Fuel pump replaced, now another fuel problem comes up. - Land Rovers Only

atikovi · 04-07-2007, 08:30 AM

I just replaced the fuel pump in my ’96 Discovery because it wouldn’t hold pressure after shut-off causing hot start problems. It starts up fine now but after taking it for a drive it bucks and misses with moderate or stronger acceleration. Feels like it’s starved for fuel. I hooked up my fuel pressure gauge and snaked the hose out the rear of the hood and secured the gauge under a wiper arm for a test drive. Sure enough, as soon as I put the engine under a moderate load, the gauge needle started to drop and around 10psi the engine stated to buck and miss at which point I let off the gas and the needle went back up to around 30psi and it ran fine.

Could it be the new fuel pump is bad right out of the box? I didn’t notice this problem with the old fuel pump. Or could the new pump just bring to light the next weakest part down the line such as the pressure regulator. I pulled the vacuum hose off the regulator but that made no difference. I’m trying to envision how the regulator works and what would happen if for example it was stuck. If it was stuck, and at idle the pressure was 30psi, and you put the engine under load with the injectors requiring more fuel, the pressure would drop but since the regulator was stuck, it couldn’t raise the pressure back up to the required 30psi. Does this sound logical? Should I just replace the regulator? It does have a new fuel filter.

pavel · 04-07-2007, 08:43 AM

Before you replace the fuel pressure regulator, check over all the rubber tubing up to the engine - is it possible that the tubing is collapsing (or having an aneurism) or is partially plugged? I had a similar problem many years ago with a Healey - I replaced several components unnecessarily until I blundered on the real problem. You did put in the correct fuel filter.... Keep that chin up, hopefully she'll run properly soon.

Disco Mike · 04-07-2007, 09:19 AM

When you replaced your fuel pump, didi you notice alot of grap on the bottom of your tank, if so did you clean it out?
Did you replace the fuel filter?
Mike

04-07-2007, 08:30 AM	#1 (permalink)
atikovi Member Join Date: Jan 2007 Posts: 13 Gallery: 0	Fuel pump replaced, now another fuel problem comes up with engine missing/bucking und I just replaced the fuel pump in my ’96 Discovery because it wouldn’t hold pressure after shut-off causing hot start problems. It starts up fine now but after taking it for a drive it bucks and misses with moderate or stronger acceleration. Feels like it’s starved for fuel. I hooked up my fuel pressure gauge and snaked the hose out the rear of the hood and secured the gauge under a wiper arm for a test drive. Sure enough, as soon as I put the engine under a moderate load, the gauge needle started to drop and around 10psi the engine stated to buck and miss at which point I let off the gas and the needle went back up to around 30psi and it ran fine. Could it be the new fuel pump is bad right out of the box? I didn’t notice this problem with the old fuel pump. Or could the new pump just bring to light the next weakest part down the line such as the pressure regulator. I pulled the vacuum hose off the regulator but that made no difference. I’m trying to envision how the regulator works and what would happen if for example it was stuck. If it was stuck, and at idle the pressure was 30psi, and you put the engine under load with the injectors requiring more fuel, the pressure would drop but since the regulator was stuck, it couldn’t raise the pressure back up to the required 30psi. Does this sound logical? Should I just replace the regulator? It does have a new fuel filter. Last edited by atikovi : 04-07-2007 at 08:42 AM. Reason: edit

04-07-2007, 08:43 AM	#2 (permalink)
pavel Senior Member Join Date: Aug 2004 Location: Vancouver, Canada Posts: 433 Gallery: 0	Before you replace the fuel pressure regulator, check over all the rubber tubing up to the engine - is it possible that the tubing is collapsing (or having an aneurism) or is partially plugged? I had a similar problem many years ago with a Healey - I replaced several components unnecessarily until I blundered on the real problem. You did put in the correct fuel filter.... Keep that chin up, hopefully she'll run properly soon. __________________ --------------------- Visit my j**p website

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04-07-2007, 09:19 AM	#3 (permalink)
Disco Mike Moderator Join Date: Aug 2004 Location: Parker, Colorado Posts: 5,325 Gallery: 0	When you replaced your fuel pump, didi you notice alot of grap on the bottom of your tank, if so did you clean it out? Did you replace the fuel filter? Mike

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