1993 F250 7.3 IDI injection pump

screwhead

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Have a 1993 7.3 idi (non turbo). I bought the pick up recently, ran pretty well when I first got it, started having some problems with it, some I have worked out but I think I’m still having a serious fuel delivery problem. These two forums pretty accurately describe what’s going on with it.



I do not think I am having a problem with the alternator as it seems pretty new, pick up also religiously starts every time besides after dying on me while driving ( I’ll have to wait a while to get it going again or crank on it a good bit while pushing ******* accelerator) batteries are also in good condition beside some corroding grounds but I’m keeping those clean and greased(have new cables on the way). I also changed the fuel injectors, glow plugs, and fuel filter. I filled the fuel filter with opti lube XPD (lubricating fuel additive) let it run a bit, and then sit overnight in the hopes that this would clean up my injection pump and fix the problem. The next day it did run a lot better and I was able to drive it around as long as I kept a close eye on rpms, if I did not sometimes it would die particularly while up shifting into 3rd or 4th. Today the problem is back with a vengeance and I can barely make it around the neighborhood, tried and it died on me several times, once even going into second. Even if I can get it to shift a lot of the time it would slowly lose power and get really quiet, by pushing on the accelerator all the way it starts to catch up and maintains speed but especially in third it will do some weird things, sounds like I’m letting on and off the throttle but I’m not I think it’s just failing to get fuel.
I do have a fuel leak from the front take, I have only been running it off the back tank till I can drop the front tank and find out what’s up with it.

Apologize for the length of this I’d just like to get some solid advice and give all the necessary info for that. Am I incorrect in assuming this is the injection pump? If I am correct that it is the injection pump would you recommend going through moose diesel to get my rebuild done? Lastly, it does not have a turbo or inter cooler but want to put one on one day does anyone know if I’d be able to run the junior moose on mine without causing serious problem to it? I did reach out to Moose Diesel today and am waiting on a call back from them.

Thanks for answering my questions in the past y’all were a huge help.
 

screwhead

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Forgot to mention that it seems to be okay idling indefinitely. I have noticed that every once in a while the engine will kind of knock quietly and the whole thing shakes.
 

chillman88

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You could have a couple different things going on but it sounds like you might have a sticky metering valve? I don't know anything about that optilube but I've had good luck with a double dose of Hotshots Extreme fuel additive. Seems to be one of the stronger fuel system cleaners. I know one of the members here got a minor chemical burn from getting it on his skin!

I'm no expert, but that's where I would start. Even though you have already tried a fuel system cleaner, at least I know the hotshots works good.
 

NeverHave-I-Ether

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I'm having the same issue. ATF trick didn't work overnight. I've had it sitting for 48 hours so far....just gonna have it wit in ATF for a ling while.

Never-Have-I-Ether
 

IDIBRONCO

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I'm no expert, but that's where I would start. Even though you have already tried a fuel system cleaner, at least I know the hotshots works good.
I don't think that Opti Lube is supposed to be a cleaner. I agree with the Hot Shot's.
you could be getting air intrusion in the fuel lines, or your fuel pump is getting ready to crap the bed
The lift pump was my first thought. The part about the knock/shake while idling made me think more along the lines of air intrusion. Screwhead, when it sounds like you're "letting on and off the throttle", does it sound quite a bit louder and seem like it has extra power after it loses the power? If so, that's a classic sign of air intrusion (which ONLY happens while the engine's running). Basically, that happens because air gets pulled into your fuel system. When that air get's to the injector pump, the pump tries to compensate for the lack of fuel by advancing the timing. When the fuel builds back up in the pump, the advanced timing plus the fuel makes it have a short burst of power That's my layman's explanation of what happens).
As for the Moose Jr., I'm currently running one on my Blue Truck N/A. I did back the fuel off 1/2 turn. My timing was off (that caused some of my excessive black smoke problem which is much less after having the timing set) and I could probably turn the fuel back up slightly, but it runs fine how it is so I'm leaving it for now.
 

screwhead

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@IDIBRONCO that is exactly what it seems like, it even jumps forward a little and does the same thing a few times before evening out. This has been happening since before I took injectors off/replaced fuel return system. Any ideas on where/how I should start to look for air intrusions?
 

IDIBRONCO

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Any ideas on where/how I should start to look for air intrusions?
It's tough to track down. Since it only happens when it's caused by air being drawn/sucked into the fuel system, it's in the suction part of the fuel system. That means that it's somewhere from the lift pump back to the fuel tank. Common places to get it are the rubber fuel line that goes between the lift pump and the steel line on the frame and the tank selector valve. Before you try replacing anything, try disconnecting the rubber line at the lift pump. Then attach a separate rubber hose and run that into a 5 gallon fuel can of diesel. If it idles fine, then you can start the search. Doing this won't let the engine run for a really long time since it will draw the fuel out of the can and return it to the truck's fuel tank. To run the engine longer, you can unhook the engine return line at the back of the engine and run another rubber hose from there back into the fuel can. This test eliminates every part of the fuel system before the lift pump. It's a good test just to be sure.
 

screwhead

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@IDIBRONCO i figured I’d give your elimination test a try, got the return off too so I could try it for longer. Tried to start the pickup and it ran for 1 second and then died, can’t get it to fire up at all now. I’d guess it’s because there’s not enough fuel in the system? Good bit drained out when I took off hose from tanks to lift pump. Any ideas on how to get it started like this?
 

screwhead

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Figured I’d hook it all back up, try starting again and maybe go through some procedures other people have done when running out of fuel/getting air in system like cracking injectors, etc. But vehicle will not even get close to turning over or warming up glow plugs now. I have no freaking clue what I did to cause this, it was still starting this morning. Didn’t try cranking on it too much whenever attempting to run test, gave it some time between cranking too.

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Me turning the key
 

YJMike92

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Seems to me you have lost electrical power. Battery cable issue or dead batteries? Make sure your battery cables are clean and tight. Charge or jump your batteries and see what happens then,
 

Big Bart

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My two cents.

Start issue.
1) Check your battery voltage. Should be +12 volts.
2) Use a jumper cable and jump the two big posts on the starter solenoid on the fender well. Starts, check the small post gets 12v from start position of the ignition switch. If yes replace solenoid.
3) Clean all the battery connections.
4) Pull starter and have tested.

Running problem

1) Put the return line back on.
2) Fill the fuel filter and put back on.
3) Fill the gas can back up with diesel. (If no other vehicle siphon out of your gas tank.)
4) Idle for 1/2 gallon then test drive with gas can tied in back of the truck. (Get air out of the system.)

Problem gone -
1) You have a blockage or a air leak in the supply line. It is likely your tank selector valve is bad/failed or the seals on the lines to it are bad and leaking. If the problem does not go away when you switch tanks it is likely a issue from the selector valve to the lift pump. It is not likely that both tanks have the same problem, generally only one tank does. These switching valves are a very common failure as they are old. They get stuck partially between tanks.
2) It could be the rubber hose between the fuel line and lift pump next to the engine. These get hot from exhaust system and crack over time. So try that first.

Problem did not go away.
1) Replace lift pump and rubber hose to it.
2) Replace olive seals on metal fuel delivery lines.
3) Replace fuel filter.
4) Fill fuel filter with ATF and run engine for 2 minutes you should hear the engine change pitch as it starts burning the ATF. Shut off engine and lit sit for 24 hours. That often cleans out the IP and injectors. Perhaps repeat with hot shot if needed.
5) Still no luck, send your IP for inspection and likely rebuild.

Less common issues to know about and consider.

1) If your ignition switch is worn, your keys just swinging might be enough to cut the power to the IP solenoid. Slow down keys swing and ignition finds a dead spot.
2) Your IP solenoid may be weak and changes to pressure or speed is causing it to close and shut off the engine.
3) You have a bad wire to the IP solenoid, so movment of the engine causes the wire to open and stop sending power to the IP.
 
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