Air intrusion
Thread Starter
|
Junior User
Joined: Nov 2011
Posts: 80
Likes: 2
Air intrusion
I posted this in the wrong area yesterday - a rookie mistake. Sorry for the inconvenience.
My dad has an '89 F-250 and I have a '91 F-350 - both with non-turbo 7.3 engines. I've searched, but can't find a thread on this issue - I'm almost sure it's been addressed before 'cause we can't be the only two owners with the same problem.
After sitting overnight, our trucks start then runs out of fuel within 10 seconds. It seems to be losing "prime" overnight through a leakdown somewhere. To solve the problem, I added an electric fuel pump to mine - Y-ed into the fuel line before the mechanical pump, then Y-ed back into the line after the mechanical pump. It's on a switch, and I use it every time I start the truck after sitting for more than a day. I told dad last weekend that i could also do his this way.
I've changed the injector O-rings, caps, and lines on both trucks, and the fuel filter on both are changed regularly. After installing the new lines, O-rings, and caps, the problem went away on both trucks for 6 months or so, then returned. There are NO visible leaks from any of these parts.
What am I missing? . . . . . & thanx.
My dad has an '89 F-250 and I have a '91 F-350 - both with non-turbo 7.3 engines. I've searched, but can't find a thread on this issue - I'm almost sure it's been addressed before 'cause we can't be the only two owners with the same problem.
After sitting overnight, our trucks start then runs out of fuel within 10 seconds. It seems to be losing "prime" overnight through a leakdown somewhere. To solve the problem, I added an electric fuel pump to mine - Y-ed into the fuel line before the mechanical pump, then Y-ed back into the line after the mechanical pump. It's on a switch, and I use it every time I start the truck after sitting for more than a day. I told dad last weekend that i could also do his this way.
I've changed the injector O-rings, caps, and lines on both trucks, and the fuel filter on both are changed regularly. After installing the new lines, O-rings, and caps, the problem went away on both trucks for 6 months or so, then returned. There are NO visible leaks from any of these parts.
What am I missing? . . . . . & thanx.
Lead Driver
Joined: Mar 2006
Posts: 5,100
Likes: 1,510
From: western SD
Finding air intrusion can be a booger to trace down. When you changed out the return line-caps did you do all one side at the same time? If you have done anything to the top of the engine, you might have bumped the return line or cap. Sometimes it doesn't take much disterbance to let air get in, as after the hot fuel runs threw the returns, the 0-rings get hard. If the caps get moved a little it breaks the seal, and the hardend o-rings can't reseal. It has been reported that the use of viton o-ring work well. Typefour, a member of this forum, sells a return line kit with these type of o-rings. PM him toget the particulars of his kit. Or get the o-rings from McMaster-Carr, they sell a bag og 50 for cheap. The size you need is 111, I believe. If you don't think it is the return caps, other places air could get in, such as the electric line plug in for the fuel heater on top of the filter head, the filter it self, the olives on the fuel line from the filter head to the pump, or any place there is a joint in the fuel line return could bet the problem.
Thread Starter
|
Junior User
Joined: Nov 2011
Posts: 80
Likes: 2
Both times, I replaced all caps, o-rings, fuel lines and clamps at the same time. At least 40% of the o-rings I pulled off had started to deteriorate (cracking), so I thought new ones would fix the problem for a few years. At one time, there was a leak at the fuel heater (both trucks), so I completely removed the heaters, tapped the hole and inserted a 1/2" pipe plug into the hole. No leaks are evident at the heater or around any cap or line as I can see and the fuel filter is less than 5,000 miles old on either truck.
I replaced the alternator and voltage regulator on one truck a couple of weeks back, but the leak down was already there when I did it.
Thanx for the help
I saw a McMaster-Carr part number somewhere on this forum in the last couple of weeks, but I can't find it now. I'll look again to see if I can use Viton o-rings.
I replaced the alternator and voltage regulator on one truck a couple of weeks back, but the leak down was already there when I did it.
Thanx for the help
I saw a McMaster-Carr part number somewhere on this forum in the last couple of weeks, but I can't find it now. I'll look again to see if I can use Viton o-rings.
Cargo Master
Joined: Feb 2007
Posts: 2,477
Likes: 21
From: Taylorsville, NC
Here are the ones Farmert talked about. Click on Viton Fluoroelastomer O-Ring, and find size 111.
McMaster-Carr
McMaster-Carr
Thread
Thread Starter
Forum
Replies
Last Post
OFD2413
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
17
Jul 26, 2019 01:13 PM
Ineedhelpfastsoicang
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
9
Apr 14, 2016 09:01 PM
tkcollin
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
6
Oct 31, 2003 10:29 PM
