truck ran like s**** pulling my 5'vr home

bluedge8 · Sep 25, 2016

So I just wanted to start a thread to bounce ideas off of you guys.
truck stats:
f350 cclb 4x4
266k miles
4:10 gears
285/75/16's
3" down pipe to 4" full exh, no cat, has a flow through muffler
6637 air filter
ts 6 pos chip, Dynoproven tunes
custom remote fuel fitler and regulator, still has mechanical fuel pump

30' 5th wheel, 9800lbs
pretty flat terrain.

I have noticed it rough running here and there but I haven't had it loaded down since this spring and it ran fine then. So I hooked up the 5th wheel and headed for home about 100 miles. Started out on 2 lane 55mph roads, it accelerated fine up to about 35 mph ok then started to fall on it's face and had trouble maintaining 55mph and then it started to miss. I would back off for a little bit and then hammer down and it would run smooth for a little bit then start missing again. For the whole 100miles.

Now, the first thing I am thinking is I either have an air leak in my fuel system. Or, I'm running out of fuel pressure. Another thought is that I'm running out of hp oil, but with stock sticks I don't think it's oil. I am going to buy a fuel pressure test kit tomorrow to see where the fuel pressure is at. I just bought a used reg return and I have an SD electric fuel pump, but I was planning on towing double on a 4 hr trip leaving this thursday, so time is limited on putting a fuel system in the truck by then.

Any other thoughts on where to look?

ghohouston · Sep 25, 2016

Definitely check fuel pressure first. Look in the icp sensor connector for oil, check the ipr pigtail, etc.

David N · Sep 25, 2016

Valve cover gasket harnesses and connections.

bluedge8 · Sep 25, 2016

thanks guys, I will look at all of that.

Magnum PD · Sep 25, 2016

See what fuel filters look like.

02BigD · Sep 25, 2016

Do OBS trucks have an OBD port?

ghohouston · Sep 25, 2016

Something that took me a bit to figure out was when my tank selector valve failed between positions, and was hardly letting any fuel by. Truck would idle all day long, first gear fine, 2nd gear okay, 3rd gear would fall on it's face and actually die. You could have sucked some trash into a fuel line, piece of rubber pickup foot, etc. Mine had pieces of rubber in them as well from the pickup foot.

ghohouston · Sep 25, 2016

02BigD said:
Do OBS trucks have an OBD port?

Yes, on my 97, it's on the passenger side, about where the passengers left knee would be, under the dash.

bluedge8 · Sep 26, 2016

it has obd II port. I've been meaning to buy AE but haven't yet. I have a scan gauge but didn't have it with me, I'll plug it in and check for codes.

bluedge8 · Sep 26, 2016

Just checked fuel pressure. idling, it's at 42. when I kicked on the high idle it dropped to 40 then oscillated from 40 to 48. When I power braked the truck in stock tune and hi perf it dropped to 36. I'd say a fuel system is a good place to start. what should a stock truck make for fuel psi? not worried about obs with mechanical vs. SD with electric, just wondering what the minimum should be?

gnxtc2 · Sep 26, 2016

You should be around 60-65 fuel pressure. You really should put a load on the engine. Idling is not loading the engine. But your readings aren't that good.

Do you still have the mechanical pump?

Billy T.
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