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96 F350 wont pull

8K views 38 replies 9 participants last post by  John Saxon 
#1 ·
Evening all,
Thanks for letting me come aboard.
I'm a technician at an agriculture shop, so know my way around a wrench and a test light but this old Ford has me wondering which approach to take.
Its a 1996 F350, 460, ZF5, 4wd with 4.10's. I bought it last year and immediately gave it a thorough tune up... plugs, wires, cap, rotor and fuel filter. The previous owner had already installed a high flow air filter and removed the restrictions in the air tubes. The truck has 170,000 miles on it, doesn't leak a drop of oil, used less than 1/2 quart of oil between changes, don't smoke, rattle or give any indication of a problem. It will run 85 mph down the freeway all day long without missing a beat. Until I hook it to my 16' enclosed trailer... (trailer wt=2200, RZR=1200... not a lot). The old girl is working HARD to maintain 60. So, I removed the catalytic converter (that was already hallowed out)
I know its 20 years old, its got some miles and its a barn door against the wind.... but I think there is something simple I'm overlooking... fuel pressure at WOT? Could my o2 sensors be causing a lean condition at speed? Wouldn't that throw a CEL? Its a SD system, so I'm not real familiar with it.... that's why I'm here.
RHP builds a great package for EFI 460's, and I may go that direction in the future, but for now I'd like to use what I have to get the weekend toy hauling done.
Its hard to diagnose over the web, I get it. Any help is appreciated.
Thanks
 
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#2 ·
Not trying to get off track but do you know the trailer is in good shape? No trailer brakes sticking or wheels otherwise hard to turn? Has the truck pulled other trailers in the past with the same slow result?

If the trailer(s) are fine sounds like some sort of fuel problem to me. You are obviously pushing down harder on the gas pedal with the trailer behind you. Dead spots on the throttle position sensor perhaps?

I'm no expert but those are my guesses.
 
#8 ·
The first trip out, about 130 miles away, I thought the same thing..."its gotta be a trailer brake hanging up", but when we stopped to get fuel I felt all the hubs on the trailer and none were out of sorts. Get off track anytime you want...there was one time I overlooked something obvious.. just that one time though. haha.
 
#4 ·
Fuel delivery comes to mind. Double check fuel pressure with and with out vacuum line on regulator. Doing this while replicating the problem will determine if fuel delivery is the issue.

Double check initial timing with the spout disconnected. OEM is 10* btdc. You can bump that to 12 or 13 and get a notable bump in torque.



S
 
#7 ·
I did advance the timing when I initially tuned the truck up, I stopped at 13 degrees and really didn't feel any seat-of-the-pants difference. There is no detonation or ping so I might play around this weekend with some timing... could be a problem in the distributor not advancing.? Ill also check fuel pressures and try to borrow a scan tool that can read some parameters with this system. Thanks for the thoughts, its appreciated.
 
#6 ·
It will maintain 5th gear pulling the trailer at 60...but at dang near WOT and if there is a hint of head wind or incline I need to down shift. The open element filter the previous owner has on it sounds like 300 Hoovers and there is no gaining speed. We are at 6500 ft elevation here.. so that's a consideration, and everywhere I go with the trailer is a slow climb. Working hard is anything above 3500 rpm for extended periods.
What really gets me though is towing the trailer around town. It feels like I have a #9 ,000 skid behind me.... really got to let the old truck rev to get anywhere.
I'll get some diag done this weekend hopefully. We had a nice snow here and every rancher with a tractor forgot to treat their fuel apparently, so its been a busy week.
 
#10 ·
Well let's look at it:

A 1996 EFI 460 is only rated at 245HP new. At 6500 feet, you're losing anywhere between 20-32% of the engine's power. Putting you anywhere between 167 HP and 195 HP. That's not a lot of power, especially when towing an enclosed trailer that's a big aerodynamic drag.

I'd start by checking the fuel pressure and giving the exhaust system a thorough check as mentioned to make sure there are no broken cat pieces anywhere.
 
#9 ·
You said you removed the catalytic converter that was already hollowed out. I had a truck that the material in the cat was broken up and pieces of the stuff would get stuck in the cat outlet causing loss of power. I gutted the cat and assumed it would fix the problem. Ran better but lacked power at a higher RPM. As it turned out,a piece traveled further down the tailpipe and lodged itself there.Took me a while to figure this out...used a drain snake to clear it.
You never know. Just throwing this out there.
 
#14 ·
Fuel Pressure results

Fuel pressures seem to be within reasonable condition. Key on- 32psi, Idle- 35 psi, Vacuum off- 42psi.
So, onto the exhaust side. What headers would people suggest? Hedman has a coupe of options reasonably priced, then a big jump in prices for Gibson and Banks. Anyone using headers with a manual transmission? Hedmans fitment guides say they wont fit with the ZF5, but there are a few reviews I've read that say different.
Thanks for the help so far.
 
#15 ·
Fuel pressures seem to be within reasonable condition. Key on- 32psi, Idle- 35 psi, Vacuum off- 42psi.
So, onto the exhaust side. What headers would people suggest? Hedman has a coupe of options reasonably priced, then a big jump in prices for Gibson and Banks. Anyone using headers with a manual transmission? Hedmans fitment guides say they wont fit with the ZF5, but there are a few reviews I've read that say different.
Thanks for the help so far.

What is WOT or near WOT fuel pressure like will driving?



S
 
#21 ·
Compression test complete: 1-100#, 2-125#, 3-123#, 4-115#, 5-127#, 6-131#, 7-128#, 8-126#. Tested #1 3 times dry and once with a couple squirts of oil with no change. 20% change between 1 and 2. Look like its time to decide exactly where I want to be, dollar wise, in this old truck..... rebuild what I have, or go crate engine.
Thank for all your help!
 
#22 ·
At 6500' the low numbers are not surprising. The variance is the issue. Methinks your rings are just tired. At sea level an oem efi will crank at 145 to 155.

If this is a combo to be used exclusively at high altitude then a raise in static c/r should occur with a new engine.

Overall I venture to say old girl is just plain tired.



S
 
#26 ·
Ultimately I will. For now, not an option. One kid graduating (and a dental bill waiting) and another maybe coming home after a tour in Iraq... 5-6k for a engine right now cant happen. Eventually, this truck will haul the mail... for now, I'm just focused on best bang for the buck, and diagnosing properly.
 
#25 ·
The one that is missed a lot and does not set a code is the map sensor on sd systems if fuel pressure is in range a out of range map sens does the exact same thing. It will make the computer think you are at an extremely high altitude and pull fuel accordingly. Ford has a chart for how many hertz the map should read at what altitude. We are normally around 156 hertz in chicago when the map sens got down to 150 the vehicle had a noticeable issue around 148 or less it was a pig no power. At your altitude you need to look up what it should be then check it to see if it's out of range. Or take a gamble and try one.
 
#28 · (Edited)
I made a few calls today to local (within 75 miles) machine shops. Only one answered. He made a lot of good points.
I started off with a list of what I have tested/checked so far.... Thank you all. Then I told him that I wasn't out to drag race the old truck.. its a 1 ton, 4 door, flatbed... I just want to yank the toys up a hill as efficient as possible with the old girl. And, here is what he suggested:
Yank the heads off and bring them to him for a refurbish. New guides, springs, retainers, seats etc. About $550 out the my door. I'm out the machine shop cost plus gaskets and a few hours of time. "You cant compress what you cant get in" and some carbon build up could contribute to the higher compression test results. So, yank the heads. Inspect cylinder walls.. etc.
So, we yank the heads. Get them back to new. Bolt back on and see what happens.... If I'm not happy, we start talking about rebuilding/decking the shortblock. Either way, the heads would have had to be addressed and I'm out the gasket set and my labor. And, I have a fresh set of heads to start grinding on when the time comes.
On a short side note.. the truck runs better since doin the compression test? I broke the #5 spark plug while taking it out... no carbon tracks on the porcelain, didn't feel it break... but it came out in two pieces. I didn't think much about it, just went and got a new plug. Now, the truck leaves from a stop much more spirited, and (might be my imagination) revs easier.... strange. (Double check ignition system... I think Scotty said that way earlier in the thread)
 
#29 ·
Been a while since I visited, but wanted to give ya'all an update. The old truck is running very well now, without any machine work. Seems to be this particular 460 does NOT enjoy timing! I set the timing back down to 11 and it pulls much better. Had a RZR on the flatbed, pulling my 16' enclosed trailer with another RZR and all the necessary gear for a long weekend in it. Managed to maintain 65-70 fairly easy (could have gone faster but the gearing likes 70 in 4th) throughout most of the drive, only dropping to 45-50 when the climbing got really steep for a couple of miles. Never budged the temp gauge, didn't burn a drop of oil. I think its all that can be expected at this point.
One question though.... Is there a rev limiter in these trucks? While playing around in the shop I went WOT and at 4400 rpms it acts like there is a limiter? I've seen two different answers browsing though the good ole web. Not that I would want to spin it any higher, being all stock. Just curious.
 
#31 · (Edited)
tnorthcutt when you adjusted the initial timing did you pull the spout pin connector prior to adjusting?The EEC IV will pull out any timing you add if you don't the pull spout pin connector first.Also the EEC IV distributor uses an octane bar and some chip kits include a different octane bar to install maybe a PO had a chip installed at 1 time and didn't put the stock bar back in when removing it?Also since it is a 96 are you sure it is a SD system towards the end they started phasing in mass air especially in CA.
Also the #5 plug may have been broken when it was installed.
 
#34 ·
You are not going to get an accurate total timing figure on an EFI 460 due to part throttle high vacuum. Rev it to 3000 rpm and you will see this.

The ECM (for the OP) handles the timing functions. The only question seems to be whether or not the spout was removed when timing was set...




S
 
#35 ·
or if the advance works at all, and thats what i was after, ive seen them not avd at all past int timing



this is why i ask all the time what the total is
 
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#36 ·
Gotcha.
I've pulled the spout every time I've played with the timing. I do know that it is advancing, I watched the marks when I throttled it up after replacing the spout connector and it is undoubtedly advancing.... where it stops advancing I cant recall though. It is also for sure a Speed Density system.
At this point, I think I've coaxed all I can out of it. It is what it is.... a 21 year old truck with dang near 200k on it, and its not too dang bad now. I'm still squirreling away for a crate engine (especially after shopping for newer 1-ton crew cab flatbeds) I can put some bucks into the old truck and still be ahead.
 
#37 ·
T you may want to explore upgrades to your exhaust also,I know there are gains to be had.There are several different manufacturers that offer cat back-full exhaust including headers systems for these trucks,I don't have any comparative experience on this setup but I am sure there are people on here that do.Ideally someone will be able to recommend a system that will work well with your existing engine and your future crate engine plans.This also has the advantage getting this behind you and easing the financial pain of the crate engine upgrade.Also it would be a good idea to map what your timing curve looks like now so you can see if there is any optimization you can do now and if you need to make any changes with the new engine you get.
 
#38 ·
Thanks John,
I still have the stock manifolds, but from the y pipe to the tailpipe has all been replaced. Here in Wyoming there are no emissions and I got happy with the sawzall one day, so its 3" from the y-pipe through a thrush to the tail pipe.(not a great sound around town but nice on the interstate) I was just talking to a friend of mine... a local shop has a special- "three pulls on the dyno for $60". We have a bet. lol. I'd be curious though, so I may take it down just for grins and giggles. Headers are no doubt on the list. Seems like most people on RV forums swear by headers. "night and day difference" and such, but I cant stomach the price for Banks, and the headman headers seem to hit or miss on fitment.
 
#39 ·
Does the shop monitor things like ignition timing,fuel pressure,injector duty cycle,and O2 during the pull?That could be very useful for determining the condition of your current setup and what you may need to upgrade for the future.Your truck must still be OBD I since it didn't light the MIL when you dumped the cat.
 
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