I'm not a great mechanic, but I can follow things in forums and on YouTube and figure most stuff out. But my truck won't start, and I've done some research but still haven't figured it out. It's a 1995 F-250 7.3L DI with 340k miles.

+ I filled the oil to the top + The Wait To Start light comes on + The tachometer registers that the engine is turning + When cranking, the oil pressure comes up into normal range. So I've ruled those things out.

So I thought it must be the Glow Plug Relay and I got out my Voltmeter. The hot terminal registers 12.44V, and when I turn it to run mode (WTS light on) the hot terminal drops to 11.30V and the glow plug terminal is sitting at 10.80V. This doesn't seem right, but the videos I've seen show the glow plug terminal is sitting about 0V when the GPR is broken.

So I tried to verify it really is a bad GPR by taking jumper cables and connecting the two terminals that way for about 10 seconds. I got sparks so a connection was made, but still nothing. Then I tried it again with the key in running mode (WTS on), and still it wouldn't start.

We're sitting at about 60F temperatures right now, so it shouldn't take a lot of glow plug time to start this thing right up. What could the problem be?

Harley

 

Keep the batteries charged between attempts to start. Fully charged battery should be better than 12.6V. With glow plugs going, and the starter turning the engine, you should still have 10.5 volts or so. You might be turning low RPM due to low voltage. Are you getting smoke from the tailpipe while trying to start?

Download the No Start Flowchart from the FAQ sticky thread here:

https://www.ford-trucks.com/forums/1149694-mod-tech-diagnostic-faq.html

Come back, ask more questions. There's a lot of other good information in FAQ sticky that can help you.

 

Could be a stuck IPR but yes, do as 867 says and follow the chart.

 

A weak starter will keep you from starting in weather like that. BTDT.

 

Thanks for the help guys, and the link to the flow chart.

I'm getting good cranking RPM but no noticeable smoke from the tailpipe. When I checked the fuel bowl it seemed to have plenty, minus what spilled out when I went to screw the filter back in...

From the chart it looks like I should now check the fuel pressure at the regulator. I see the photo that it is linked to, and it shows an IPR and a Fuel Pressure Test Port. I see the test port is a Schrader valve, but I'm guessing I don't want to just plug my bicycle pump on their, and not my tire pressure gauge either. Any recommendation for which gauge to buy from O'Reillys?

Thanks again,

Harley

 

Buy a cheap stick type one and watch for it to spray you in the face while someone cranks it over for you.

 

Well,do you get just steady crank.What I mean is,does it stumble like its trying,or just steady turnover by the starter.Returning to gaser engines,if you have
spark and gas,you will get something other than a steady crank per the starter.A stumble,a trying to "catch" kind of thing.It may not start,but different
than steady starter cranking.
So,going to diesel,if you have oil pressure to the injectors,plus fuel pressure to the injectors,you should feel it trying to "get with it".Sorta.
Trying to help.Not a7.3 guru by any means,just stabbing in the dark.But at 60,i would think it has nothing to do with a GPR.
Did you unplug the IPR sensor,and then try starting?.

 

It will not start with IPR unplugged. I'm guessing you mean ICP, yes its worth a try unplugging that and trying to start. Like I said above, if the IPR is stuck you can crank forever and it will not start. Follow the flow chart.

 

 

OK - finally had the chance to get back after this. Borrowed a fuel pressure test kit from O'Reilly, and needing adapters it was really long and a PITA to get attached, but I managed.

So, I get it installed, then I step inside the cab and turn the ignition to "run" position. The WTS light comes on, but I go and check and the pressure has not budged. I cycle it a couple more times, still zero pressure. Now I'm thinking I have a bad fuel pump even though there is fuel in the fuel bowl. But I go ahead and turn it over, and the son of a bitchin' truck starts right up! When running the pressure is fluctuating right around 50 psi.
So now I don't know what to think. I shut it down pretty fast, and it started again. Shut it down, packed everything up and drove to O'Reillys to return the tester, and it continues to start just fine.

Ideas? Intermittent ICP? Could it have been a plugged/stuck IPR that somehow freed up when I put the test tube on - like it released the pressure enough to let something shake loose?
Sort of glad my trucks running, pretty bummed that I have no idea why.

 

Anything is possible but the IPR might have gotten unstuck, unlikely though. IDK

 

Unless the truck has had electric fuel system added by someone, the engine has to be turning over to get fuel pressure, as the fuel pump from the factory is mechanical, ran by the cam. The IPR is located below the fuel bowl, so maybe you jiggled the wires to it so they started making contact. Unlikely in my opinion, but strange things happen. Glad it is running.

 

My truck came with an intermittent No Start problem. PO was open and honest about it. He said he always just plugged it in and it always started a few hours later. For me, the first time it failed to start, intermittent had become persistent. It wasn't gonna start, period, no way. It was the IPR. I had to learn to diagnose and work on the truck so I made an elaborate big-deal out of diagnosing the no start. I had a lot to learn, still do.

The no start was one reason I got a good deal on my truck. PO's knee and the clutch were no longer compatible, another reason.

 

OK, so this morning it wouldn't start again, so at least I got to continue trouble shooting. So I went down the flow chart to 'unplug the ICP sensor', and sure enough there is oil all over in there. So I left it unplugged and tried to start it, and now it is running. So I finally figured it out, and that's a weight off my mind.

It also leads to the next question. O'Reillys wants $179 for the part, I can find OEM parts on eBay for $133, and then there are parts that include a replacement pigtail for only $13 bucks. Is this one place where it is worth paying $100 more for OEM parts?

Also, my backup vehicle is also waiting for replacement parts. Am I going to hurt the truck if I drive it for a couple days with the ICP unplugged? Risk of damaging something?

Thanks - Harley

 

I think I bought mine from Riffraff or Dieselorings, yes go OEM on these sensors. If you receive 10 years from a $140 sensor that is $14 a year, cheap. Not sure if the $13 for the pigtail is for an OEM/Navistar unit, I would want to know before buying it. I spent extra for a new IPR pigtail that was OEM/Navistar.

No clue on it unplugged, sorry. I am sure someone more knowledgeable than me will reply!