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1995-2002 Range Rover P38A
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36 Posts
Discussion Starter #1
I have been diagnosing a random stalling issue with my 4.6 gems(160k miles). I’ve cleaned and inspected idle valve,TPS,MAF,Throttle body. Replaced the Crank sensor because most posts pointed to that being the main culprit.

So.... the only code I have seen is “random multiple misfire-drive cycle C”. No MIL light or any other notification that anything is wrong. However, my butt dyno tells me she is sick and not running well.

I believe I have narrowed down the issue to either my fuel pump or cam sensor.

My question is..how quickly should I see the 34-37psi fuel pressure? Mine seems to slowly build pressure over time, to an acceptable value. Takes about 5-10 seconds,and sometimes I’ll need to flip the key again to get it up to 34psi. But I believe that it should be almost instant..Iam not sure..

Also, I’m not sure if the 34-37 psi should be at a relative constant. I get about 25psi at idle and maybe a little more or less while revving.

Seems like a weak/dying fuel pump to me. Anyone got any ideas for more testing or tips?

I did pull the vacuum hose off the regulator and it seems good. Psi went up very quickly to around 50psi. My next test will probably be fuel pressure before the fuel filter and a volume test..

Thanks in Advance
 

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1995-2002 Range Rover P38A
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770 Posts
Has the filter ever been changed ?. I guarantee there’s plenty of p38s driving round with original filter, most are seized on now and a slight modification is needed when changed, the fact the pumps taking its time to get to pressure could be either a blocked filter, or dodgy pump, go for the cheaper version first.
ive never come across a cps failing, although I won’t say it doesn’t happen.
 

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1995-2002 Range Rover P38A
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36 Posts
Thanks for the quick reply. I forgot to mention that the fuel filter was the very first thing I changed out.

I also have two brand new relays that I’ve been swapping in/out with no difference.

Also alternator is new and good. 13.6V charge @idle.

Any idea if fuel pressure should shoot up to the correct value when testing. Or does it take some time to build?
 

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1995-2002 Range Rover P38A
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484 Posts
fuel pressure should be instant, pressure should not drop at all . only 2 3 psi difference from idle to run
 

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Registered
1995-2002 Range Rover P38A
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36 Posts
Discussion Starter #5
fuel pressure should be instant, pressure should not drop at all . only 2 3 psi difference from idle to run
Great! Thanks for the confirmation. I thought that 10psi difference between “accessory 2 position” and “running at idle”was way too much.

Looks like I’ll be replacing a fuel pump very soon.
 
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