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Discussion Starter #1
I've been working this angle for a while finally got around to doing something about it. I was looking at a dual lift pump install if you look in my pic here http://dieselplace.com/forum/showthread.php?t=15002 the extra elbow below the vac switch is for the 2nd feed line pending install 2nd pump. Anyway got to looking at the IP inlet and saw it wasn't same size as the rest of my plumbing 3/16" OD roughly is OEM inlet size fitting, well "that ain't good enuff" for a stock rig IP OEM concept is okay, but watching EGT when hauling freight vs rpm vs lift pump pressure, more fuel is needed.

So I started thinking 2nd factory lift pump in parallel, key is volume not psi as if IP has too much psi it dumps back to the tank what it can't use.

Well GM has by design limited just how much flow one can possibly have. look over the attached photos and you will see what I'm talking about. What i fainally wound up with is 1/4" supply all the way to the IP. has is made a difference I think so, I got way more black smoke when I kick it in the rear until turbo spools up, more smoke = more fuel, I haven't had time yet to do last piece, install a Cummins lift pump & see what scanner says for fuel vs rpm data.

Special fitting made for IP inlet to replace OEM, then bored & tapped out the filter housing outlet pipe to accept 3/8 NPT X 1/4" OD barb fitting, hire professional machine shop to do your work if you tap too deep you will ruin the filter housing (YOU have been warned).
 

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Discussion Starter #2
More pics

More pics
 

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Your making me think about making some changes...... on second thought i've got all the black smoke i need at this point. Probably a great idea if not running a high output pump. With my dual filter set-up i should really be checking my LP pressure at the IP to see whats happening in there, maybe i do need to do that.
 

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Great work and really nice pics!! :ro)
 
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Glad to see ya got around to gettin' some things done. I was going to attempt your suggestion on modifying the fuel fittings, but then mine blew up again... Looks good IMO.
 

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Excellent work, and great pictures to boot.
I recently upsized my puny supply return hoses to/from the IP, and I was pretty pleased with myself until you started this thread ;)
 

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What are your fuel pressure readings like now at you IP? Just curious as I'm sure you must still be using the stock return fitting on the IP which has the little pressure control valve built into it.
 

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Discussion Starter #8
Haven't plumbed the IP housing to know IP case pressure, yet, got the fitting just haven't plumbed it yet. The lift pump pressure, now more steady minimum now is 2 psi where before when I was gittin it, pressure would go down to .5 psi.
 
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Discussion Starter #9
There are some clearance issues also to installing the fittings on the IP, I had to mill down the new IP inlet fittings flats to the same size as the old one so I could get a socket to fit on it and also clear the shut off solenoid. I also had a socket turned down for a little more clearance.

BTW the fitting was custom made to begin with, there must be a store bought one available but not here, but I know a good machinest that is fair on his labor so it was easier to have it made rather than track one down, for same money.
 

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INTERESTING!! I like this, I have a spair LP and some time on my hands to make a little more fuel appear in my IP. I have a flow meter I might borrow from work. I will rig it up and see what kind of GPM flow the one LP has and post that and I will then link my spare with my current one and see a combined flow.

This is a CHEAP way to increase fuel!! I like cheap:D (and easy);)
 

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Did a flow test on the Cummins electric supply pump verses the GM unit. I was quite surprised.

Used a flow meter calibrated in
PPH Liquid G. 0.81175 Visc. @ 95 degrees. using VISCOR test fluid (about the same as diesel)

Cummins Supply Pump
PSI-Flow PPH
9- 260
10 -242
11- 217
12 -184
13 -146
14 -115
15 -92

GM
4 -115
5 -94
6 -88


You'll have to convert that to gallons I guess. I guess you can see the GM unit is very lame. No wonder the unit loses pressure at speed. The flow meter is used in the calibration of Cummins PT type pumps on Cummins big engines.

Both tests made with good used units. From what I see the Cummins unit should be able to maintain 13 PSI on the GM at W.O.T.
 

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Discussion Starter #13
More pics

Some more pics
 

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Flow test an injection pump on the test stand to check for total flow through the pump and the injectors to get an Idea as to how much fuel flows through the pump and injectors. I used a rebuilt DS4-5521 injection pump. Please note different rates can be obtained by various pumps due to wear and return rates back to the tank.
I used a flow meter calibrated in PPH* Liquid G. 0.81175 Visc. @ 95 degrees. using VISCOR test fluid (about the same as diesel)

3000 rpm----70mm 3/stroke------165 PPH ----OEM Calibration
3400 " ------50mm----" --------140-"
3400 " ------20mm----"---------110-"

3000 "------80mm---- " --------180 -''-Maximum Pump output
3400 "------82mm-----"--------192--"------"-----"-----"

GM Supply pump
4PSI - 115PPH
5PSI - 94PPH - (desired pressure)
6PSI - 88PPH

At high full load demands the stock unit falls short. When the flow rate exceeds 94PPH the pressure will fall off.

*PPH > Pounds Per Hour ( pounds of fuel flowing through system in an hour)
 

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I have been running a 2nd filter and a second lift pump for about 2 years,
All are in series... The ' add on ' lift pump is back by the tank, I switch it on when the fuel pressure drops under load.

The reason I did this is as follows:

Was not very confident that the OEM filter was very good at traping water
. I had never drained water from the OEM filter, therefore I installed additional filter before OEM lift pump. ( note in filter install info, filter should be before lift pump to allow water seperation in filter). The add on filter does trap water/rust that i never was able to detect from th OEM filter. I assume the water was going through the OEM fiter.

After I installed the 2nd filter , I would see a fuel pressure drop , ( never really checked it before mod's ) sometimes to ZERO under a hard pull.
Therefore I installed the 2nd lift pump with a switch for control.

When pressure drops, I turn on the Switch...

I drain the add on filter periodically, usually I get a 1/4 teaspoon of brownish water,
The add on lift pump , in series, allows flow through it with no power applied.

I also use the 2nd lift pump To purge air, after filter change,: Turn on Sw, 2nd lift pump pressurizes system.

Plus: I like gage and switches!!!!
 

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Perma cool kit, from JEG'S catalog... kit was about 40 US and filters are 13 US,

Solid metal spin on 2 mc filter ( like an oil filter ) with a drain valve as part of the filter.
real easy to change..

Down side, only place I have found to get filters is the Jeg's catalog
 

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I am returning an old post (because I haven´t seen it before now). This was very interesting conversation, but I would have a few guestions.:confused: If the stock lift pump fails to pressure the stock IP, it obviously does´nt cut it to a lets say a marine pump either, right? Has`nt anybody tryed the Dodge Ram`s pump? And what I red, It produces more pressure, does this hurt the IP?? or something. And could an ordinary gasoline engine hi volume pump be used with a regulator?(I`m new to diesels) I know the flow thru problem, when pump not running, but otherwise. Then the filters, why use orginal filter on top of engine and make it bigger, isnt there aftermarket filters that would flow better and would be easier to chance?(after being installed somewere else). Thanks for answers.
 

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Discussion Starter #19
Some more pics for you here is the filter screen for the IP threaded into the IP body. I was helping another member out offline and shot these after we discussed possiblity of it being clogged, his truck is reacting like it has poor fuel supply. All other basic flow checks are satisfactory.

One of the things that got me to thinking about it is member did not know the plastic last ditch screen in bottom of fuel filter bowl was missing, I'll have to look and see if I can find pics of that. They sometimes get stuck in center of the old filter element and get tossed away, but it is supposed to be in the bottom of the filter bowl of the on engine mounted filter, make sure you don't throw yours away.
 

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