According to the gauge I've almost emptied the front tank. I'll run it dry and switch to the rear to get hard and fast numbers but if my gauge is close to accurate I'm getting about 10 mpg on my 97 350 with the 351 auto.

I'm aware I should expect crap mileage from a giant truck but that doesn't mean I shouldn't try to improve it. The seller told me a previous owner had pulled the emissions equipment. I hear that the EGR will help improve mileage a little bit so I figure I should look and see if it's blocked off or not then hunt to see how bad it will be to fix.
I'm not sure what the valve will look like though. I'm assuming some sort of tube between the exhaust/headers and the intake. Can anyone show me a picture of what I'm looking for?

 

I don't have a picture and the camera batteries are dead but in you open the hood and look at the motor, the egr is on the passenger side of the motor, right above the first spark plug at the front. It is mounted to the front left side of the upper intake and is (vaguely) mushroom shaped. It has a metal tube coming out of the bottom that goes down to the front of the pass side exhaust manifold. There is also an electrical connector plugged into the top of it. Hope that helps.

As a side note, the fuel gauges on these trucks are pessimistic, I find, and I usually can travel quite a ways when the gauge says empty.

 

Manufacturer Info

The Photo link above is for a non-California emissioned truck. It would attach to the passenger side of the upper intake manifold just behind the throttle body. The EGR tube for the 351 runs up from the front of the passenger side exhaust manifold to the EGR. The vacuum tube runs to the EVR on the driver's side of the intake valley, which in turn gets its vacuum supply from the vacuum can (which has a one way valve on it, and its vacuum supply comes from the motor.

You should consider how well in tune your motor is, the mileage, gearing, tire size, and your driving characteristics for fuel mileage as well.

 

I wouldn't count on your gas gauge being anywhere near accurate. See how much gas you've actually used and do the math.

Removing the emissions equipment can mean different things. If the EGR has been removed then you should definitely put it back on, it will get better mileage for sure with it.

 

ok so it looks like this is the EGR valve


so that is in place. However on the opposite side I find this unplugged and plugged vacuum hose

so is it safe to assume that this is the EVR and it should be hooked up to have this system working?

I'm not getting a check engine light and the bulb is working so I assume the computer has been tampered with as well?

More info, I drive slower then my dead and buried grandma, the truck has 4.10 gears the tires are stock size 235/85-16's I just replaced the old dead set that was under inflated with a new set of properly inflated goodyear silent armors. They shouldn't hurt the mileage and the proper inflation should help. I did 200 km on the old tires, 100 on the new so far.

 

Are you talking about the green plastic vacuum line just to the left (in the picture) of the ignition coil? That should be hooked up to the EVR for proper EGR operation. The large open tube in the center of the picture is the air injection bypass silencer and should be open as pictured.

The check engine light should come on when the key is in the run position before the engine is started, so you can check the bulb. It is also possible for codes to be stored without triggering the check engine light, so it might also be worthwhile to pull the codes and see what comes up.

 

nope right in the center of the picture there is a short red hose with a screw in the end.

I'll grab a computer and check for codes tonight

 

Oh I see it now. It looked at first like it was plugged into the bypass/diverter valve, but I can see the screw now. Does that connect on the other end to the EVR solenoid (red wire, green vacuum tube)? How far will that red hose reach? The fuel pressure regulator also uses a red plastic vacuum hose, which could cause fuel mileage issues if that was unplugged.

 

This is a pic of the EGR valve.




This is a pic of part of the thermactor(air injection) system, it has NOTHING to do with the EGR. The capped pink line would normally be connected to the open nipple on the diverter valve visible just to the left of the vacuum line. That valve and another down by the air pump are controlled by the TAB and TAD solenoids by the coil, see next picture.
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Neither of these system affect fuel milage a great deal, if your truck has a 3speed auto then you can forget getting good milage at speeds above 60mph. if you have OD then look at fuel pressure and for the transfer problem between tanks.

 

I have overdrive and never get above 55 (90km/h) anyways.

At this point i need to wait for the tank to run dry and get some hard numbers. I've been below empty for 50 km now and still haven't had a sign that it's empty. This gives me 340 km to the front tank. Way better then the 300 I was at when I hit E. I still don't see making the 400 I was hoping for though.

 

That red line with the screw in it attaches very close to where its at. Just to the passenger side and down is the diverter/bypass valve vacuum nipple it is to attach to. As I am not familiar with your air injection system routing I dont know which valve it is from the picture. Just guessing it is the bypass valve which it may always be dumping to atmosphere instead of pushing the air to the diverter valve. It wouldn't throw a code as only the switch underneath of it is monitored by the computer and as long as the computer sees the rtn signal from the switch it thinks the system is working.

 

In the second photo in this thread the Thermactor bypass valve has the front of the valve just running into atmosphere. In the photo the opening is near the center of the photo at the bottom of the photo. I have purchased a new to me 1997 F-350 with 351W and noticed mine is the exact same way. Is that correct or is that supposed to be hooked somewhere? I could not find any where there is an open port on the intake etc so I am guessing this is correct. I have been working on cars for years and this is my first truck.

Many thanks and sorry for reviving an old thread. It just happens to show the exact part I have questions about.

Shane

 

It is supposed to be OPEN.... Re read post #6.

 

Yep it's supposed to be open.

I figured out the mileage issue as well.

first - the gas gauge/senders are crap. 80+km still to go when I hit E.

Second - at that time the brakes were in various stages of being frozen on. I gained 25% in mileage when I replaced everything from the master cylinder back.

Third - the truck is huge, weighs a lot, has an auto(with OD) and has 4.10 gears. Good mileage is never going to happen.

 

I feel dumb for missing that. Thanks!