power loss in 3406b cat

AFRC Diaphragm replacement.
Part # 6I1564

[@johngoldsmith6629]

Your Air Fuel Ratio Control Valve (FRC), is used to restrict fuel until you have sufficient turbo psi, mainly on acceleration. You two types on a 3406B/C Cat, 1989 and back cocks with turbo psi, and 1990 and up cocks with oil psi. The difference is in the bottom valve and you cannot tell which you have by looking at it. So you may not know which style you have. The mounting seals to the rear of the governor housing is serial number specific. Also in the governor housing is a filter, 2N6680 and a 2D6392 seal. I recommend to replace them if FRC is off. The early FRC's used on 7FB engines had a extra screw under the outer cover. Theses was used for CARB engines. If your engine is not a CARB, I always remove it as it drags on the adjustment shaft. Next is the outer cover, type one used a gasket. When Cat was forced to remove asbestos out of gaskets, the replacement gasket was cheap and it would blow out. Also Cat changed the material in the outer cover and it was cheap and the cover would warp. Thus you had a boost leak around the gasket joint. Then Cat changed the cover material and made it better, along with an improved gasket. Second type used an o-ring which is better. However you cannot put the o-ring cover on the old style unless you change the matting cover, as it has holes in it and you won't seal the boost off. Next where the valve hooks into the governor, sometimes it can drag on the side of the valve. When I have the governor off. I take that part out and on both outer sides, I use a washer out of a PEEC 4CK timing advance. They still allow side movement but now they won't drag on the shaft. Testing, you can get a small radiator pump and make up a hose. Remove FRC intake tube and connect the pump. PSI test it to a max of 15 PSI. Naturally if it won't build any psi your diaphragm is blown, or you can have a small leak if psi drops of slowly. Leak can be the outer cover or more than likely a worn seal in the adjustment shaft.Other option is to get a block off plate and install it in place of FRC. If problem goes away, repair your FRC. Repairing, take FRC completely apart. You have a seal in the bottom around the valve. Also the valve sometimes drags on the housing. Take emery cloth and polish up the valve and inner part of the lower housing. Adjustment housing, (aluminum part), count the threads above the nut. Make a note of how many is above the nut and take it apart. The seal use to be a 7J0204, that would leak over time. The improved seal is a 3E6760. Aluminum housing part, (what the diaphragm set on), the bottom edge comes in contact with the metal spring retainer. It can cause the edge to become sharp. I have seen it cut a brand new diaphragm. Take the aluminium part and put a beveled edge where it contacts the metal spring retainer. Bottom valve, check for excessive wear where it hooks. Also the stem screws into the valve, make sure it is not loose. Have seen them unscrew and fall off into the governor. Put clean oil on the lower parts and assemble. Installing, make sure it hooks on the inner lever in the governor housing. Adjusting, leave outer cover off. Start the engine and push in on the valve to cock it, (as you may not know which type you have). Rev the engine up real fast and look at exhaust smoke and how fast engine speeds up. Loosen nut and turn the screw out to reduce smoke, slower response, cleaner burn, not wasting fuel. Turn screw in for faster response, more black smoke, wasting fuel. Find the spot that you are happy with. If your in a EPA state it will have to be set with a dial indicator.

[@hedgeborn92]

Excellent job, good troubleshooting and repair bro

[@RJ1999x]

You dont want a hole in your rubber!

[@jjoneshauling6104]

Great video. I have the 3406b fld. Jst trying to learn as much as possible about my motor. Im in houston jst wondering where did you get your pump rebuilt and what price range should i expect. Thanks

[@tylerkeleman8933]

I’m having this same issue right now on my 1984 Peterbilt 359. I also have a 3406B.. It’s normal power until I hit the splitter and it doesn’t want to go any faster than 60. I had my fuel injector pump rebuilt and new fuel lines.. I’m going to try this and see if it works as well

[@wesleyjackson200]

Did that fix your problem? I always start with the fuel filters first.

[@eusebiohernandez7146]

Same issue I was having. Just finished replacing this & problem solved ! $7-$8 part at CAT dealer here in Irving TX.

[@tylerkeleman8933]

@@wesleyjackson200hey I’m glad you commented back. No it did not. But my issue is fixed I’m thinking I had bad fuel and it made it past my filters I’m not sure what exactly but I ran it out completely like even used the hand pump and ran the last bit out and haven’t had an issue sense

[@eddiemendoza3908]

Do you know the part number

[@eddiemendoza3908]

@@eusebiohernandez7146 do you know the part number

[@americanmuscleup2497]

Did this fix your problem ? Mine is similar to your when I pulled it out and it is hard waiting to get the diaphragm from cat in the morning

[@wesleyjackson200]

Sorry so late to respond but yes it did. I bought 3 extra just to have on hand. They were cheap

[@americanmuscleup2497]

@@wesleyjackson200 I did the same for $6 can’t beat it

[@user-rf3yi5if6k]

I need one

[@wesleyjackson200]

What do you need?