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Mike, Mechanic
Category: Car
Satisfied Customers: 39198
Experience:  Hi, I have been a Car/vehicle mechanic 34 years. 29of -running my own repair/diagnostic business.
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Hi,My wife has a 2000 4.0 P38. It stalls and has trouble starting.

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Hi,My wife has a 2000 4.0 P38. It stalls and has trouble starting. It had run fine since new plugs and wires, but this is a new problem. Fuel pressure (at fuel rail) is erratic. Swapped out relay. Installed new fuel pump. Pressure is intermittent – will stay low, then, once in a while it starts, runs, then stalls and won’t start. It seems as though there is a stuck pressure switch – but the entire in-tank fuel pump / sender is new. Please help! Best regards, XXXXX XXXXX

hello thanks for using just answer

It sounds like you may have a defective fuel pressure regulator. this is located on the fuel rail. Make sure the vacuum hose going to it has vacuum and is not kinked or broken.



Customer: replied 5 years ago.

Hi - That would be nice, but I think that the regulator refers to GEMS engines (up to '99). Ours is a Bosch engine - according to RAVE:


There are eight fuel injectors, one per cylinder which the ECM operates sequentially. All the injectors are fed from a common fuel rail as part of the returnless fuel system. Fuel pressure is maintained at a constant 3.5 bar (52 lbf.in2) by a regulator that is integral with the fuel pump.

Am I wrong?

My info is showing me a regulator on the fuel rail. I looked up a 00 land rover with 4.0 engine. look on the fuel rail and see if it has one will be easy to spot. should be a goldish color small canister looking piece with a vacuum hose on it. I will try and do some more research but it will likely be tomorrow morning before I will have access to all my resources. If this is too late let me know and i will opt out and see if another expert can assist you
Customer: replied 5 years ago.



I am not in a hurry, so I will check it out and get back to you in the morning.





sounds good
Everything I can pull up shows a fuel pressure regulator on the fuel rail. you do have a bosch electronics system.
Customer: replied 5 years ago.



I have searched with inspection mirror & light. Also, I have been reviewing the workshop manual. For the pre-99 4.0 the pressure regulator is obvious in the diagrams, and addressed in the repair guide (page 416) - just as you describe. But post-99 diagrams do not show a regulator on the fuel rail, nor do the fuel rail refit instructions mention it. The only reference to a regulator is in the tank, which was just replaced.


Any other thoughts?



Ok, What is the fuel pressure doing? when you say low how low? May have a voltage problem to the pump
Customer: replied 5 years ago.

I know this is not an easy fix and I appreciate your patience.


I attached a fuel pressure guage to the fuel rail - when the car runs, it reads @ 51psi - normal. When it stalls, it's reading @ 48psi. I can try to start the car and after several tries - it may start. Pressure is back to 52 untill it stalls.


I just tried starting it again. Here was the sequence. Pressure was low (20psi). Released pressure to 0. Turned on ignition. Pressure 0. Started car - pressure jumped to 51psi. Car ran for @ 10 minutes till it warmed up. Car stalled. Pressure reads 48psi. Can't restart. I am beginning to wonder if there's a temperature relationship -???

And you were having this problem before replacing the pump? I would hook a voltmeter into the fuel pump wires and see what the voltage is doing when pressure starts dropping. if voltage is dropping with pressure then we know we have some high resistance in the wiring.

Do me a favor. clean your battery cables good. make sure there is no corrosion at all. i remember working on a land rover doing some crazy stuff and had a dirty battery terminal. worth a try

Customer: replied 5 years ago.

I will give it a shot and get back to you - I agree - you never know....



Customer: replied 5 years ago.



I have cleaned both battery terminals and repeated the test again, the engine starts right away when cold and runs fine. It stops as soon as it warms up and cannot be restarted.



it is possible the fuel cutoff switch is getting hot and dropping voltage. this should be down on the right hand kick panel. check the connector and see if corroded or melted looking. the power runs thru this for the fuel pump. if looks ok we need to see voltage going into and out of switch when acts up



Customer: replied 5 years ago.
The Fuel cutoff switch seems fine - could it be that the throttle position sensor or Idle Air Control Valve could be sending bad signals? Oh I yearn for the days we could simply check the plug for spark and the carburetor bowl to see if it were full.
tps possibly. when it cuts off does it only do at idle or if revved up some will it still die down?
Customer: replied 5 years ago.
Not sure - will test that - thanks for your patience
Thanks for your patience as well. we will get there eventually.
Customer: replied 5 years ago.
Relist: Other.
The original expert was patient trying to work through the issue - but this problem rwquires insight of someone who knows P38s well - original suggestion was to check a part not on the Bosch fuel system - we have been struggling to diagnose since - good effort but no result
Hello and Welcome ... My name is XXXXX XXXXX as you have re listed your question - I can now come in and endeavor to help you ..

Can I first ask - have any actual plug in diagnostics been done - any fault codes retrieved?

Plus - when the engine does eventually start - does it run smooth -or does it misfire?

Too, when trying to start it - and it wont - do you have any warn light on the dash to do with the alarm / security system at all?

Rgds - MIKE.......................................
Customer: replied 5 years ago.

Hi Mike,


There had been a fault code relating to a weak signal some time ago. But the check engine light is off now and has been for some time. I am assuming that there are no new codes.


As far as alarm - I had trouble with the front driver side door causing the locks to jump up and down repeatedly -- I was afraid that the circuits would burn out. Also, when there was an alarm issue, the starter was completely disabled.


The car starts when cold and runs smoothly, no misfires (plugs and wires replaced over the summer), but it stops when it warms up. It won't restart until it cools down. Low fuel pressure appeared to have been a problem, but I replacd the pump. Perhaps it was a symptom or a cause of the alarm issue.


I fear this is a quirk with the P38s - I welcome a solution.





Hello there Pat - thank you for your reply and info...

It easy to hurtle completely down the wrong line - Fault codes do help,.. but when you have none - Live Data diagnostic testing is often needed to trace the fault down.

However - before we go there, I note a couple of times you have said this seems temp- related - in that too, its has trouble when warm / hot..

That being the case, you have to at this point, replace the ECT sensor... This is the Engine coolant temp sensor, that sends engine temp info to the ecu...(management ecu) and that ecu then commands the fueling etc etc accordingly..

That sensor will often not show up as a fault code even when faulty.... Given it does definately cause such starting issues - and too, its not expensive or difficult to do - replace that now..and see if that cures it.

Also though - check the wire and connection to it.... as they can give trouble - bad connections / chaffed wire etc..

Too - be sure to get a genuine LR one.. not an aftermarket one.

At this point we leave the fuel pressure alone until we know the Ect sensor is done - as fuel pressure will fluctuate when struggling to start...

So thats the way forward for now at least Pat...

You are welcome to click the accept now - you can get back to me at any time after that no problem just by using the reply button or you can do that sensor and come back to me to let me know whats happening - either way...

BUt that must be done before anything else now...

Best Rgds , MIKE...
Customer: replied 5 years ago.

Hi Mike,


I will do as you suggest - looks like a challenge to get a wrench around it. Before I order, the temperature guage seems to be working fine. Wouldn;t that eliminate the engine coolant temperature sensor as a potential cause?



Hello again Pat - Thank you for your reply - Im sorry I couldn't get back to you earlier...

No this sensor is for the Ecu -to transmits engine temp data to the Ecu for it to command the fueling / ign properly etc - not the gauge.

Sorry if I didn't make that clear above. The dealer parts dept though will know what yuou are wanting if you say Ect sensor to them ( some call them CTS sensors ..same thing )

Just a note Pat, this post is due to time out in around 4 hours as of now.

I'd appreciate the accept if you wouldn't mind but just to let you know that even if you use the accept and / or the post times out, while it will close , you can then get back to me at any time after , just by coming back to this post and use the reply button again.. That way I can be sure of seeing this through with you ;)

Best Rgds, MIKE.
Customer: replied 5 years ago.

Thanks Mike,


I have ordered the part. I am going to accept this answer as well, though I am sure I will have additional questions. I feel bad that the original mechanic was unable to resolve the issue - I wish there could ba a way to pay partially.


But I believe this is the right direction.


Thanks for your response.



Hi again Pat...

No problem - Im glad to have helped you ...and by all means - as I mentioned, you can get back to me anytime at all if needed..

Dont feel bad as you mention happens to us all ! but justanswer want experts to be paid for correct help / answers so its just how it is .

To do the accept Pat, you should see a button there on your screen , you just use that and the system does the rest automatically. Thank you again.

I really hope all goes well Pat...

Best Rgds to you .. MIKE.
Mike, Mechanic
Category: Car
Satisfied Customers: 39198
Experience: Hi, I have been a Car/vehicle mechanic 34 years. 29of -running my own repair/diagnostic business.
Mike and 5 other Car Specialists are ready to help you
Customer: replied 5 years ago.

Hi Mike,


I hope you are having a good holiday. I replaced the ECT sensor (Land Rover part) and see the same result. The car stalls as soon as it warms up.


What would be the next step.



Customer: replied 5 years ago.

Hi Mike,


Just checking in - I assume you are on holiday, but I would like to follow up as soon as you are back. please see my last post - the car still shuts off as soon as it warms up.


Best regards,



Hello there Pat -

Im sorry -for some reason..until now, I was not notified of your reply as above - the post was then old / timed out so I had to apply to get it reopened so that I could get back to you ..

So - here we are.. Hows things going Pat - whats the current situation / whats been done meantime etc...?

Best Rgds - MIKE...........