Engine/Transmission (1998.5 - 2002) cool VP44?

[rmackay1]

Just helpped a buddy put in our 1st VP44 on his 99 the other day, I got to thinking about how high of pressure that little pump makes, and what the temperature might be on the input/return/and high pressure side of the pump, I was wondering if someone would like to make some comments on the idea of these oversized fuel input/return and high side fuel lines to possibly move more heat more quickly through the lines,not even considering the performance aspect if there is any, and I was even thinking that I may put a small cooler in series to the incoming fuel to the VP44, maybe the pump is not junk at all, maybe it's just not getting fed what it requires

 

[Ncostello]

I think the flow through the VP44 and the corresponding amount back (idle, high idle) to the tank doesn't vary a whole lot even with minor mods added. I think MoparMuscle did some flow meter tests on that.



At the same time... if you shove too much through too fast... it could make heat removal worse. There is a rate which allows the best collection and removal of heat. The fluid must remain in contact with the hot items for some time "T". If you simply double that it may not have time to absorb heat properly. Diesel isn't instantaneously able to conduct and absorb heat. I don't know if Bosch did any thermodynamic calculations on the ability of the VP to keep cool (within operating parameters) with incoming fuel. I'd be betting they did. You'd have to measure before and after temps of the units internals. Hard to do.



I think Bosch engineers have it as right as its going to get. All we have to do is make sure our lift pumps dont quit pumping properly.

 

[rmackay1]

nice comments Neil, I have a Fluke meter with a flexable tempuerature probe and some metal A/C ductting tape and am going to take a measurement of the in/return and hi side lines out of curiousity

 

[Spunkys Ram]

Any new information we can get on these pumps is great. I'm curious to see what readings you get. Although, Neil hit it on the head with the cooling ability of diesel. What one needs to find out is how much time it takes for diesel to conduct heat at a specified flow rate. Now it's just getting beyond me.

 

[Rattlin_Ram]

Is there any possibility of adding some sort of "fuel cooler" kind of like an oil cooler inline somewhere????

 

[rmackay1]

Got some numbers, just did it today here in Palmer Alaska, overcast skys, 47 F. , 7600lbs trailor, 7. 9miles per test run,10 trips, 79 miles total, 3/4 tank to 1/2 tank.



The numbers indicate what I belive, your inlet fuel temp will be the coolest temp, your return will be the next highest temp, and then of course your hi-side of the pump will be the highest temp due to the compressing of some 17,500 psi according to the shop manual, also the numbers relect another suspition of mine is that as you drive the vehicle the temperature of the diesel in the tank will increase as the level goes lower, due to the fact that your recirculating more and more warm fuel into less of a tank full.



diff. between return / in was 106. 6 F. - 88. 2 F. = 18. 4 F.



diff. between hi-side / return was 114. 6 - 106. 6 = 8. 0 F.



diff. between hi-side / in was 114. 6 - 88. 2 = 26. 4 F.



The differance between the incoming fuel and what is going to the injectors is almost thirty degrees, this leads me to the assumption that installing a fuel cooler might not be a bad idea, I would think that the incoming fuel would be more benificial to cool than to cool the return fuel. Now that I have actually done this and wrote down the figures, I will hunt for a cooler and try to hit about the same temperature day ( which might not be until next year) and do a comparison

 

[tractorface]

Your on the right track

I agree that cool fuel is one of the keys. We never let return fuel dump into the suction fuel directly, we always seperate by at least one baffle, in our diesel genset tanks. See my reader rigs pics for my solution. See our fuel tank module holds about two quarts of fuel or so and DC dumps the hot fuel directly into the module to be immediately used in the suction line. Every fuel system guy I talk with says that is a really bad deal, includin the Cummins fuel systems specialist I worked with on a nuclear project.

My solution was lazy and not perfect, but still much better than DC

 

[Ncostello]

You could always run the return line to the fuel fill neck/pipe. That would keep it away from the module somewhat.

 

[R-N-R]

Ever wonder how many people with auxiliary tanks (with pump return plumbed to the aux tank) have problems with lift and/or injector pumps?

 

[Sticks]

I definitely believe that the fuel needs to be kept at or below a certain temp. When my VP was on the way out, it would only show the 0216 code either when the ambient temperatures were above 90*f or I had been driving for more than 1 hour continuously.



The VP44 likes it's food to be plentyful, and cool.

 

[WestTN]

Cooling the fuel coming in will increase the fuel viscosity and decrease flow through the injectors. That is why Cummins installed a fuel heater at the fuel filter. Some things are already engineered for us.

 

[mhenon]

Cool fuel!

My wifes Jetta TDI (Tiny Diesel Inside) has a "T" on the fuel filter (which is close to the engine). If I remember this right, the T shunts fuel from the return line right back to the filter and then to the engine. . when things are cold. Once eveything warms up the fuel goes all the way back to the tank and then to the filter which gives it a chance to cool down. Slick!

Sounds like they did it a little better than Cummins.



Mike

 

[rmackay1]

the shop manual states the heater comes on below 45F. +/- 8 degrees and shuts off @ 75F +/-8 degrees and also goes on to say that it's purpose is to prevent diesel fuel from waxing in cold weather opperation, now I know my current address may have some wondering, but if my plans come together, I'll be in Florida this coming summer... ray