Quote:
Originally Posted by RoadWarrior
However, on many engines the fuel rail is nice and cozy against the head, often shielded by intake parts or valve covers, and it soaks near to coolant temperature anyway... but that happens after the FPR and tank return... so I'd say there's probably no risk to the injectors, o-rings etc at that end, because they should be designed to cope with heat soak from the head.
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Heat soak will get the temps up for a short time but during normal use the fuel flow with the gas tank acting as a radiator keeps the temps down everywhere the fuel goes. The hot intake valve is the first time the fuel sees heat that it can't beat. In the winter it is easiest to observe. Feel the temp in the notch between the injector coil body and the engine which is the very last part the fuel flows through before dropping into the intake. The coil body will be hot but the fuel part will be stone cold which means the fuel leading up to it is just as cold.
On my GM 3.8L rail the upper o-ring is black (n-buna) and the lower o-ring is bi-color brown/black (viton/n-buna). The black (n-buna) part faces the little bit of cold fuel back spray and vapor and the brown (Viton) part holds the seal in the hot intake bore. Neither color can last under the conditions the other sees. GM's top ring is all black which sees continuous liquid fuel but little heat. After 240,000 miles these bi-color o-rings functioned like new. I have rebuilt rails and the rebuilder knowing nothing about o-ring chemistry put all black o-rings on. Within 70,000 miles the bottom rings split during removal and were flattened to where they wouldn't hold a seal. The upper o-rings are like new. I bought 12 brown o-rings (Viton) from Advance for two rails and put those on the bottom and left the black rings on the top. Now I'm almost as good as GM who has spent quite a bit of time optimizing the o-ring materials for the conditions. The pushlock supply and return o-rings are light green (not HNBR) or tan, probably Viton. Changing the conditions without also changing the materials might lead to early failure. Has OP checked into this before installing fuel heat? I think not. Then he goes and recommends it to everyone else who also haven't.
My only weakness to heat is the injector top o-rings which can be replaced with Viton.
GM now supplies a blue o-ring as a replacement for the black and brown/black o-rings over on RockAuto. Lesser but sufficient companies supply brown on bottom and black on top o-rings with instructions. The worst companies supply all one color hoping you won't have the car long enough to notice the leak.
Do use fuel heat if it works. Don't use it if it causes leaks when you're not watching.
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