1996 7.3 cranks hard but won't start

ac3496 · Jul 7, 2016

Purchased a 1996 7.3 diesel with 75,000 original miles completely stock. Truck cranks hard but won't start. I have checked fuses and relays. The fuel bowl fills up with fuel quickly. Also the check engine light turns on for a fraction of a second when you turn the ignition and then turns off. There is also no smoke coming out of the exhaust when cranking. Batteries are also new. Wait to start light turns on and then off after about 5 seconds which should be normal. Any help would be great thank you.

Sent from my iPhone using Tapatalk

Baker42 · Jul 7, 2016

Check the 30 amp fuse under the hood. if its popped the fuel heater most likely shorted out.

Magnum PD · Jul 7, 2016

Check oil in HPOP Rez

wipersnapper_99 · Jul 7, 2016

Also remove and replace fuel filter.....could be clogged.

Sent from my SAMSUNG-SM-N910A using Tapatalk

SAVAGE_DIESEL · Jul 7, 2016

I am stumped on fuel bowl fills up quickly once full it should never empty if it is then that's why it won't start there is air in the system and no fuel is being delivered. (yes? no? don't take my word for that as gospel I am sure someone here with way more experience will let me have it if that is incorrect) when I rebuilt my fuel bowl and replaced lines there etc.. I pre filled the fuel bowl and still had the old girl stall on me but if I remember correctly my buddy had me open the Schrader valve and I did bleed air out of it. Also pay no attention to the wait to start light that is a "dummy" light wait another 30 seconds after it goes out the GPR should be running you can hear it click on and off with the hood up and windows down or reach in through the window. But as stated by MAGNUM PD if the Hpop res is empty or low the truck wont start it doesn't get fuel I had an issue with broken Valve cover harness connectors for the glow plugs and my truck would crank sometimes when it had sat for a long time and would puke smoke out the pipe until she fired. so....

Rico · Jul 13, 2016

Check your IPR near the HPOP. If the tin nut came off it won't start but will crank. Happened to me!

Justin@DP-Tuner · Jul 14, 2016

Do you have access to a scan tool? If so, what kind of ICP numbers are you seeing when cranking?

Bugman · Jul 14, 2016

If you don't have access to a scanner I would check the oil level in the high pressure oil pump. There is a allen head screw that you can remove and look inside, the level should be within 1/2" of the top. If that looks OK I would pull one of the valve covers and watch the injectors as someone cranks the engine over. Look to see if the injectors are squirting any oil, if they are that is good, no oil equals bad.

Constructionworker · Jul 14, 2016

Just throwing this out there cause it happened to me.. the IPR circuit in the PCM is known to cause similar symptoms. I ran full ground to one of the two wires (don't remember) and it fired right up and had very little power. Swamps diesel can diagnose and fix the problem. Make sure you tell them to check the IPR circuit

Rico · Jul 15, 2016

I bet it's the IPR nut

ac3496 · Jul 15, 2016

I checked every wire coming out of the pcm and idm for voltage and resistance using a pin voltage chart etc. and have narrowed it down to a bad idm. I will keep you guys informed if the engine starts. I will be ordering a remanufactured one shortly

Sent from my iPhone using Tapatalk

Bugman · Jul 15, 2016

Have your checked the wiring from the IDM harness into the injectors? It's a simple test with a volt/ohm meter. It won't tell you if the IDM is bad but the wiring to the injectors along with the resistance of the injector.

Also you can pull the IDM off of the fender and give it a shake and see if you can hear water sloshing around inside of it. They are prone to getting water into them the way that they are mounted.

dmd · Jul 15, 2016

Borrow and IDM from a friend and see if it fires up.

Bugman · Jul 15, 2016

^^^^^^^^

This will also work. Any IDM from any 7.3 Powerstroke will work

ac3496 · Jul 19, 2016

Bugman said:
^^^^^^^^

This will also work. Any IDM from any 7.3 Powerstroke will work

I checked all of the wiring with a multi meter. Everything checked out good. And I don't know anyone with a 7.3 that is willing to let me borrow their idm

Sent from my iPhone using Tapatalk