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1998.5 24v NO Start

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Hello,My 1998.5 24v would not start after a short trip to UPS. Had the truck towed to my shop. Sat for a few days until I could get a new fuel filter and water seperator for the FASS fuel pump, installed and primed,fired right up. Died after a 15 mile trip home.Sat for a few hours until I could get a 3/4 wrench to prime again. Got it started and drove 3 miles to my home. I had a hot rod injector pump that I really did not like so I figured it was time to replace. Changed pump,fresh injectors, no start.Read codes. Found bad connector for the mapps/boost sensor,repaired, new mapps sensor also installed along with a crank sensor. Also found a bad ground to the block located between the emc and the starter. Two different grounds one terminal. Ihave 20psi of fuel pressure. Having trouble bleeding the lines, some just do not want to bleed . Will not start. After clearing codes. No new codes . Any thoughts

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  • Author

Is the VP44 new? :shrug:

The vp44 is new / rebuilt thru Diesel Auto Power. My thoughts is the the fuel is not going thru the pump.My next step is to put the old pump back on and see what happens.
  • Owner

Something just doesn't strike me as right...

[*]Is the low pressure fuel system primed at the entrance of the VP44?

[*]Is there enough flow and pressure from the low side?

Then typically you just crack 1,3, and 4 and crank till you see fuel spray or it attempts to start tighten the lines and start the engine...

[*]Is the VP44 getting good +12V at the socket? (Controlled by the fuel pump relay)

[*]Are you sure the ground is good behind the starter?

The only thing I can thing of that might go wrong with the pump is...

[*]Did you use the new key that came with the pump?

[*]Is the arrow on the key pointing towards the pump?

[*]Is the key number the same as on the pump?

  • Author

I am only getting 9.4 volts to termimal 7 with the key on. The key was the one that came with the pump and was installed correctly,removed nut and washer to double check key to gear position and is correct.Not sure of the best way to check ground other than the ringer on ohms on the meter. I would say i need the full 12 volts.

  • Owner

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Double check the relay in the PDC box it might have a bad contact and if you swap with a like the horn it might fix the problem. Just means that you need to replace the relay...

  • Author

Thanks for the diagrams, I do have the manual and I am getting a little better at reading them each day. The problem is in the grounds/system of grounds. I charged the batteries and now reading 12.4 v at termial 7. When I test the ground,meter set on audio ringer, I get a low/scratchy wisper -vs- a shout. When I repaired the ground down by the starter I discovered that the actual copper wire was oxidized ,black in color not shiny as a new penny. I would say the ground wires have Taken a beating over the last 12 years. Looks like running new wires is in my future.I will be studying those grounding diagrams.Thanks for your feedback and focus.:cookoo::thumb1:

The audio ringer is pretty sketchy. See if you can get a resistance reading in ohms. You should be getting 0.1 to 2 ohms if you have a good ground 5 ohms being the max, though it should be more in the 0.1-2 range on most everything. If it has any higher ohms than that, you know the ground isn't connected very good.

  • Author
:shrug: Fuel Injector Pump term. 6 :3.0ohms to Engine block ground location, 5.7 to (-) battery.

This may be out in left field and off the troubleshooting track but 20 psi fuel pressure is borderline to high fuel pressure. What fuel pressure are you showing during start attemtps? High fuel pressure to the VP-44 can create a hard start condition: http://www.bluechipdiesel.com/vp44diagnostichelp.html http://www.bluechipdiesel.com/diagnoseliftpump.html

  • Author

To follow up. With a temporay fuel pressure gage set up I was able to get started. Watching the gage ,things were looking good, about 15-20 psi but then droppped to 0 psi . The fass unit sounded a different tone. Lost prime to the tank. I decided to start from the beginnig at the fuel pick up in the the tank.Time to remove the bed. Long story short, the suction metal line coming out of the tank had a small pin hole hidden under the rust. I fabricated a a new fitting/lines and reinstalled. Have not tried start yet. I am installing a set of gages,fuel pressure,boost and egt. I will let you know how I make out over next few days. Enjoy your labor day.

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