Starting Point
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FTE Chapter Leader
Joined: May 2020
Posts: 2,924
Likes: 2,180
From: Langley B.C. Canada
Latest update.
FRx is reinstalled.
Tank is full now.
Fuel pressure with the Riff Raff black spring is 62lbs.
Drops to around 54lbs under foot to floor in 3rd TC locked in hot tune.
Fuel pressure still doesn’t bleed down after 20second timeout. Problem with return line. FPR poppet does have the bleed down hole, and FRx being post poppet that shouldn’t matter.
Gonna run it for now. 2nd day into my vacay and supposed to be 400 miles north of where I currently am.
Most people have to drive by the EGT, I’m gonna drive by the fuel pressure if it becomes an issue.
Thanks to all for being a sounding board.
FRx is reinstalled.
Tank is full now.
Fuel pressure with the Riff Raff black spring is 62lbs.
Drops to around 54lbs under foot to floor in 3rd TC locked in hot tune.
Fuel pressure still doesn’t bleed down after 20second timeout. Problem with return line. FPR poppet does have the bleed down hole, and FRx being post poppet that shouldn’t matter.
Gonna run it for now. 2nd day into my vacay and supposed to be 400 miles north of where I currently am.
Most people have to drive by the EGT, I’m gonna drive by the fuel pressure if it becomes an issue.
Thanks to all for being a sounding board.
Lead Driver
Joined: Jul 2017
Posts: 6,846
Likes: 2,326
From: WV
Originally Posted by F350towing
5 gallon in the bed is such a pita because you have to run the return line there too with no good spot to splice into that line without cutting it.
I also have a canopy/ topper/ shell so length of fuel lines to make that happen is outrageous.
But I get what you’re saying. That’s why I used the 5 gallon on the floor with only the feed line into it. Was hoping to see a pressure increase. None Noted.
I also have a canopy/ topper/ shell so length of fuel lines to make that happen is outrageous.
But I get what you’re saying. That’s why I used the 5 gallon on the floor with only the feed line into it. Was hoping to see a pressure increase. None Noted.
For now I hope you can enjoy your vacation and worry about all this later.
I checked again the pressure drop after pump times out. Mine goes to zero very quickly. It’s an electronic gauge so can’t check that since going key off kills the gauge.
Took a video with hopes it would be small enough to upload.
Looks like unloaded after all!
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FTE Chapter Leader
Joined: May 2020
Posts: 2,924
Likes: 2,180
From: Langley B.C. Canada
Ah yes, I didn’t think about the return side. How long does it take to lose 5 gallon to the tank during this process with return going there? If it’s a few minutes that could still work for a quick confirmation. Carry an extra 5 gallon with you just in case. I understand the topper makes this much more difficult though too.
Thinking about the return restriction and shouldn’t that be similar to a deadhead but not fully plugged off.
Going off that thought, shouldn’t that cause higher pressure? Yet here I am with a 70lb FP spring sitting at 62lbs at idle.
Once I get back from this trip the tank will come down for the 3rd time. I will flush the return line and snake out the in tank pickup and return.
Im rambling my thoughts as I type this.
FTE Chapter Leader
Joined: Jan 2005
Posts: 13,076
Likes: 4,692
From: Henderson, NV
Sometimes when I have a problem where a seemingly logical progression of troubleshooting steps does not yield definitive answers, I go all the way back to first principles and start over. You may have to do that with this fuel pressure problem.
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FTE Chapter Leader
Joined: May 2020
Posts: 2,924
Likes: 2,180
From: Langley B.C. Canada
Ahhh, Sensei with words of wisdom.
If it were you where would you start the second time around.
https://www.canadiandieselonline.ca/...IaAgO2EALw_wcB
Add a sump to tank with pickup and return.
That aught to fix it.
FTE Chapter Leader
Joined: Jan 2005
Posts: 13,076
Likes: 4,692
From: Henderson, NV
I would rebuild the entire fuel system from the pickup in the tank through to the fuel line fittings in the heads. That does not necessarily mean I replace everything with new. I would take it all apart and clean the ever loving crap out of everything. Is it tedious? Yes, very, but it forces me to examine each and every part of the system and ensure it is functioning like it is supposed to.
https://www.canadiandieselonline.ca/...IaAgO2EALw_wcB
Add a sump to tank with pickup and return.
That aught to fix it.
As tempting as it is to add another cool mod to the truck, I refuse to go with a sump because that is the first place where all the crud from a bad tank of fuel will plug up.
https://www.canadiandieselonline.ca/...IaAgO2EALw_wcB
Add a sump to tank with pickup and return.
That aught to fix it.
Cargo Master
Joined: Apr 2022
Posts: 3,189
Likes: 1,695
If it were me I would start with 5 gallon bucket in bed and run rubber line to pump. Then another rubber line from pump to the flex lines at engine. Then you could run another piece of rubber from other flex line at engine back to the bucket. That will rule out almost the entire fuel system besides the engine side. Then if it's good then start adding the metal lines back in from pump to engine. Then add stock return back in and just let it return back to tank and pull out of bucket. That should narrow down where the problem lies.
Lead Driver
Joined: Jul 2017
Posts: 6,846
Likes: 2,326
From: WV
I agree that a restriction in the return side should create higher pressure. One of my previous bosses used to say “when it doesn’t make sense, we don’t have all the data.” There’s something we’re overlooking. And like FTN said it may be something that’s already been “fixed.”
The pump seems to respond to varying FPR springs so it’s unlikely to be the culprit, at least on the idle pressure end of things. But a quick check would be to pinch the return line briefly to see if the pump spikes high. Doesn’t tell us anything about during high flow demand but is a quick check.
The pump seems to respond to varying FPR springs so it’s unlikely to be the culprit, at least on the idle pressure end of things. But a quick check would be to pinch the return line briefly to see if the pump spikes high. Doesn’t tell us anything about during high flow demand but is a quick check.
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FTE Chapter Leader
Joined: May 2020
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From: Langley B.C. Canada
Truck performed well for the drive. Fuel pressure has dropped at idle to about 59, but never dropped below 50lbs even when I was flogging it.
Took a while for me to have confidence in it, and more than once ( read 100 times ) wife asked me if everything was ok.
Whatever was blocking the return line has flushed out because it’s dropping like a rock now.
Took a while for me to have confidence in it, and more than once ( read 100 times ) wife asked me if everything was ok.
Whatever was blocking the return line has flushed out because it’s dropping like a rock now.
Got Data?
Joined: Dec 2012
Posts: 4,236
Likes: 1,368
From: Lake Stevens, WA
Is this this happening - slowly reaching your nominal fuel pressure? That seems odd to me - I wonder if this is a clue. What would cause that - poppet starting to open maybe? Pump pressure/volume should be more than the flow past the fuel return poppet by quite a bit I would think.
Just checked mine. Pressure goes up to 65-66PSI quickly. While I rebuilt the fuel bowl, it still has the OEM FPR.
When the fuel pump relay kicks off, the pressure slowly drops. It's still over 25PSI after 3 minutes on my truck. Looks like I have a restriction too, but it does not appear to affect FP under load. It does not drop more than 5-6PSI with these 160/30's, though have not checked that with this latest tune.
Is the fuel pump getting full voltage in all running modes? Wondering if there's a voltage drop in the circuit that is reducing voltage to the pump. Just spitballing another idea.
Cargo Master
Joined: Apr 2022
Posts: 3,189
Likes: 1,695
I mentioned checking voltage at pump as well on it but don't think he got a chance to check yet.
Thread Starter
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FTE Chapter Leader
Joined: May 2020
Posts: 2,924
Likes: 2,180
From: Langley B.C. Canada
Gives me a baseline to go off of.
As I said in text last night 400miles north of my volt meter. Be a week before I can check that.