Fuel temperature question for the rail system?

[badams1]

I remember that on my 01 that the VP 44 cooling requirements could raise the whole fuel system potentially to 190F on a summer day during extended driving. On the fuel return line I installed a fuel cooler in front of my A/C condensor (a good 7 pass 1/2" tube dia. X 3/4" thin X15" long) transmission cooler to help the problem. I live in Houston so we don't worry about fuel freeze here.

The question is does the rail injection system generate the same fuel temperature problem as the VP44 used to and does it have the same potential to cause this effect? Hot diesel fuel at 190F and low pressure like at the suction of our lift pumps can change many operating variables. (1). Vapor pressure changes a lot at low pressures (1-5 psig. or less at 190F) causing centrifical vaned lift pumps to cavitate and that really can reduce longivity. (2). Cool fuel (less than 100F) means more power and efficiency because of a number of reasons but for this case, let's just say it just pumps better because of a stable viscosity and vapor pressure. (3). Lubricicity and viscosity at 190F being sucked from a fuel tank are probably at the limit or beyond the operating design parameters of the present stock lift pump and other parts.



Do some of you smarter than me guys out there have any data as to how much the rail pump cooling requirements effect the total fuel system temperature on a hot summer day pulling a load for extended periods?



I am planning to install a Holly pusher (blue head) pump sucking through a 10 micron Baldwin BF5813 prefuel filter water seperater going to the suction of the stock lift pump but now is the time to cool it on the way too if necessary. I have to custom build this thing because of a two fuel tank application so the FASS won't get it OK!

 

[badams1]

30 hits and no response yet? Come on guys, I would really appreciate some feed back because I am wanting to install this fuel mod. soon and if fuel temp. is not a problem like the VP44 was then I'll just skip the cooler and get on with it. Thanks in advance, I ll check thread in the morning.

 

[R.M.THOMPSON]

I got one for ya. I've heard of a subcooler method of wrapping the suction line of the a/c compressor with aluminum tubing and wrapping over that with insulation after a nice coat of heat conductinve compound (loks like antisieze with a butter like consistantcy) The concept seems effective due to if it to hot for fuel , we probally have our a/c on by that time anyway. Have not tried this, but ,the concept does seem interesting.

Mark T.

 

[rbattelle]

Probably the lack of responses is because no one knows what the fuel temperatures on these trucks is like. In fact, until your post, it never occurred to me to bother checking fuel temperature. Certainly fuel supply from the CP3 will be warm, since the injector pump is doing work on the fuel. But going to the pump, the only advice I can give is to plumb your system in anticipation of a fuel cooler, then connect up a temperature probe and measure it for a couple weeks. If it turns out to be too hot for your liking, then it can be simple to plumb in your cooler.



I never knew that inlet temperature to the fuel pumps can be a problem. Your reasoning for why hot fuel can be bad is quite sane. Only right way to proceed is to take some measurements with the system as-is, then go from there...

 

[badams1]

The lift pump failures on the 2nd generation pumps caused me to look for reasons other than just bad fuel. The cooler worked on the 01 truck. I am familiar with centrifugal pumps as an Exxon retired Mfg Coordinator. The vapor pressure and suction pressure of the fluid are critical to keeping this type of pump within its design parameters. With diesel the flashing vapor bubbles at high temperature 190F and low pressure can cavitate these pumps and result in the low flow problems that I have been seeing in these threads. Diesel should be kept less than 100F to stay in the curve for a simple vane centrifugal pump with the very low head pressures that are avalible fom sucking from a fuel tank. Cool fuel is essential for better flow and pump reliability. I'll take a 100 mile trip tommorrow and try to get some numbers on my new 03 truck fuel temps. I'll just feel of the lines and the tank, that should tell me enough to do something or not. I just thought that surley somebody else had remembered this issue from the past from my old threads from a couple of years back and questioned the causes of the lift pump problems we are having now. Chime in guys, I am going with pre filtered, and possibly cooled fuel to the stock lift pump suction just to cover all the bases. Hot, dirty or watered fuel will kill a pusher pump too so think about it.

 

[rbattelle]

Certainly what you're saying is good advice. Probably no one remembers your older threads about fuel cooling because the 3rd gen forum is populated by so many new people. Even me, a member since 2001 and a reader long before that can't recall reading about fuel temperatures.



I am curious to see what sort of benefits/effects you see on an '03 with a cooling system.

 

[Yo Hoot]

The GM Dmaxes have a little radiator in front of the fuel tank that the fuel runs through so GM thinks it's an issue.

 

[badams1]

Hold everything! I just talked to a very knowledgable engineer with ExxonMobil products division and he gave the following opinion about diesel fuel. At the given pressures both suction and discharge of our lift pumps there should not be a problem with the design of that system. Even at 190F, cavitation should not occur but lack of lubricicity, particulates, contaminants and water could be a factor for this unprotected pump design. Given the fine mesh suction screens in our tanks I suspect contaminates(microbiotic, asphaltines etc. ) and water are the culprits. That is not considering that the lift pump might just be cheap but I distinctly remember that DC and Cummins said that these lift pumps were supposed to be a more robust higer quality design. I am going without the fuel cooler this time and use the blue Holly centrifugal pusher pump, sucking through a Baldwin BF3513 spin on and drainable big rig 10 micron fuel filter & water knock out cartridge mounted in a protected area under the truck. A fuel cooler is overkill according to this engineer and I agree with his expert opinion. Last time I was over engineering the problem but when you remember the 2nd generation lift pump failures I really went after every aspect of prevention and protection for that bugger. I carried a spare lift pump in my tool box all of the time and it was one of the reasons that I bought a 3rd generation truck. Turns out that unpredictable fuel quality is the most probable cause so I am once again building a lift pump protection system. "See there", it just goes to show ya theres allways somthin! Quote, Rosanna Danna!

 

[AGrubbs]

Cool fuel? More power?

I have not had much time to look into the control systems on my CTD, but on my VW TDI, I know that

fuel temps are important. VW even puts a fuel cooler on the fuel return line to the tank on the automatic cars.



The VW ECU monitors the fuel temps and will adjust the amount of fuel injected depending on temperature.

With VAG diagnostics I can look at the fuel temp that the ECU 'sees'. In fact, several people have had engine drive-ability problems due to the fuel temp sensor going bad in the injector pump in VW TDI's.



I would think that the requirement for emissions compliance requirements means that Cummins watches closely so the exact amount of fuel and at the proper time must be injected. I suspect the temperature of the fuel comes into play in adjusting the amount of fuel delivered to keep the engine running smooth at idle, and it is probably used to help determine the amount of injection advancement. Cold fuel would take a little longer to ignite.



I have an OBD-2 software package from Alex Pepper on my laptop PC, but its not as user friendly as the VAG-com software I am used to. I have not spent much time with this new software for that matter. . I would be interested in e-mail from people who have a better handle on this software so I could learn a few things about it.



Does anyone know if you can get at the fuel temp readings in the ECU with the diagnostic software? OR even if the temps are there for the ECU to read?



I wish that there was better 'how to' info for the obd-2/diagnostic software someplace... Inquiring minds want to know whats going on in the engine. .



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