So I have a 1993 F250 351w zf5 it’s got about 195k miles and starting this summer when it started getting hotter (80s-90s) I’m experiencing some problems starting (lots of cranks 5-6 seconds) before it fires up, and also after around 30 minutes of highway driving 60-70 miles an hour it starts to get sluggish and when I go past 50% throttle the engine bogs down and bucks especially in 2nd and 3rd gear and will sometimes get bad enough that I can’t gain any speed and it breaks down but after sitting an hour or two it’s right back to normal, I’ve replaced the fuel filter and fuel pressure regulator after doing some research although I don’t have a fuel pressure gauge I can definitely tell it’s gained alot more pressure (before I replaced the fpr I attempted to drain the pressure that was in the fuel rail using the valve stem and no pressure came out, I later changed the fpr and did the same after driving it and sure enough pressure released as I did the same thing) not sure what it is might be a clogged injector maybe multiple? Been researching but haven’t solved it yet. Thanks for taking the time to read this and hope for some feedback. Thanks -Kent

 

Get an extension for your fuel pressure gauge and set it up somewhere you can see it while driving, one of the possibilities is that you are gradually losing fuel pressure due to a weak pump of low voltage at the pump, or the tanks are not vented properly and a vacuum is being created in them as you drive and consume fuel.. and eventually the pumps can't overcome it. A test for that is to remove the tank filler cap immediately after stopping the vehicle, if you hear air rush in the tank had a vacuum on it.
Another possibility is a melted cat or otherwise restricted exhaust, does the truck still have any of the factory exhaust on it or is it long gone?

 

Without a fuel pressure gauge, you're just guessing what the problem might be. That's like a doctor assuming your blood pressure is fine when you come in with a fainting problem.

It's much better to get a fuel pressure gauge from eBay or borrow one for free from your local auto parts store.
Here's how... https://www.ford-trucks.com/forums/1715944-how-to-check-fuel-pressure-on-1987-1997-gasoline-ford-trucks.html

 

My Snap on Gauge was 90 bucks 35 years ago
I still tape it to the windshield of cars / trucks with the original hose
You buy yourself a good one
You can take the Schrader valve out and rig up a few feet of 50 psi fuel injection hose (1/4 inch and use a hose clamp) to any gauge you can find
Be careful and test the rig several times before you hit the road

 

Conanski thanks for the response I will try that and no I removed the stock exhaust has a flow master fx to a 3 inch straight pipe

 

Alright I’ll buy a pressure gauge good to have one anyways. Thanks for the responses much appreciated.