Rebuilding the Fuel System

Tomaco1

Tomaco1

Well-known member
https://www.hydradynellc.com/product/w169plp-6-8/prestolok-metal-w169plp?q=W169PLP-6-8

I ran 10mm parflex diesel tubing, so I thought I might try the above fitting at the lift pump.

Still trying to figure out what to use to connect the same 10mm tubing to the fuel return. Was thinking about trying below, not sure if it will work with the platic 10mm end and the medal 6mm tubing on the fuel return.

https://www.hydradynellc.com/product/m10rum6-316/a-lok-metric-tube-reducing-union-rum?q=M10RUM6-316
 
RBBailey

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I emptied the fuel out of the tank this evening, in preparation for resealing, and replacing the sender and pick up, when I realized that my low-fuel warning light actually does work! (I've never been able to test it since the truck runs out of fuel at 1/4 tank.)

But then the thought occurred to me.... I'm now not going to be able to use that light, am I? It won't work with the new sender I just bought....

I wish I had the ability to figure out how to pipe a new set of lines! My imagination isn't working on this one. But really, I have no clue what to even buy. Right now I'm just going with a rubber line, which I suppose isn't a problem, just....
 
Napalm00

Napalm00

Technical Excellence Contributor
The trucks running out of fuel at a quarter tank you need to pull the sender and just bend it. Either the pickup tube is too high or the float is too low. Or it's just broken
 
RBBailey

RBBailey

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Callsign: KF7KFZ
Napalm00 said:
Replace the v8 top pickup/pump assembly with the top return elbow part number Ntc2156, it's gasket and probably new mounting screws. Move the return line from the vent to the top return elbow you just installed. Block off unnecessary vent you just removed the line from. Install diesel pickup /sender prc8463 and It's gasket and lock ring in side of tank connect diesel feed for engine to this. PRC8463 has two spades and a ground lug; ground the threaded lug, connect the two spades to the same sender wires from the old v8 top mounted pump/sender. The wiring colors may not be the same and you may need to swap the connections. One spade sends the level, the other in conjunction with the ground is the low fuel dummy light on the dash
Click to expand...

Before I start this job, I need to break this down a bit to make sure it's going to work. My current set up is a line that goes into the top of the passenger side -- return? And a line that goes into the top center of the tank -- pickup? The top of the tank also has a set of wires that I assume is the old fuel pump wires?

What it sounds like you are saying is that both of these need to shift over. That is, the return on the side will now be in the top of the tank. While the pick up will now be along the driver's side of the tank, where currently there is only a sender, it will soon be a sender and the pick-up?

Finally, it would help me to understand the whole thing if I knew why the current set up doesn't work just because of diesel instead of gas.
 
RBBailey

RBBailey

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Callsign: KF7KFZ
Napalm00 said:
The trucks running out of fuel at a quarter tank you need to pull the sender and just bend it. Either the pickup tube is too high or the float is too low. Or it's just broken
Click to expand...

The sender is accurate. When it is at 1/8 of a tank, there is 2.5 gallons. 1/4 tank is 5 gallons. etc.... I've tested it several times, including this evening. 6 gallons really was just a needle width above 1/4 tank.

The tank was untouched during the fitting of the 300Tdi. Either way, I have the new parts already.
 
RBBailey

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
Strange. Since the pickup comes in from the top, it is still coming through the V8 style pick up, and I never had this issue with the V8, I can't think of what might have changed. The only thing I can figure is that since the gasoline in-tank pump is no longer used, maybe at a certain level, there isn't enough fuel weight to help push it through the pick-up/fuel pump/filter in the tank, and that level just happens to be right at about the 5 gallon mark. The fuel pump would normally lift it out of there, but now it's actually hindering fuel flow.

I'll take a look at it when I pull the tank. I have to fix the leak one way or another. And I confirmed that the new sender works with the fuel light, and seems to be reasonably accurate.

In the event of needing a new tank, which one should I look to buy, assuming I would rather avoid spending $800 for a new genuine?

Thanks, I'll post when I know more. Hopefully I'll have time to get this done this week.
 
Napalm00

Napalm00

Technical Excellence Contributor
I was assuming you had already corrected all of this.

the reason you running out at a quarter tank is because the pickup is above the fuel line.

Need to convert the tank to diesel style pick up and then you can get the whole tank
 
RBBailey

RBBailey

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Callsign: KF7KFZ
Why would the pick up be above the fuel line? Diesel sits at the same level as gas! The pickup is unchanged. And when it was a gas engine I purposefully ran it dow till the warning light came on a few times so that I could learn how accurate the gauge was after I bought the truck.

No. I got the parts last spring, and have not had the time to do the work yet. It is still 100% original V8 style.
 
Napalm00

Napalm00

Technical Excellence Contributor
Probably because they took off the fuel pump and now the physical pickup is higher.

But it could be one of a billion reasons because your tank is also plumbed incorrectly.

Start with getting it to stock
 
R

Red90

Well-known member
Man, what a mess.

I may have missed it as this is a long thread, but what filter is being used?

The pickup should be a straight tube that sit in the recessed area at the bottom of the tank. It should be able to suck the tank dry.

The return should go close to the bottom to prevent the lines and pumps draining out when sitting.

Personally, I would use proper stock tank connections in a proper stock tank and then plumb up properly with line types that you prefer. I like to use air brake tubing. Cheap, easy to work with and lasts forever.

Tank / sedimenter / lift pump (electric or mechanical) / fuel filter / injection pump / return to tank.
 
RBBailey

RBBailey

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Callsign: KF7KFZ
Napalm00 said:
Probably because they took off the fuel pump and now the physical pickup is higher.

But it could be one of a billion reasons because your tank is also plumbed incorrectly.

Start with getting it to stock
Click to expand...

I would think this is the case, except that the tank wasn't removed. The rusty bolts holding it to the truck, and just the word of the guy who did the conversion who told me that he simply left it as it was. I suppose it could literally be broken off inside the tank???

Here's how it is:
  • The filler and vent are on the passenger side, as I suppose they should be.
  • The return is in the top side of the passenger side of the tank.
  • The pick-up is in the top center, and is almost certainly one of these, or equal.
  • The sender unit is in the driver's side of the tank.

That's not stock for a Saudi V8? I suppose it could have been changed at some point, but I wouldn't know the difference. The truck never ran out of gas before switching to a Tdi, even when I ran it down to the idiot light.

I have the new sender and pick-up for the side of the tank. Tested it last night, and confirmed that it works, and that it allows the idiot light to come on in the dash.
I have the new return for the top of the tank.
I plan on capping the return that is in the side of the tank, exactly as you did in the photo you showed earlier.
 
Napalm00

Napalm00

Technical Excellence Contributor
Only real way to tell is to look inside. get the tank to less then half full and pull the side "return"

it doesn't really matter tho whats in there. Replace it with the Side mounted pickup/level sender, put the return in the top and cap the extra vent.

Use 5/16 diesel rated rubber hose and clamp it on to all the existing connections using hose clamps. Cut the old black plastic fuel line off with a razor.


fuel flow is: tank output from side mounted pickup, Sedimenter in (if equipped), sedimenter out (if equipped) lift pump in, lift pump out, fuel filter in, fuel filter out, injection pump input front banjo bolt pipe, injectors, injector overflow pipes, back of injection pump overflow banjo bolt, return hose to top of fuel tank

Dont bother even trying to figure out what is currently setup, since you are removing all of it.


FYI you dont have to fully drop the tank to remove and replace the top port. just take out the front mount bolts and you should be able to let it droop enough to get in there. Keep an eye on the side mounted pickup as the metal pipe coming out of it clears the frame rail by about 2 mm (dont snap it off)
 
Napalm00

Napalm00

Technical Excellence Contributor
Red90 said:
Man, what a mess.

I may have missed it as this is a long thread, but what filter is being used?

The pickup should be a straight tube that sit in the recessed area at the bottom of the tank. It should be able to suck the tank dry.

The return should go close to the bottom to prevent the lines and pumps draining out when sitting.

Personally, I would use proper stock tank connections in a proper stock tank and then plumb up properly with line types that you prefer. I like to use air brake tubing. Cheap, easy to work with and lasts forever.

Tank / sedimenter / lift pump (electric or mechanical) / fuel filter / injection pump / return to tank.
Click to expand...



he is using a mix of gas and diesel pickups and filters...trying to get him to return it to stock
 
R

Red90

Well-known member
Napalm00 said:
he is using a mix of gas and diesel pickups and filters
Click to expand...

Yes, which is a bad idea. As I read it, he is fixing the pickup and return issue with the correct parts. That is great.

What I did not see was specifics of the filters and the rest of the system. If he is using a gas filter, that would account for a lot of the problems that he complains of in many other threads.

It needs to be this way: Tank / sedimenter / lift pump (electric or mechanical) / fuel filter / injection pump / return to tank for reliable, trouble free operation. With the items suitably chosen for diesel usage at the flowrate they will see.
 
RBBailey

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I'm curious about why it is failing at 1/4 tank only because I'm curious. It makes sense that this is not the correct set up, and could be causing the other issues I've asked about. (I've always had a feeling that it may be fuel related.) But I am baffled by why the gasoline pump/pick-up, that should be, and was confirmed to be, reaching the bottom of the tank just decides not to pull fuel when I get to 5 gallons.

But I'm going to convert it to the diesel version we are talking about, so hopefully that issue won't matter. I think I got confused about what you were saying when you said to take it back to 'stock'... it is stock... for the V8. I want to convert it to what it should be for diesel.

I'm putting a sedimenter inline. Currently using just the stock lift pump, but may put an electric in by the time this project is done.

I'm going to pull the tank out completely, clean it up, paint the outside, install the bits while it is on the workbench, and check for leaks. I am pretty sure the leak I'm seeing is just coming from one or more of the seals, but I need to be sure.
 
Napalm00

Napalm00

Technical Excellence Contributor
yea when i said stock, i meant stock for diesel. Using a diesel filter or a stanadyne fm100 fuel manager instead like red said

I cant tell you why its not pulling fuel at 1/4 tank, unfortunately you will have to take it apart.
 
RBBailey

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I have a stock fuel filter set up under the hood. Using a NAPA 5 micron right now. would like to know of a tighter filter that fits the stock mount -- ?
 
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