ADJUSTING/REPLACING THE P7100 FUEL PLATE - Diesel Bombers



94-98 12V Cummins 5.9L P7100 Tech Talk '94-'98 5.9L Cummins 12-Valve P-9100 Tech Articles

 
 
 
 
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Old 07-28-2007, 02:50 PM
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Default ADJUSTING/REPLACING THE P7100 FUEL PLATE

Here's my first attempt at a tech article. I am FAR from an expert at this and any knowledge I've gained is due to reading several tech articles on various websites.

What follows is my interpretation.

IF YOU DON'T HAVE A PYROMETER (EGT) GAUGE INSTALLED STOP READING NOW AND INSTALL ONE FIRST!!!

First step is getting the hood open and locating the Aneroid Fuel Control (AFC). It will be on the driver's rear side of the engine by the brake booster.



Don't be alarmed if you don't see the big red thing. It's a Bank's TwinRam Intake (Or as I call it, Big Stupid Motherf***er that's always in my way) and it's optional. You're probably better off without it.





Once you locate the AFC I would suggest removing the boost line from it first. It's located at the rear of the AFC housing and looks like this.



Now comes the fun part. You can leave your intake on to remove the AFC as there is plenty of room. I have even gotten comfortable working around the TwinRam and no longer remove it. On the engine side of the AFC you'll find a Slotted head bolt towards the rear and what looks like a rivet in the front. This is the factory break-off bolt. There's lots of ways to remove this. My personal method is to drive a sharp chisel into the top of it to create a slot. Then you can use a standard screwdriver to remove the bolt. This picture is taken from the front of the AFC and you will see that I've previously removed my AFC and have replaced the break-off bolt and Slotted head with 2 10mm bolts. Hindsight being what it is, use Allen head bolts to replace these instead of hex head bolts. I just used what I had in my toolbox. Yes, you can drive to the hardware store with only 3 bolts holding the AFC down.



I tend to remove these first but you can remove the fender side bolts first if you want. The fender side AFC bolts are an 8mm head. Once these are removed I pry the fuel shut-off solenoid bracket towards the fender and with a little wiggling the AFC comes out. Once the AFC is out of the way you'll see the fuel plate sitting there.



It is critical at this step that you wipe the area clean and scribe a mark in the pump to show your stock plate location. This will give you a base line for adjusting the plate later. (Most plate kits come with a plastic piece that is molded to fit around the fuel plate and has slots in it to bolt in where the AFC sits on the pump to help you put the plate back in the stock location. If you don't have this then make a scribe mark as I said above.) Go ahead and remove the fuel plate at this time. Or if your only adjusting it just loosen the screws.

This photo shows the Governor Arm.



This arm rides up and down the plate and is responsible for "telling" the pump how much fuel to deliver. You MUST make sure that this arm does not go under the fuel plate once the fuel plate is replaced and adjusted where you want it. If it goes under the plate you'll either need to slide the plate back until the arm hits or adjust the arm level. (Adjusting the arm level is a whole other write up) To check the arm height you'll want to turn the ignition on leaving the engine off then pull up on the fuel shut-off solenoid. After the solenoid is all the way up move the throttle by hand and see if the arm hits the plate. As far as adjusting the fuel plate the basic rule of thumb is towards the front of the engine lets the Governor Arm travel farther forward adding more fuel and towards the firewall lessens the Governor Arm travel reducing fuel. I have found with the plate I use that about 1/16th of an inch from full forward gives me the best power.

Once this is complete put the AFC back onto the pump. You will notice that the bolt holes in the AFC are slotted. This is another adjustment you can make. You can slide the AFC forwards or backwards in these slots. The arm at the bottom of the AFC housing limits also serves to limit how far the Governor Arm can move forward. Once under full boost the AFC really has no effect on the Governor Arm. (You can change the effect the AFC arm has on the Governor Arm by adjusting the Starwheel inside the AFC housing and the "Smoke Screw" in the back of the AFC housing.) Sliding the AFC housing forward lets the Governor Arm travel further forward before being limited by the AFC arm resulting in more power from a stop. Feel free to experiment with this until you're happy with the best setting for your truck and modifications.

CONTINUED BELOW.

Last edited by Johnny Cetane; 07-28-2007 at 03:11 PM.
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Old 07-28-2007, 03:01 PM
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One more adjustment you can make is the Starwheel inside the AFC. It is located inside the 8mm Allen head plug on top of the AFC housing. This Starwheel basically controls the preload on that AFC arm I mentioned above. Adjusting it forward lessens the preload while adjusting it backwards increases it. Once you have the AFC where you want it use this to fine tune the setting. You'll want to adjust this so that you only have a slight "puff" of black smoke under initial throttle. Any more and you are only wasting fuel. (Some people adjust the AFC and the Starwheel full forward in an attempt to get the truck to smoke. While doing this will make your truck smoke more, this is not their purpose. You will also raise your EGT's and possibly decrease power by doing this.)



Now that you're all adjusted up it's time for one of these. (I tend to start all projects with one just for good measure.) Feline mix inspector optional.





Feel free to post below and correct any terminology I've gotten wrong or any steps/warnings that I might have missed. Please don't nit-pick just for the sake of nit-picking.

Possibly we can make this a sticky if everyone agrees it's useful and important enough.

Last edited by Johnny Cetane; 07-28-2007 at 03:15 PM.
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Old 07-28-2007, 03:07 PM
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Excellent info and great job stud

you are the man of the hour.....enjoy
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Old 07-28-2007, 03:19 PM
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Whit, seriously, coming from you that comment really means alot bud as i've always considered you an expert and have learned tons of info off of your posts and articles.
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Old 07-28-2007, 05:39 PM
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Well Done Thanks Johnny!

DM
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Old 07-29-2007, 03:58 AM
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, bud. you're another one i owe alot too. a certain database you may or may not have helped create gave me the knowledge to do this the first time.
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Old 07-30-2007, 09:55 AM
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i do need a bigger bottle of rum, doc. that one didn't live through the night.

WTF is a macro button. i might even have one and not know it.
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Old 07-30-2007, 10:09 AM
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Macro is for close ups (looks like a little flower)...
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Old 07-30-2007, 10:26 AM
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oh yeah i have one of those. i was using it but i was i lil shaky. too much fun friday night.
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Old 07-30-2007, 10:27 AM
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I should have seen the rum and put two and two together....
 
 
 

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