IDI starting issues

[GunnerJ]

Hello, I'm new to the forum, but I have been reading on it for a long time. I have a 1993 f250 with a 7.3 na IDI. When I start it, it runs for 4 to 7 seconds, and then dies if I don't immediately force it to a thousand rpms, and its a pain to get it started again. I have replaced the return lines and fuel filter, and I still have the same issue. It acts like air intrusion, but I am worried that it is the IP because just recently if I make it idle at 1000 it will jump to 1600 and immediately die unless I floor it.

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[1994Diesel]

I think you are on the right track with air intrusion. Have you done an injector return line kit?

 

[GunnerJ]

Yes, I did, and it fixed the problem for about a week

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[icanfixall]

WElcome to the forum.
Is there any fluid leaking down on the starter? If so you still have a fuel leak allowing fuel to leak out and cause the hard starts. Sometimes the fuel leaks from the hard line off the filter to the injection pump. In the top and bottom brass nut is a seal called an olive. They usually harden and cause the hard start you have described. Whats happening is the fuel leaks out into the valley pan and runs to the back drain then down over the starter. when it drains the injection pump the engine will start and run for as few seconds. Then die out. Just like what you posted. Sometimes this also mean the mechanical lift pump anti siphon valves and failed so the fuel runs back the the tanks. Also looks at the brass nut on the hard line from the lift pump to the filter inlet. that also has an olive in it too. If you try tightening any of these 2 brass nuts they might tighten up some but. If they are all the way tight then those olives will need to be replaced. The feed line to the injection pump is 5/16 and the feed line to the filter inlet is 3/8 line. Any good injection pump rebuild shop has these seals cheap too.

 

[GunnerJ]

Ok I tightened the nuts between the filter and injection pump, they were very very snug but not totally tight, and the nuts between the filter and the lift pump were totally tight. I did a test startup and it shot to 1300 rpms and died, have not taken the time to start it back up yet, I am going to see what I am leaking out of the bottom first. Either diesel or oil is leaking pretty well from somewhere, and its hard to tell on the dirt, but I know there is an oil leak that sprung up when I first started getting this problem 2 months ago

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[79jasper]

Replace the rubber line between the frame and lift pump.

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[icanfixall]

I'm betting what you feel is an oil leak is really a fuel leak on top of the engine somewhere. An oil leak will ot cause hard starts like you described. A wet valley pan under the injection pump usually tells us the injection pump failed. Occasionally the plunger on the drivers side of the injection pump fails and most of the fuel leaks out of the injection pump causing your kind of starting issues too. If the plunger seal has started leaking its time for a rebuilt injection pump and be very sure to never remove the gear cover that pump bolts to. If that aluminum gear cover is removed with the pump attached then the injection pump gear is removed with it and you loose the gear timing. We have found several ways to fix that but they are technical in detail we should not get into now.

 

[GunnerJ]

I understand what you are saying, but I am sure there is an oil leak, the level went down about a quart in two weeks

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[GunnerJ]

Ok I did a drip test on level ground and it is diesel leaking from the injection pump. Is there any way to fix it and not need to buy a new pump?

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[sassyrel]

Ok I did a drip test on level ground and it is diesel leaking from the injection pump. Is there any way to fix it and not need to buy a new pump?

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NOPE!! get a GOOD shop to do the rebuild,,and as icanfixall told you,,DONT remove it by taking the mounting cover off!!!!!!

 

[GunnerJ]

Is there any specific reason I can't rebuild it myself? I'm very mechanically inclined

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[cpdenton]

Yes, you can open it up and reseal it...but, getting all the advance plungers and head and rotor all seated back in? That's a different story. The machine used to properly set all the fuel delivery inside the pump is about 100,000 dollars.....

 

[GunnerJ]

Well shoot, thank you for the quick reply, is it going to be cheaper to get it rebuilt rather than buying one, and is it the same quality end product?

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[79jasper]

Easier to just buy one and use yours as the core.

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[GunnerJ]

Ok thank you

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