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'89 R3500 Crew Cab 2wd to 4wd conversion & beyond

Started out with 2wd TBI350 with SM465 to current 4wd with 454, 700r4, NP241
Overview Gallery Discussion
folkenheath said:
If your test shows you can blow air into the tank without it, I would just eliminate it and install the rollover valve you mentioned.

It's possible its defective and won't work even with the engine vacuum, a test with a hand vacuum pump would tell you that. I guess it would tell you if that worked, if it didn't you wouldn't know if it was defective or wasn't supposed to work that way.
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That's exactly right. I was trying to find out more about how it worked because I was curious how you would know if it was functioning properly. But I figure I might as well just get rid of it since I don't have the evap. And I can't find any info about it.
 
Since we are on the subject...Does anyone know if this is a rollover valve? If not, what it does?

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That is the vent line (I assume you know that). That is a good question because it might explain why it looks like a complicated contraption for the end of a vent line.
 
Yes, was sure it was the vent line.

A check valve as in a floating ball valve to prevent fuel going out, a spring loaded one way valve, or a gravity type rollover valve?

I'm asking because a rollover valve after a rollover valve might be redundant.

Perhaps a little testing would determine it. Does it open with pressure, fluid level, flow direction, or as long as it is not upside down?
 
My understanding is that it floats to restrict "top off" fuel from going into the evap system. And works as a roll over valve. But only works when close to full rollover. I don't think they work if the vehicle is on is side.

In the movies they all leak and then explode.
 
I have my old saddle tank I could test the operation with.

The aftermarket ones are supposed to allow air pressure or vacuum past but block flow for a rollover or even a flop.
 
I have a sending unit that came out of the TBI saddle tank in the crew cab. I can blow thru the vent line when it is upright. If I turn it 90° or further, I cannot blow thru it. So it does have rollover protection. Also side flop protection.
 
mrk5 said:
I have a sending unit that came out of the TBI saddle tank in the crew cab. I can blow thru the vent line when it is upright. If I turn it 90° or further, I cannot blow thru it. So it does have rollover protection. Also side flop protection.
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Good research. Handy information for us offroad.


And I won't go for any of the potential bad jokes.

I'm gonna go find my halo now. :D
 
I had an epiphany this morning. Nicole was asking me if I was going to replace the sending unit and questions along those lines. It got me to thinking about the wisdom of re-using the one that bent. I'm most concerned about the return line now being kinked.

The epiphany came when I remembered I had noted the fuel pressure was running about 10psi higher than it should for the past few months. It occurs to me that it's probably because the return line has been bent and kinked. So I'm thinking I'm going to go ahead and replace the sender to be on the safe side.

As an info tip that might help others in the future; every time I've had a high fuel pressure issue with aftermarket EFI, it has been due to return line restrictions. 3 out of 4 times now it has been a kink in the return line; either the rubber hose or, in this most recent case, the hard line on the sender was kinked. The 4th time was due to connecting the return to the vent on the sender, the rollover valve we've talked about previously is not compatible to return flow.
 
Also, I think I've figured out something that is going to help with my hip issue. When my back was bothering me, I started sleeping on my side. My hip was hurting that night after the wheeling trip and laying on that side made it worse. Since that night, I have been staying off my side when I sleep. All of the aching I've been having in my hip has gone away. It seems that sleeping on that hip has been a big contributor to my issues. I'm curious to see how the next long day in the seat goes now that I've figured that out.
 
Sorry finally logging back on to read about this. So funny we both kinked our sending units... I thought vented gas caps opened under pressure or vacuum . I have my canister and all the lines connected air goes through everything fine. I did replace that dodad loop thing on the vent line when I replaced my tank. I have a newish vented gas cap.... I'm really not thinking vacuum caused my issue with my sender getting smashed but who knows. I plan to stick a much larger pump in my truck soon so I really hope it's not some vacuum issue that will get worse with more flow. I'm hoping one of us gets a solid 100% answer before we bend another one ;)

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@the_blaze, what brand is your sender? Mine was Spectra.

I'm pretty sure mine has a vented cap as well.

My pump is the higher flow pump from the mid 90's to feed the aftermarket EFI; same you'd use for an LS swap. I wonder what size vent line they use on those systems. Maybe 1/4" isn't big enough?
 
mrk5 said:
@the_blaze, what brand is your sender? Mine was Spectra.

I'm pretty sure mine has a vented cap as well.

My pump is the higher flow pump from the mid 90's to feed the aftermarket EFI; same you'd use for an LS swap. I wonder what size vent line they use on those systems. Maybe 1/4" isn't big enough?
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My last sender was spectra my new one is Delphi. I tested my vented cap today and discovered it's not working. I wonder if the ls guys running a 255 pump have any issues.
 
I have a new sender coming. Not a lot of choices available for the 40 gallon tank so it's a random eBay unit. Still thinking I want to brace the return line on the new sender.
 
I wouldn't bother, if you prevent it from being crushed it should have very low load on it, just from the small mass of the pump. There are likely millions of them without extra bracing.
 
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