Cleatus12r can run circles around me in my wheelchair with experience on the 7.3L, but I know a bit about sensors and I say there are a few things we can look at before we rip into turbos and stuff.

Cleatus12r - I have a quick question, just to make sure I'm not chewin' on shoe laces: Doesn't thePCM use the MAP signal to decide how to control the fuel dosage and timing?

SNIPER168308 - You say you're getting 1.5 pounds of boost at 55 MPH. OK. I don't know if you have a speed limit above 55 near you, but it would be nice to know if you can get up to 4 PSI with the cruise control set at 60-65 MPH on the flat with no wind. We have more resolution to compare at the higher speeds: 1.5 pounds of boost makes it hard to see a 10% or 20% discrepency. As for the MAP reading at KOEO, you can look directly at the voltage with a meter.

https://www.ford-trucks.com/forums/a...1&d=1334277856

 

Fuel only and it's in regards to limit fuel "dosage" at low boost levels for smoke control. Speaking in generalities, on most 99-03 trucks, anything over 12 PSI is going to command max fuel (as long as the RPM is between about 2100 and 2800 RPM) with stock tuning.

 

Here's my less-obscure take on this whole thread:

People are far too quick to just start blurting out suggestions regarding "fixes" for a problem, that in my mind, doesn't exist. It's an 8000+ lb. truck (brick). Those mileage figures look right in line with what I'd expect for coming/going trips and towing. Keep in mind that taking a road trip somewhere will ALWAYS result in an average of elevation loss or gain...and it will be completely opposite on the return trip. Where I'm at, head winds wreak havoc with fuel consumption heading west; and that's also the uphill direction for me.

If the truck runs fine (perceptibly) with no abnormal noise, smoke, missing, roughness, etc., then NOTHING you come up with on a "buzz test" or "contribution test" is going to give you any definitive answers. Those tests are an absolute waste of time and people put far too much stock in them. Hell, even when there is nothing wrong with the truck (like when it was driven off the showroom floor 15 years ago), it STILL came up with false data. In a nutshell, a buzz test will tell you NOTHING and will be a huge waste of time in this case. I'm surprised that nobody mentioned valve cover harnesses yet.

To the OP, if you NEED to maximize fuel mileage due to fuel price concerns, stop driving a truck. It's that simple. Oh, and I prefer 150gr. SPBT in my 308.

 

Although fuel gains can't be guaranteed, I think the obvious is being ignored. Sometimes the simplest thing is the culprit. Going from 19.2 to 14.2, I'd be pissed losing 5 miles per gallon overnight. Talk about biting at the pump.

With that said, I would not discount a possible injector issue having this huge decrease in fuel mileage. Only saying because of personal experience. This is why having a scan tool on hand is important. Take a look at the fuel filter. Make sure the fuel pump is working correctly. Staving the injectors will ruin them and kill your fuel mileage. This leads to cracking a nozzle and potentially hydro-locking the motor. Have the fuel checked from the station you went to. Very concerned the station got a bad batch of fuel.


Diane

 

I guess I'll go ahead and break it to you. 40 isn't that big a deal. Compared to Gene you're easily considered a young buck. Heck age is relevant anyway. What you consider old today is different than what you considered old 15 years ago. I've got a neighbor that sold his place and moved to a newer house on only 2 acres on the other side of town when he hit 65. I was talking to another neighbor about it who's 89 and his comment was he knew that kid wouldn't stay out in the country and he would give up and move back to town. (He thought that "boy" was trouble when he was younger and that the "girl" he married could have done better)

 

It's hard for an engine to "run great" (and I'll take that as meaning "has plenty of power"). If a fuel filter or pump can pass enough fuel to have good power, then it's hard to imagine that there would be a problem at a much lower demand. Besides, there are quite a few other symptoms that go along with a lack of fuel supply and "runs great" isn't one of them.

Good grief. These last 17 posts are going to be TOUGH.

 

[quote=F350-6;12478080]
Now for a question from me. Two injector changes? I assume you mean you have replaced two different injectors at separate times? Why did you replace them, and how did you determine they needed to be replaced, and what did you replace them with?

Also, are you filling up to the exact same "full" point each time you calculate your mileage?[/quote]


Yes, two injectors... One was acting up at the Dealership. The tech told me it needed replaced, so it was. The other was an injector failure on the way to work at 0600. It just stopped working. Cyl. Contribution test pointed out that culprit. Not sure which injectors. I know the Style (AB, AC, etc) was matched with the others. I bought new injectors, they were either Alliant or Bosch, I just don't remember. Yes, I fuel at the same location/ pump each time, to the same level..

 

I replaced the Injector Harness several years ago, as suggested by the Ford Diesel Tech. (who advised the factory ones have a high failure rate) Also did the .50 cent mod as a precaution.

I just remembered a couple things. First, when I bought the truck from my brother, some yrs ago, he said he was getting 17-19 mpg out of it. I got 19 ish, when I drove it home from his house 160 miles away. I put a K&N filter on it, and watched the MPG's fall off the planet. Then I learned K&N flat filters will not feed the 7.3's needs. I removed the K&N and went back stock. Now I run the big WIX. The 17-19 MPG never returned on a consistent basis..

Second; Once upon a time, the engine would make (what I describe) as a "deep in the bowel's groan" (I presume, good boost and fuel delivery) when I dropped the hammer on it. The sound would change, under WOT, to what I just described and the injectors would dramatically quieten down, as it was making good power. Now it seems the Injectors make more noise and I don't get the "groan" I once did at WOT.

 

As many have suggested, I need to get a ScanTool and get it checked out.. I know a reputible mechanic who can do such and will not charge me a forturne. Tell me exactly what to look at, besides what's already listed in this thread? Will the Scan Tool give me real time fuel pressure data when driving? or do I just need to hook up gauge and take it for a spin?

The other morning, on my way to the deer stand, I paid close attn to the ScanGauge II readings. I drove 70mph, very little wind, level roadway: Boost 4.7, ICP-1537, EBP-22.8, IPR-24

 

Honestly, there isn't anything that a scan tool will show you that will "tell" you anything about your assumed poor mileage.

There is no fuel pressure input to the PCM so you'll have to attach a mechanical gauge for that one.

 

Interesting. Which injector did the dealer replace because it was acting up? #8 because the computer said it was acting up? Perhaps #3 instead of #8?

I'd guess there's a fair chance you didn't need that injector from the dealer. I'd also guess they stuck a reman injector in since Ford no longer deals in new injectors for our trucks. (unless you replaced it yourself based on their diagnosis).

How did the other injector stop working? Usually a failure on the electrical side will cause the IDM to shut down the entire bank. Broken nozzles on old injectors while driving would be rare. What was the mode of failure and how did you determine which injector was bad?

 

Quote:

Originally Posted by F350-6

Interesting. Which injector did the dealer replace because it was acting up? #8 because the computer said it was acting up? Perhaps #3 instead of #8?

The second injector was on the passenger bank, I just don't remember which one... I'm not sure what the failure was, I just know when it was buzz tested, little to no response from injector, and the cyl contribution test showed it being dead... and, I purchased the "new" injectors from an International Dealer in Florida. (I really don't trust some of the reman stuff) Sorry, I don't remember who... been about 4 yrs now.

 

I know I opened a can of pondering and different avenues of diagnosing problems. But, I don't trust some of these "self-proclaimed" diesel tech or even some from the dealers. My experience has been from them is to "throw parts at it", as long as your wallet holds out, and maybe we'll get lucky. For example, several yrs ago I owned a 94 Bronco that would start shifting really hard when the ambient temps would exceed 85 degs. I mean "shift hard" as in, when driving normal w/ no load, it would shift from 1-2 or 3-4 was like doing a neutral drop. The engine would continue to rev up well past the shift point, then it would slam into the next gear. Long story short, the Dealership, Trans-shops, and everyone else wanted to replace the tranny for $2k, I told them I didn't believe it to be a tranny issue. I called everywhere looking for the best tech in the business, when I was told of a tech at a dealership in Oklahoma, whose one of the best, when he comes to work. Apparently he had a drinking problem and was a bit rough around the edges. Took it to him. He agreed, it wasn't the tranny. He narrowed the issue down to the PSOM loosing AC voltage on an intermittant basis. (of course it took two multi testers hardwired into the system and checking the voltage when it would start the shifting issue).. Bottom line, he diagnosed the problem (said he hates just throwing parts at issues) and it cost me $150 for a PSOM, a couple after hr trips to the shop, $100 bill and a case of beer to the tech. So, now I research as much as I can and do the work myself. And, did I mention that a shop put in a right front drum brake auto adjuster in backwards that causes me to roll a pickup? Another reason I do my own wrench turning.

Sorry for the story, but I do appreciate everyone's input. Give's me areas to look and things to eliminate from the equation.. Thanks again..

 

cletus12r:: a side note... I shoot 180gr Nosler Bonded bullets, either loaded by me or the same in Black Hills Match (for work), out to 1000 yds. Stopped shooting the 168 Sierra, good flight ballistics and accuracy, but unpredictable upon impact (wound ballistics)..

Sorry fellas, need to get back to the topic at hand....

 

Which is why I'm once again giving up on trying to change the internet forum world. Everybody wants you to throw parts at your truck based on regurgitated guesses and it irritates the **** out of me. Oh well.....

Good luck with your issue.