95 LR Disco 3.9 hard starting....running weak and not re-starting all the time after running for 15 or 20 minutes.

I hooked up a pressure gauge to it, and when the pump is activated it jumps up to 32 PSI and then drops to nothing ....that's without cranking....

The pump is about 2 years old...

Next steps?

 

I read on another post that when the key is turned on, the pump only works for a few seconds, if not cranking. Not for sure tho.

 

Hmmm..okay good point maybe it drops out after initially coming on... So second part of this before I go any further. After I crank it and get it started, then shut it off the pressure immediately goes to 0.

 

I found my 04 doing similar. I have gone through several pumps thus far and found the issue to be the pressure regulator within the pump assembly which also acts as a one way check valve keeping forward pressure to the fuel rails after the pump is turned off. I decided to install an in-line check valve at the frame rail since I have a leak there anyhow. My current issue stopping me at the moment is the type of fuel line I have on the 04 and what type of connections I need to connect to the line... Just posted on it.

 

I'm running through the rave manual checklist right now and will let you know what I find. The regulator for the 95 is on the rail in the front. Not sure if it has one within the pump....I'm not very knowledgeable about the fuel system....yet....

 

Oh...and THANK YOU for for reply!

 

I would def replace the one at the rail.

 

Fuel Pressure Regulator. When vacuum is applied at idle (high vacuum) the regulator diaphragm is opened pulled open to allow fuel to return to tank (less fuel required to idle). Throttle wide open is opposite - regulator diaphragm closed (low vacuum) to allow high fuel pressure (more volume) to injectors. What happens is the FPR does not open or does not close depending on fault. That doesn't explain why the hard starts/no starts when warm problem. Usually the hard starts/warm restarts is due to the coolant temp sensor for the ECU, loss of line pressure or the fuel temp sensor. Can also be blocked fuel filter (canister), pump screen or fuel leakage.

 

Okay! Thank you...Very insightful. It threw a 14 code the other day but did not come back after I reset it. So you think both FPR and the temp sensor? They have never been changed since the truck was new to my knowledge...

 

They're both inexpensive, why not if never replaced? Code 14 is for the Engine Coolant Temperature Sensor........