93 K3500 Fuel/performance problem

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Acesneights1

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I recently got a 1993 K3500 Dump with a 454 TBI. Truck starts good, idles ok and runs ok on flat ground light thottle. It feels like its starving for fuel when I hit a hill, i went under the truck to change the fuel filter only to find out the PO felt the truck didnt need one and bypassed it.....So I am assuming the TBI unit is probaly damaged. I have no idea how to trouble shoot this thing since I work on mostly diesels. Also can I just rip the TBI setup off and throw a carb on it ? Its old enough to be exempt from emissions here and over the weight anyway so no problem with that. Just need a running reliable truck.
 

Acesneights1

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I didnt see any obvious place to attach a fuel pressure test gauge. I don’t have a DA5 adapter for my Solus Edge to scan it ut the Mil light is off and I dont think these older trucks have much for testing I can do with the Edge anyway ?
 

PlayingWithTBI

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I didnt see any obvious place to attach a fuel pressure test gauge.
You can "borrow" a fuel pressure test gauge (for TBI) from an auto parts store. Usually you hook it up where the fuel filter goes. You should have 10 - 13 PSI on a 93, IIRC 94 - 95 7.4L were 18 - 20 PSI.

There is plenty of data you can get from these OBDI systems with the right scanner or software and laptop. We were just talking about it on this thread, go to post #8 and see. @Schurkey posted a link to another thread where he shows what a "red brick" can do too.

https://www.gmt400.com/threads/engine-shutting-off.53235/
 

smdk2500

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I didnt see any obvious place to attach a fuel pressure test gauge. I don’t have a DA5 adapter for my Solus Edge to scan it ut the Mil light is off and I dont think these older trucks have much for testing I can do with the Edge anyway ?
You sure can use your edge with the correct adaptor. That is what I use on both my 95's
 

Acesneights1

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You can "borrow" a fuel pressure test gauge (for TBI) from an auto parts store. Usually you hook it up where the fuel filter goes. You should have 10 - 13 PSI on a 93, IIRC 94 - 95 7.4L were 18 - 20 PSI.

There is plenty of data you can get from these OBDI systems with the right scanner or software and laptop. We were just talking about it on this thread, go to post #8 and see. @Schurkey posted a link to another thread where he shows what a "red brick" can do too.

https://www.gmt400.com/threads/engine-shutting-off.53235/
I have a Mac tools fuel pressure test kit. Ill have to see if it has the adapters but the PO bypassed the fuel filter with homemade rubber lines from the tank. This thing is a mess. So was there a test port on the lines or do I t in ?
 

smdk2500

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Schurkey

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...and be careful, because the threaded connector on the fuel pressure tester may not have the same thread size as what the TBI adapter has on it's Schrader valve.

I wound up buying a Schrader valve to convert my TBI adapter to the same thread size as my gauge unit.
 

LC2NLS6

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I wouldn't even diagnose, I'd replace the fuel pump (verify its getting goo voltage too), fix the fuel filter situation, and pull the TBI unit and carefully tear it down to the baskets in the injectors and clean it up. Putting it back together, be super extra double top secret careful, they are fragile as glass tightening the injectors back on...
 

RichLo

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Yep, TBIs are just as easy as carbs to rebuild, just fix it an forget it. And worst case you'll need new injectors but that is still less $$ than a new carb.
 
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