M1078A1 fuel starting issue

[MatthewWBailey]

Yep, thats it, they made it real easy on the 3116 with a 1/8” npt port. Had an old oil pressure gauge from the junk drawer hooked up in a few minutes…

IMO, this is something everyone should check whenever you change filters… or install a dedicated gauge… I don't think I can possibly count the number of fuel supply issues I have troubleshot over the years.

i am kinda surprised cat stuck with the mechanical lift pump on the 3126/C7. Even ford, when they licensed HEUi from Cat fitted a 60 PSI electric pump/filter unit back near the fuel tank… At least that way any leakage leaves a wet spot a fixed pressure electric pump could be monitored with a pressure sw and an idiot light…

Here's the fuel psi at startup

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[MatthewWBailey]

Got it back together and it fired over immediately. No codes showing. I let it run 15 minutes. See video of fuel gauge above. I guess the new sensors did the trick. Fuel psi shows 80+. Gauge is a NoShok 0-100.
so far no leak on the compressor.

 

[Ronmar]

80 PSI at idle? Does it go up any when you rev the engine to high idle? Depending on where you look the pressure spec can vary. I have seen A0 specs from 7.5 minimum low idle to 65 psi max high idle. Are you sure the fuel return line or reg at the back is flowing properly?

just came across another one that says 58-76 high idle and 58-65 low idle, which is the first one I have seen that didn’t have a significantly lower pressure spec at low idle vis high idle…

 

[MatthewWBailey]

80 PSI at idle? Does it go up any when you rev the engine to high idle? Depending on where you look the pressure spec can vary. I have seen A0 specs from 7.5 minimum low idle to 65 psi max high idle. Are you sure the fuel return line or reg at the back is flowing properly?

Not sure of the regulator function. I was kinda surprised to see it shoot up that high. Could that return line or regulator be clogged with the same crap that was lodged in the primer pump check valve? I guess the filter would prevent that thou. I'll check on the high idle pressure tomorrow. My gauge line is leaking a little bc I was rushing and forgot to put Teflon tape on the npt threads.

 

[Ronmar]

Its possible… you have another regulator on your second engine to play with? A quick test for the return line would be to simply connect a different line to the regulator output and run it into a bucket to take the installed line out of the equation…

 

[MatthewWBailey]

Its possible… you have another regulator on your second engine to play with? A quick test for the return line would be to simply connect a different line to the regulator output and run it into a bucket to take the installed line out of the equation…

Yes the other engine has a complete set of lines. That's a good idea. I'll try that.