Fuel pump, How much pressure should it have?

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YZFAndy

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Hi first post on here hope someone can help on this. My mother has a range rover p38 2.5dse that’s now a non starter. Will just about fire but never really gets going and then cuts. If i can get it going its very lumpy, obliviously not running on all cylinders and any throttle input cuts it instantly which made me think it was a fuel starvation problem.

Now have dropped the tank, took the pump out and hooked the pump up to some power and it seems to be working (as in its pumping water) but not sure how much pressure it should have.
I can stop the flow quite easily with my thump over the end but it still seems to have enough flow to feed a diesels needs.

How much pressure should this pump have or does it sound like something else?
Thanks in advance for any help.
 
I have checked that and no, it looks old but doesn't seem to offer too much resistance. Before i took the tank and pump off i checked how powerful the fuel was going into the filter and coming out off and there didn't seem to be much different
I don't really want to reinstall the tank and pump to find out its not that.
 
How much of a pain was it to remove the tank? Need to replace my lift pump. Probably going to take it to the garage, but if it is easy?..

Can you do it without jacking the vehicle up or not? Looks like you can't.

I don't think the lift pump is particularly powerful. If you check after the diesel filter you'll see bubbles (my problem when there is less than 1/4 in the tank) if the pump isn't pumping properly, or there is a leak somewhere. Check the two clear tubes on the pump assembly for cracks/holes.

Matt
 
Hi i am new hear to. and i may be able to help you could you tell me the milage the vehicle ? if you want to cheak you fuel pump running the best way is to use an amp test if the pump is less than 1.5 amps when running this would surgest you are out of fuel the range you want to be is 4-5 amps any more would surgest that the pump is slow and drawing to much current ? fuel pump needs to be in fule to test though . richie
 
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mmaddock said:
How much of a pain was it to remove the tank? Need to replace my lift pump
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To get the tank off isn't too bad, Just two nuts at the front of the tank, two blots at the back and then another nut between these at the back on a very long threat. I undid everything except this nut with long thread (will need a deep socket and long extension) then I undid this and the tank with guard along with 30 litres of diesel dropped on my head. Wasn't expecting the tank to come off that easy, i thought i was just undoing the guard.

Hardest part was getting the car high enough to get the tank out and of course pipes that have been on there the past 8/9 years don’t want to come off easy. Best to lower the car so that while under it you don’t touch a height corrector and the thing comes down on you (I did this with an xantia and its not nice). I kept jacking the car up at the axle so the wheel was off the ground, then just put blocks of wood under the tyres. That was the only way to get the height as the tank is about two foot high at the back, fitted right up under the rear seats.
. If you check after the diesel filter you'll see bubbles
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No bubbles.

could you tell me the milage the vehicle
Click to expand...
135,000 ish.
1.5 amps when running this would surgest you are out of fuel the range you want to be is 4-5 amps any more would surgest that the pump is slow and drawing to much current
Click to expand...
I'm i understanding this right! What you're saying is the car can measure this current and shut off the pump when it thinks its out of fuel?
 
Just to add to this I was having a look around the injectors and noticed there was a build up of old sticky diesel on the first injector. Had a closer look and one of the rubber pipes that are interconnected to the other injectors in a chain was split. The one split was the first one on the chain.
Would this cause a major problem, even stop it from starting? What do these do?
 
Yup, probably the easiest thing to fix and mostly overlooked .. Leak-off pipes. Get a metre or so from a motor factors for a fiver and cut them to length yourself, they only push on/pull off, but should be very tight. Very prone to getting brittle and cracking and causing poor starting issues.
 
Rights, lets start at the beginning.
Replace your fuel pump back in the tank. Connect all wiring and fuel lines back up, and make sure you have sufficient fuel in the tank.

You need to obtain 4-5amps current draw for a pump to be deemed working correctly. Because we dont have an in line fuel pressure guage, the next best thing is a multimeter. You need to locate the fuel pump fuse and remove it, set your multimeter to amps. Insert the probes into the fuse holder (one each side). Then switch your ignition on to stage II, and you should obtain a reading which would approx 20 seconds (this is your pump priming). The multimeter should read around the 4-5amps mark.
Anything above 5 amps would suggest that the pump is drawing too much current, this would suggest you have poor connections somewhere along your electrical circuit or your pump os on its way out. If your reading is significantly below 4amps the this points to a lack of fuel or the impeller in the pump is broken and not turning therefore drawing no current.

The next check is the windings inside the pump. To check this, set your meter to Ohms (resistance) and probe the pump's positive and negative terminals. You shold obtain a reading of 80-120 ohms. If it is open circuit it is broken. If it is very high your pump is indicating its seizing. Which should match up to high amp draw.

Do make sure you are recieving voltage to the pump, and also check the earth is good.

If all that checks out ok, then your problem is further up the line rather than the pump. But i suggest you check this first before moving on to something else.



Regards

Rich
 
Checked how many amps the pump is drawing and it's 3.5 amps no load and 4 amps at full load so i'm guessing its not that.(But now i see you postwed just before me. Is3.5/4 amps too low?)

Also took all the glowplugs out and checked them, they are all ok. Checked the glowplugs are getting current and they are. Took all the injector feeds of to check for any blockages and they seem to be spotless. Replaced all the injector run off's with fresh tubing.

Just cant figure this one out. Only thing i can think of is it has a sticky fuel cut of solenoid. Where do i find that?
 
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the fuel solinoid is on the back of the diesel pump just above the fuel pipes the the injectors, after replacing all that lot you had of its going to take a bit of cranking to get going so dont jump to the conclusion its something else until your sure the system is bled properly and free from air.
 
YZFAndy said:
Checked how many amps the pump is drawing and it's 3.5 amps no load and 4 amps at full load so i'm guessing its not that.(But now i see you postwed just before me. Is3.5/4 amps too low?)

Also took all the glowplugs out and checked them, they are all ok. Checked the glowplugs are getting current and they are. Took all the injector feeds of to check for any blockages and they seem to be spotless. Replaced all the injector run off's with fresh tubing.

Just cant figure this one out. Only thing i can think of is it has a sticky fuel cut of solenoid. Where do i find that?
Click to expand...

Yes, the amp readings you are getting are about right, so you can now isolate the pump from one of your potential problems. It's not that.

Put your lines on, crack the injectors and make sure yor getting fuel at each one. Just because its a fly by wire system, its still a mechanical pump, wih an electronic valve on it.

If your not getting any fuel then its clearly your main pressure pump with a problem. I suggest taking it off and getting it looked at by a diesel pump specialist.


Regards
Rich.
 
Got it all fitted back together, turned it over on a partially charged battery until flat and nothing . Charged the battery all the way up and it fired up quicker than it ever has done, almost instantly on the turn.
Left it a day and still fired up quickly. Took a lot of charge out of the battery and it still fires up.

A working car isn't the biggest of problems i must admit but i wish i new what the fix was as i've got no faith in it any more.
 
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