MY LB7 has been lossing prime lately and now it wont even stauy running if i can get i primed good enouh to start. I know that this tells me i have a small leak in my fuel system some where. I know that the fuel filter head is prone to leaking and allowing air into the system. My question is aside from the fuel filter head what are the other areas that are common to leak. Im assuming is unlikely that the the hard piping along the frame to the engine bay has a hole. It must be a very small hole because there is no obvious leaks underneath after sitting for days.
LB7: Won't Stayed Primed
- Thread starter MADD*MAX
- Start date
check the rubber lines after the fuel filter also. They also had a problem with the rubber lines along the frame collapsing if i remember right.
It isn't always on the supply to the engine. It can be on the return to the tank. Check tightness on the banjo bolts to the heads, drivers side rear head and passenger side front head. Hard too get to but worth a check. Just a slight leak in the fuel system will cause the engine not to run.
Heres my update. I change fuel filter and checked water in fuel sensor for cracks. So far no everything checks out ok. I got the truck started and it died after a minute. I also dropped the tank because i could see fuel running down in but it turns out my truck used to have a lift pump because there is a return line plumbed into the fill spout that i can see leaks a bit when filling up as there is about a foot of blue hose tucked up around the fill spout. As far as i can tell there is no leaks on the short lines on top the tank. Tomorrow i'm gonna swap my fuel filter head with the one from my dads lmm a I'm sure they are the same. This will rule out whether or not its the filter head. Ive heard of filter heads cracking which i can see with cold fuel and the heater in the head shocking the metal. If this does not solve my fuel issue then im lost.
Ive been doing ome reading and i have an idea to figure out and if i truely have any leaking fuel lines on the low pressure side of the sysem. Im under the understanding that i could run a hose from the inet of the filter housing to a bucket full of fuel and see if the truck wil stay primed that way. My only question is doesnt the fuel go through the FICM before the inlet of the filter houing. Will the FICM be ok not being fuel cooled for a quick test. Probably run the truck for 5 minutes to see if it will stay running. ùnder hood temps should not be very bad.
If its the filter head I jus pulled mine off after pulling my motor out.. It's got 50,000 miles on it and about 1500 on the wix filter.. I'd be happy to send it for small cash
yes
You are correct the fuel goes through the FICM out to the inlet side of the fuel filter, then to a distribution block, then to the inlet of the CP3. FYI, I had this problem on mine. It was a nightmare to figure out. My leak was on the return side of the system. I borrowed a vacuum pump and connected it to the suction side first, no leaks. Then connected it to the return side, Bingo vacuum leak. Not a big one, but a small one, only detected with a vacuum gage. And the hunt was on, following the lines are Fun, not. Any where there is a banjo gasket with bolt, tighten it down, is all you can do. Then prime it up and hopefully, crank it up.
You are correct the fuel goes through the FICM out to the inlet side of the fuel filter, then to a distribution block, then to the inlet of the CP3. FYI, I had this problem on mine. It was a nightmare to figure out. My leak was on the return side of the system. I borrowed a vacuum pump and connected it to the suction side first, no leaks. Then connected it to the return side, Bingo vacuum leak. Not a big one, but a small one, only detected with a vacuum gage. And the hunt was on, following the lines are Fun, not. Any where there is a banjo gasket with bolt, tighten it down, is all you can do. Then prime it up and hopefully, crank it up.
Well I was really banking on it just being my filter head but that is not the case. I ran a temporary line from the filter head inlet to a bucket of diesel and the truck primed and fired right up. Now i at least know my leak is on the supply line from the tank somewhere between the tank and filter head.