1992 Ford F-350 7.3 IDI NA drives 1/2 mile then dies and has hard starts...

foundonroaddead

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Hi all,

I recently began working on my dad’s old 7.3 IDI in mid November since my LB7 Duramax has faulty injectors (again). It’s been sitting since 2008 so I’ve done a decent amount of maintenance on it so far. I’ve replaced batteries, return lines, injector orings, oil, transmission fluid, dumped the old gas, changed all the filters, new glow plugs and GP wiring, cleaned all the injectors, replaced lift pump with an electric Facet pump, new front and rear brakes and hardware, etc. Plan on replacing the alternator and water pump as well. Finally got it somewhat running about a week ago.

Anyways, my problem is something i’ve yet to see after searching at least 50 different forum posts. the truck will idle just fine, have had it idle an hour straight and no fuss, hovers around 650-750 RPM. When i floorboard it and let off it doesn’t die out either. (it used to, but seemed to stop after i got a new fuel filter and filled it with Diesel Kleen and let it sit a day.) However, as soon as i take it on the road, i drive roughly 1/2 - 3/4 miles down the road and it suddenly gets a power boost of sorts then completely kills out and comes to a stop. Then, i have to crank it for about 10 seconds before it finally starts back up again and i go about 500 feet then it dies once more. This makes it a PITA to get home even when it’s just a 1 minute drive away.

When it was originally parked a buddy of my dad’s said it was the injection pump going out. Can the IP manage to work just fine idling and then crap out when it’s put under load? my only other conclusion could be the facet lift pump simply cannot pull fuel through fast enough to supply the IP and thus kills out. meaning that the fuel tanks sending units may be clogged or faulty. my rear tank runs the engine fine (until the above happens) but even when in idle if i switch to the front tank my clear fuel tube from lift pump to filter fills with more air than fuel, rough idles, then dies after about 15 seconds. maybe fuel sitting in there for 12 years corroded or rotted the sending unit?

Had to start it so many times today that it killed the battery and i had to get a buddy pull it home with his car.

Would really like for this to not be the IP cause of how expensive it is...

Any help or advice is appreciated! Thanks.

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BR3

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Sounds like air getting in the fuel system. Read up on air intrusion, and follow the same diagnostic process as you would for that, and you should find your problem. Its unlikely to be the IP causing this particular issue, more likely your other thoughts, but there are many ways and places air can enter/ cut fuel supply.
 

foundonroaddead

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Sounds like air getting in the fuel system. Read up on air intrusion, and follow the same diagnostic process as you would for that, and you should find your problem. Its unlikely to be the IP causing this particular issue, more likely your other thoughts, but there are many ways and places air can enter/ cut fuel supply.

Air intrusion before the lift pump then? The injector lines have all been purged twice and are getting a steady flow of fuel. Considering I see air being pulled into the lift pump directly from the fuel tank lines, probably is a bad fuel tank unit/shower head/filter gizmo. Will try to pull the tanks off sometime this week and take a look. thanks!
 

miles1400

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@foundonroaddead welcome to Oilburners, Facet pumps are hit or miss. alot of the guys dont like them and some do like them. you could have busted shower heads in your tanks and with the fuel sloshing around when you drive it could be causing air intrusion.
 

foundonroaddead

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So i’ve heard, naturally after I installed it haha. Any other brand or model you’d recommended instead?

That’s the conclusion i came to as well. Didn’t think it would because both tanks are over 3/4 full, but with how finicky the rest of the engine is regarding air intrusion, i’m sure of it.
 

Slicknik

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@Cubey your just biased cuz you like red heads and her name Holley

@foundonroaddead, sounds like you need to drop the front tank and do a shower head swap or mod. Or chase red heads and go electric .

If you move away from stock, read up
 

Shadetreemechanic

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As other have said, its either your lift pump, or further back. Its not your IP.
The power boost you get just before it dies is air in the IP. That makes me doubt its your lift pump. When I had fuel delivery issues from my facet pump (I switched back to mechanical) It was a loss of power. The system was sealed so air couldn't get in.
Based on what you have written I am wondering about your FSV. It would affect both tanks, but not necessarily in the same way depending on what is wrong with it.
I wish the FSV were easier to bypass. If it didn't have those stupid quick connectors on it you could just bypass it with some rubber fuel line. As installed you can bypass it, but its a pain in the ass.
 

notenuftime

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I had this issue in the past. It was my front tank shower head. Got rid of the two tank system and did away with that BS selector valve. Running just the rear tank now, replaced the shower head with PSD showerhead.
 

John Scott

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Sounds like a fuel delivery issue... I would put a clear fuel hose in a couple of places before the filter and then after the filter.. does it do this on one tank or both.... depending on where the air is getting in u will see it in the clear hose...
 

foundonroaddead

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As other have said, its either your lift pump, or further back. Its not your IP.
The power boost you get just before it dies is air in the IP. That makes me doubt its your lift pump. When I had fuel delivery issues from my facet pump (I switched back to mechanical) It was a loss of power. The system was sealed so air couldn't get in.
Based on what you have written I am wondering about your FSV. It would affect both tanks, but not necessarily in the same way depending on what is wrong with it.
I wish the FSV were easier to bypass. If it didn't have those stupid quick connectors on it you could just bypass it with some rubber fuel line. As installed you can bypass it, but its a pain in the ass.

Thanks,

is the fuel shutoff valve in the tanks, part of the tank selector switch, or a separate piece back in the line? i ask because the only similar thing i’ve been able to find is the fuel shutoff solenoid on the IP, however that’s ahead of where the problem is coming from like you already stated.
 

foundonroaddead

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Sounds like a fuel delivery issue... I would put a clear fuel hose in a couple of places before the filter and then after the filter.. does it do this on one tank or both.... depending on where the air is getting in u will see it in the clear hose...

the problem happens on both tanks, just happens way sooner on the front tank. I have clear line from my lift pump to my filter and at idle the rear tank doesn’t get any air leaks, completely solid. as soon as i switch to the front tank the tubing fills with air bubbles and runs for maybe 15 seconds super rough then dies. i also first did my return lines all in clear to troubleshoot and the only air leak even then seemed to be from what i explained above. have since replaced the return lines with the default black tubing though.
 
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