I need some opinions on what I'm dealing with. I'm going to try and make this as short as possible.


I seem to have a (well I'm having all sorts of issues but I'm working to resolve them) intermittent issue of overheating my fuel. If I drive the car for a length of time, over an hour at least and getting stuck in traffic, it will lean out (wot). I had a dead head system with a single aeromotive 340. It was worse with the dead head. I made it a return system and fabricated a large capacity bucket and put a second aeromotive 340 in it. One runs full time and the second one kicks on at 2psi of boost with a hobbs switch and my boost controller (redundant just in case). I started collecting parts to redo some things. The main thing I'm thinking is I bet that main pump is weak from being worked hard and overheated in the dead head and the current config I have probably isnt helping much either. I'm swapping one pump out for a 525 hellcat pump and I wonder if I should replace the other pump with a smaller pump for driving? Maybe like a 255 ltr per hour pump. Whats a good reliable pump suitable for daily duty? Or maybe put a stock pump in it?

 

Any chance you can measure fuel pressure when it's happening?

What's your IAT when this happens? Heatsoaked? Long shot, but one of my original issues tuning my turbo was the computer was (mis)using the heatsoaked IAT making it lean out for me in traffic like you describe, apparently untunable in my 99 I had to relocate my IAT from the Huron Speed intake pipe to where it measured real air temp on hot days. Yea not the best answer but that's the way I went. Your symptoms just make me think of that problem, some deep tuning GM did in my 99 computer. You can plop a single 4.7k resistor in the IAT plug to simulate 57 degrees as a test, then let it get hot and see if the problem remains. Of course watch your AFR when testing this. I can't remember if it was WOT or normal driving that it'd throw it lean but something for you to check.

LOL you and I having similar issues with our fuel on our winter DD cars...I appreciate your input on my thread so chiming in to get you a bump and start some convo

I'm not a pro, but from all you've done I personally I don't feel like it's your fuel boiling. Return systems are really kept cool from what I understand, fuel is hard to boil under high PSI that our cars use, just my gut feeling and the conclusions I came to with all the googling I've done on my problem with the bubbles. That's why I don't think my bubbles are boiling fuel. I'd really be curious to see your fuel pressure when it happens if possible.

EDIT this is what I ran in to where it'd lean out when hot: https://forum.hptuners.com/showthrea...h-IAT-lean-AFR

I see you have an 04 so if this is your problem it might be tunable.

 

yea, I don’t think this is the issue. Iat’s are usually around 100F max. It might see 120 every now and then. Also I don’t get on it if I’ve been in traffic and it’s heat soaked. Only after it’s cooled off at cruise.

my return system is “rigged up” to be honest. Stock fuel rails with a return adapted to the pressure port. So that return fuel has had to go through that small threaded hole in the pressure fitting….i think less than ideal. I have drilled it out recently but haven’t driven it since. I’m pretty sure one of my pumps is weak too. Now that I’m thinking about it, the car has refused to start from the primary not kicking on. I don’t remember what I did to get it working again. I think I beat on the tank or something. The more I think about it, the more I come to the conclusion that both pump need to be replaced because the problem is intermittent. Well I posted a thread a while back about the issue I’m having now outside of the driving for a while in the heat. Right now, 2 out of three runs over 17psi boost, it’s gonna lean out at wot. Lean out as in 12.xx:1 afr. Then another run might be 10.8 or lower. Same conditions. I don’t have a way of checking fuel pressure right now. As of yet. But with the new rails I’m going to put a fitting for that. I have a set of aftermarket rails to replace the factory with.

 

Yep I agree, sounds like a different problem than I described.

But I know someone's going to ask you, how is your FPR set up? This also gets you another bump LOL

PS I'm jealous of your 17psi.. I don't have the nerve to hit 14PSI on mine any more LOL

 

I have a 525 single pump that runs full blast all the time with no issues. Ive been on several 3+ hour drives. I do not think fuel pumps make the heat that people think they do.
I did have an issue of vaporlock/ fuel boiling though. My fuel lines were close to my exhaust for nearly the entire length of the car(3rd gen fbody), and it would stall out on hot days in traffic and refuse to start until things cooled down(2+ hours). IATs would be getting pretty warm like 120*, coolant 210*, combined with exhaust heating the lines and hot pavement, I think the fuel just boiled.
I think you probably just need a proper return style fuel setup.
I moved my fuel lines out of the trans tunnel/driveshaft area where stock routing was to where my subframe connectors are on the outside of the car, and run them into the engine bay through the wheel well. No issues anymore. Fuel rails feel much cooler to touch after driving where before I couldn't touch em.

 

hell I was running 22psi and tickling 24 on many occasions before I started having issues.

I have an aeromotive boost referenced FPR screwed into the fuel pressure port with a return line I ran to the tank.

 

nice to know. Where are you located? Just wondering for climate comparison. I’m down here in hot, humid Louisiana.

 

I am in Southern Michigan. The days that were giving me problems were 80*F+ and humid, full sun intensity on pavement.
Probably not as warm as you. Ha

 

lmao. Nope, not even close! We were seeing over 100 last summer. Yikes.

 

Did you use the stock fuel pump relay to power two new 40a relays for the new pumps with much larger wires? Or are you using the stock relay to power the pumps? I know if the wires/relay get hot enough, they will not power the pump. With you running that much boost, plumb your regulator between the two fuel rails in the front and feed both rails from the rear. And I hope your fuel lines are big enough.

 

no I ran 12 ga silicon wire and used relays. I have a 3/8 fuel line which should be plenty for my power level. I really didn’t want to run the fuel lines like that because I have no room to do that on the front for the regulator to fit in the middle.

 

If you get really desperate, you can use a scope and watch the waveform of the power wire to the pump (one at a time) and you can actually calculate and datalog the pump RPM, would also allow you to track amp draw of the pump(s) for clues while it's happening. I have a picoscope 2204 and would recommend.

 

You don't have to put the regulator in the middle of the fuel rails. Use flex hose and mount it somewhere else. I mounted mine (when I had a GTO) on the pass firewall and still had it setup as regulating between the rails. On my 4th gen, the reg is mounted on the drivers side frame rail---flex lines so it is still between the rails. Both rails are fed in the rear with a Y. You need larger wire than 12ga and are the relays in the trunk by the fuel pumps?

 

Dead heading shouldn’t add heat… if anything it helps remove heat. The fuel picks up heat from the engine bay and longer line (of any diameter) is more of a restriction all the way back to the tank.

If your return/FPR is closer to the tank (mounted to the tank in the rear in my case) Its less restriction on the return side and also doesn’t route it through areas to pick up additional heat. I’d guess your return line isn’t large enough… ditch restrictive fittings and run a true -6 (-8 would be better) return and I bet your issue goes away. Having true ½ diameter ports on your FPR is also a plus.

 

I run a dead headed factory rail setup and I had a similar issue when trying to run a single walbro 495 hellcat pump(495/525..whatever) on days above 90, about 2 hours of driving highway speeds. Stfts were stupid high. Parked and forgot about it. Next time after leaving my job the car was idling about 15 minutes in the parking lot and AFRS were lean under WOT, 12.5-13.5 on low boost and same thing with stfts. Pulled over and filled tank. Car was fine again for about 10 minutes. I initially swapped to the bigger pump as my IDCs were going over 100%

Ripped that pump out and put my 340 back in. I would say from my xp it wasnt really the fuel boiling in the rails directly but pump cavitation as it draws a vacuum on the warm fuel in the tank and lowers its boiling point causing it to cavitate in the pump.

At the time my return was ran from my regulator on the shock tower behind the fuse boxes, I drilled a hole next to my brake booster and the line is routed down behind the fake vents in front of our doors behind the wheel well plastic, down the side skirts and cuts across at the rear and goes up to the tank. I’ve since added an 8AN feed and never ventured into the 525 pump again. IDCs are higher than I’d like(less than the 100s I was seeing before I added the better feed setup) but I spray water/meth and AFRs are always good. Also if you do add on/already have fuel lines the Aeromotive 12375 is a huge hp flowing filter with 10 micron rating and comes with 8AN ports. If it’s a pump cavitation issue like I had then I would wonder what will happen when the 525 kicks on under boost with warm fuel that’s been cycling through the fuel rails..If Lonnie’s is still around you may want to contact them and see what they suggest.

 

Most people don't post back what they did to fix the issue. So here goes....

I fixed my issue. I installed a walbro 255 for driving and a walbro "hellcat" 525 for under boost. Both have check valves for better starting. Evidently one of my pumps was weak or going bad because this fixed all my issues. I think the primary pump was the culprit because after I drove it for a while, the issues would arise, so I think the pump was over heating.

 

.
.
.Use Hobbs switch to turn on relay for 525 Hellcat ?
. Presume your Y is IN the tank, to a common fuel supply line ?
What do your check valves look like ? simple rubber hose and clamps to fuel pump(s) ?
Pics ?

 

the check valves are built into the pumps. It Y’s in the bucket. This is pics when it had the dual 340’s. I fabbed the bucket.