Horrible air intusion while running.

[Idilarry89]

Ok so I've had my current idi for exactly a year and I'm having my first issue after 50k miles. This is odd for me and I might figure it out tonight.

So I noticed a couple weeks ago and intermittent Miss at idle had no issues at high speed. At least until last night. Went to Rapid which is a city about an hour away drove around all day running errands no issues. Then coming back I started feeling a surge at highway speeds about 10 minutes from my shop. So I pulled up to the gate got out could tell it had a miss and went to go open the gate and it stalled. I couldn't get it started so I pushed it in and took the service truck home.

Before I left this afternoon I took the fuel filter off and noticed it was dry. No biggie fuel pumps bad or I've got an air leak from the tank to the pump, or from the pump to the filter. So I cranked it over with the filter off and I had good fuel flow (by the way replace the fuel filter about a week ago) So I thought fuel filter was bad replaced it bled the system. Got the truck started it ran for about 45 seconds then stalled out again. So I pulled the fuel filter off and it was empty again.

I know I have one return cap leaking on the back passenger side. But I've never seen one put air into the system that fast let alone while it's running at a high idle. I'm going to do a pressure and flow test on the fuel pump tonight to make sure it's putting out enough pressure to keep the filter full, but considering it's not that old and how much fuel put out the first time I cranked it, I doubt that's the issue.

I'm curious, I don't know how many miles are on the injectors because they were out of the donor truck that I got the engine from, but considering the miss, do you think one of the injectors could be letting compression into the injection pump and into the rest of the fuel system?

Like I said I'm going to test the fuel pump first and then move on to possibly the injectors. but I need my truck .

By the way this is also the 1991 that you will see in my signature

 

[pelky350]

It could be leaking air from somewhere before the lift pump, the little hose just before lift pump, selector valve can leak air(maybe pulling from wrong tank is possible too) or shower head could have fallen off inside tank making you run out of fuel at a 1/4 tank is possible as well. Saying ou have fuel coming out of lift pump it is possible the shower head is filling with tank junk while running plugging and cutting off fuel supply?

 

[catbird7]

Sounds like fuel tank selector valve. Take a peek at it, see if it's wet, sweaty, and looks like this.

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[Shawn MacAnanny]

I've also had these pull air from the metal line leaving the fuel sender at the tank. Right at the bend.

 

[Idilarry89]

. I had checked the selector valve and the outlets from the tank and narrowed it down to lift pump. Warrantied out the pump. And everything was fine. So I thought. I let it run at my shop for an hour over lunch came back and it was still running drove it yesterday and today. Went to the store and made it halfway thorough town and it pulled air again.

And before anyone questions ANY fuel lines on the truck I had ALL lines bypassed and the suction line ran straight into a bucket of diesel fuel with the same issue.

Waiting on a friend now to go get my service truck to pull the filter and make sure it's dry. Any ideas?

 

[Shawn MacAnanny]

Have you checked the fuel olive on the inlet to the injection pump? Or fuel olives to/from filter? I don't know how far you bypassed it

I always bypass with in electric fuel pump to rule out the mechanical. If you have a leak anywhere on the suction side you WILL hear air returning to the tank with an electric pump. A $15 electric inline pump will work fine from s bucket to check this

 

[bj_idi]

maybe your having lift pump failure and the ip is sucking down the fuel from filter housing? I second bypassing with an electric pump and checking the olives

 

[Idilarry89]

Checked the olives. Even put 10 psi air to the filter head and checked for leaks. I haven't used an electric pump to bypass but I have a new mechanical. I guess it's possible the new pump is bad out of the box. This is odd. I haven't ever run into this before.

Thanks for the help guys. I need my truck back soon lol. I'm about ready to buy back my old 12 valve! Lol

 

[Shawn MacAnanny]

Electric pump is the ticket to finding any air intrusion issue.

 

[Macrobb]

Electric pump is the ticket to finding any air intrusion issue.

Actually, yes. I've had excellent luck with a cheap electric pump - something like this:
http://www.ebay.com/itm/New-Fuel-Pu...al-Inline-Electric-Pump-HEP-02A-/132224092810

The good thing about one of these is that it will 'flow through', so you can mount it after the lift pump, before the filter housing and use it to 'prime' the system or test... you don't have to have it running all the time, only when you need it. And if it dies, it doesn't matter because the mechanical pump will take up the slack.

Also, I'm not sure what you did about bypassing the lines... I'm guessing that wasn't that way during your trip?
I'll bet your tank pickup is all screwed up, and it's intermittently sucking air, depending on how the tank is bounced. So when sitting it's fine, but occasionally while driving... air gets sucked in.

I'd take a jerry can of diesel, strap it to the front bumper, and run a line from that to the lift pump. Make sure to cut a V notch in the end of the line that's in the jerry can, to keep it from 'sticking' to the side.

Then, drive around and see what happens.