Hello, I've been fighting a low fuel pressure issue on my disco for a while now. I have a few symptoms I believe to all be related so I will list them all here. For context it is a 1996 Discovery, just rolled over to 130,000 miles.

Slow acceleration when driving uphill, often it will just slow down while the pedal is on the floor.
Lowish fuel pressure. I am getting 30-32 when idling and it will drop slightly when revved
Have a frustrating issue where when disco has sat for around 30 minutes it will kind of "cough" back awake when started again. It starts and then almost has to catch itself before stalling and then idles normal.
Now that its winter here in South Dakota the disco turns over slow in the morning when started. Again it likes to "cough" awake like the previous issue. During the summer or when at least 20 degrees out it starts alot better.

I just put a new fuel pump in it today which is why I am now here asking help from people who know better. Fuel filter is about a year old I replaced not long after I bought it. New battery about 1 month old.

Thanks

 

Do you have to prime it a few key cycles in order for it to start? Could be a bad fuel pressure regulator.

 

I don't. Most of the time I turn the key on and let the pump run for a second before starting but I am not sure it really makes a difference. When I turn the key on before starting the fuel pressure jumps up right away when I have a gauge on the rail.

 

Since you have changed fuel pump and your fuel filter is rather new too, I would definitely check fuel pressure switch - look at this older thread for location: https://landroverforums.com/forum/di...gulator-92410/
Also, you may try to add seafoam to the tank and run on it for the duration of the tank, see if maybe this helps...let us know how this will end please.

 

Okay thats what I was thinking too. Just wanted to check here first. I have a new regulator coming and I am going to replace the vacuum line to it as well.

I will try seafoam again after I test everything new. I ran a can through the tank a couple months ago which is what started alot of this other searching.

I will update when the new regulator is on.

 

Okay, finally got around to changing the regulator and no change . Still starts and has to catch itself. It seems like it can hold pressure fine it just doesn't get up to pressure very fast. When I go to prime it after I have depressurized the system, the fuel pressure builds slowly to around 35. Then when I start it it drops to 28. When I give it a good rev it revs up fine but when I let off the gas the rpms drop down to under 500 before going back to normal idle rpm.

So thats where I am at now. Not sure if this could be an injector issue or if I should look somewhere else.

Thanks

 

Maybe try a new fuel filter first. It possibly had a dirt clod break loose in the tank, even though it is not very old. I think the fuel pressure should build rapidly if the pump/filter/regulator are all good.

Going to very low RPM before getting to normal idle could be related to bad/clogged/dirty IACV, or a slight air leak, or dirty base idle screw. The IACV can also impact how it starts. MAF also gets involved there. Hard to troubleshoot remotely, especially something that is just broken a little. In my experience a failed injector causes misfiring with very rough engine operation.

 

How's your vehicle's battery? Don't rely on a voltage reading. I would consider doing a load test or taking to a parts store and have them do one. Esp since you say it cranks over slow. At least to rule out a flaky battery. Those black toaster-style H/F battery load testers give less info but they get the job done.

Quick story: I struggled with a bad battery on a non-disco vehicle of mine for the last year. The battery was never right...from the get go. I kind of had a feeling something was wrong when it took FOREVER to charge up on day one. Over the yr I thought my (hummer in this case) had electrical issues and other problems. Starter was a bit slower too. I was going to replace it, but I'm glad I procrastinated on it. Finally the batt wouldn't hold a charge at all, failed the load test. I took it back ...it was within the first year warranty. I never let it go flat or abused the battery whatsoever. They tested, it failed & they gave me a replacement (no cost), that was great. Vehicle has been 100% ever since. I had something similar ...but less dramatic on a DD pickup I drive...but that battery was old, reaching the end of it's life. On my H3, I never did have any excessive parasitic drains or other issues. It was just a flaky battery the whole time and has been running great. (insert banging head on brick wall icon!)

So...worth a free check to rule out bad batt. And check the cables/connections/ground over real well too. Wiggle/inspect the fuse for possible corrosion. Maybe swap the fuel pump relay if you haven't already, in case the internal contacts are badly pitted. Good luck!

 

I had this issue with leaky injectors. I had one on each side causing a leak down and effectively flooding those 2 cylinders. I would pull the fuel rail with all the injectors attached. Then just turn the key on and let the system pressurize. You will see gas leaking from the bad injectors almost immediately.

 

Replace
1) fuel filter $15
2) fuel regulator $225
3) fuel pump relay $225
4) fuel pump $225

These prices can be a lot cheaper if you chase parts