However, there's only one 3 port valve and it's dedicated to the diesel. What determines the tank to be drawn from?  In other words, how is the switchover accomplished? 


Switchover is accomplished by switching which pump (VO or diesel) is pushing fuel to the IP. The single 3 port valve  switches where the "return" fuel goes. This is either back to the IP in a "return fuel loop" or to the diesel tank.

Quote:
Is the switch for the valve wired to turn on the VO pump when switched off of diesel?
 


Yes..and visa versa.

Quote:
If I use my stock pollak and have the VO line t'd to the supply line (to the engine) with the pump after it, will this accomplish the same thing?
 


I am pretty sure that it would not.
But to be absolutely sure you would need ot preovide more info...and since I try to keep the info on this forum as indexed and easy to find please try to find the right area/discussion to post to. Perhaps posting under the area provided for your specific vehicle would be best for such questions.

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roverhybrids

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Reply with quote  #22 

Quote:
Originally Posted by danalinscott
That is a pretty strong statement.
Why do you think that?

If you have the T after the pump then the pump will be pressuring the return of the IP.  This could have the same effect as plugging the return port off.  Not all vehicles are the same and have the same pressures, Generally the IP return has a pop off pressure and is designed to be able to flow back to the tank.  Pressurizing this will increase the pop off pressure and could damage parts of the injection pump and/or increase the inlet pressure.

danalinscott

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Reply with quote  #23 
I have never seen any damage to IPs due to the low pressure provided by a lift pump.  I doubt that the pressure gets as high as if the return were plugged.

Do you have any specific engines/vehicles that have IPs which will be damaged by the relatively low pressure that the lift pump provides?

Quote:
Originally Posted by roverhybrids

Quote:
Originally Posted by danalinscott
That is a pretty strong statement.
Why do you think that?

If you have the T after the pump then the pump will be pressuring the return of the IP.  This could have the same effect as plugging the return port off.  Not all vehicles are the same and have the same pressures, Generally the IP return has a pop off pressure and is designed to be able to flow back to the tank.  Pressurizing this will increase the pop off pressure and could damage parts of the injection pump and/or increase the inlet pressure.


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roverhybrids

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Reply with quote  #24 
My point is you have these listed as sort of universal system examples.  With that in mind you should have the loop in the right location.

I know of a VP44 that was damaged from looping after the pump.  It caused the diaphram to rupture.
Any othe IP with a diaphram could have the same problem.

In all applications you are increasing the pop off pressure, and yes that is not always a bad thing.

On a powerstroke it would be increasing the fuel pressure to 100+psi which would likely kill any fuel pump..................
danalinscott

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Reply with quote  #25 
Quote:
My point is you have these listed as sort of universal system examples.  With that in mind you should have the loop in the right location.


I only intend these to be used as basic examples of commonly used configurations.  For the majority of engines I believe that the loop IS in the right location.

There are of course some exceptions such as the VP44 (24v Cummins). If you would care to provide  more engine  specific configurations please do.

This is why I provided a component key as the first post in this discussion.





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roverhybrids

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Reply with quote  #26 
Dana,
I deleted my previous post because you posted your reply in my post, under my user name, after it was deleted I realized I should have edited it instead.

What I said basically:
Dana, have you contacted a diesel injection shop to see what they say?

Looping like you show will deadhead the return from the IP.
Causing the lift pump to pump to it's maximum pressure.

Parts of the IP are lubricated by the flowing fuel, deadheading could lead to damage from lack of lubrication.
danalinscott

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Reply with quote  #27 
Quote:
I deleted my previous post because you posted your reply in my post, under my user name
  Didn't know that was possible.  You could have just asked me to correct that.

Quote:
What I said basically:
Dana, have you contacted a diesel injection shop to see what they say? 

Yes..a long time ago.
What they told me was essentially "At the pressures most lift pumps provide the small amount of back pressure is not a problem."

Quote:
Looping like you show will deadhead the return from the IP. 


I have never heard the term "deadheading" used in this way. Normally "deadheading a pump" means that the outlet is sealed. In this case it is not. If the return were actually deadheaded the pressures provided by the IP and injector spill lines would blow off the return lines. As it is they are just raised to lift pump pressure.

Quote:
Causing the lift pump to pump to it's maximum pressure. 
Again I have to say..so what? Lift pumps often run at their maximum pressure. Most are desinged to do exactly that.

Quote:
Parts of the IP are lubricated by the flowing fuel, deadheading could lead to damage from lack of lubrication.
 
    Even ignoring the higher lubricity of VO the IP is not truly deadheaded so fuel flow through it is essentially unimpeded.  A deadheaded pump allows no fuel to pass. A return looped to the pressure side of the lift pump cannot be considered "deadheaded".


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gavin8or

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Reply with quote  #28 
rover and dana: have either of you experienced problems with too much pressure on a mechanically injected 6.5L (with the Stanadyne DB2 pump)? I would REALLY love the simplicity of just switching over by turning off one lift pump and turning on the other, but I don't want to break anything and I've been told that the DB2 doesn't like pressures of more than 6PSI (which is weird because a replacement Delphi lift pump claims it puts out 15+).

Secondly, is it possible to have both a Needle Valve Air Bleed Return with the option of Purge To Tank (veg tank of course)? I've been trying to diagram it out but it seems like I'd have to add at least an extra 3-way valve
danalinscott

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Reply with quote  #29 

Quote:
have either of you experienced problems with too much pressure on a mechanically injected 6.5L (with the Stanadyne DB2 pump)?

I have never knowingly overpresssured an IP. The rule of thumb I have is "use a replacement (electric) pump that puts out the same psi as the stock one.

Quote:
I don't want to break anything and I've been told that the DB2 doesn't like pressures of more than 6PSI (which is weird because a replacement Delphi lift pump claims it puts out 15 


Really? I am sure that is possible..but I would double check the disparity.

Quote:
  is it possible to have both a Needle Valve Air Bleed Return with the option of Purge To Tank (veg tank of course)? I've been trying to diagram it out but it seems like I'd have to add at least an extra 3-way valve  


A "two way" valve will work..even a manual one. You plumb it so when closed it forces all return through the needle valve "circuit"  along side it (teed in before and after the 2 way valve) and when opened it allows all return fuel to bypass the needle valve.


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gjain89

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Reply with quote  #30 
I wanted to know the difference between the heated fuel line and the coolant fuel heat exchanger.  I'm guessing the heated fuel line is connected to a 12V supply, right?

Also, can't you just use a coolant fuel heat exchanger instead of the heated fuel pickup?

And if you are residing in place where lowest temperatures will never fall below 55F, what are all of the necessary heating components I should include in my configuration?  Is the FPHE required?

Lastly, do you need injection line heaters for direct injection engines?  Won't the ILHs heat the diesel when its being used as well?

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