Need help 7.3 idi

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Fordfan90, Sep 13, 2017.

  1. Fordfan90

    Fordfan90 Full Access Member

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    hey guys I'm working on a farm pickup for one of the farmers that comes to are diesel shop. He said the truck won't stay running they had to prime the air out of the system but then it's runs a little bit then dies out on them. So I have it here and it won't move because it dies right after you get the air out of it. It's a 1990 f250 7.3 idi N/A 5 speed. The pump looks damp. The rear fuel tank leaks but it's does the same thing on both tanks and they are completely full.
     
  2. Thewespaul

    Thewespaul Supporting Member Supporting Member

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    Lift pump or injection pump leaks? I would start by putting a clear hose between the filter and ip and seeing if the ip is getting solid fuel once the air is purged out
     
  3. Macrobb

    Macrobb Full Access Member

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    I'd go one step further - jerry can into the lift pump input, or better yet, jerry can with a little E-pump straight to the fuel filter.
     
  4. Fordfan90

    Fordfan90 Full Access Member

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    I replaced the guys returns lines I'll have clean fuel hoes in the morning to put on it. I'll get some diesel tomorrow and put the hose into it and see what happens.
     
  5. Fordfan90

    Fordfan90 Full Access Member

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    How do you put clear line in that spot? Do you just go off the return?
     
  6. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    If was going to throw parts at it, which I'm NOT recommending, I would say lift pump first.
     
  7. Fordfan90

    Fordfan90 Full Access Member

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    I would think lift pump after it runs then dies the fuel filter is empty but then primes back up. But I don't want to just throw parts at it.
     
  8. Macrobb

    Macrobb Full Access Member

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    Probably the fuel tanks; I'll bet the pickup is failing - remember, it has that rubber valve at the 1/4 tank level, so if the pickup gets clogged, it sucks from the 1/4 tank level. This could be the problem - when priming, you aren't flowing any fuel really, so it pulls from the tank. Engine starts, starts pulling more fuel, the 1/4 tank valve opens and it sucks air.

    Again, jerry can to inlet of the lift pump will test this for sure.
     
  9. Fordfan90

    Fordfan90 Full Access Member

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    Both could fail at the same time correct? I'll definitely try putting the lift pump running off a can of diesel tomrrow.
     
  10. icanfixall

    icanfixall Official GMM hand model

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    My guess from what has been posted is the tanks are near the 1/4 level and the pickups are broken off. so essentially you run out of fuel with 1/4 tank of fuel left. Try tightening up the "wet" areas. Many times the filter to injection pump line seals get hardened and leak fuel. They are inside those brass line nuts. Same with the lift pump to filter head line at the filter. Those seals can be replaced too.Most any good injection pump repair shop sells them. You need one 3/8 for the supply line at the filter and two 5/16 line seals for the filter to injection pump.
     
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  11. sjwelds

    sjwelds Full Access Member

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    He said in the first post that the tanks are both full...
     
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  12. Fordfan90

    Fordfan90 Full Access Member

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    Yes they are so I'm thinking something to lift pump up maybe? I redid the return line kit yesterday because of them leaking and the lines be cracked
     
  13. Fordfan90

    Fordfan90 Full Access Member

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    So the truck runs off a hose put into a can of diesel with no problems. So I'm thinking it's the Slector valve or the tanks cause if you flip the tanks it does it on both so I'm confused on it
     
  14. madpogue

    madpogue Full Access Member

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    Yes, that ^^^^^ finding puts the selector valve high on the suspect list. Another "finding" option, that would also at least put the truck on the road temporarily - find a way to bypass the FSV using "jumper" lines for supply and return, from either tank to the lines going forward to the engine. If it still continues to run, then that further points the finger at the FSV, and provides you with a running truck.
     
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  15. Fordfan90

    Fordfan90 Full Access Member

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    So I don't have a fuel line connecting set to bypass the valve so I called the shop down the street to see if they have a set I could use. I put more fuel in the jug and let the truck get up to operation temp with no problems. It ran great just need bypass that valve to make 100 sure.
     

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