Engine/Transmission (1998.5 - 2002) Modifying fuel system so temperature input to VP44, 80* - 100*, your inputs.

[CORed]

You bring up another interesting point Texas Diesel... just what amount does the FF heat the fuel. Obviously, the fuel is sitting in the canister for a bit. So it is definitely heating the fuel to some extent... but to what?



From a few posts up, it seems that the FF canister is taking heat off the block since it is mounted to it. When the FF canister is removed, it is not nearly as hot. So given this, even if the FF is "only" heating the fuel until, say, the fuel reaches 100*, that doesn't mean that is where the temps stop. The block continues adding heat and the aluminum (as someone said above) of the FF canister acts as a heat sink so it easily pulls more heat from the block into the canister.



So it would be nice to know what is the operating parameters of the FF heater. Does it start running if the fuel is less than 75*? And does it stay on until some preset temp?



But larger than that, our blocks run much hotter than 75* and probably are closer to water temps eventually which can be near 200*. If this kind of temperature is being drawn into the aluminum FF canister, then your mathematical equation is using the wrong numbers... and a cooler on the return line is helpless to do much about it IMO.



We need more data, that's for sure. But I believe based on the data so far, I may be a fool, but I seem to believe a FF-VP cooler will do me the best good. But I haven't installed one yet with fall knockin' on the door and temps dropping. It's something I'll do next spring probably.



Steve

 

[nps]

Justin,



There are a couple of things that have been speculated/observed to heat the fuel:



1. The Fuel Filter placement and heating.

2. The return line to the fuel module causing newly returned fuel to be picked right back up again by the feed line rather than 'mixing' in the tank as everyone expects it to do.



So by design or accident, both things cause the fuel to be heated, and serve to negate the effectiveness of cooling the fuel at any point other than the VP input. That is why the return line has been suggested to be relocated, as well as the fuel filter.



While I will agree that the effectiveness of any cooler is the greatest when temp differentials are the greatest, one could argue that the temp will be highest just before the VP input given observations on the stock fuel system. Of course, two coolers, one on the feed and another on the return, would provide the greatest cooling benefit even though each cooler is operating at less than its greatest potential radiation capacity.



Having said all that, are the effects of hot fuel evident? Don't think anyone has proven that one yet, although most believe it is highly possible. Do you doubt it?



My VP seems to run fine pulling a 10K trailer over mountain passes in 115* ambient temps. Personally I feel that the mechanical aspects of the VP may be more susceptible to heat than the electronics, but I've got no way to prove it and I am doing nothing to mitigate it other than to follow this thread at this time.

 

[Texas Diesel]

Steve, I dont know I'm just throwing out ideas.



I met a man who had a Bosch Team meet with him and discuss the VP operation and internals. They took two internal parts that fit perfectly and turned easily. They took the two pieces apart and handed him one to hold in a tight fist, to warm to 98F the other laid on the table. After a few minutes they asked him to put them together. He couldnt. They said the clearances were so close that the thermal expansion of the part he held made it not fit.



The point was to demonstrate the precision of the assembly, he was impressed.



Can excessively (?) high temps cause wear/siezing of the flux capacitor? Who knows.

 

[keimmmo]

Bob, sorry to hear of your loss. One of my greatest fears in life is having my tools stolen. It would really be hard when "turning wrenches" is one of the loves of your life.



Let me throw out some of my observations. The head of the motor, where the filter is mounted, has water close by. I run a 180* thermostat. Some of you guys still have the 195*, which would make the overall temperature of the motor even hotter. The filter is mounted to the intake manifold. There is hot air on the inside of it. The intercooler helps cool the inlet charge, but it is still hot. Just touch the intake horn if you don't think it is hot. That thing will almost burn you after a long hard drive on a hot day. That is a pretty hostile environment for the FF... it is going to soak some major heat from the head!!!



I have the FF mount made and the filter is mounted in the new location on the frame rail. I do not have a digital camera and wouldn't know how to post a picture if I had one. If I like the results, I will give a good written discription of it later.



While there is no proof that high fuel temps kill the VP, it stands to reason that cool fuel will lubricate better than hot fuel and cool electronics will live longer than hot electronics. Also, several of those who have installed a fuel cooler have noticed an improvement in fuel economy. I am quite interested in that!!!



Yes, the tolerances inside the pump are close. Heating one part more than the other will cause them to not fit. But, when assembled, all the pump parts heat at the same rate... really hot or just warm.



I'll keep you all posted as I progress with my project. With a little luck, I might get it running tomorrow.



Steve

 

[Hohn]

Easy Justin,



I (we) hear you and, at first, your theory made sense. But with the research a few guys on here have been doing (thank you all), having a cooler on the return side is basically MUTE. The fuel is heated up again in the FF so any cooling you accomplished on the return side is negated.



And secondly, the cooler that is being talked about and employed between the FF and the VP will be located behind the front grill where it will get direct outside air, not under the hood where, as you rightly say, the temps are much hotter. I was not sure you realized that. It sounded from your post like you thought maybe the cooler was going to be placed in the engine compartment itself.



So maybe during the first couple minutes of driving, yes, a cooler mounted between the FF and the VP on the front of the radiator may be ADDING heat to the fuel... especially if it is hot out. But after those few minutes, it will be cooling the fuel since the OAT will most likely be less than the temp of the fuel. And from some guys' estimates, the FF is making the fuel so much hotter, that a cooler setup on the supply side WILL be cooling the fuel substantially before hitting the VP... where it can do some good and accomplish the goal of this thread / experimentation. And if the outside temps are even more reasonable (cooler), you will REALLY be cooling the fuel just before it is to be used by the VP.



Again, any cooling you did on the return side just made your plastic fuel tank cooler which does nothing to help the VP44 when the fuel is heated back up again in the FF.



I (and I believe most) will continue to respect your opinions and appreciate them. But this post sounded like you are everyone's daddy and YOUR way is the ONLY way.



Keep the data coming guys!



Steve

1) Yes, I thought you were mounting it underhood, so up by the grille makes more sense to me.



2) *IF* the FF is such a source of heat, then simply eliminate it and go to a remote FF setup like a Stanadyne fuel manager or somesuch. The spacer idea has some merit, as even a thin piece of Phenolic can be effective.



3) The heating of the fuel in the FF does NOT completely negate the cooling effected by a return-side cooler. Cooling the fuel in the tank DOES help, but not as much when the fuel it re-heated.



The temperature of the fuel at the VP is a function of 1) the temp of the different pieces it is exposed to 2) how long it is exposed to them 3) the specific heat of the materials in question, and 4) the temperature of the fuel to start with.



So, if you start with cooler fuel in the tank, you get cooler fuel at the VP, plain and simple, right? Unless, of course, the fuel is exposed to the hot FF long enough for it to be raised up to the temp of the FF. How long would this take? Obviously, the higher the flow though the FF, the less effect the temp of the FF has on the fuel. If flow is slow, then the FF has a lot of time to transfer energy, and the fuel gets hot.



So I'm more onto what you guys are thinking now, having gone back and read the thread after making an @$$ of myself.



Some questions to guide our reasoning on this problem:

-- what are the sources of heat into the system? It appears mostly to be LP, FF, IP, and injector overflow, right?

-- At what point it the fuel hottest? Coldest?

-- Can we modify it so that the coolest temps are right before the VP? IS it necessary, or was the VP designed to handle the additional heat from the FF?

-- Do we know that cooler fuel enhances VP life?



-- The fuel sytem, being return-style, is best modeled as a loop. What are the effects of increasing the capacity (volume) of that loop. What about flow rate? Does pumping more fuel cause temps to go up or down?















Anyway, my apologies for the pi$$y attitude of my last post. I was so frustrated after reading all the whiny posts about fuel prices, that I was about to cancel my TDR subscription and throw the comp out the window. I'm sorry. I'll try to make it up to you all with some brilliant posts

 

[Hohn]

Oh, something else. The effect of the FF hsg on fuel temp will vary A LOT. it will vary with 1) engine temp 2) beginning fuel temp, and 3) flow rate.



We can't just say that it adds 25 degrees. Or 50. Or 5. As much as I'd like to say that (because it appears to help my case for the return side), it's simply not true.



What the worst case scenario for FF heating? Probably idling down after a hard run of heavy towing. Why? Because the engine is hot, and flow rate is lowest at idle. Thus, the fuel is exposed to the FF for the longest time, when the FF is at its hottest.



That said, the fuel temp will most likely ALREADY be hot, so maybe the FF won't add much heat?



I've seen posts where Scotty saw fuel temps while towing of almost 170 degrees!! This was when he was running high fuel pressure. Lowering fuel pressure dropped tank temp. Anyway, that's HOT fuel. How hot does the FF get? Would it have any real-world effect on fuel that was already 160 degrees or so??

 

[Fishin Guide]

I still prefer the cooler in the return line for the reasons that Justin listed. The proper location of the cooler is in the return line away from engine heat. I would like to see it in the front of the truck. Bearing in mind, that the fuel will pickup heat off the CAC and or radiator when the truck is stopped. A fan would negate some of this.



I do like the idea of adding anything to the pressure side. Anything after the lift pump and before the VP adds restriction. This slows the fuel and allows it to pick up heat. I just got done with a 12V pump swap. After shutdown, that sucker was hot! But, when it was running, everything cooled right down.



Now, I would suggest trying to keep the heat away from the FF as it has a large volume. This slows the fuel transfer allowing it to pick up alot of heat. The lift pump in my case has so little volume and is moving so fast, it does not have a chance to pick up much heat.



Now, if that fuel return was in a location other than the fuel pickup, there would be a great case for some type of cooler between the VP and lift pump. As we are recycling the same fuel over and over, I really thing the cooler on return makes more sense.



Dave



Not saying anything is right or wrong here. It's great that you guys are taking the time to try to make some positive changes.

 

[rweis]

What I do know by measurements:



1. The ff heats fuel approximately 10*. Measured at tank output + RASP pump output to ff body.

2. I have a H7B fuel cooler back on the return line by the tank and with the fan on it will cool the fuel 10*

3. I dump the output of the fuel cooler into the tank vent line. Prior to dumping the fuel into the vent line the ff body temperature would vary inversely to the fuel level in the tank. The lower the tank, the hotter the ff. With the fuel cooler and the return to the vent line there is much less inverse relationship of tank level to ff body temperature.

4. I am very close to having a closed temperature loop system. All I need to do is get rid of about 5*- 10* of fuel heat and I can put fuel back in the tank cooler than when it came out of the tank consistantly.



My fuel temperature gauge and sensor came today. Of course I have no tools to install it now. However when I do, I will have direct readings going into the VP. Then I will move the ff or cool it with a heat shield and be able to read the differences on the fuel temp gauge.



Also knowing what the VP input fuel temp is directly I can also measure the VP output fuel temp and know exactely what the VP is contributing to the heat question.



IF there are no fuel temp differences diferences by moving or cooling the ff, then it is on to a fuel cooler between the ff and VP and placed somewhere in free air with a fan.



I did learn something today. I idled the engine for about 30 minutes (Vp fuel psi 14#). The body of the VP rose approximately 30*. I idled the engine for another 30 minutes at a higher rpm so the RASP was outputing higher psi to the VP (17#). The VP body temperature dropped the 30* temperature rise as well as another 5* to OAT + ff rise (10*) + 10* (work being done by the VP internals). By opening the VP bypass without working the engine (ie more engine heat) the VP body temp dropped 35*. Remember the fuel cooler drops the fuel 10* and I dump into the tank vent line. Lesson learned. Bypass fuel has a beneficial cooling effect on the VP. If you are going to engine idle, engine idle at more than 14 psi input to the VP to get the VP bypass open some IF your input fuel is cooler than the VP body.



Bob Weis



Oh learned one more thing in the last couple of days. DC replaced the lp about 2k ago. On start the fuel psi would jump ~ 7# on start correctly, engine start, RASP begins to turn and fuel psi goes to 14# idle. Last couple of days, key on, NO lp jump, hummm, bump starter, jump out, hold lp, dead as a doornail. However in my plumbing system it seems that this is a classic case of the Vp low pressure pump sucking fuel from the tank. Key on, 0 psi, start cranking, 1 second, engine starts, RASP now pumping normally (14#). How or where the VP is getting fuel for that 1 second until the RASP comes on line, other than the VP internal low pressure pump I do not know. Borrowing tools to change the lp this weekend.

 

[Fishin Guide]

Bob, the truck will start with just the fuel in it's own body. I just finished my 12V lift pump conversion and with the VP overflow valve, there is no pressure at startup. It does climb rapidly, however.



Upon inspection of the VP overflow valve, I observed a small hole that would function as an air bleed. At least that's my theory. I think that this would allow the electric pump to purge any air in the line to the VP. Therefore, no pressure would be held like the 12V overflow valve would. And for that matter, maybe they bleed off too.



Anyway, back to the topic at hand. I can say that I can feel the difference in temp at the VP with the new lift pump. I am bypassing a huge amout of fuel and it appears to be keeping the temps down. Nothing scientific, just the difference in my hand.



Dave

 

[Hohn]

A couple points to ponder:



Bob-- Shooting the FF can and interpreting those temps as FUEL temps is misleading, imo. As the fuel flows through the FF, it will COOL the can as the temp of the fuel itself rises! So, your temps off the FF housing are LOW readings, and the actual fuel temp should be higher than we think, but not necessarily = to FF temp.



I'm also not sure that we can say that FF= Fuel temp. I'd expect the FF to be hotter than the actual fuel.

 

[rweis]

Oh, no doubt shooting the ff is not the true fuel temp. Absolutely true.



It is only some sort of data gathering to guess as a guage. When I get the fuel temp gauge installed then I can say fuel temp = ???? when ff = ???? when under hood temp = ???? and get some sort of a delta to apply maybe. Just have to do it and see what it yields.



However I did get my gauge and temp sensor that will be in the fuel flow so as soon as I get tools to get it installed I will have true fuel flow temps to the VP. I think the neat thing about that will be to be able to vary a procedure and see what happens to the fuel temp. That is why I am not moving the ff yet. Run a week with ff stock location and see what it yields, then move the ff and see what it yields. Do another 30 minute idle at 14# then 30 min at 17# and see what the fuel temp does. That type of thing.



Bob Weis

 

[Hohn]

This should be fascinating!

 

[Fishin Guide]

Bob, can I ask where the fuel temp will be taken from? Is it a few inches from the VP in the fuel stream or somewhere else?



Thanks for all the data!!



Dave

 

[keimmmo]

Well, I have the pickup running again. I took it out for a 10 mile "blast". Not enough to know a lot, but enough to feel things are working right, there are no leaks, and start getting an idea of what I have.



The FF is now mounted on an angle iron mount off the frame. The FF is a little lower and farther back than original. You would think that would make it difficult to get to, but it isn't at all. While it is a little longer reach, access to the filter lid is better and it is easier to get the filter in and out because there are less cables and things running across the top than in the original location. I have NO complaints about changing the filter in the new location!



I am still running a small automotive inline fuel filter just ahead of the VP to catch any crud that may be inside my home made fuel cooler that I have mounted in front of the radiator. I'm sure it is a little restrictive and I expect the fuel pressure to improve when I remove it in a couple of weeks. I had been running the factory fuel line with drilled out banjo bolts between the FF and VP. I replaced those fittings with drilled out straight fittings and 3/8 high pressure rubber fuel lines.



My fuel pressure is actually UP after adding the extra length of lines... certainly due to the larger lines and fittings. I have 15 psi with the motor off. 14psi at idle. About 10-12psi at cruise. I can't pull the pressure below 7 1/2 at WOT. Now, I live 6,000 ft above sea level. When I go down to near sea level, all pressures increase about 2psi. That has been proven by dozens of trips up and down the mountains, and I don't expect it to change now!!!



After the 10 mile drive, the FF was still cool to the touch... the head was good and hot. The way I see it, eliminating a source of heat is as good as running a big cooler! It yields the same end result!!! I only wish I had a way to actually measure the temperatures.



If any of you are interested, I can give a good detailed discription of my filter mounting bracket. It only involves cutting and welding 4 pieces of angle iron... not tough at all. The trick was figuring out how to make the first one... those that follow will be easy! Like I said earlier, I had that FF mounted every way but up-side-down trying to find a good location for it!!!



Keep up the good work everyone. Sharing information is a great way to learn about our trucks!



Steve

 

[CORed]

Steve,



That sounds like great work. It would be great to see a pic of your setup. I know you said you don't have one, but if you come across anyone with the camera and can upload it, it would be most beneficial. Welding is out as an option for most I would guess so a pic of what you did and where you put it would help others determine how to make a bracket if they desire.



I did not know that fuel pressures increased about 2lbs when you were at sea level. Never heard that before. Interesting. I live at 6800 feet and my pressures at idle are around 13-13. 5 and cruising is around 12. So, unfortunately, I do not benefit from opening the bypass in the VP44 like I wish I could. But this could indicate why others have higher pressure than some (or at least provide one more possible explanation).



Thanks for the good work on this. Like you, it would be nice to get some real emperical data on the fuel temps going into the VP both before you did this and after.



Bob, if you can, please provide the info for the temperature gauge and port you bought. A pic of the parts / gauge / and where and how it attaches to the line would be most helpful to learners like me.



Steve

 

[keimmmo]

It is a quiet evening for me, so I will try to discribe how I made the FF bracket. I know a picture would be worth a 1000 words, but I THINK I can get the job done with less than 1000 words!



First, I don't see how you will be able to make one without welding. You also need a drill and assorted bits and either taps for cutting threads or self tapping bolts. (Not metal screws. )



The first step is to tap the holes you will use as mounts. I recommend you remove the air intake horn and the APPS to open up access to where you will be working. I also removed the original fuel pump mount and cut off the top of it so it becomes just a plate to plug the mechanical fuel pump hole in the block and mount the wires that pass by it. It looks neater and gives more clearance for working. I have my factory lift pump mounted just in front of the fuel tank on the inside of the frame.



There were two holes on the top of the frame rail of my truck right behind the motor mount. The front one was the right size to tap to 5/16. The rear one was oval, so I drilled it out to 3/8 and tapped it to 7/16. There is another one on the inside of the frame rail beside the starter. You have to either remove the starter to use a 5/16 tap or use a self tapping bolt. I used a self tapping bolt.



Cut a piece of 1-1 1/2 angle iron about 5 inches long. Drill a hole near one end and mount it pointed up on the inside of the frame rail. This is the side support for the bracket. You will need to clearance it as needed to clear the starter.



Cut a 4 1/2 inch long piece of 2 inch angle iron. This goes lengthwise on top of the frame rail with one side against the support brace and the other down against the frame. Clamp and weld it to the upright to make a bracket that will bolt to the top and side of the frame. You want the rear bolt hole to be about 1 1/8-1 1/4 from the rear of the bracket and the front hole as needed to fit.



Cut a 9 1/2 inch piece of 1 1/2 inch angle iron for the rear upright. Position it with one side across the back of the bottom piece and the other side toward the inside of the truck. You might need to clearance it a little at the bottom to fit the two pieces together for welding. Weld it pointed straight up at a 90* angle



Cut another piece of 1 1/2 angle about 4 1/4-4 1/2 inches long. Drill holes in it to mount the filter housing. The angle should go up against the filter housing... like the corner of the head in the original position. I used 5/16 bolts to bolt the FF to the bracket.



Lay the top piece across the upright so the outboard bolt hole has just enough room to clear the upright. You will need to notch the upright so it will fit nicely.



NOTE: The filter is mounted SIDEWAYS with the inlet pointing out toward the inner fender... not with the inlet toward the rear like original!!!



This bracket will allow the outlet to point down between the frame, motor mount, and starter. It will work best with a 90* fitting pointed straight forward, but there is enough room to point the fitting straight down and loop the hose up around the back and forward. The inlet will also work best with a 90* fitting pointed down and back, but will work with a straight fitting. You might need to bend the brake lines over and up a little to clear the FF housing and fitting.



The wires going to the FF reach with length to spare. It isn't hard to get to the water drain... and the extension hose clears the cross member for draining. There is plenty of room on top to get a wrench on the filter top and nothing above it in the way for changing the filter. (TIP: I zip tied a few things out of the way so they would STAY out of the way for changing the filter!)



I hooked up everything with 300psi burst strength 3/8 hose. It isn't much more expensive than regular fuel line. I also used a straight fitting going into the VP... eliminating all banjo fittings. I have a 3/8 tee fitting about 6 inches from the VP to hook up my fuel pressure gauge.



In summary, the first two angles make a bracket that goes on the top and inside of the frame and it is held by 3 bolts. From there, there is a tall "T" that attaches to the rear of the bracket over the frame with the top of the "T" setting SIDEWAYS to mount the FF... not lengthwise!



I probably have many of you totally confused. Forgive me for the long post, but I hope it is enough for some of you to be able to make a bracket like mine... and hopefully post a picture.



Steve

 

[rweis]

Reminds me of assemblying a swing set on Christmas eve about 4 o'clock in the morning on the living room floor: Insert tab A into slot B while sliding tab G into slot K. Using bolts supplied, bolt assembly together Oo.



Gonna have to reread that one a couple of times. However THANKS, and in daylight I'll try to read it while looking at the frame etc and it should make more sense.



-----

I got a Westach 2C9-12 temp gauge. It is a 30 - 150 F.

I got a Westach 399s1 temp sensor 1/8 npt 5/16 tip



The mount is a 3/8 npt T. 3/8 so that there is NO restriction to fuel flow when you mount 3/8 npt - AN-6 fittings on the ends and a 3/8 npt to 1/8 npt reducer on the T and then screw the temp sensor into that. The tip of the temp sensor sits in the well formed by the 3/8 npt - 1/8 npt reducer in the top of the T without actually portruding into the moving fuel flow. There is a small well where the tip of the sensor will sit that the moving fuel should keep accurate as to fresh flow without interfearing with the flow.



I plan to mount it in the line between the ff and the Vp as close to the VP as I can get it. With the RASP I also have a bypass back to the tank vent line between the ff and VP. Not a huge amount of room between the ff outlet and VP inlet to get 2 line fittings between the them. I also use full flow Aeroquip fittings, a 90* on the VP and a 135* on the ff (stock location for now). Tis going to be a little tight to get it all in .



I chose 30 - 150 because: 1. it was a standard aguge, 2. I darn well should be able to keep the fuel temps below 150* since the max fuel temps to the VP44 from Bosch is 160*. The 30* end should be adequate to know that fuel will be above the gell point (something like 6*?). I use Stanadyne PF anyway that pushes the gell point to -60*.



Bob Weis

 

[keimmmo]

I know the bracket sounds complicated in words, but don't try to make it into something difficult. There are only 4 pieces!!! A couple of them are pretty easy to figure out. Set the filter housing in sideways and it shouldn't be too tough to figure out where the pieces go!



Steve

 

[keimmmo]

Bob,



I am interested in knowing how you modified your fuel return to dump the fuel in a different part of the tank. How complicated is it to make the modification? I run used motor oil in my fuel and relocating the return would mix the fuel better.



Steve Keim

 

[rweis]

Well, not hard actually.



I used the vent pipe on the OEM fuel filler line.



The smaller metal vent pipe is 3/4".



Take out the screws that hold the fuel filler mouth to the fender.

Go under to where it fuel filler goes into the tank. There is a big hose to the fill tube and a small hose to the vent pipe.



I used a 1/2" npt T and put 1/2 NPT - 3/4" hose adapters in each end. Some 3/4" hose. A couple of hose clamps. We will talk about how to get the VP / injector return line into this T in a minute.



Take the metal fuel filler and vent assembly out from underneath. Measure the length of your T adapter and cut that much off the vent pipe. Remember you are going to use the OEM hose that is on the fuel tank that went to the vent line in the first place to go into one end of your 1/2 npt to 3/4 hose adapter ends. So actually I just cut enough to get the T onto the vent line.



Now how to get the VP / inj return line to the tank. Well, the return line is the bottom line in the pair that are attached to the frame (I think). It is the smaller of the two. I cut mine back by the tank just about as it bends up to go to the top of the tank. A 3/8 plumbing coupling WILL NOT WORK because the return line is less than 3/8, something like . 31, but a 3/8 id fuel line hose with hose clamps (no pressure on the line, I used 3 small hose clamps) works fine. Then route that back to your T and use however you want to attach it,ie 1/2 npt to 3/8 barb, 1/2 npt to 1/4 npt with a 1/4 npt to AN-6, what ever you choose.



I also put some 3/8 fuel line on the part of the return line that goes to the tank and plugged it so fuel could not spill out through what now is now an open return line.



I did mine to disperse the heat from the VP / injectors to the entire tank.



There is a good article about the fuel canister in this months TDR mag.



Bob Weis



I think this week or this weekend I will get the fuel temp gauge installed.