ISX: Wanna come to Virginia for a weekend?

[Rogan]

I'll cover your room & board, and lotsa good grilling/smoking cow and pig... :)Just bring your specialty tools for timing and such.. I need your 12V expertise..

[ISX]

Whats the problem lol. I have you and this other guy who want me to stare at their engines but I am broke (college) and yeah it comes up to $300 round trip for gas (same for him almost, ironically enough).. A shop would set your timing for half that. Well, unless it was the shop that I went to and paid half that and all they did was loosen the nut and kick the engine then tighten it. I can show you how to do that easily

[Rogan]

What's the problem?low powerpoor fuel economytimingrocker adjustment........ filled up yesterday, 8.9mpg

[ISX]

Jeessuss! You sure it's not the tranny? If it locks up then I guess I couldn't imagine 8mpg. Does it smoke or start bad or anything at all? Gauge readings?

[Rogan]

everything 'appears' normal.only some hazing exhaust on cold morning starts. Aside from that, it rarely rolls coal unless i flatten the go-pedal.Starts fairly easy, but seems to have no top end. No exaggeration, it's a STRUGGLE to keep the truck above 60mph. Just seems to take way too much pedal to do so.sub 45mph, and it feels okay.. any time I call for more power or speed, though, it just seems as though it doesn't want to do it.

[ISX]

Do you have any gauges on it at all? Boost and EGT would help a lot haha. Maybe even fuel pressure.

[Rogan]

I don't have FP, but do have BST and EGT.EGTs at 60 mph usually hover around 6-700 and boost ~3-6psi, not towing.Towing the 20ft enclosed, the psi goes to around 7-12psi, and the EGT climbs to the 800-ish mark, IIRC..This is with mostly flat roadway and small hilly sections.towing/cruising, the trans temp (when locked) hovers around the 140-160 range.The EGT probe is in the downpipe, though, post-turbo.. I didn't put it there, mind you.. :ashamed:I live a few miles from work (7) and it's mostly all city/rural travel, with some stoplights. I can plug it in at 5am, start the truck at 7, leave at 7:10, be at work by 730, and the coolant temp 'may' be up to around 160-170, if I am lucky.If I don't plug it in, it's closer to like 140-155ish by the time I get to work.(the above stuff is with high 20-low 30 ambient temps.)

[ISX]

According to this http://www.cumminsforum.com/forum/89-93-tech-articles/25484-egts-pre-post-turbo.html that means your EGT's are pretty damn high. Basically the temps you see are what I see pre turbo.. However, everything else you mention is completely normal. This 8mpg thing though....was that unloaded driving? If you just doing stop and go and it's always under operating temp then that will have a big effect, though not 8mpg big What do you get pulling the trailer on the highway?

[Rogan]

According to this http://www.cumminsforum.com/forum/89-93-tech-articles/25484-egts-pre-post-turbo.html that means your EGT's are pretty damn high. Basically the temps you see are what I see pre turbo.. However, everything else you mention is completely normal. This 8mpg thing though....was that unloaded driving? If you just doing stop and go and it's always under operating temp then that will have a big effect, though not 8mpg big What do you get pulling the trailer on the highway?

This was the first time I've gotten THAT low mpg in it, but it's always been low. Normally, I get a consistent 12-12.5mpg, whether towing or not, over the course of a tank. Sometimes (in the summer, when I'm towing a lot) I'll fill up after towing the trailer 100%, and average hand-calculated 12.0-12.5mpg. It would bump ever so slightly, maybe 13, if I didn't tow, or towed very little amount of the time. It has 235-85 ATs (about worn out), 4.10:1, auto, no boost elbow, #0 plate (set middle, IIRC), and star untouched, afaik. I need to scale it, since it has the Western Hauler bed, to get an accurate weight. My '96 5spd 3.55 SCLB 2500 would get mid-high 20s on the highway.

[stodg73]

I don't have FP, but do have BST and EGT. EGTs at 60 mph usually hover around 6-700 and boost ~3-6psi, not towing. The EGT probe is in the downpipe, though, post-turbo.. I didn't put it there, mind you..

Add anywhere between 200* to 300* to your EGT for your newer readings. You are using lots of fuel. You might think about going to a bigger tire to get a better ratio.

[Rogan]

Well, I know I've seen 1100*F + towing up some 6-8% grades at speed, so I can only imagine how hot it "really" was.. :whistle:I know it's using a lot of fuel, but the tailpipe isn't saying that, which is confusing. My '96 smoked like a freight train every time you flicked the go-pedal, and got almost 2 times the economy.It also felt strong as hell and would flat out haul asss...This one is responsive down low in the rpms, but quite lethargic and feels like it runs out of steam above 50mph. Just to maintain 65mph (about 24-2500rpm) while towing, I'm deep into the throttle..

[ISX]

The only thing I can think of is bad fuel pressure, along with other things. The P7100 will actually suck in fuel on it's own, I talk to a guy who has started it with his raptor turned off. I'm sure not as much fuel gets into the plungers but it does run. But the "other things" I mean is dirty injectors, timing is off, etc.. I just can't see 8 damn MPG out of any one thing, though the guys on CF seem to pull it off haha. In other words, I have a pop tester, compression tester, can clean injectors, can set the timing, can test fuel pressure, and check other crap on the engine....but if it's beyond that (in the transmission or something) then it's beyond me.. I've spent my whole time with the engine on my truck so besides the 5th gear nut, brakes, u joints...I can't say which stuff beyond the engine would cause it, other than the common brake drag thing. I will say this though, it does sound like something in the engine haha. Possibly just a bad overflow valve causing the low fuel pressure which is why you have to give it more fuel to get anywhere. The EGT's are high because it retards the timing when it does this. Basically at say, idle, the whole thing is full of fuel, as the plunger goes up it covers the spill port for a second and injects some fuel then the spill port is uncovered and the rest of the fuel above the plunger gets shoved down the vertical slot and forced out of the spill port. When it comes back down, it fills back up until the spill port is covered for that second again and forms a void (vacuum air pocket thinger) above the plunger. But it's a small void equal to the amount of fuel injected since the spill port is covered for the same duration during the upstroke and downstroke (if throttle remains the same). So the plunger forms the void but keeps going down and then uncovers the spill port again so the spill port can then fill up the void as the plunger waits for it's turn to inject fuel. SOO!!! IFFFFFF that void ISN'T able to be filled by the spill port for whatever reason (low fuel pressure, too small of spill port hole, etc.) then what happens? The plunger goes up, covers the spill port, but then instead of injecting fuel, it just compresses the void back into nothing until the fuel fills the gap, meaning injection is late, also known as retarded... Retarded timing has NO top end. Maybe you saw my video of 0* timing, it wouldn't even run past 1500 (maybe it would if I let it warm up, but the point got across). It also means you have to be farther down on the pedal to get it to the same "power" as before, since a void of fuel obviously has en effect on power...you need fuel to make power.. So at WOT you might be the same as 1/2 throttle on a truck with good fuel pressure.You can be really cheap about it and just unscrew the bleed screw and screw a hose fitting in there and to your gauge and even a needle valve. Then just rev it up and see what happens. If it is under 25psi at like 2000RPM then you got a problem. Though it sounds to be more like it's running at under 20psi. If you do have that issue, you can take some pliers and clamp the return line when it goes to a rubber hose past the back of the injection pump. You don't close it off, just apply pressure and see if you can get fuel pressure out of it. Aim to see 35psi at least. If you are able to completely clamp it off and still nothing, then the lift pump is junk. Basically you are doing the overflow valves job for it. The springs in them get weak routinely. MAKE SURE you use something to round the edges of whatever you clamp the hose with...you wouldn't want to cut the fuel line up with the sharp edge of some pliers. I use those vice grips, 11R's or whatever, they have rounded over ends. Or I'll come fix the thing haha

[dorkweed]

How many miles on this engine???? Any blowby????? Ever done an oil analysis to see what that says??

[Rogan]

135-140k I believe..I've never done an oil analysis. No blow-by, no oil smell, no nothing..

[dobienut]

Dang ISX....go fix that thing!

[Mopar1973Man]

I think ISX has it correct its going to be fuel pressure related most likely. Since everyone with a P7100 pump knows that fuel pressure isn't a issue (or is it?!). So I would follow ISX idea of checking the fuel pressure and the over flow valve to verify if there any fuel system issues. I gotta admit with ISX everything has to be measured one way or another (no guessin'). Here is a killer tidbit... http://www.torkteknology.com/products/TORK-TEK-CUMMINS-ADJUSTABLE-OVERFLOW-VALVE-OFV020.html

[Rogan]

coolant temp 145, ambient 40. 40mph in OD. [ATTACH]4883[/ATTACH]Sent from my SPH-L710 using Tapatalk 2

[Mopar1973Man]

coolant temp 145, ambient 40. 40mph in OD. [ATTACH]4883[/ATTACH] Sent from my SPH-L710 using Tapatalk 2

Too cold you need to get you coolant temp up more. But the pyro and boost would look good for 55 MPH but alias you only rolling 40 MPH.

[Rogan]

I'd have to idle it for a long time before leaving, in order to get the temp up higher. that was about 10 minutes into my morning commute.The truck was plugged in last night, as well, and this was one of the warmer mornings we've had here, recently.

[ISX]

Too HOT! Thats 500F post turbo at only 40mph with 4.10's...........that damn thing should be freezing, not boiling. Do you know how to confirm stock timing with that timing tab thinger in the injection pump?