From experience and intense reading here, there are two problems with the fuel supply system: foaming Diesel fuel caused by elevated temperatures, and the fuel heater 'puck' in the fuel manager head - both result in aerated fuel hitting the IP.
First, the second problem is Chrysler's, but you may have to solve it yourself, with a Racor\equiv - where fall\winter temps head way south of 30deg you will need a fuel heater - not a big problem down here where 40deg is freeze-a** cold, but would be interesting to run a poll for verification of geographical damage incidence.
Second, the first problem you can address by installing a return-fuel cooler in the return-pipe, and, if necessary, a lift pump near the fuel tank, with, for now, a return bypass tee'd into the oem return line - again, for those north of the Mason-Dixon line, a t-stat controlled bypass-valve is available to bypass the cooler in frigid climes
I've been reading thru MrMopar's responses to find that a lift pump is not recommended, causing CRD EFI snafus, but other posts indicate that it doesn't seem to cause any problems - I tend to believe him, as he has access to much more system-specific info than I ever will - I will get my scantool on it first available chance for verification, but #2 son would rather drive it than let dad investigate stuff - go figger............
I also read that in the '80s, 120deg fuel was considered ideal for Diesel combustion efficiency - remember, those were strictly mechanical IP's and systems, where the fuel was jammed into the cylinder all in a bunch - these CRD systems ain't yer grampaw's Diesel - the fuel hits the CRD IP at some ambient temperature, which is immediately elevated by contact with the engine-heated IP, where it is boosted to pressures they couldn't even imagine, back then=more heat - from there is it passed into the injectors, also heated by the engine=more heat - then the ECM sprays a little into the cylinder where there's a bunch of incredible heat, ~1625degF, initiating the burn - as burn increases, more and more fuel is injected, then tapered off as cylinder temperature and pressure decreases and oxygen is depleted - that's ruff, but generally descriptive of the event in these engines, as compared to the violent explosion in those old rattlers
I rather suspect that they were indicating that supply-system fuel temps should never be higher than 120degf, prolly for the same aerated fuel problem that's going on, here - but, Detroit Diesel seldom consults with me - in fact, never - so that's just my educated opinion.
However, you won't get return-fuel to drop below ambient temps with any size of cooler, even forced air-over coolers, so it will be within several deg of ambient in summer, much better than the ~140deg coming off the engine, with much less foaming - which results in less aerated fuel at the head.
Another problem I see is the position of the inlet and outlet ports in the head - IMO that arrangement should be mounted down low, as on a frame-rail, below IP level, and particularly out of the hot engine bay - 200deg ambient temps ain't gonna relieve the foaming in a 'draw from tank' system - also IMO, and from GM experience, the feeds on a hi-mount fuel manager should be at the bottom of the cannister, with a top-removeable filter element - no matter how foamy the surface of the fuel in that configuration, the bottom will be tranquil and smooth - a lift pump ahead of the filter ensures supply to the IP internal transfer pump, which is similar to the C3 version.
The Cummins 12v configuration is top-feed intake-mount with bottom-replaceable filter element like Jeep, but with lift pump ahead of the filter - for the 24v engines, they went to a side-feed top-load cannister, similar to GM's, with lift pump ahead of the filter
Sorry, guys - my son won't let me play with his Jeep, and I got nobody to talk to about it, so you guys get the gab...................................
_________________ '05 CRD Limited Pricol EGT, Boost GDE Hot '11; EDGE Trail switched SEGR; Provent; Magnaflow; Suncoast T\C, Transgo Tow'n'Go switch; Cummins LP module, Fleetguard filter, Filterminder 2.5" Daystar f, OME r; Ranchos; K80767's, Al's lifted uppers Rubicons, 2.55 Goodyears Four in a row really makes it go
Last edited by gmctd on Thu Sep 27, 2007 8:18 pm, edited 5 times in total.
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