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Oh sweet Racetronix is in here! Yes I called yesterday and spoke with a salesperson who pointed me to that, should arrive today. I wasn't sure about it because the terminals looked like they weren't in the same locations. I should also be getting a Uni-T DC amp clamp today or tomorrow so I can properly test amps and volts back there. Do you have any thoughts/ opinions/ advice on this circus I'm going through?
It was supposed to be in the mid 90's here all weekend but because of the wildfires, central Oregon currently has the worst air quality in the world and temps have cooled off because of the smoke. Today was my last shot, it was about 88-90 outside and I went driving for about 45 minutes. The pressure dropped off 3 psi and that was it.
Using the Uni-T clamp, I got 14.5 volts and 12 amps on the fuel pump wire at the alternator and back at the bulkhead before doing the drive. Idle fuel pressure was 41. After the drive I got 13.9 volts and 10.55 amps at the alternator and 13.5 volts and 10.55 amps at the bulkhead. The alt-bat wire had 22.5 amps. Idle fuel pressure was 37, dropped to 35 if I revved it. At this point I swapped in a new fuel pump relay and after starting it back up and taking another reading, numbers were all the same. I feel like the only thing left that I haven't touched is the actual power wire for the fuel pump. I must be missing something.
Also Racetronix: could you please respond to my email? It's been almost 2 weeks since I sent it.
I wonder if I never actually fixed the issue and just put a really strong band aid on it this whole time to the point where it isn't really noticeable.
Looks like 2012 is when I installed the Racetronix hotwire kit and upgraded the big 3 wires. Since then I've done the alternator a couple times, the fuel pump and filter a couple times, the FPR, the bulkhead and pump harnesses, cleaned out the tank vent, cleaned out the EVAP lines, installed a fuel cooler, installed 24x, tried LS2 injectors...
what am I missing that would get affected by a hot day???
I gave Racetronix a call since they haven't answered the email. The person I spoke with seemed a little impatient and annoyed for the first few minutes of the conversation but once I told my story and explained the troubleshooting steps I've taken and how I'm thinking through everything, they became very interested and helpful. To my surprise the person I was speaking with was the owner of Racetronix! We ended up having a 30 minute conversation that got super technical, I loved it. What it boiled down to is that he now shares one of my earliest suspicions: cavitation. Since the current draw is so low, there is most likely air going through the pump since air would cause less resistance in the pump. The more resistance any electric motor works against, the higher the current will be. So if it was all fuel going through the pump, I should be seeing 12 amps, not 10.5. That would also explain why I typically smell gas fumes whenever I lose fuel pressure. His suggestion is to ditch the bucket and see what happens. The bucket is the only thing I haven't ruled out since I first noticed these symptoms 9 years ago. I'm also going to throw the Aeromotive FPR back in because that seems to be way more sensitive than the stocker and I want to notice any pressure difference no matter how small. I also went to a local auto electrical specialist today and he gave my electrical system a solid thumbs up so I can be confident the pump is getting the juice it needs. He also suggested I start running what he called "clear gas" aka non-ethanol gas. Apparently it has a higher boiling point than E-10 so if ditching the bucket doesn't work, I can try running E-0.
Have you monitored your fuel trims when the pressure drops? Does one or both banks make a sizeable shift either up or down when it's happening? How about the injector pulse width at idle? Does it shift at idle when the pressure drops vs when the pressure is fine? Do the O2's show rich when it smells of fuel when the pressure drops?
I'm not sure how cavitation would contribute to causing fuel fumes. However, the thing running rich would.....or fuel leak of some kind....leaking injector as well.
LTFT's went from -4 to -6 to +3/+4 in one of my recent logs. I didn't log injector pulse width unfortunately but that's a great idea! Haven't noticed the O2's when I smell fumes but I can keep an eye out.
I was thinking hot fuel mixed with air bubbles would more likely send fumes out the tank vent. I might be way off, just grasping at straws to be honest.
I spent the day removing the bucket. Here's the trap door:
Here's the door removed:
Disassembled a bit:
Inside of the bucket looks pretty unremarkable.
The 28 amp fuel pump harness I modified and was using before (pics higher up in this thread) was getting dissolved so I went back to using the old (but still upgraded 12 gauge) fuel pump harness that can handle 20 amps. I also used the old bucket overflow tube as the new return tube so I could point the return fuel away from the pump in case there are bubbles coming in through the return line. Not sure if that's possible but I don't want to risk it.
Since the pump harness has 1 power wire instead of 2 now, the blue wire isn't being used anymore. The pump is now getting electricity from the red wire only. It looks like 14 gauge, good for 15 amps according to google.
Tomorrow I'll throw the Aeromotive adjustable FPR back in and if the forest fire smoke is below hazardous levels I'll take it for a rip.
Are those the right clamps on the pump and plastic line going to the hard line? I seem to remember folks having issues with the wrong clamps on the plastic hose coming from the pump. I have not seen them come from Racetronix with screw clamps. Should be some kind of crimp clamp. My Racetronix pump has the crimp clamps.
There was also an issue long ago of the plastic lines from Racetronix having pin holes in them. That was causing pressure/fueling issues on a few installs. I think Racetronix started pressure testing the plastic lines after that, but it's something to be aware of.....
Generic screw clamps, I have others but the tank is all sealed up and I won't be going back in for a while. I'm going on a 2200 mile road trip for the last week of September. Vegas and Death Valley will be in the 90's and 100's while I'm there so we'll see how it does.
Just drove it for an hour today but all the smoke is keeping temps down. It only hit 75 I think so the car did perfect. Pressure solid at 60psi, no fumes, even at WOT. After the drive volts were 14 and amps were 13.
Welp, just set a new record low: 23 psi! I'm in the middle of a road trip and it happened around hour 7 of driving. Every 2-2.5 hours I stop to gas up and have a snack. Car was doing fine until I got to an area in Nevada where the temps hit 86. Then it started losing fuel pressure. It took about 10-15 minutes to lose 1 psi from 60 down to 53, then the bottom fell out. By this time it had also cooled to 80 degrees but it didn't matter, pressure kept falling. It dropped to the mid 40's and quickly fell to the 20's. Long and short fuel trims were maxed out but amazingly the car held its 80mph cruise up a hill with no knock retard. I don't know what the afr was since I removed the wideband for this trip. This proves it wasn't the bucket and also the temperature where it happens is a gray area in the 80's.
Once I crested the hill and started coasting down, pressure recovered to the mid 50's and stayed there until I got to the next gas station an hour later. After about 20 minutes to fill up and snack, we hit the road and it was solid at 59 psi with ambient still at 80. After about 30 minutes, ambient started to drop and it ended up around the mid to high 60's. For the next two hours the pressure was 59 psi cruising, 58 psi going up hills, and 57 psi with WOT passing.
I'm going to try calling Racetronix before hitting the road tomorrow but in the meantime, what else even is there to rule out??
If I were in your shoes and had tried all that, I think I'd put a stock regulator on it, a delphi stock pump back in it using the stock wiring, and see what it does.
If I were in your shoes and had tried all that, I think I'd put a stock regulator on it, a delphi stock pump back in it using the stock wiring, and see what it does.
I was just thinking that today. Might be heading in that direction. Although I'm 1,000 miles from home so it wouldn't happen for a while. What I would most likely do is adjust my current FPR to 3 bar, throw in the Walbro 255 I still have, then return the pump wiring to stock to eliminate the hot wire kit. I could also build a new power wire since I've already ruled out the relay... I dunno.
So today was even worse, saw it fall to 10 psi. Made it to Great Basin National Park Visitor Center with no issues. Then things went to crap on the drive up to one of the trail heads. It was a 12 mile narrow 2 lane road with about 3,000 ft of elevation gain from ~7,000 up to 10,000. IAT was showing 75 so I thought I was in clear but pressure dropped off quick on this stretch. Tank was 3/4 full and speed limit was 35. Pressure slowly fell to the low 50's, then quickly to the 40's. It bounced around in the 40's for a few miles then fell to the 30's and bounced around in the 30's for a few miles. Then it sank through the 20's into the teens. That's when I found some gravel to pull off because I was sure the thing had to be running lean. There must've been almost no fuel flow for the pressure to be that low. When I pulled off the engine couldn't idle, it just died. I noticed what sounded like bubbles in the fuel tank. My trunk sounded like an aquarium with all the bubble noise, like it was boiling or something. It took a good 10 minutes for the noise to stop. I tried priming the pump by going key on a few times and the pump barely made any noise and it did not build any fuel pressure. After the bubble noise stopped, I tried priming again and got 7 psi this time. I tried starting it but the starter wouldn't crank! This is new. I could hear the gas draining back into the tank after priming it, it wasn't the same noise as the bubbles.
After a total of maybe 20 minutes I got it started and idled with fuel pressure in the 30's. Once the car was moving the pressure shot up to the 40's but within the minute it fell back to the 30's. After about 2 more miles of driving the pressure was at 10 and I pulled off again and it died. I left it there and went on a 4 hour hike. When I got back, the car fired right up and fuel pressure was 59. Made it all the way down without even flinching. For the next 2 hours even in 90 degree heat the pressure held at 59 although I could tell the flow volume was still a little low because any time I went WOT, pressure would fall to 54. This throws a wrench in my temperature theory because it was only 75 when it fell on its face but then did fine when it was 90 later in the day. Unless the direct sunlight has an effect? Anyway the last hour of the drive was in the 60's and the car did perfect, didn't lose any pressure even under WOT. I wasn't able to get a hold of Racetronix like I wanted so that will have to wait until Monday.
This thread has basically turned into my diary, sorry guys.
Didn't drive much today, did maybe 40 miles. Most of it was flat and half the time I was doing 25 mph at very low load so I didn't run into any problems even though it was pushing 90 outside. I was thinking about that bubble noise and had an idea. ACE mentioned the flex tube could have a pinhole leak but what about the sending unit? Maybe that has a pinhole leak somewhere. A few years ago I bought some 17x11 TT2's and the day after I got the tires mounted one of them was at 10 psi. Turns out there was a leak in the wheel itself:
This has proven to me for the rest of time that even metal stuff that you never thought would leak, can leak.
The no-start had me thinking too. Twice on this trip when the fuel pressure has been struggling and cruise control was engaged, I would press the clutch in to down shift and the engine revved up to red line. Apparently the clutch switch doesn't work when the pressure is struggling. I think that's what happened with my no-start, the clutch switch wasn't working so the starter didn't even crank. Makes me wonder if there's an overarching electrical component to all this after all. Maybe a bad ground somewhere?
Well things were going okay the last 2 days because I wasn't driving it a ton. Then today's stop was Vegas and it was pushing 100 outside. Sure enough, pressure was low for the last hour of the drive. I was trying to keep the tank full, stopping about 50 miles or so to fill up. That didn't seem to delay the pressure issue unfortunately.
Something new that's happened on this trip: twice I overfilled the tank and fuel gushed out of the tank vent hose. I figured it would come out of the filler neck but no, it came out under the center of the car. At first I though one of my lines popped loose, it was a ton of fuel.
I called a local Corvette shop before rolling in: MCR Corvettes. He was super cool and agreed to take a look at it. His neighbor who is a different auto shop got interested and came over to look too. There were half a dozen C4 Vettes in the parking lot which was I thought was a good sign. Unfortunately neither of them could give me a straight answer. This was the first they had heard of or seen anything like this. The car was barely holding 40 psi while idling in the parking lot (should be 60) but volts at the bulkhead were 13.8, amps were 10.5, and it reeked of fuel vapor the whole time.
I did discover one new thing. At one point I peeled back the carpet in the trunk with the car still idling to show them the trap door. When I touched the metal of the body under the carpet it was SCALDING hot. I couldn't touch it for even a second. This can't be normal right?
The other take away is that the fuel pumps pitch was frequently changing. I already knew it did this but didn't think it was a huge deal. Apparently it's a sign of changing loads on the pump which is bad. I wish I could mount a gopro in the tank. For now maybe I'll look into how to measure fuel temperature. He also said I should touch the wires going into the tank and make sure they aren't scalding hot too.
After reading a bunch my problem is sounding a lot like vapor lock. Especially since the fuel was boiling at high altitude. This obviously never happened to any new F-Body so why is it happening to mine? I doubt the fuel is getting any hotter than it ever did when the car was new, not like I installed heat soaking carpet or anything. Pressure can raise boiling points, vacuum can lower boiling points. I've already mentioned there is no pressure or vacuum when removing the gas cap. There used to always be pressure though. Maybe I need to look at the tank vent valve.
Today I'm going through Death Valley, it will be 110. My plan is to tape my windshield sun screen to the back window and see if that makes a difference. Not the best option for rear view mirror usage but modern problems require modern solutions.
With the windshield shade on the back window, the car didn't have any symptoms for 2 hours. Made it from Vegas to Death Valley in temps ranging from 90-100. I wasn't celebrating though, this car has pulled the bait and switch on me many a time. Got on the road to Dante's Point which was very similar to the short steep road in Great Basin where fuel pressure bottomed out at 10 psi because it too was short and steep. It was about 12 miles and gained 2000 or so feet up to the viewpoint at 5000. The car did horribly, it was about 107 ambient at this point and I started losing pressure like crazy. I had to downshift to 3rd and was driving about 25 mph to keep engine load low. Eventually the trims were maxed, coolant temp was 215, pressure was in the 20's, and O2 mV's were dropping too.
At this point I said "screw it. I wonder what will happen if I steer the car side to side violently and really slosh the fuel around?" To my amazement, pressure immediately shot up from 20 to 50! Unfortunately it fell back to 20 within a few seconds so for the rest of the drive up to the view point, I was steering the car side to side keeping the pressure in the 40's. Car was running much better, the wife and I had a blast.
When we left the viewpoint, the car started with some difficulty but eventually idled and ran at 45 psi initially. I wasn't worried because on the way down, I was able to coast in gear in DFCO. Coasting down took a few minutes but after we made it down, pressure had fully recovered and was rock solid for another 50 miles.
This brings me to another thing I've noticed on this trip: going up hill will cause the pressure to drop faster and lower compared to mostly flat cruising. Going downhill will allow it to recover slowly and if the car can enter DFCO, it will recover much quicker and stay recovered for a while. I don't have a theory for this one yet.
Anyway since steering the car back and forth brings the pressure back up, I feel confident that the problem lies in the tank and not in the electrical system. I had to use that method two more times today after Death Valley and got some footage of it working:
Also the metal under the carpet in the trunk wasn't as hot today, I could actually set my hand on it and leave it there. It was still pretty hot, but not hot enough to injure this time.
Does anything in my last couple posts give you guys any more ideas?
Ever wonder what the inside of the evap canister looks like?
The canister is full of what looks like black cat litter (charcoal obviously). Mine smelled like a mixture of pure gasoline and super glue.
What I did today:
Changed that evap canister
Made sure the all the evap lines were patent
Checked the evap solenoid for functionality
Check gas tank vent line + valve
Leak tested fuel pump sending unit with flex tube attached
Inspected tank interior as best I could.
Everything passed with flying colors. I swapped the Walbro back in with the bucket and a new strainer. I also used a new flex tube that I've had in a box. It's much shorter than the last one so there's no loop. I'm also using two crimp clamps instead of the screw clamps. It's cooling down like crazy here so I probably won't know if this works til next year.
Haven't had anyone post here besides me for the last two weeks. I'm really interested to hear what anyone has to say about how steering the car side to side improves pressure then it falls off immediately.
Also what anyone has to say about the boiling noise in the gas tank at high elevation and
Pressure getting worse on an incline and
Pressure getting better on a decline...
Here's how it looks now:
I used the prime connector to run the pump and check for leaks under the hood. Is the fuel supposed to be this noisy?
I am still following along, just have nothing much to add thats helpful.
I will say that on my car, with a low fuel level, taking a turn too fast/tight will uncover the sump and FP dives. Never tried the hard decel, but hard accel has never caused that.
I run a large fuel pump (~450lph) and have not had issues with fuel boiling. How are the tank vent(s) on your tank?
