Air intrusion I've ever seen before

[Kevin 007]

I went from a perfectly tight fuel system with no hard starting/air intrusion issues ever to having no start issues every morning. There are no visible leaks and it's only doing it on the rear tank, which is full. My truck pre dates the shower head fuel pickup tubes. So the leak must be between the tank and fsv.

 

[icanfixall]

Try tightening up the inlet and the outlet to the filter head. Both have the olive seal in the brass caps. Also the brass cap at the injection pump inlet too.

 

[FarmerFrank]

Does the pickup tube have rust pinholes at the top elbow before the factory line? I've had that. Drives ya nuts finding it

 

[Kevin 007]

Well it might, ya know. It was always fine before but this certainly rust around here. It's kinda hard to tell with the tank mounted, I guess ill need to have a look

 

[Agnem]

Let's not make any assumptions here. Are you in fact encountering air, or something else? If, before you turn the key and unscrew the fuel filter, is it in fact not overflowing? I've never heard of an air leak that only happens on one tank. That would be a new one if true, but possible if the leak is at the FSV or RETURN side of that tank.

 

[Kevin 007]

The filter is not overflowing when I unscrew it after a failed start attempt. Ok so, today I realized that every time it has happened; it's been at an altitude of 600+ feet. Strange right.
All my return injector return lines, caps and prongs and olives are new, tight and not leaking. 8,000 miles on the baby moose pump

The lift pump has about 90,000 miles on it. It's stock, a Carter. Once the truck is running; the schrader valve will spray fuel as far as the IP so I'm assuming it's ok. Maybe a bad diaphragm that only leaks sometime?? Or.....only at altitude???

 

[79jasper]

I recall shooting fuel all the way across the engine to the fender.
Might as well replace the pump anyways. If no change, now you have a spare.
But seems more like somthing with the tank.

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[mobilemech]

check the check ball in the filter head. the symptoms you describe sounds like the ball is not sealing and allowing the fuel system to drain off through the return line.

 

[ironworker40]

I would replace lift pump like 79jasper said. Mine took quite a lot of cranking to prime when changing filter with old pump. When I replaced pump It was like a tenth of the cranking time. I was having no issues I just replaced for insurance. I used a dephi pump. Put the clear hose in the returns like the service manual says you will see air if it is leaking. Also did you change filters recently? I have had new filters leak air.

 

[GENIUSLOERTS]

What has the temperature been like? Since it has been below freezing here the last few weeks I have been having a start and die issue like air intrusion. I had replaced my return lines this last summer and have not had any return line leaks or start up issues until the temperature dropped.

 

[Kevin 007]

Just put a new lift pump in it. A Carter. Fired right up and stayed running
It's been about 35degrees F. We will see how it does for morning and alpine starts. I'll post back in a few days with results

 

[79jasper]

What has the temperature been like? Since it has been below freezing here the last few weeks I have been having a start and die issue like air intrusion. I had replaced my return lines this last summer and have not had any return line leaks or start up issues until the temperature dropped.

That's when air intrusion problems really show their head.
You still have a leak somewhere.

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[Agnem]

That's when air intrusion problems really show their head.
You still have a leak somewhere.

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That's correct. It is impossible for the filter to drain back if the return line system is air tight. Don't discount any possible leaks in the fuel line back to the tank either.

 

[Kevin 007]

So far, no air intrusion with new lift pump.....