LS Fuel Pressure Issue High Hot

wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
FJ62 with 5.3 2011 Erod gremlin. I’ve only been in situation at high elevation 2 times when hot. Both times fuel pressure loss. Here’s what’s been done to take some guess work out. These were all legitimate issues eliminated:

Rewire harness, bad grounds and power
New intake tubing and tuned/dyno
Fuel evap system removed
Cats removed open tuned to MAF
New MAF wires checked good
New MAP wasn’t functioning
New fuel cap
New fuel regulator and filter
New fuel pump 18 months ago
New Oxygen sensors NGK
New throttle sensor ACD
Throttle removed and cleaned
Vacuum leak smoke checked - good
Fuel rail bleed down hold 50+
In tank pump
Regulator and filter same mount on frame, no return check (that I know of other than disconnected evap)

Ok so leave sea level and get to 4000ft warm outside and like clock work starts leaning out, maxed out stumbles and dies, cool off runs 10 minutes and does it again until I get to lower altitude.

Stopped at auto parts and put a gauge on rails, read 60 psi drive again to duplicate and after heat soaked pressure dumps rapid, Fuel pump in tank pegs out at 60 and dumps again. Over and over. All that said I’m thinking 3 things: injectors won’t bleed like that, seems like vapor lock but FI, pump runs strong and less than 2 years old. WTH!?

Ok I’m done
 
Last edited:
L

Lead Head

Joined
Jul 21, 2012
Messages
364
Location
Rhode Island USA
So you took everything that made your E-Rod engine an E-Rod, and chucked it in the trash???

...anyways. Really the only things that could be causing that are a failing fuel pressure regulator, intermittent pump power, vacuum in the tank, or fuel starvation. I'd probably start by first verifying all electrical to the fuel pump. Then I'd start looking at potential tank vacuum issues.
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
So you took everything that made your E-Rod engine an E-Rod, and chucked it in the trash???

...anyways. Really the only things that could be causing that are a failing fuel pressure regulator, intermittent pump power, vacuum in the tank, or fuel starvation. I'd probably start by first verifying all electrical to the fuel pump. Then I'd start looking at potential tank vacuum issues.
There is nothing special about Erod. The crate came a crap Compushift trans controller, the sensors aren’t better, $2k for cats that was a kill joy. You should see the pieced together s*** they put together on this motor. Turnkey in LA doesn’t even know what they sold, I’ve counted 4 different vehicles making 1 motor, on the paperwork it says 2011 Silverado complete. However I’ve had to start a log with 4 columns to track new parts based on 1 engine. The fuel pump shows as a firebird from 2002 and this was sold and installed in 2013. Maybe all of it is the same stuff. Unless you were joking about taking the Erod thing serious. If so go me wound up

I ordered the cap that vented, the PO had wrong one. I’ve got a filter on line where evap capped, today if recalled someone asked if I pulled the cap off after this happened, had slight pressure, lastly when it died first time today I head the tank gurgle some. Don’t know about that?..
 
L

Lead Head

Joined
Jul 21, 2012
Messages
364
Location
Rhode Island USA
What I am saying is an "E-Rod" engine is a complete package from GM Performance that specifically includes catalytic converters and a complete emissions system. You only buy an E-Rod because you want the emissions stuff. Buying an E-Rod then tearing all the emissions stuff off would be like ordering a purposely ordering a pepperoni pizza and then individually removing every single pepperoni by hand. However, after more closely reading, you do not have an "E-Rod" engine like your first post claims. An E-Rod is a 6.2 LS or LT engine from GM Performance. You just have a random 5.3 truck motor yanked from a Silverado - and it DOES make a difference in terms of diagnostics and approach.

You should not hear/feel any pressure or gurgling from the tank if the evap & venting is functional. You likely have a plugged vent line going to or coming from the vapor separator.
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
What I am saying is an "E-Rod" engine is a complete package from GM Performance that specifically includes catalytic converters and a complete emissions system. You only buy an E-Rod because you want the emissions stuff. Buying an E-Rod then tearing all the emissions stuff off would be like ordering a purposely ordering a pepperoni pizza and then individually removing every single pepperoni by hand. However, after more closely reading, you do not have an "E-Rod" engine like your first post claims. An E-Rod is a 6.2 LS or LT engine from GM Performance. You just have a random 5.3 truck motor yanked from a Silverado - and it DOES make a difference in terms of diagnostics and approach.

You should not hear/feel any pressure or gurgling from the tank if the evap & venting is functional. You likely have a plugged vent line going to or coming from the vapor separator.
You are really front loaded with opinionated statements, I didn’t ask for a lecture.

Yes it’s an Erod so stay with what you know.

Offer feedback is great but don’t get off in the weeds with arrogant comments that you don’t know about
 
L

Lead Head

Joined
Jul 21, 2012
Messages
364
Location
Rhode Island USA
There's a lot of unnecessary detail and information that's just causing confusion.

- In my experience, drivability issues with most vehicles I work on result from people haphazardly ripping emissions components. This is an extremely common issue here on ih8mud, where people have to deal with the fallout from previous owners incorrectly "desmogging" a vehicle. So I wanted to 100% verify that you bought an E-Rod engine, and then ripped the emissions stuff off it. Knowing this can help with diagnostics.

- I apologize, you are correct that at one point GM offered the LC9 5.3 ERod engine. It wasn't on the market very long, and has been discontinued for a very long time, so I forgot they even offered. But we really need you to be clear and concise with what you have: You say it was an ERod, then you say it was a pieced-together motor, then you say the engine was sold to you as a 2011 Silverado motor, then you said it was an ERod again? Which is it, what do you actually have?

It's time to take a step back and look at the major red-flag symptom to me:
- You claim the evap line from the fuel tank vapor separator just has a filter on it.
- The evap line comes from the vapor separator in the back right quarter panel. 4 hoses from the gas tank go into the vapor separator, and those get combined into the one evap line that goes to the front of the vehicle.
- This evap line is a direct connection to the tank vent, through the vapor separator. If the line going to the vapor separator is open to atmosphere (through a filter), the fuel tank cannot build any pressure.
- If you're pulling the cap off and getting hissing/wooshing/gurgling, this indicates the tank is building pressure, which can't happen if that evap line is open to atmosphere. It indicates your evap lines are plugged and not allowing the tank to breathe.
 
tmxmotorsports

tmxmotorsports

SILVER Star
Joined
Jul 3, 2016
Messages
2,519
Location
OBX Nc
Jist going to throw this out there because it happened to a build I did the fuel tank was sealed with por 15 tank sealer and it became compromised and would release from the tank and cut off fuel supply. Has anything like that been done?
Tommy
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
You are really front loaded with opinionated statements, I didn’t ask for a lecture.

Yes it’s an Erod so stay with what you know.

Offer feedback is great but don’t get off in the weeds with arrogant comments that you don’t know about
You are really front loaded with opinionated statements, I didn’t ask for a lecture.

Yes it’s an Erod so stay with what you know.

Offer feedback is great but don’t get off in the weeds with arrogant comments that you don’t know about
What I am saying is an "E-Rod" engine is a complete package from GM Performance that specifically includes catalytic converters and a complete emissions system. You only buy an E-Rod because you want the emissions stuff. Buying an E-Rod then tearing all the emissions stuff off would be like ordering a purposely ordering a pepperoni pizza and then individually removing every single pepperoni by hand. However, after more closely reading, you do not have an "E-Rod" engine like your first post claims. An E-Rod is a 6.2 LS or LT engine from GM Performance. You just have a random 5.3 truck motor yanked from a Silverado - and it DOES make a difference in terms of diagnostics and approach.

You should not hear/feel any pressure or gurgling from the tank if the evap & venting is functional. You likely have a plugged vent line going to or coming from the vapor separator.
FJ62 with 5.3 2011 Erod gremlin. I’ve only been in situation at high elevation 2 times when hot. Both times fuel pressure loss. Here’s what’s been done to take some guess work out. These were all legitimate issues eliminated:

Rewire harness, bad grounds and power
New intake tubing and tuned/dyno
Fuel evap system removed
Cats removed open tuned to MAF
New MAF wires checked good
New MAP wasn’t functioning
New fuel cap
New fuel regulator and filter
New fuel pump 18 months ago
New Oxygen sensors NGK
New throttle sensor ACD
Throttle removed and cleaned
Vacuum leak smoke checked - good
Fuel rail bleed down hold 50+
In tank pump
Regulator and filter same mount on frame, no return check (that I know of other than disconnected evap)

Ok so leave sea level and get to 4000ft warm outside and like clock work starts leaning out, maxed out stumbles and dies, cool off runs 10 minutes and does it again until I get to lower altitude.

Stopped at auto parts and put a gauge on rails, read 60 psi drive again to duplicate and after heat soaked pressure dumps rapid, Fuel pump in tank pegs out at 60 and dumps again. Over and over. All that said I’m thinking 3 things: injectors won’t bleed like that, seems like vapor lock but FI, pump runs strong and less than 2 years old. WTH!?

Ok I’m done
Quick history to clarify. PO bought from Icon then had the swap in 2013. I bought a year ago and drove it home after a pre-purchase. The shop that maintained it did a poor job of maintaining it. I dug into the records after the fact and chased down the shop that did the swap (not shop PO had work done for 8 years) the swap shop lead tech said oh yeah I recall that. Then said the owners shop called me 5-10 times after the swap asking questions that made it apparent they had no business maintaining it. In conclusion they butchered the hell out of it. Problems that came up they did repairs that patch or masked the problems. One example is the ECU was replaced 3 times in 5 years, instead of fixing the issue they kept replacing the fried ECU. All the rewiring is because they rigged wires not knowing what they were doing, hooked power feeds to wrong post on fuse block, added a switch to bypass or cut power signal to downstream 02 sensors some how to drive better between annual smog and added lines caused resistance and became corroded and system failures, they actually removed the ground system to the engine and the entire frame/battery/ECU was shorted in OL. They fried everything in time and just kept throwing parts at it. I spent the last year gutting it, rewiring it to fix it all. They forged documents to cover their mistakes and I’ve uncovered the issues. But I’ve filed suit and opened investigation with California air board. It’s a s*** show.

I had many moving parts and they’ve been fixed. Im sure you know you can have an issue and it will only reveal itself in certain conditions. From OP I’d mentioned this problem only happened on 2 trips and this is second one. High and hot, I live at sea level and after spending thousands of $$$ having various shop tear it apart they never could recreate the issue at sea level so im stuck in NM in a hotel with trip canceled waiting on $500 a day mechanic to arrive to troubleshoot while im at the scene, I can recreate the issue while im here today.

-The evap line was removed at the fire wall and filter installed on the 1/4 metal line at firewall. The manifold was capped and vacuum test done to determine it was sealed at manifold. The breather on the line vents ok because I can smell fumes. After reading this as a solution on Mud.

-the tank has only made a gurgle noise when I change altitude. The minute I broke down yesterday I ran back and popped the cap and it vented but not a huge amount just a woosh and after that it was adjusted to altitude. During several hours of scan tool I made it continue to fail to watch for clues on scan, every time it failed I’d check tank for pressure and there wasn’t any. I even left cap off on one run with rag stuffed in it to see if that would relieve build up but with or without the cap it did identical failure, ran great in between, heat soaked then failed.

-Stopped at auto parts store and bought gauge and duct taped to windshield, drive until I saw trims start leaning out then watched fluctuation in trims. The trims would oscillate at beginning and I’d hear tank pump cycle to prime line then turn off, I could see trims go to zero, within 5 second pressure would bleed off and trims would max lean, over and over max trim to zero, quickly over and over.

I’ve got video of the wild fluctuation in rail pressure but can’t post video so here’s screen shots that shows the pressures within a 10 second interval.

I hope this helps clear up anything that wasn’t represented in OP. Initial post I wasn’t going to write a book and knew I’d have to elaborate so here we are. And thank you for apology, accepted.

I’m not an ASE mechanic so much to learn but I’ve got thousands of hours in restoration, give or take $15-20k in parts and shop bills. PO literally destroyed the LC from the inside out.

8F23A52E 93BF 427C 8E15 D25A8618152C


98F5FF00 FB10 41A7 8119 2BC75A0029C5


27070400 60C6 4AAB ACCE B3BA6D98ED74
 
Last edited:
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
Jist going to throw this out there because it happened to a build I did the fuel tank was sealed with por 15 tank sealer and it became compromised and would release from the tank and cut off fuel supply. Has anything like that been done?
Tommy
Hey Tommy, the tank external was cleaned and painted. All the issues have been repaired except the altitude part. That has remained based on 2 trips 2 failures. Everyday driving at home no issues.

When you say the restoration paint would released and compromise and release and cut off fuel supply, how was this happening? Meaning it was choking off from fumes, swelling under heat? Permeated the lines and contaminated. If you can read my response to other comment we got some stuff cleared up to clarify. If that helps with responding to your post.
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
To give perspective here’s a snapshot of my repair log in the last 12 months. No, those aren’t the same page, first is mechanical and 2nd is the restoration page….

CBF96C19 BB7C 4DF5 9537 C6AE952CDDE3


A705ECF0 6966 4633 9BFD E030B358B6E7
 
cruisermatt

cruisermatt

Un-manufacturable
Supporting Vendor
SILVER Star
Joined
Jul 22, 2012
Messages
10,786
Location
Winter Park, Florida
Website
www.facebook.com
What fuel rails do you have, what FPR do you have, what do you have for fuel lines, what do you have for pump wiring, this is probably a simple issue made wildly complicated for no reason
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
Granatelli 720-2 250lph and whatever filter that’s the corvette filter and regulator on same mount. Connectors are Redhorse and nylon wrapped hose to match.

9010FF1E 367B 4A52 83B8 C568B0252CBE


1D46DA71 8CDF 46F6 ADE9 275A1E86CB42


B2EED9D2 746A 4199 891A 6BBFD9F69AE8
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
What fuel rails do you have, what FPR do you have, what do you have for fuel lines, what do you have for pump wiring, this is probably a simple issue made wildly complicated for no reason
I forgot to reply to your message and posted accidentally
 
cruisermatt

cruisermatt

Un-manufacturable
Supporting Vendor
SILVER Star
Joined
Jul 22, 2012
Messages
10,786
Location
Winter Park, Florida
Website
www.facebook.com
Does it hold fuel pressure after you shut the truck off?
If no,
I would try another FPR. That’s a easy check and should be available at any auto parts store.
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
Does it hold fuel pressure after you shut the truck off?
If no,
I would try another FPR. That’s a easy check and should be available at any auto parts store.
I picked up a pressure gauge yesterday and it hold 50psi after shutdown hour+. When it becomes heat soaked at altitude the fuel leans out progressively worse until pump starts short cycling. Eventually can’t keep up and shuts down. From post above here is what gauge looked like last night in 10 second intervals at idle. Pump brings it to zero and 10 seconds later it’ll go to 25+

59E33B1E 2066 44BD 9652 803D28A53ABB


193C28CD B789 4B0B B5C4 DF41BAAA3FBB


A9DDA9F1 8543 4AAC B011 92C5C7FCB097


2D568072 CDDA 4540 A58E 7C8704C6DC29


4218BE19 E4AA 4406 9B3E 61711D6919AC
 
L

Lead Head

Joined
Jul 21, 2012
Messages
364
Location
Rhode Island USA
What do you mean the fuel pump is short cycling?

The ERod motor doesn't have fuel pressure sensors or feedback/control. The PCM will send a signal to the fuel pump relay, and the pump will run continuously. The fuel pressure regulator should then supply a constant 60 PSI to the motor. If your pump is turning on/off and "short cycling", you have a failing pump or electrical issue. If the pump is running continuously but your pressure is dropping at regulator intervals, then the pressure regulator is failing or the pump is starving of fuel.

With the evap line vented to a filter, there should be no pressure or vacuum in the tank. Zero. Absolutely none. You should be able to take the gas cap off, and then blow through the evap line into the tank without much trouble.

Where is the return line from your regulator plumbed into?
 
cruisermatt

cruisermatt

Un-manufacturable
Supporting Vendor
SILVER Star
Joined
Jul 22, 2012
Messages
10,786
Location
Winter Park, Florida
Website
www.facebook.com
I would say if it holds +50psi after shutdown then the regulator is failing. I think the pump is probably junk

Get yourself a nice Denso pump. Skip all that Walbro autozone trash
 
wester11

wester11

Joined
Nov 13, 2020
Messages
254
Location
Dallas Texas
What do you mean the fuel pump is short cycling?

The ERod motor doesn't have fuel pressure sensors or feedback/control. The PCM will send a signal to the fuel pump relay, and the pump will run continuously. The fuel pressure regulator should then supply a constant 60 PSI to the motor. If your pump is turning on/off and "short cycling", you have a failing pump or electrical issue. If the pump is running continuously but your pressure is dropping at regulator intervals, then the pressure regulator is failing or the pump is starving of fuel.

With the evap line vented to a filter, there should be no pressure or vacuum in the tank. Zero. Absolutely none. You should be able to take the gas cap off, and then blow through the evap line into the tank without much trouble.

Where is the return line from your regulator plumbed into?
The short cycle is when it leans out at idle, it’ll kick on and can hear it. When I start it it’ll run for 2 second and stop and don’t hear after that. Only time I’ve heard it is when it leans and tries to die or prime to start. I’ll check the supply line to the filter on the end of the vent line
 

Users who are viewing this thread

Top Bottom