Engine/Transmission (1994 - 1998) Air Bound

[NMongeau]

Hey guys, having trouble with my truck and could use some input. Has been intermittently hard starting, especially with the nose uphill. If parked slightly down hill (and I mean just slightly almost level) starts fine every time. Thought it might be the lift pump but was doing some reading and it seems that lift pumps are also associated with a power loss. I don't have a power loss or seem to have a lack of fueling issue (plenty of smoke/haze from a stop to max speed ). Truck has 143K on it and I was thinking of replacing the lift pump anyway just to eliminate any guessing. There are no visible signs of a leak and the filter was replaced in the fall. Any help would be great because I can't keep driving it like this. Thanks guys.

 

[tp0d]

If you havent replaced any fuel lines yet, its now time to. You could have a dry-rotted hose that allows air in, but doesnt leak out. Same thing happened to my return line, when I found it, it was just slightly moist and getting ready to leak. I changed my suction and return lines from the motor to the tank with high-grade marine diesel line, made by tridentmarine.com (#365 hose). Suction is 3/8" ID and return is 5/16" ID.



If your lift pump was a problem, it would lose prime at any angle.



good luck



-j

 

[bdcraig]

Sounds like the rubber return line. The crack and allow air to get into the system without ever leaking. Put 2 on my truck. They are a booger to get to. Runs from the metel line comming off the overflow valve to another metal line down beside the bellhousing. Good luck!!!



Brian

 

[NMongeau]

Tests

cheched all my fuel lines thoroughly. all lines are still plyable. not hard or cracked. put a vacuum pump/gauge on the quick connect coupler for the return line to the tank and pulled 25 in/HG of vacuum and let it sit. within 20 minutes the gauge was down to 6 in/HG of vacuum and the vacuum canister was full of diesel. I removed the overflow valve and when blew into it could see air bubbles around the checkball. disassembled the valve and found slight wear and pitting on the ball. am going to change the overflow valve today and see what happens.

 

[JFaughn]

When I had a similar problem , would not start easy when got down to about 1/4 tank it was also less millage , do a fuel pressure check , I ended up replacing the LP & overflow valve .
My 1st starting issue with this truck was bad points in the relay controling the shutoff solinoid , filed them 1-1/2 yrs. ago , now its a problem again , time to get the file out .

 

[pwerwagn]

Dont overlook the small stuff either. I had the same problem about a year ago and turned out the overflow valve was slightly leaking.



Also, I have had the fuel filter assy leak once and bleed off pressure, and Ive had the preheater/screen assy leak once also.



--Jeff

 

[McLaughlin]

Had a lift pump on a 96 loose prime if the truck sat overnight pointed downhill. If parked pointing up hill it didn't loose prime.



Like Pwerwagn, I also have had a preheater/screen assy leak and a leaky overflow valve.

 

[JLEONARD]

Mower man,

Put a little air pressure in the tank via the fill. You can use a rag wrapped around an air gun and that will give you enough pressure. Any slight leak will become visable. I've helped Mike find leaks this way... it works well.

Yes I'll help you if you stop by some evening.

Jay