Fuel Delivery Redesign: "Project Number Two"

[Tomeygun]

One should work fine, but I went 2 just to give a little extra push.

hehe, in true TDR B. O. M. B fashion, If a little is good, ALOT must be better :-laf



Gotta love it!

 

[PatrickCampbell]

I wanted to add my 2 cents in here.



I was previously sitting at about 12 PSI idle and 7 PSI WOT *before* the fuel filter housing before I made some modifications.



0) Junked the stock fuel filter assembly, the stock fuel lines, removed the stock fuel pump.

1) 12mmx 1. 5 metric adapter at the VP44

2) Then -6 AN 90 degree adapter

3) Then -6 AN fuel pressure take off (1/8 NPT)

4) Then -6 AN to 3/8" barb

5) Goodyear fuel emission hose (60 cents per foot)

6) Carter 4601HP pump mounted on inner frame rail just in front of the fuel tank; powered by extended factory pump 12v line

6. 5) Some more rubber hose

7) Racor 6120 10 micron filter assembly mounted on outter frame rail to the left (drivers side) of the tank

7. 5) Fuel shut off valve (for security and when I change filters)

8) Gravity fed bulkhead fitting in fuel tank



Misc parts were a few hose clamps, a 3/8" NPT coupler for the shut off valve, zome zip codes, and a few nuts and bolts.



I spent a LOT of money testing and fitting, but you can put this together for < $400. I was considering making a kit, but I don't know if it'd be worth it.



I am confident that the pump will last a LONG time. For a few reasons: it's away from engine heat/vibrations, it is working the way it's meant to (push not pull) and it's pre filtered. Even if it breaks in 100K miles, it's a $85 pump and takes 5 minutes to replace (whereas a stock pump might take 30 minutes to replace but... by now we're all used to doing that job every few months right?!?!)



I am now seeing 14 PSI idle and 12 PSI wot. I gained 2 MPG. Filter interval changes are longer and easier. I have a see-through fuel bowl so I can see if there's water needed to be drained, and when I drain it doesn't **** all over the engine.



http://xj.cdevco.net/photos/fuelsystem/



Basically, in my humble opinion the stock pump location is garbage, the stock lines and fittings are garbage, the stock fuel filter assembly is garbage, and the stock fuel pick up is garbage.



I know a lot of people like to keep that stock fuel filter assembly but why? It is restrictive, uses a crappy filter and you should not need to heat your fuel to begin with. I would not be relying on that fuel heater to keep the fuel from gelling.

 

[rbattelle]

Research continues...

Got a fancy-pants new multi-meter last week and went to work taking some thermal data from the PWM circuit I've got. I've also changed my under hood junction box (pictured) to one that is a bit larger (to accomodate the PWM circuitry) and a lot beefier. It's also water tight (it's a NEMA enclosure).



Aeromotive told me to expect 5-7 amp nominal current draw from their pump, so I set out to find a 5-7 amp load I could put on the circuit for testing purposes. I found that my large vertical drill press draws 6. 3 amp continuous from the PWM. I conducted 2 experiments using a small thermocouple contacting the MOSFET chip on the PWM. One experiment was with the lid removed from the junction box, the other was with the lid installed. The data are exactly as I expected: a logarithmic temperature profile with respect to time, with a horizontal asymptote of around 230-235 for the no-lid case and 235-240 for the lid-installed case.



240 degrees is pretty warm (it will burn your finger), and it would be better to keep the MOSFET chip cooler for durability purposes. So I've removed the MOSFET from the circuit board and connected some 18 ga. wire to the pins. I will bolt the MOSFET to the side of the junction box and connect it into the circuit board via those wires. This will effectively make the entire aluminum junction box a heat sink for the MOSFET chip. I coated the pins on the MOSFET with some silicone in order to protect it, so I can't test the system again until that dries.



But I thought people following this thread might be interested in some data.



-Ryan

 

[rbattelle]

Here's the thermal data I took...

 

[roverhybrids]

One thing about your fuel filtering system that I don't know if you have considered is that most all filters are designed to be pulled through, and most all electric pumps(even mechanical ones) are designed to push.

 

[PatrickCampbell]

Yes they're designed to push. . they only need to pull from the tank, through the high flow filter (advertised ". 35 PSI pressure drop") and then they are pushing to the VP44. With the gravity fuel feed they're getting some help there too.

 

[rbattelle]

One thing about your fuel filtering system that I don't know if you have considered is that most all filters are designed to be pulled through.

In all my research I have never heard this. Exactly what are the features of a filter that make it specifically biased toward having fluid "pulled" through it by the pump? And why does the stock LP arrangement, every fuel injected engine I've ever seen, every carbuerated engine I've ever seen, and every oil filter I've ever seen "push" fluid through the filter rather than "pull"?



The whole point of filtration in this case is that the filter should be the absolute last item in the flow path. This is done to ensure material shed by the lift pump is filtered out before entering the injection system.



From a fluid flow standpoint, there is no fundamental difference between "pushing" or "pulling" a fluid. [That statement, having generated considerable opposition in the past, may be taken as purely my opinion and not based on any fact or truth. I encourage everyone to independently research fluid flow on their own and come to their own conclusions. ]



-Ryan

Disclaimer: the information in this post is purely my opinion and should not be assumed to be based at all in truth or fact. Please do your own research and come to your own conclusions. Also, I intend absolutely no flaming toward anyone, and my tone is by no means one of "ill will". I mean no disrespect or insult to any person or group of people.

 

[roverhybrids]

I believe that main reason for having the filter on the suction side of the pump is that the water can become emulsified and won't drop out. Just saying look at the filter you are going to use. I know the Davco unit you were looking at(beginnung of post) is designed for vacuum side, same for a Vormax, and all the Racor filters that I've seen say on the side "Vacuum side only".

 

[Gauthier]

Most fuel filters on heavy diesel trucks (and the Duramax) are on the vacuum side, but I can't think of a reason why there would be an advantage to this arrangement, other than saving the expense of a transfer pump. I think a pressure side filter would be better as the introduction of air would be eliminated.



I must admit that I'm skeptical that additional filters will be a significant help in preventing fuel injector problems as there are no real filters between the injection pump and the injectors. Wear from the injection pump cannot be prevented from reaching the injectors, except for the so called edge filters at the injector.



There have been many reports of injector failures on the Duramax with 2 micron filters added to fuel system. Even when the filters were installed with few miles on the engine.

 

[PatrickCampbell]

Most fuel filters on heavy diesel trucks (and the Duramax) are on the vacuum side, but I can't think of a reason why there would be an advantage to this arrangement, other than saving the expense of a transfer pump. I think a pressure side filter would be better as the introduction of air would be eliminated.



I must admit that I'm skeptical that additional filters will be a significant help in preventing fuel injector problems as there are no real filters between the injection pump and the injectors. Wear from the injection pump cannot be prevented from reaching the injectors, except for the so called edge filters at the injector.



There have been many reports of injector failures on the Duramax with 2 micron filters added to fuel system. Even when the filters were installed with few miles on the engine.

Interesting point about introducing air through the lift pump... . I would think that these are "sealed" but maybe not.



Maybe relocating the lift pump is enough to keep it alive for longer than 50-75K miles.



Racors are in fact "rated" to be vacuum or suction. See http://xj.cdevco.net/auto/fuelsystem (incomplete website... but working on it)



The question is - is putting the filter before the pump going to hurt or help?



My racor is huge and highflow. Yes it's still only 10 micron, but I would bet it filters better than the stock filter assembly.



However, if by putting the lift pump AFTER the Racor, it is introducing more air to the system that the Racor COULD eliminate, I'd rather put the lift pump BEFORE the Racor... . my $10,000 engine is more important than a $87 lift pump.



Very interesting stuff... .

 

[rbattelle]

I must admit that I'm skeptical that additional filters will be a significant help in preventing fuel injector problems as there are no real filters between the injection pump and the injectors. Wear from the injection pump cannot be prevented from reaching the injectors, except for the so called edge filters at the injector.

This is an outstanding point. It's almost impossible to test, though. If, after this, my fuel system lasts 300k miles it would not prove that additional filtration is the answer. The only way to find out if additional pre-injector pump filters work would be for thousands of people to install identical units and then report their failure rates against those with purely stock systems.



I do think, however, that there is a small filter between the CP-3 and the injectors. According to my Cummins service manual for the common rail engines (I started a post about it), there is a small metal mesh filter located at the end of each injector supply line designed specifically to "break up" particles that make it into the system. Admittedly, the manual is for the "normal" ISB engines, but I assume a similar arrangement is on our trucks. Only way to tell would be for someone to look for it when they replace an injector...



-Ryan

 

[rbattelle]

The importance of heat sinks

I moved the MOSFET chip to the enclosure, and I think it's safe to say I've cured the heat problem. Assuming the trend in the plot continues, after 12 hours at 6. 3 amp the chip temperature would be about 100*F.



Experimental conditions in this experiment were similar to those in the last experiment (6. 3 amp continuous, lid removed).



-Ryan

 

[PatrickCampbell]

I've updated my fuel system page a little bit (still not done)



http://xj.cdevco.net/auto/fuelsystem



Thoughts?

 

[rbattelle]

I've updated my fuel system page a little bit (still not done)



http://xj.cdevco.net/auto/fuelsystem



Thoughts?

Outstanding work! Don't know why I never stumbled on your site before.



How is your bulkhead fitting attached to the fuel tank? I assume you had to drop the tank and bolt it up on the bottom? Have you considered protecting that tube with a skid plate of some sort?



Very nice work, Patrick... I'm very impressed.



-Ryan

 

[PatrickCampbell]

Thanks for the good words...



I dropped the tank, drilled a 7/8" hole in the bottom and threaded the 1" bulkhead fitting into it. The fitting I used is big, bulky and heavy--it works but I would use the Russell version (same price anyway).



MLR1 from DTR did a similar job but a lot cleaner... check it out:



http://www.dieseltruckresource.com/pics/showgallery.php?cat=500&ppuser=23620



He used the bulkhead fitting that I now recommend which is I think much lighter and requires a smaller hole to be drilled. I think it has a lower profile too (drops down less?) He also has a nice skid plate. I would definitely like a skidplate... the bulkhead is very exposed there...

 

[rbattelle]

The equipment is now ready for testing. I checked the pump and found it will pull a vacuum, so it should be quite self-priming.



My plan is to test the plumbing and electronics by pumping fuel through a closed-loop circuit in a 5-gallon fuel container. However, I've become concerned about the danger of static electric buildup over time and the potential for an explosion. I'm now considering performing my tests using some vegetable oil instead of diesel fuel.



I don't know why static buildup would be any more of an issue than it is on a vehicle that's totally insulated from the ground, but I have a nagging "gut" feeling that it might not be safe to be pumping fuel around in open containers that are not grounded.



-Ryan

 

[PatrickCampbell]

I don't think diesel is anywhere near as likely to explode as gasoline (?)

 

[rbattelle]

Yeah, you're right. I'm doing some reading on the static spark danger of diesel, and it's considered very low. In fact, there has never been any recorded incident of diesel fumes igniting from static discharge.



MaybeI'll just connect a ground wire to the pump.



-Ryan

 

[EEdmondson]

Bond everything together with a ground wire so there can't be any sparks. We don't want to lose any members.

 

[rbattelle]

Bond everything together with a ground wire so there can't be any sparks. We don't want to lose any members.

Amen. I took some time to educate myself on static buildup as it relates to fuel transfer processes. There's some interesting (and frightening) stuff to be read out there! Anyway, as long as I bond everything like Rick says so it's at a common potential, there should be no problem.



I'm working up a test plan now and may test as early as tomorrow.



-Ryan