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1993 low power questions


kstossel

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I am chasing a low power condition (trouble pulling hills) and trying to rule out various components.Can anybody detail out (very simply) the symptoms of a bad lift pump or a bad ecm.When you can only take a 3% grade at 35 mph something is wrong.Fuel filter changed out, injections bled, air filter replaced, currently installing a boost gauge but Iexpect it will show turbo is fine.After lift pump and/or ecm it becomes more serious I imagine (trans tq or injection pump?)When I downshift manually from 3-2 (no OD) the engine rpms go up but no change in torqueor vehicle speed.

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I have a 92 5 spd. CTD and I can only suggest a couple things. Waste gate? Air intake boots, hoses for cracks? Esp. feel around down near the bottom sides for breaks in the hoses..About 5 years ago I had the fuel module in the tank almost completely disintigrate from rusting away. It was choking off my fuel the way it fell and was laid in the tank.I don't think the first gen trucks have an ECM do they?I'm at almost 400 k on my second mechanical lift pump. That could be a problem too. My fuel lines went bad too had to replace all the way from the tank. They were so brittle they'd break with little pulling.Hope you find it...... keep us posted.

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on the first gen trucks there's basically only 2 things that it could be, either its a air problem or a fuel problem. If there is more black smoke than you usually see I would start looking at your intercooler and intercooler boots for leaks, also check the waste gate on the turbo if your truck has a waste turbo. If you don't have smoke I would be looking at the fuel supply, checking all lines for leaks and making sure the lift pump is pumping, then lastly get the injection pump checked. Also there is no ECM on the first gen trucksSent from my DROIDX using Tapatalk 2

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Something else I just thought about is if there was a crack/hole in the boost diaphragm in the top of injection pump. What it does is once you build boost it move the fuel pin down to give the truck more fuel, so if it has a hole in it the fuel pin won't be moved and thus you will have low power. This doesn't happen very often but its something worth checking if everything else checks out okay.

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Something else I just thought about is if there was a crack/hole in the boost diaphragm in the top of injection pump. What it does is once you build boost it move the fuel pin down to give the truck more fuel, so if it has a hole in it the fuel pin won't be moved and thus you will have low power. This doesn't happen very often but its something worth checking if everything else checks out okay.

You might search a while for the diaphragm. It's a tough part to find around here in Idaho. :rolleyes: But he's right the whole AFC housing is based oon boost pressure and the ability of pushing that pin down inside the pump. You could loosen the starwheel to allow fuel on earlier. But double check all the boost parts for damage wear or sticking.
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Thanks for all the suggestions.

I have no history on this drivetrain and I can tell someone has messed around in various places

so I know I am searching for the same thing some other owner did.

I will try the lift pump just so I know it has been replaced and cross my fingers, but if that doesn't do

it I will concentrate on the injection pump. The injection pump is much cleaner than the engine so maybe

it suffered a backyard rebuild that went bad. I also saw a Q/A comment on a youtube video where the guy suggested it was an incorrect banjo bolt on the pump. Maybe the previous owner tried to adjust the fuel pin and messed it all up.

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"i did this on my 92 d350 automatic. After i rotated the fuel pin, i noticed that it shifts through the gears a lot faster but i have a lack in power, especially top end or coming up hills. I cant seem to get it back into the original position. Any advice ? thank you

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Sounds like you might have a boost leak, make sure the line going into the top of the pump has the correct banjo bolt in it and it's tight. "

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I need to get this one running so I can get back to work on the other 2 drivetrains that will be transplanted into other vehicles. If I knew it was the injection pump I would just buy one, but I do not have the tools or know how to replace an injection pump. If any readers live in Southwest Va, feel free to make me an offer to do the labor on removing/replacing the injcection pump.

Thanks again for all the advice, I will update when the issue has been found and corrected.

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  • 4 weeks later...

It turned out to be the worst of everything, bad injection pump and bad lift pump.At least the injectors checked out OK.But engine runs great now, thanks for the help, suggestions, guesses, educated guesses and so on.But in this case, it wasn't anything tricky, just 2 major components that went out very close to one another.Thanks again

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  • 5 weeks later...

I would read through the above comments, there were many good ideas for the not-so-common causes of low power.To start with the easy and cheap causes: clogged air filter, water in fuel filter (most common)(even if the water light isn't on)After that, if it only happens on hills of somewhat steep grades, lift pump will cause that. The injection pump will suck a little fuel on its own, but it needs the lift pump to overcome gravity, especially under load. Lift pumps cost about $70 and isn't that hard to replace, but sometimes you need 3 hands if you are using a jack.After that, to avoid paying $1000 for an injection pump, read through the comments above and see if you see anything else that can be checked.In my case it was the worst of everything, a non-working lift pump combined witha barely working injection pump (very gummed up and dirty). So the little, cheaper causes I couldn't take advantage of, I had to spend the money. If it turns out to be an injection pump (assuming the money doesn't effect you that bad) you will be surprised how well everything works after replacing it. A new lift pump, injection pump, confirming injectors are good etc... will give you another 300,000 miles of high power

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