fuel return priming system...

[Nick_Rego]

So ive recently switched over from the factory style rubber hoses and plasric caps on my 91 7.3 too the R&D style fuel rails. i installed new O-rings and a few new fittings and what not to make everything work how it should. the trucl runs fine actually runs better than it ever has mostly becasue i finally changed the oil filter while i was doing the rails...
anyway i did thos swap mainly becasue my hoses leaked and i was having the typical loosing prime issues these trucks have when you get some air in the lines. I alos happed to have a buddy who hd a truck he was parting out that had them on it and only wanted $100 for the whole setup so figured beata the nearly $300 R&D asks for them, and they were in grear shape.
Anyway i am still having the same issues in the morning with it starting up and stalling shortly after and then needing to crank the fuel back up to the filter and into the pump...
from what i understand is the air allows the fuel that would normally return to the pump and that stays in the lines for next time you start runs back to the return hose that runs all the way back to the tanks. i was wondering would it be possible to put in a small electic fuel pump into the return line to restrict the return to the tank and also to send fuel back up to the rails just when the keys on and glow plugs are warming up so it is essentially just a priming pump? would doing this potentially cause any damage or issues with fuel not being able to drain back to the tanks while its running? the other issue i thought of that fuel being pumped back from the tank would need to be filtered as well meaning even more restriction for the return when its running. mabye use a simple gas style inline filter but id also be worried about water if for some reasom there was ever some in there.
my second option is dedicating one of the two tanks to a priming tank and having that pump inline before the selector valve and hook the pump to a simple toggle switch or the glow plug relay so its only on when the trucks not running. only issue i see there is if i dont run the pump all the time the mechanical pump will have to pull fuel threw that pump and i feel like that restriction might be an issue when running that tank. does any one make a run threw pump that would solve these issues where i can just run it when im warming the plugs pump fuel up to the mechanical pump so its got plently of fuel to get it started. any suggestions or help would be much appreciated thanks.

 

[Randy Bush]

Another thing to do is install a check valve before the mechanical fuel pump . Really helped on one of mine was having problems with.

 

[Nick_Rego]

Another thing to do is install a check valve before the mechanical fuel pump . Really helped on one of mine was having problems with.

what kind? any part numers or images of what you used?

 

[79jasper]

You are way over complicating things.
1. Changing the oil filter will in no way affect how your truck runs.
2. Maybe something has changed, but some members that tried the early rails had trouble getting them to seal. There's a lot of tolerance in the injector height and spacing. Basically what I'm saying is the injectors may not be centered in the rail. IE: causing drain back.
There's a duck bill in the tank on the return line that is supposed to help keep it from draining, when not under pressure. Maybe yours is gone. You don't want to add anything else to the return system, as that will affect ip housing pressure.
Long as the check valve is diesel rated, it will work.
You could also just swap to a electric pump. I don't think I've seen anyone do it, but you could put a electric pump between the mechanical lift pump and the filter.

Sent from my SM-N960U using Tapatalk

 

[Thewespaul]

https://classicdieseldesigns.com/collections/fuel-delivery/products/billet-3-8-check-valve

 

[Nick_Rego]

You are way over complicating things.
1. Changing the oil filter will in no way affect how your truck runs.
2. Maybe something has changed, but some members that tried the early rails had trouble getting them to seal. There's a lot of tolerance in the injector height and spacing. Basically what I'm saying is the injectors may not be centered in the rail. IE: causing drain back.
There's a duck bill in the tank on the return line that is supposed to help keep it from draining, when not under pressure. Maybe yours is gone. You don't want to add anything else to the return system, as that will affect ip housing pressure.
Long as the check valve is diesel rated, it will work.
You could also just swap to a electric pump. I don't think I've seen anyone do it, but you could put a electric pump between the mechanical lift pump and the filter.

Sent from my SM-N960U using Tapatalk

haha woops ment to say fuel filter. and i thought about that as well was going to loosen the lines and try to re seat the rails.Before i had the return line to the fuel filter housing leaking since somone didnt put a clamp or anything on it and then i fixed that and the truck would have no issues starting in the morning but then it started leaking in other places and the hoses were obviously older...

 

[Scotty4]

haha woops ment to say fuel filter. and i thought about that as well was going to loosen the lines and try to re seat the rails.Before i had the return line to the fuel filter housing leaking since somone didnt put a clamp or anything on it and then i fixed that and the truck would have no issues starting in the morning but then it started leaking in other places and the hoses were obviously older...

Just go to Wes’ link above and be one step closer to no air for a great price.

 

[nelstomlinson]

I watched a Stanadyne video on our pumps, and now I am totally confused on how a leak in the return line causes trouble. Near as I could make out from the Stanadyne video, the fuel comes in from the supply line, and that's all there is to it. How would air in the return lines be a problem? Is it because the return lines are hooked to the fuel filter, so the pump sucks return air through the filter? Do the return lines HAVE to be hooked to the filter?

Edited to add: the problem is that the return line leak lets the supply side empty back into the tank, right? So removing the return line to fuel filter connection should help a lot. Can we do that?

 

[Thewespaul]

Thanks for the order, got your check valve shipped should be there Saturday.

 

[steve phillips]

eliminate rubber line between fuel filter and return fitting. it is not needed. that is the common connection between return and supply fuel system. glad someone else knows orange flapper is a check valve. air can also leak at Schrader vale easy to replace. hope this helps. there are lots of threads here about air intrusion

 

[nelstomlinson]

One more air intrusion question: is that Schrader valve just a standard tire valve? Or do we have to get some sort of special, fuel rated valve core?

 

[steve phillips]

standard tire valve. are you sure fuel is not draining out of filter overnight?

 

[nelstomlinson]

No, steve, I'm not sure. Temperatures have been low enough that I'm not trying to work on anything I can't start and drive into the shop.

Next time I get my problem child into the shop, I'll put in a new e-pump, change out that Schrader valve and the fuel filter, and remove the return line from the fuel filter housing. I also have new seals for the supply hard lines between mechanical pump and filter, and between filter and injection pump, and some low-durometer orings to try to seal the stupid return caps that won't stop leaking now that I put on new caps and new orings.

Yes, I did carefully check the inside of the new caps and they were smooth. I did lube the orings, and I did feel the return caps snap down into place.

 

[Nick_Rego]

Thanks for the order, got your check valve shipped should be there Saturday.

thanks you have some other cool stuff i may be doing in th future like the 38 gallon rear tank swap.

 

[Selahdoor]

eliminate rubber line between fuel filter and return fitting. it is not needed. that is the common connection between return and supply fuel system. glad someone else knows orange flapper is a check valve. air can also leak at Schrader vale easy to replace. hope this helps. there are lots of threads here about air intrusion

Glad to know this.

Ever since the shop put in a brand new rear tank... My return lines have been draining overnight.

I'm thinking this is just one more thing they did not have a clue about, about my truck...

Where exactly is this valve? Does someone have a pic of it?