Air intrusion on 1990 7.3L f350 with banks turbo
- Thread starter danda
- Start date
Update: I'm calling this issue resolved and returning the truck back to service. Finally!
After sitting 24 hours it will now fire up after 1-3 seconds of cranking. I haven't left it sitting for many days yet, hopefully that will be fine too.
In the hopes it can help somebody else, I will summarize here the things I found that were actually causing the problem, in addition to some other improvements along the way.
The top 3 that finally resolved the issue:
1. Re-routed injector return lines to exit from front driver-side injector near IP and tee into the line from IP which now runs along the side of the engine, so the whole line is easy to inspect and repair. I had first diagnosed leaky return line by cutting the line under the truck, plugging it, and then blowing compressed air into the hose where it connects to IP. Lots of hissing at inaccessible area at the back of the engine was a real big clue.
2. Replaced faulty check-valve at top of IP. This was allowing air from (leaky) return line to enter IP. Once I did this, it went from "no fire at all" to "fire, then die". So, an improvement. After replacing the check valve, I blew compressed air through the old one and was surprised to see the little ball snap back into place and now the valve looks exactly like the new one and I can't blow through it anymore, so I probably could have saved a few bucks.
3. Replaced faulty check valve between fuel filter housing and #1 injector (return line). I could easily blow through the old one. This enables fuel filter air bleed mechanism to work correctly without air getting back into the filter.
Things that helped along the way:
1. Developing a clear understanding of how fuel flows through the system, and in particular the two check valves and return lines.
2. Installed electric fuel pump and removed and blocked off the mechanical pump.
3. Installed a napa fuel filter with its own drain and deleted the factory water separator.
4. replaced the injectors with some remans from russrepair.
5. replaced o-rings, caps, and return lines between injectors.
6. removed and plugged the fuel pressure sensor. ( I might put it back soon )
edit: Well, I was going to link to this post from the thread-starter and also mark the thread title "resolved" so anyone starting reading could find the solution, but the forum software won't seem to allow me to make any edits, I guess because it is an old post. so.... bummer.
After sitting 24 hours it will now fire up after 1-3 seconds of cranking. I haven't left it sitting for many days yet, hopefully that will be fine too.
In the hopes it can help somebody else, I will summarize here the things I found that were actually causing the problem, in addition to some other improvements along the way.
The top 3 that finally resolved the issue:
1. Re-routed injector return lines to exit from front driver-side injector near IP and tee into the line from IP which now runs along the side of the engine, so the whole line is easy to inspect and repair. I had first diagnosed leaky return line by cutting the line under the truck, plugging it, and then blowing compressed air into the hose where it connects to IP. Lots of hissing at inaccessible area at the back of the engine was a real big clue.
2. Replaced faulty check-valve at top of IP. This was allowing air from (leaky) return line to enter IP. Once I did this, it went from "no fire at all" to "fire, then die". So, an improvement. After replacing the check valve, I blew compressed air through the old one and was surprised to see the little ball snap back into place and now the valve looks exactly like the new one and I can't blow through it anymore, so I probably could have saved a few bucks.
3. Replaced faulty check valve between fuel filter housing and #1 injector (return line). I could easily blow through the old one. This enables fuel filter air bleed mechanism to work correctly without air getting back into the filter.
Things that helped along the way:
1. Developing a clear understanding of how fuel flows through the system, and in particular the two check valves and return lines.
2. Installed electric fuel pump and removed and blocked off the mechanical pump.
3. Installed a napa fuel filter with its own drain and deleted the factory water separator.
4. replaced the injectors with some remans from russrepair.
5. replaced o-rings, caps, and return lines between injectors.
6. removed and plugged the fuel pressure sensor. ( I might put it back soon )
edit: Well, I was going to link to this post from the thread-starter and also mark the thread title "resolved" so anyone starting reading could find the solution, but the forum software won't seem to allow me to make any edits, I guess because it is an old post. so.... bummer.
Cant Write
Full Access Member
@danda my driveline vibes are solved so now I’m onto air intrusion.
I need to study your thread further but it seems you had drain back issues vs air intrusion while under power.......is this correct?
I think I have slight drain back as well as it takes 2 shorts cranks in the morning to fire. My biggest issue is bucking and sputtering after pulling Mtn passes.
I’ll start my own thread, thanks!
I need to study your thread further but it seems you had drain back issues vs air intrusion while under power.......is this correct?
I think I have slight drain back as well as it takes 2 shorts cranks in the morning to fire. My biggest issue is bucking and sputtering after pulling Mtn passes.
I’ll start my own thread, thanks!
yes that's correct. The truck would run fine and strong once started. But getting it started would require bleeding injectors if it sat even overnight.
might be related. Another thing to check is if there is air coming from the fuel tank. I'd suggest putting clear hose between the fuel pump and filter. If there is air, it could be your fuel selector valve or a corroded "shower head" pickup inside the fuel tank. I hear this typically manifests when the tank is less than 1/3 full.
edit: you might want to install a fuel pressure guage as well, perhaps you do not have enough pressure under load.
k, good luck!
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