cucvrus
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Yes any air leaks and it will drop the fuel. The fuel system must be tight. How did the feed line install go for you?
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6.2 on its way out?
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2INSANE
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Wow! Sounds like an exact problem I had 2 years ago! It ended up being the fuel filter and small air leak that was sucking in not out. Damn near impossible to find it until I blew compressed air into the tank
14k on the IP... hmm. Try fixing the obvious first before dropping loads of cash. Your problem is a fuel problem for sure! IMO I would start with pressurize fuel tank, check hoses under tank too. Those hoses are 30+ years old and tend to leak or suck air. There is a nipple by fuel tank that could be leaking too. Installing a clear rubber hose on the return fuel nipple on the IP helps determine if you are getting air in lines.
Could also try advancing the timing on the IP a little because of chain stretching.
Keep us posted
Btw cucvrus is probably spot on!
14k on the IP... hmm. Try fixing the obvious first before dropping loads of cash. Your problem is a fuel problem for sure! IMO I would start with pressurize fuel tank, check hoses under tank too. Those hoses are 30+ years old and tend to leak or suck air. There is a nipple by fuel tank that could be leaking too. Installing a clear rubber hose on the return fuel nipple on the IP helps determine if you are getting air in lines.
Could also try advancing the timing on the IP a little because of chain stretching.
Keep us posted
Btw cucvrus is probably spot on!
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erasedhammer
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Pretty straight forward. A bit tight getting the whole line around the frame. Thanks.
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I would also add a can or two of seafoam to the fuel tank.
Will help clean up any dirty injectors that might also be causing issues.
Definitely won’t hurt.
Will help clean up any dirty injectors that might also be causing issues.
Definitely won’t hurt.
erasedhammer
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I guess I spoke too soon. Took it for a drive today and after about 20 minutes it was struggling to stay alive at all.
I got back home and it was an awful idle, dropping almost 300 rpm then revving back to 800rpm.
I took a volt meter to the batteries, and it was 11.49v!
Apparently I've been driving it around with a dead battery, I guess having to jump start it every morning should have told me that.
Didn't remember to measure voltage at the ip shut off, but I would assume it be just as low there.
I took a look around the alternator and the exciter wire is missing, so I guess it's a real easy fix.
I suppose extremely low voltage could cause the ip shut off solenoid to struggle to stay open?
Times like this it makes me want to have a mechanical lever on the ip, could drive around with no electrical system
I got back home and it was an awful idle, dropping almost 300 rpm then revving back to 800rpm.
I took a volt meter to the batteries, and it was 11.49v!
Apparently I've been driving it around with a dead battery, I guess having to jump start it every morning should have told me that.
Didn't remember to measure voltage at the ip shut off, but I would assume it be just as low there.
I took a look around the alternator and the exciter wire is missing, so I guess it's a real easy fix.
I suppose extremely low voltage could cause the ip shut off solenoid to struggle to stay open?
Times like this it makes me want to have a mechanical lever on the ip, could drive around with no electrical system
2INSANE
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Nice! Can we all get an E for effort? Lol! Alternator wire... Was not expecting that one!
erasedhammer
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I'm hoping that's the root of the problem. Definitely makes sense to me, low voltage=intermittent ip shut off
erasedhammer
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Well didn't get to test my theory, cause now it wont start again!
Injector lines are dry!
I guess my issue is the IP? I dont understand why the fuel is draining back to the tank. Its certainly not going anywhere else. No leaks at all.
Not that this might matter, but the truck is parked up hill all the time.
Injector lines are dry!
I guess my issue is the IP? I dont understand why the fuel is draining back to the tank. Its certainly not going anywhere else. No leaks at all.
Not that this might matter, but the truck is parked up hill all the time.
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2INSANE
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Finding Air In The Fuel System, A Tutorial!
Air in the fuel system always has some kind of negative impact on the overall engine performance of a diesel engine. Unlike gassers that don't have a big issue with it, our diesel's object to little air bubbles. I had to troubleshoot air entering the fuel system of my '82 shortbox truck...
www.thedieselpageforums.com
erasedhammer
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I would think if there was air leaking into the system, fuel is leaking out of the system. I dont see any wet spots or fuel sitting anywhere.
That method does look good, but I think it would actually be easier to replace every fuel tube in the entire truck and be done with it....
cucvrus
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Fuel does not need to leak out to allow air is. If it gets air it also allows for back feed of fuel. This puts massive amounts of air in the lines and then the system must purge that air to operate and start as designed. It really isn't that difficult to keep the air out. But like I stated. If you have no knowledge of the age of the lift pump, Injection pump, and fuel sock in tank. That is where I would start. Make sure you have the correct lift pump. They list incorrect ones in many books and I have fallen victim to that once and had serious issues trying to resolve an issue. https://www.steelsoldiers.com/threads/cucvrus-repair-projects.192437/page-4#post-2290204 I hope that helps. If not then it is time for https://dieselcare.store/products/r...cgFLlVs25_xHJojFLyHJ86aChES8VuuRoCicQQAvD_BwE
Good Luck. You need the J code intake manifold gaskets https://www.amazon.com/Fel-Pro-MS91586-Manifold-Gasket-Set/dp/B000C2GELU
Good Luck. You need the J code intake manifold gaskets https://www.amazon.com/Fel-Pro-MS91586-Manifold-Gasket-Set/dp/B000C2GELU
erasedhammer
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As annoying as this whole thing is, I guess I should just bite the bullet and start replacing things.
I definitely have the correct lift pump.
linemech31
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I have chased an air leak before on a different diesel powerplant. You wont see a vacuum leak drip. Smoke test it.
erasedhammer
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Smoke test? do tell
linemech31
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Here is a picture of one. Cap any vent lines and apply the smoke to pressurize the system you suspect leaking. It helped me find a suction side air leak in a duramax that was allowing fuel to drain back from the filter into the tank as it sat overnight. Works on other applications as well intake/boost leaks etc. Pretty handy.
Attachments
erasedhammer
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I'm trying to pin down the aproximate location for where air is getting into the system.
In addition to going around checking and tightening hose clamps I also plan to add a check valve between the filter and the IP, and a manual ball valve on the main return line.
I'll shut that off and leave the truck overnight to see if the truck will start after 12+ hours. If that resolved the problem then I'd say air is getting into the system somewhere between the filter and the return line, which is much more manageable to service.
One question:
How does fuel sitting pressurized in the injection lines leak into the return line with the truck off?
I thought fuel only goes into the return system when the injector fires?
In addition to going around checking and tightening hose clamps I also plan to add a check valve between the filter and the IP, and a manual ball valve on the main return line.
I'll shut that off and leave the truck overnight to see if the truck will start after 12+ hours. If that resolved the problem then I'd say air is getting into the system somewhere between the filter and the return line, which is much more manageable to service.
One question:
How does fuel sitting pressurized in the injection lines leak into the return line with the truck off?
I thought fuel only goes into the return system when the injector fires?
shotty
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You replaced all the rubber fuel lines, including the one feeding the IP from the filter? Had that one loosen itself up before...
When I had air leak issues I put a clear tube on the short fuel return line from the IP so I can see the bubbles. I noticed parking uphill made it worse.
When I had air leak issues I put a clear tube on the short fuel return line from the IP so I can see the bubbles. I noticed parking uphill made it worse.
erasedhammer
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I have no doubt air bubbles will show up. Im just tracking down the source.
cucvmule
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erasedhammer how was the truck running before you had the leak in the original fuel line? Is this a continuation of, Hard cold starts hot weather thread?
erasedhammer
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No problems in regular weather. No drain back issue either.
It did take some cranking in 11F. But I didnt have a fuel heater so that may just be fuel gelling.