*Thank you in advance for reading this lengthy post.*

Well, my truck has been totally problem free since I replaced my rear brake lines about a month ago, so now I'm able to turn my attention to my other concerns in the truck.

Basically, the truck is a dog. I know that they aren't as "peppy" as the second gen 7.3, but holy cow, mine is just a PIG. I'll try my best to relay everything I've observed, and hopefully y'all can help me make some sense of it all.

- Abysmal fuel economy. Sitting right at 7.5MPG average. My driving habits (short commute, lots of idling in cold weather) have something to do with that I'm sure, but the worst city fuel economy I've seen others reporting is 10-12.

- Appears to build boost slowly, has low boost. Note that my only point of reference is a '00 7.3 with a chip that just screams, I don't have any other stock first gen 7.3 to compare to. But the highest boost I've seen is 12 PSI according to Torque Pro, and that's at WOT in 3rd while pulling a hill. According to what I've seen on here, other members with stock OBS trucks have no problem hitting 18-20. On a tangential note, I've read that boost leaks will kill fuel economy. Possibly these are related?

- SUPER doggy when cold. Now, because I bought this truck in December, I've driven it in winter conditions only, literally as long as I've owned it, so I don't know if this behavior will continue in warmer weather. But when it's cold, if it doesn't have a LONG warm up time (15-20 minutes) then when I start driving, I can floor it and it is SLOW to accelerate. And it will rev up close to 3000 RPM in second gear (I believe) at about 30 MPH and just won't upshift. Eventually it accelerates enough to upshift, but wow it takes awhile.

- Weird sound on hot starts. It doesn't have any issue with hot starts like extended cranking times or whatever that would normally be attributed to injector o-ring issues, but it does do something weird. On hot starts, it will fire within a second or two as usual, but then it'll lope, just once, and then idle up as normal. You guys know what a loping diesel sounds like, well this will happen one time the second it starts, then idles normally. Haven't been able to find any info on this online. According to Torque, the HPOP hit about 1400PSI when it started when I tested it today. Although it's possible it went higher momentarily and just didn't display on m app. I always read that it takes a minimum of 2000PSI to start.

- Torque Pro numbers, pulled today:

Hot idle:

EOT 166.6
IPR 12.0-12.4% (fluctuates)
HPOP 581 PSI

3rd gear, WOT at the top of a hill:

EOT 173.3
IPR 32.9%
HPOP 2480 PSI (The truck will hold 2500 most of the time but I was watching for max boost and took the screenshot as it dipped to 2480)
Boost: 12.1 PSI

In both instances the IPR seems to be good (from what I understand "good" values are) but the HPOP pressure at WOT seems low, and boost definitely seems low. Thoughts?

- Additional thought, is it possible the dogginess could be explained by a clogged catalytic converter? I want to delete it, just haven't gotten to it yet.

I want to try and get this truck running in tip-top shape, for a stock truck. Then and only then will I start pursuing some mild performance upgrades.

Thanks for all your input, guys. It's been a huge help to me.

 

What is fuel pressure at idle and at WOT in third?
Does it blow black smoke?
Have you done a boost leak?

 

Fuel pressure I've not tested. I haven't found a testing procedure online that I really understand. I'm sure they're out there, I just haven't searched for them yet. I've only seen abbreviated "how-tos" in other posts. However, when I had the truck in the shop for a no start issue, I was told "fuel pressure looks good, 50 PSI." I didn't think to ask how they tested it at the time, but the guy is a lifelong diesel mechanic for everything from pickup trucks to semis to heavy equipment. Presumably he knows something about them. In any event, that's the only info on fuel pressure I have, and I know it isn't much.

Never seen a lick of black smoke out of the truck, or even a haze. Never.

Haven't checked for boost leaks yet. Still trying to understand the testing procedure for this as well. That was part of the plan for tomorrow, at least to figure out what I need as far as fittings/parts to conduct the test and get everything bought.

 

A clogged cat will for sure make it doggy.

As for fuel pressure, you can check it with a tire gauge on the schrader valve on the side of the fuel bowl. Just be careful you don't get sprayed with diesel.

Checking for boost leaks you need to build a piece to put in the intake before the turbo and put about 20 psi of air to it and spray soapy water or the like around to see.

It takes about 550 psi on the hpop to start, not 2000. I'd guess your psi is close for a stock truck at wot.

 

1. Can you monitor "Exhaust Back Pressure" with your scanner? That will answer a lot of questions.

2. On cold startups the EBPV (valve) will cycle closed then open. Does it do that? You can watch the valve mechanism to verify while someone starts the truck. Should occur within 5-10 seconds after startup. Sometimes they will stick closed causing poor power, MPG and high back pressure issues.

3. These rigs don't have cats but a particulate filter, although it looks like a cat. A clogged cat will definitely cause high back pressure, although rare it does happen.

 

Thanks for the replies, guys.

- I thought the truck needed 2000 PSI to start, and 500 PSI was idle. If that's not the case, then is the way my truck acts on hot starts normal? Or is there still something off, and I'm just looking in the wrong direction by suspecting the HPOP pressure?

- Still not following with the fuel pressure test. I thought it was supposed to be tested while driving? Not sure how you can do that with a tire gauge?

- You say "put the piece in the intake before the turbo." Any particular spot? What is the "piece" that I need? I seem to recall reading about PVC fittings? I assume it doesn't go in to the actual air intake on the truck (mine is the stock intake).

- I can monitor EBP. I'll pull values today and post them up for interpretation.
Anything else that would be worth checking while I'm there?

- My EBPV is unplugged, although I can't say with certainty that it's stuck *open*. Can I determine whether it's open or closed simply by looking at the mechanism standing beside the truck?

 

The valve should be open, look at post #2 below ...

https://www.ford-trucks.com/forums/1...ebp-valve.html

Oil pressure pushes on the rod and that closes the butterfly valve, with a working EBPV system.

 

Thanks. That makes sense.

 

So I got a few more numbers to report.

First off, on a cold start, the HPOP jumps to 2200 PSI max. I've only watched the hot start once, but that time it peaked at 1400 PSI.

EBP at idle is 14.3 PSI. Max at WOT was 25 PSI. About 19 cruising.

Today I was able to "get on it" on a flat straightaway from a stop, with a hot engine, and it did feel more peppy than it has in the past. Perhaps my perception was somewhat skewed because up until now I've only been able to floor it from cruising speed. During this test it hit 13 PSI boost right before the upshift to third.

 

I know I posted this in the OP but it happened again yesterday, seemingly worse than before, so I wanted to mention it again. Hopefully someone can shed some light on whether this is normal or not.

It was maybe 20-25 degrees out, went out and started the truck, hopped in and drove away. Pulled on to the main road, and with the pedal floored it was running about 10mph, high rpm. I pulled over in to the next driveway, just let it idle a minute more, and then pulled out. This time it would go up to about 20. Pulled over again, let it idle again, then when I got back on the road it would get up to speed.

Wondering if this is some type of engine or transmission protection deal in the computer?

 

I can tell you what I think the problem is, but don't know for a fact. Back in 2007 is when I purchased my 97. During that year and into early 2008 I did experience what you are describing. The problem always went away but it was somewhat concerning. One thing I noticed was it was when first started or during long periods of idle, low EGT's.

I felt my CAT (actually a particulate filter) was probably clogging up due to low exhaust temps and of course old age. I finnanly just deleted it sometime in 2008 and have not experienced the issue since.

Once removed I did some inspection and actually cut the CAT in half. Inside there is packed extremely small mesh wires (line a screen) from one end to the other. Below is a picture of the actual CAT cut in half on the right. The picture on the left is where I held the CAT up looking into the Sun and took a picture from the intake end. The bright spot is about the size of a dime showing sunlight and the rest is diesel particulates clogging it, I guess.



It's not to hard to remove the CAT. It just unbolts from the down pipe but removing it from exhaust pipe is changeling. Most just cut it off at that point and install a CAT delete exhaust pipe from down pipe to exhaust pipe.

 

Use band clamps on the ends of the delete pipe so if you ever face an inspection you can put it back on real quick.

 

Yep. Cat delete is in the works. Just gotta pull the trigger on the delete pipe. I'm still shopping around, I'd rather not spend $50 shipping on a $40 delete pipe unless it's the only option.

 

Awhile back I helped a local guy just gut his CAT. It's not hard, just use a piece of re bar to beat out the inside stuff. Kind of messy so wearing a mask is recommended, then reinstall using a band clamp on the rear. Depends where you live, here in Oregon these diesels are exempt on emission inspection.

 

Alaska has no inspections of any kind.

I'm a welder by trade, I'm thinking it may be easier to just buy a length of exhaust tubing the appropriate length, and remove the flange from the cat, weld it to the new tube, and bolt it right back to the pipes.