LS Fuel Pressure Issue High Hot

cruisermatt

cruisermatt

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when you re wired everything did you verify that the pump wiring was done correctly?
I'm still not buying that a single charcoal canister line can get clogged (what would it even get clogged by? Rust maybe? This truck doesn't look rusty) and cause enough vapor lock to prevent an intank EFI pump from sending fuel. Maybe a carb mechanical pump. but not a submerged electric pump.
 
wester11

wester11

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when you re wired everything did you verify that the pump wiring was done correctly?
I'm still not buying that a single charcoal canister line can get clogged (what would it even get clogged by? Rust maybe? This truck doesn't look rusty) and cause enough vapor lock to prevent an intank EFI pump from sending fuel. Maybe a carb mechanical pump. but not a submerged electric pump.
Top line Engine in LA did the conversion for engine and tank. It’s a scavenger hunt. Just got home so I’ll know this weekend. I don’t know what meaning In venting the line but it’ll go from trim whacked out to 0.0 as soon as I do it. Question is the plenum or vent whatever in the rear, I know it’s to keep liquid and fumes where they are supposed to be, I’ve vented the line back to the tank 2 times to make sure it wasn’t just a one time thing. You can hear what seems to be a heavy amount of fuel being pushed out of that separator. Normal? I’ll look at wiring this weekend but this has been at tuners 3 times, hours of computer time summer and winter, surely a tech would have picked up on a incorrect wire situation
 
White Stripe

White Stripe

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So is the issue when you've been driving hard up a mountain pass on the highway pulling some steep grades at speed? Or are you just cruising casually around some mountain town that is at 4000ft? Or are you 4wheeling slowly from sea level up to 4000ft?
 
wester11

wester11

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So is the issue when you've been driving hard up a mountain pass on the highway pulling some steep grades at speed? Or are you just cruising casually around some mountain town that is at 4000ft? Or are you 4wheeling slowly from sea level up to 4000ft?
When It gets heat soaked, at altitude above 4K. After some long debate it seems to be around tank pressure. If it stalls I can let cool down 15, pop the cap and it’ll run fine for 15. Or if it’s acting up and I go down in elevation
 
wester11

wester11

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You keep saying “heat soaked”. What exactly are you referring to
200 degrees, running for more than an hour, only does it higher elevations, if I stay at same elevation and drive won’t do it, heat soak as in everything is hot been underway for more than an hour. If temperature outside is above 80 will stall and die. Colder ambient temps like 70 or lower it’ll have the same symptoms but manage to continue to run. When I see the fuel go real lean I’ll pull over turn off and go back and pop the fuel cap which releases a lot of pressure. Which doesn’t make sense if I have the evap removed with clear line to tank.

-Wired correct with 12v indicated
-Clear evap line
-New regulator filter
-Does not refuse fuel before topping off full meaning throw up gas 3/4


Fuel tank pressure sensor?

I’m back home runs fine but this isn’t over. Taking somewhere to have looked at. Probably have evap put back on and taking tmx comment about tank por15 in account.
 
wester11

wester11

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You keep saying “heat soaked”. What exactly are you referring to
Here’s what I did tonight.

-Connected air to vent tube with cap off to confirm flow
-Fuel cap spring loaded to relieve vacuum but not pressure
-Had spare cap and same (is the cap for this supposed to relieve pressure as well?)
-Put purge and can back on and pressured tank to kick on purge
-After I’d pressured tank ran super rich
-Purge kicked in not much better
-Checked for vacuum leaks on evap system
-While purge was running and kicked on from added shop air put propane into evap can on the tank side to propane to see if goes rich - no
-Plugged tank side line and ran propane into fresh port top of evap can to see if it would go rich - no
-Checked vent lines to tank and volts all good and no pinched lines - lines fairly new

Thoughts:
-Tuner guy said his last tune he’d turn off purge but it wasn’t - fail
-Did propane change fuel trim direct into purge itself yes
-Did fuel trim change when pumping through fuel can - no
-Having purge pulling before I deleted fuel evap create suction on tank yes, but did fuel cap relieve that vacuum…, but same symptoms of full lean with or without purge. (Keep in mind that clearing the vent line while at altitude did alleviate temporarily the lean and able to keep it normal now I’m home it’s managing on its own)
-Does tuner guy have it tuned to a problem and my cross check avail me nothing?…

Thoughts?
 
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burningoil

burningoil

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Put the fuel pump from mostly motors in the tank and put the vapor emission back on the tank
 
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onemanarmy

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Have you run it hard with no fuel cap on? I had an issue with my LS swap by a shop where the vent lines werent run correctly and got super high fuel tank pressure.
 
wester11

wester11

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Have you run it hard with no fuel cap on? I had an issue with my LS swap by a shop where the vent lines werent run correctly and got super high fuel tank pressure.
Yeah, so this week headed to higher altitude when it first started that I’d remember buried somewhere on this site someone drilled a hole in the cap and it fixed their deal. So I stuffed a rag in it and when I started up after sitting I took off and it did it again with rag only.
 
White Stripe

White Stripe

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Sounds like the tank may be plumbed incorrectly and the fuel pump is bad. I would make a access hole cover in the floor so fuel pump repair is easy. Then I would drive around with the cover off so you can hear the pump in the cabin if it sounds funny.
 
wester11

wester11

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Put the fuel pump from mostly motors in the tank and put the vapor emission back on the tank
Halfway there, last night I plumbed it all back in. I
Sounds like the tank may be plumbed incorrectly and the fuel pump is bad. I would make a access hole cover in the floor so fuel pump repair is easy. Then I would drive around with the cover off so you can hear the pump in the cabin if it sounds funny.
About to start throwing parts. So the short version is tuned, runs perfect Texas, drive 1000 miles in Texas, leave Texas to higher altitude starves eventually above 3-4K feet, pop cap massive air, with or without evap system tank pressure, if I broke down with stalled leaned engine at 4K feet and let sit for an hour relieve tank pressure it’s drive fine at 4K ft. If I go back to Texas lower altitude everything is fine, but if I go up to 6,8,10k ft does it again. This is becoming clear it’s a pressure vacuum issue.
 
White Stripe

White Stripe

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Halfway there, last night I plumbed it all back in. I

About to start throwing parts. So the short version is tuned, runs perfect Texas, drive 1000 miles in Texas, leave Texas to higher altitude starves eventually above 3-4K feet, pop cap massive air, with or without evap system tank pressure, if I broke down with stalled leaned engine at 4K feet and let sit for an hour relieve tank pressure it’s drive fine at 4K ft. If I go back to Texas lower altitude everything is fine, but if I go up to 6,8,10k ft does it again. This is becoming clear it’s a pressure vacuum issue.
Well I believe going up hills to higher elevation will strain a pump more than driving across Texas. You said you drove with the fuel cap off and still had issues right?
 
L

Lead Head

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Fuel pumps with a return-style regulator experience the same amount of strain no matter what. Up-hill, down-hill, idle, full throttle. They're always going full speed and always pumping the same amount of fuel.
 
wester11

wester11

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Well I believe going up hills to higher elevation will strain a pump more than driving across Texas. You said you drove with the fuel cap off and still had issues right?
But it shouldn’t stall and stall every 15 minutes, have to drive at night because the higher temps impact on it. The first time it stalled on this trip I pulled the cap stuff a towel in it for dust then, let it cool down and tried again. Made no difference.
 
L

Lead Head

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I think at this point you need to drop the tank and ensure the supply/return lines are plumbed correctly. You need to make sure the fuel pump strainer is properly attached, and that the whole fuel pump sending unit is properly oriented in the tank. You need to make sure the return pipe is returning back into the fuel pump "well" inside the tank. You then need to take every breather hose off the tank, make sure each one is clear, and make sure the fuel vapor separator is completely clear, including the top vent line that goes back to the vehicle. Then you need to make sure all of the breather ports on the tank are clear.

I almost wonder if someone connected the fuel return pipe to one of the breather ports. With the FJ62 fuel tank, the fuel pump sits inside a baffled "well" inside the tank. The well has small ports to allow fuel in/out. This prevents sloshing, and keeps a steady supply to the well. The return line returns back into the well, so fuel is constantly circulating inside of it. If the return line was plumbed "outside" this well, it's possible for the well to be pumped empty. Which could cause some of the issues you are seeing.
 
deliverance

deliverance

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I may have missed it, but what fuel pump are you running? I had an issue with two A/C Delco in-tank pump fuel hose. It softened and under a load would collapse and starve the engine of fuel. Replaced with Gates EFI submersible hose and problem solved. This was on an LS swapped square body with dual tanks. Both pumps had the exact same issue within 100 miles and both are in-tank setups.
 

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