7.3 idi Air intrusion, need help

[1991 f-350]

Alright so I got my 1991 7.3L IDI about 4 months ago and the guy I bought it from recently replaced the entire fuel system. Truck had absolutely no problem. Fast forward a few months and I decided to do a full service including engine oil, transmission oil, new transmission filter and oil filter. My problem started when I noticed a small diesel leak on one of my caps. I decided to change all return lines, caps and o-rings myself. Then the hard start problem has been happening ever since. Because if I this I feel that the air intrusion problem is on my return lines or caps. I feel like my problem is so inconsistent, at first I got it to start up every time for a few days in a row, now I can get it to sit for maybe 2-3 hours at most sometimes and it’ll start. Bought the kit from Amazon and caps were loose, so I ordered a better kit and installed it. There’s no diesel leaks from the caps or injectors but I still have the hard start problem after I bleed it and it dies. Need my truck back up and running any suggestions would be much appreciated.
For reference I don’t know much about this engine it is also my first diesel truck.

 

[Ky85]

If you need it to work, etc

I've had this problem before, and just would hold the accelerator down a wee bit and purge all that air out.

if caps and injectors are good check the rubber lines and the clamps

 

[Minuteman96]

Alright so I got my 1991 7.3L IDI about 4 months ago and the guy I bought it from recently replaced the entire fuel system. Truck had absolutely no problem. Fast forward a few months and I decided to do a full service including engine oil, transmission oil, new transmission filter and oil filter. My problem started when I noticed a small diesel leak on one of my caps. I decided to change all return lines, caps and o-rings myself. Then the hard start problem has been happening ever since. Because if I this I feel that the air intrusion problem is on my return lines or caps. I feel like my problem is so inconsistent, at first I got it to start up every time for a few days in a row, now I can get it to sit for maybe 2-3 hours at most sometimes and it’ll start. Bought the kit from Amazon and caps were loose, so I ordered a better kit and installed it. There’s no diesel leaks from the caps or injectors but I still have the hard start problem after I bleed it and it dies. Need my truck back up and running any suggestions would be much appreciated.
For reference I don’t know much about this engine it is also my first diesel truck.

So you’re saying it starts hard and dies, you bleed it and then it starts fine? If it runs good when you’re driving it, I would say that you’ve just got a knicked o ring or something is wrong with one of your line connections at the caps. If the problem wasn’t there but now it is after messing with the return lines, I’d say theres where you’re problem is. Do you have any white smoke at start up or while it’s running?

 

[Ferdy Mint]

We run electric fuel pumps. Minor air leak problems solved. Just let the pump run for 5 seconds before you start.

 

[Austin86250]

i agree with minuteman, your issue is most likely a nicked o ring but as idibronco says no amount of leak on your return causes air intrusion which is an interesting point as i find that not to be true

and for electric pumps are a great "solution" to air after i installed mine 0 issues with air its been great but some people argue that just a band aid and not an actual fix but you make your own choice on that

 

[IDIBRONCO]

as idibronco says no amount of leak on your return causes air intrusion which is an interesting point as i find that not to be true

This is because you're confusing air intrusion and fuel drain back. Air intrusion is ONLY caused by air being drawn into your fuel system while the engine is running. If your return system is leaking, fuel may leak out, but no air is being drawn in. A leaking return line/cap won't make your engine run differently since the only fuel that is present there is the "left over" fuel that wasn't used by the injector(s).

 

[IDIBRONCO]

and for electric pumps are a great "solution" to air after i installed mine 0 issues with air its been great but some people argue that just a band aid and not an actual fix but you make your own choice on that

If you're not fixing the issue, it's still there. If you have an issue that you just work around instead of fix, it's a Band-Aid, not a fix.