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Ever since I got my fuel pressure gauge installed, I've noticed the fuel pressure drops when it gets hot in the summer, like 90 and above. I suspect this has been happening ever since I got my 383 in '09. Well I'm finally taking action.
I bought an Earl's fluid cooler part # EAR-21900ERL. This is their 5.875" tall cooler with 19 rows which is the tallest that would fit in the fender well. It would have been much easier to install this in the engine bay right in front of the fuse box but I wanted the cooler out of the engine bay's heat.
I'm using nylon hose to keep with the stock look, that could change some day.
That day was almost yesterday. It took hours of trial and error to get those fittings in those hoses. I must have melted or kinked 6 feet of that hose. I'm using Earl's vapor guard -6AN to 5/16 fittings.
Next step is to cut a slit on the underside of the loom, cut the stock return line, and get the cooler plumbed in. Last step will be getting a bracket made to mount the bottom of the cooler to the cruise control module for extra support and piece of mind.
However,
Aeromotive says the fuel pump can contribute Aeromotive:
Excessive pump noise along with fluctuating or dropping fuel pressure often indicate that fuel temperature is high enough to cause hot fuel handling problems. A combination of high fuel temperature and low pressure can result in cavitation, where liquid fuel changes to vapor. In a return style EFI fuel system, the most likely place for these conditions to exist in the same place, at the same time, is at fuel pump inlet. Once cavitation starts, it will feed upon itself. As vapor enters the pump, it displaces liquid fuel required to lubricate the mechanism, allowing metal to touch metal, creating even more friction and heat. Once the pump begins to super heat, a complete vapor lock will develop.
In order to prevent cavitation and vapor lock, correct fuel system design and installation are vital. Ensure supply lines and inlet filters meet hi-flow, low restriction requirements and are kept clean. Keep the tank full on hot days. Reduce fuel pump speed and recycle rate with a fuel pump speed controller during low load, idle and cruise conditions. Carefully route fuel lines and plan component placement to avoid exhaust heat. Do not overlook proper tank ventilation, if the vent line or vent valve do not allow ample air to move freely in both directions, fuel delivery problems will never fully resolve. Any conditions that restrict the pump’s access to fuel in the tank must be addressed.
A. Interesting that they mention "reduce fuel pump speed and recycle rate", this leads me to believe that the fuel pump manufacturer is acknowledging the fuel-heating due to pumping is a potential contributor.
B. from what I know from fluid mechanics (textbook) pumps always heat their (gas/liquid) output component.
IMO it all matters. Local heating, routes, recycling, pumping, do your best to clear everything of that fuel line.
Ex. My current system returns fuel before the rail so it never cycles over the intake manifold (dead head fuel rail)
However,
Aeromotive says the fuel pump can contribute Aeromotive:
A. Interesting that they mention "reduce fuel pump speed and recycle rate", this leads me to believe that the fuel pump manufacturer is acknowledging the fuel-heating due to pumping is a potential contributor.
B. from what I know from fluid mechanics (textbook) pumps always heat their (gas/liquid) output component.
IMO it all matters. Local heating, routes, recycling, pumping, do your best to clear everything of that fuel line.
Ex. My current system returns fuel before the rail so it never cycles over the intake manifold (dead head fuel rail)
All plumbed in and idling. There is a little seepage around the left -6AN fitting. I thought I snugged it pretty good. I read that if AN fittings are too snug they can leak. Does this look like that type of situation?
The -10AN fittings are torqued to 30ft/lbs, but couldn't get a torque wrench around these 45 degree fittings. The fittings were installed dry.
Had to bail on the nylon lines, leaked immediately. I'm using some NAPA fuel line for now, I'm eyeballing Earl's vapor guard.
Got the new -10 to -6 reducer and -6 fitting installed with the conical seals. No leaks! Drove the car around a few miles but ambient was high 70's so I still haven't put it to the test.
There was a pleasant surprise: my fuel rails used to get so hot that you couldn't touch them for more than a second. Now even after driving around, they're only lukewarm. Awesome!
I do have one question though. I had to use these "nylon fuel line unions" to connect the stock nylon line to the new rubber line.
Is anyone aware of a fitting that is barbed for nylon on one side and rubber on the other?
Currently I have the rubber line clamped on the middle of the union because that's the only spot that's thick enough for the rubber line.
I prefer fuel line clamps or high quality hose clamps and (rubber/braided) hose like the OEM uses, very short runs of EFI's "best" quality hose and a (fuel line style or high quality) clamp over flared ends is absolutely track legal
Then cover it with several types of preventative materials. Braided especially rubs on everything and damages anything, an extra, larger fuel hose sliced open to go over it seems to work well but I put stuff over that too because its pretty much one of the biggest ways to completely lose a project is to burn it to the ground with gasoline or temperature related mistakes. Make sure you have fuel pressure cut-off switch, so if the pressure drops below say 30~ the pump turns off. A huge leak will instantly drop pressure telling the pump to stop, saving it
I think AN fittings have high chance of being unreliable unless you are buying all of the materials from the 'same' quality manufacturer. (aeroquip + aeroquip + aeroquip = yes) but most of us don't do that...
Steel line with short runs of clamped fuel hose has my vote for simplicity
Still you want to minimize how many in the system. Four becomes eight and then the chance of a leak goes up proportionately?
No leaks yet. Just finished fashioning up a lower bracket for the cooler. It was already rock solid with just the top bolts but this gives me piece of mind.
I'm curious, did you measure fuel temp or just assume it was causing issues? Back in Japan I had a Corolla and it would run lean on a hot restart, then a few minutes later when enough fuel had passed through the rail and returned, it would come back to normal. Sometimes if you sat in traffic long enough it would lean out too. That was really the last time I ever gave fuel temp a second thought.
I'm curious, did you measure fuel temp or just assume it was causing issues? Back in Japan I had a Corolla and it would run lean on a hot restart, then a few minutes later when enough fuel had passed through the rail and returned, it would come back to normal. Sometimes if you sat in traffic long enough it would lean out too. That was really the last time I ever gave fuel temp a second thought.
I assumed based on this happening only in summer. I've noticed that even when the intake is piping hot, the fuel rails are luke-warm so I guess it's working?
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Installed new fuel cooler 
good job 
