96 7.3 random shutdown, stumble, etc - Ford Powerstroke Diesel Forum
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Old 10-22-2011, 12:08 PM
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96 7.3 random shutdown, stumble, etc

Alrighty, working on my dads 96 7.3 again. Has roughly 90k miles (yeh it sits alot). Anyway, it had gotten to where it didnt want to start when it got hot, and would randomly develop a stumble or miss at idle. Also it would stumble and act like it was going to choke down when you would coast down from a moderate cruise with it still in gear. Changed the fuel pump & the IPR valve awhile back and it seemed better, for awhile.

Last week I drained both fuel tanks (fuel was nasty), treated them, replaced fuel filter and it ran without a hitch for me for several hours. Left it with him, and when he went to drive it yesterday, no dice, wouldnt fire. Just spun over. He tried it 4 or 5 times and then drove his other truck to work. Now it was between 35 and 40 degrees yesterday morning.

Figured it must be a GP problem, so today I checked, relay is good, it appears to have 2 bad glowplugs (front on pass side, rear on drivers side not sure of the ford numbering system).

While I was checking the GP's I noticed a fair amount of fuel in the lifter valley. I thought I cleaned it all out last weekend after doing the fuel filter, but maybe not. Anyway, washed it all out and so started the truck to dry it out. Let it idle approx 15 mins while I picked up tools, etc.

Got in it, backed out of the driveway, turned the corner and got on it hard. Made it to third gear and it was like the throttle just quit working. It quit pulling wouldnt rev, nothing, pushed the clutch in and it cut itself off.

Hit the key and it turned over for approx 5secs before it caught and after that it ran just fine.

WTF is wrong with this thing?!?!?! Im just thinking here (afterall Im a chevy guy and not well versed in the ford injection system) that perhaps the filter bowl has a leak and him trying it friday was enough to reprime the bowl so that it fired up for me late in the day yesterday, and that today when I started it it had leaked down to a point that when I got on it hard it drained the bowl again, and it shut down, making the longish crank necessary.

Sorry for the long post but I want to get all the details in so maybe someone can give me some advice, ideas, etc.
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Old 10-22-2011, 01:35 PM
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Alright, just to add more info. Went back out and drained the filter housing again just to see if any water had collected since last weekends tank draining. So I had it idling and was rinsing out the lifter valley again and when I got up behind the HPOP, and was spraying down the truck kinda stumbled. I quit spraying and started looking.

From the passenger side, I reached down towards the HPOP (on the pass side there is a large hex headed plug), and when I pushed the high voltage (red wrapped) harness out of the way, the truck shut down just like somebody turned the key off. Went around and it fired right back up and shut right back down. Hit the key again, blipped the throttle and it idled just fine. Went back around and wiggled every wiring harness in site and it wouldnt do it again.

Is there any kind of known issue with a chafed wiring harness (or a particular place to check). I know on the d-max LLY's they are known to chafe in a couple particular spots, didnt know if it was the same w/ the 7.3.

Thanks for any help guys Im kinda lost at the moment.
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Old 10-22-2011, 01:47 PM
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You gotta wiggle everything around with these trucks when it acts up sometimes. If there's a problem with a 7.3 sometimes you just gotta wiggle everything around and stuff just magically gets fixed.
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Old 10-23-2011, 08:57 AM
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Since the truck has leaked fuel in the valley, do a real good check of the fuel bowl wiring harness since this harness also contains the wiring for the Injection Pressure Regulator (IPR). Leaking fuel turns wiring insulation into goo, causing problems such as shorts, etc. You may even need to remove the harness and check inside the loom as well. Cheers!
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Old 10-23-2011, 09:37 AM
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Well I was out messing with it some more this morning and I MAY have found the problem. I was degreasing the engine to make it a little easier to work on. When I was rinsing it off, I decided to fire it up and see if I couldnt find out what yesterday was about with the shutdown. So its idling along and the second the water hits the CPS, it shuts down like you turned the key off. It will refire as soon as you turn the key, but if you hit the CPS with water its dead.

I repeated that 2 or 3 times just to check myself. Now, what is the latest number for the CPS? Ive replaced it once before, but thats been several years and when I did it it was right when the gray vs blue vs black was going on so I dont even remember which one is in it right now.

Which p/n should I order? Also is there any known issue of a bad plug on the CPS? I checked and its not loose so perhaps the sensor itself is cracked and the water is shorting it.

Also gonna go ahead and do a set of GP's since it is hard to crank and 2 tested as being dead, any hints or tips to them?
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Old 10-29-2011, 01:35 PM
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Alright guys, changed the CPS today, p/n F4TZ-12K073-C. Also changed the glowplugs. While I was at it also changed the oil (it was about time anyway). Now it will actually start when its sub 50*, power seems up slightly. However, again, I had it sitting idling, warming up while I was picking up tools and it shut off . So I hit the drain valve, get just a little water/nastiness out. So I take off the 2 bolts that hold the regulator on the side of the fuel bowl and there is alot of sludge (algae looking crap) stuck to that screen.

Cleaned it off, put it back together and then it just wouldnt fire. Turned over and over and over, let the starter cool off and did it again. Had to repeat that 3 times, then it fired up and ran fine. Also didnt notice any smoke while it was turning over, but its hard to tell its windy out and its got the dually fenders blocking a straight view in the mirror. It should not take that long to reprime, I didnt let but maybe a few ounces out when I drained the bowl and hardly anything came out when I took off that regulator.

Gonna drive it some more and see what other symptoms I can come up with, see if there is a pattern, but yall have anymore ideas? I checked the UVCH while I was doing the glowplugs, they are still good and tight so I dont think those are the problems.
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Old 10-29-2011, 01:56 PM
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I'd remove your fuel bowl and change o-rings and give it a good cleaning. I cleaned mine and it was a quarter full of sand and dirty and sludge.
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Old 10-30-2011, 06:43 AM
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Well this morning it is 30* out.....what happened to fall?

Anyway, before I tried anything, popped the hood, checked the HPOP resevoir, its full. Hit the key WTS light came on, when it went off, turned the key it fired right up. It ran at a slightly elevated idle (approx 900) for about 45secs. Then the tone of the engine changed a little (almost hollow sounding), check engine light popped on and engine died immediately (those 3 things happened in a span of about 5 seconds). Turned key, restarted. Same deal, except it ran slightly longer, about a minute. Third time it only ran for about 30 seconds then died with no check engine. Once more and it ran for about the same amount of time except it didnt go into the elevated idle, it just ran at its normal 600rpm.

Checked HPOP again, its still full, so atleast to what I have read the ICP isnt telling the IPR to dump all the oil due to high pressure, and the IPR isnt sticking and dumping all the oil, or could those still be culprits?

Oh and if I was to try to find someone with a scanner to borrow, what kind do I need to get to be able to read this truck?
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Old 10-30-2011, 08:36 AM
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Check all the valvecover harness connections for evidence of burning/melting or oil in the connections (which indicated the pins may have gotten very hot). Cheers!
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Old 10-30-2011, 09:25 AM
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checked those when I had it apart yesterday.

Anyway, I think we may be getting closer to resolution or atleast narrowing it down.

Drove it up to the store about a mile away, went in, came out everything is fine. Coming home, it bucked like it was gonna shut off coming away from a stop sign, about the time I hit third gear (apparently it just doesnt like third), and I was getting on it good. Well, it was fine, up until the next stop sign. As I was slowing down for it, no warning, just boom, dead. Hit the key and it just spins over. Did that several times, get out, open hood, wave idiot around who doesnt know what hazards and a hood open means, hit the fuel drain, and nothing comes out?!?!?

Nothing, no fuel, no water, all I hear is a slight sucking/gurgling sound. Walk home, grab a can of diesel and toolbag, walk back to truck, take lid off the filter and as Im threading it off I hear more gurgling and when I get it all the way off its full of fuel and the fuel drain works.....get in hit the key and it fires straight up......

Seriously guys.....what in the name of all that is holy is wrong with this thing.....when its running if you barely even crack the fuel drain it shoots a geyser out (I have the redirect tube taken off so I can see the fuel come out the drain easier), so I know the fuel pump is giving it good pressure, but its like when I got on it away from the stop sign it sucked the filter housing dry and thats why it died, almost like a vapor lock issue.
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