Intermittent Weak Power

1983idi

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As the title states I have intermittent weak power. Only notice it when towing on the highway. I am only towing 5000 lbs at the most. Probably closer to 4500. Most of the time I can tow at 70 mph no issue on the flat and mild grade hills. Obviously it slows down going up larger hills a little bit. But sometimes I will loose speed (either from going up a hill or just not paying attention to my speed) and the truck will not get back up to speed even when matted to the floor until it decides it wants to start accelerating again so I'll get stuck at 55-60 mph for several miles. Problem is not new but seems to be very slowly getting worse. I have a Facet lift pump installed and a 3G alternator but truck is stock other than that. I have the issue with both front and rear tanks and it doesn't matter if they are empty or full so its not broken pickup tubes. I'm thinking possibly high pressure injector pump or injectors but I'd really like to verify before throwing almost $2,000 at the truck to replace all that.
 

frankenwrench

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Have you tried the old atf trick? Twist off the filter and dump it and re fill it with atf. Start it. Wait till the sound of the engine changes and kill it then. Wait till morning and start it and run it hard. Also running a hot shot fuel treatment sometimes clears things up as well. How old is the pump and injectors?
 

Big Bart

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Some other thoughts
1) Replace your fuel filter and air filter. If either is clogged it will rob power.
2) If you have a separate water separator drain it.
3) Check your compression. It will tell you a lot about peak power available.
4) Blow air back from the hose going to the intake side of your electric pump with the gas cap off. Not 150psi more like 8psi, maybe junk is stuck in your lines causing a restriction. Blowing diesel and air back to the tank may clear it. Then you will know you need to address.
4) Check your timing. Your timing changes as your injectors wear, IE “it is slowly getting worse”. If off, correct and be back where you want to be.

To your point spending 2k to find out the IP and injectors was not the issue would be disappointing. The above is just cheap maintenance that should be done periodically anyhow. Will likely get you some improvement even if it is the IP and injectors.

Curious what you find so let us know.
 

gnathv

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Your restriction may be your facet pump, if blowing lines doesn’t do it, I’d check fuel pressure.
 

1983idi

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Since a lot of your suggestions come back to fuel supply issues I think I'll buy a gauge I can put on the valve on the fuel filter housing and see if it stays steady or drops. Then if I don't see any issues there I'll try cleaning the injectors with ATF or another treatment. I have no idea how old the pump or injectors are. Previous owner claimed the truck only rolled over once but who knows if thats true. Guy also said it started great in the winter but the glow plug system wasn't even working so I'm not trusting anything he said.

I have ready 4-7 psi is where the pressure should be with a facet pump?
 

IDIBRONCO

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That's what you should be seeing in order to properly supply your IP. What you're doing is to check your fuel pressure when the truck is under load. That's while going down the road. Empty or loaded, either way would work, but loaded would give your the same conditions that are happening when you suffer a power loss..
 

TNBrett

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How about spending $40 on a mechanical lift pump. It’s been pretty well noted on here that the Facet lift pumps don’t always provide enough fuel volume when under load. Maybe it wasn’t as noticeable when the pump was new and you had clean fuel filter. Now with a little bit of age on the pump and maybe a few thousand miles on the current filter and it just can’t keep up.
 
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