No start...has me stumped

gnxtc2

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So I get a call to help a 17 year old kid to start his '96 7.3.

Background:
He parks his truck to fix the driver's window. The window got stuck in the down position. So he begins to jump wires on the window switch to diagnosis if it's a bad window motor or switch. He shorts some wires until he finally finds the correct wires. He is able to get the window. So he tries to start the truck and it doesn't start.

The kid changes the fuel pump (mechanical). While doing the fuel pump, he replaces the drain valve on the fuel bowl. Don't know why. Still doesn't start.

I get a call from a friend to ask me why the truck doesn't start. I tell him what is the ICP and fuel pressure? I get no answers as they have no way of telling.

I go over the house. Plug the scanner in and the ICP is 0 and no smoke out the tailpipe. I get cranking rpm of 125. Find that the tin nut on the IPR was loose. I have no tools with me to fix it but use a screwdriver to "tighten" the nut. I get a ICP reading of 1500. Try starting and the batteries die. Tell the kid to charge the batteries as he only has a homeowner type charger and to call me later.

The kid asks another friend to help him as he can't wait for me. So they decide to change the IPR and ICP sensor for unknown reason(s). He tries to start the truck and it would start. They shoot it with ether and the motor backfires. The kids ears are ringing from the backfire. :pointlaugh: I wish I was there for that. Thinking to myself,drained the HPOP reservoir and didn't fill it.

He tows the truck to my friend's shop. My friend has no idea on how to work on diesels. So I go to his shop. Atleast he has the proper tools. I scan the truck again.

Cranking ICP I get 0. Check the reservior, empty. Put about a quart of oil in.
Cranking ICP now is 3500....WTF???? That reading is not correct. Hook up my mechanical gauge to the head. Cranking ICP is 1500-2000. Check the ICP sensor, the connector is cracked. I unplug the senor to put it into default and it still doesn't start. No white smoke out the tailpipe. WTF???

Do a buzz test and it passes. Externally check valve cover gaskets and no burnt pins. Removed chip from ECM.

Check fuel pressure 30 psi....marginal. I open the drain valve on the fuel bowl. No fuel is coming out. I start loosening the the filter cap, and fuel comes pouring out the drain. I attempt to close the drain and it does stop. Apparently he put the drain in wrong, the clocking. I look at the cap. The cap doesn't have the tabs to hold the filter in. The filter is jammed into the cap. I have to pry the filter out the cap. I leave the filter out temporarily, put the cap back on and play with the drain to close it. I try to start....nothing. This time, I'm getting white smoke out the tail pipe. So I ordered another cap for the truck.

I jump the GPR. Put the jumper cable from the positive battery post to the GP post on the relay. Now I try to start it, it wants to fire but doesn't. Then the batteries die.

I have ICP and fuel (white smoke) but doesn't start.

Would the motor run with a filter in the bowl?

Billy T.
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7.3obs

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Do you mean without a filter in the bowl? I have ran my truck without a filter in the bowl before no problem. Another question, what brand icp and ipr did they put in the truck? Off brand might be why it pushed 3500 psi. But if you’re getting smoke and all is reading out, should fire...
 

gnxtc2

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Yep, put my known working spare in. The CPS I removed was an aftermarket piece that the point just fell off.

Also checked all the fuses. No funny skips when cranking. WTS light comes on, tach bounces, got rpm reading on the scanner, got over 500 ICP, got white smoke out the tailpipe while cranking. Has ICP and fuel, it should start.

The only thing I can suspect is bad glow plugs. It's been in the 20s at night and high 30s during the day. But the amount of cranking I've done, cylinders should have some heat in them.

Billy T.
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lincolnlocker

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Yep, put my known working spare in. The CPS I removed was an aftermarket piece that the point just fell off.

Also checked all the fuses. No funny skips when cranking. WTS light comes on, tach bounces, got rpm reading on the scanner, got over 500 ICP, got white smoke out the tailpipe while cranking. Has ICP and fuel, it should start.

The only thing I can suspect is bad glow plugs. It's been in the 20s at night and high 30s during the day. But the amount of cranking I've done, cylinders should have some heat in them.

Billy T.
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What is voltage while cranking? I assume you had it on a charger with a jump start setting so voltage stays above 10.5v? Did you unplug icp again after new possibly junk sensor was installed?

live life full throttle
 

mandkole

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Did you leave the chip unplugged? I find that mine is far more sensitive to low voltage with the chip plugged in than not. I'd leave it unplugged.

Agree that it should fire. I'd also plug it in to rule out any glow plug issues. A small 10a charger won't properly charge two good batts quickly-- it will take 8 hours.
 
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I know the superduty fuel bowl has a spring/valve inside the prevents running the truck without a filter. When you install the fuel filter it pushes down on the spring/valve and opens the fuel line to the injectors.

I know high hp truck deeleetee it so it doesnt restrict the fuel flow. Of coarse only if you decide to keep the fuel bowl in those applications.

I looked up the diagram of the obs fuel bowl and it looks simular to the superduty. Try and take out the spring that activates the valve or put the filter back in it.

It might be getting some fuel thats why your getting white smoke, but it may not be enough to fire.

It's a plastic stand pipe in the middle of the fuel bowl like in this pic.
 

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lincolnlocker

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Never knew that about the fuel bowl. I'm going to put a new filter in.

Yes, the chip has been totally removed from PCM.

Billy T.
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You can just cut the tip off the stand pipe and gut it also. That way it keeps crap from bottom of bowl out of it. That is what i do to the trucks i work on.

live life full throttle
 

gnxtc2

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Put in a new Motorcraft fuel filter and new Ford fuel bowl cap....still no start.

High pressure oil in the heads was in 2500-300 range on a manual gauge. Have fuel pressure. But this time, no white smoke out the tailpipe.

IMHO: something is telling the injectors not to actuate. Even though it pass a buzz test, could the IDM be no good?

Billy T.
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rusty1161

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IPR wiring harness? I know you already mentioned the ICP connector, but it was my IPR harness that caused my no start.
 

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psduser1

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If youve got 25-3000 psi hpo while cranking, your ipr definitely isn't working, lol.
Unless I misread.
If the injectors aren't firing at that pressure, than it has to be a control issue, which could be the ism. Might check continuity (resistance) from the firewall through the 42 pin connector. :popcorn:
 

gnxtc2

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If youve got 25-3000 psi hpo while cranking, your ipr definitely isn't working, lol.
Unless I misread.
If the injectors aren't firing at that pressure, than it has to be a control issue, which could be the ism. Might check continuity (resistance) from the firewall through the 42 pin connector. :popcorn:

After I keep cranking, the pressure goes up. Correct me if I'm wrong...applying voltage to the IPR closes it, raising pressure.


Are the injectors clacking while cracking?

Can't hear them while inside cranking.

Billy T.
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DEEZUZ

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Um.. you can leave key on and jump starter relay and have your head right over the engine...

I can even hear them if I stick my head out the window and crank from cab....
 

psduser1

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I thought the pcm would limit hpo based on throttle position?
Either way, you have plenty of oil pressure to fire the injector, lol.
I was referring to the idm circuits when I mentioned checking wiring. Sorry for the confusion.
You mentioned a passing buzz test, so, for some reason, maybe the pcm isn't actually commanding the injectors to fire when you are trying to start.
I would think the idm is working if the injectors buzz correctly.
 

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