First of all I am new to this forum and a new owner of a Range Rover. Love the vehicle. Am having one issue that I need some help on.

It is a 1999 Range Rover 4.0S

I am having a hard starting problem. After sitting overnight, it starts fine. When the vehicle is warm, it is hard to start. If you just turn the key and crank it, it won't start. If you try to start it and give it gas and rev the engine it will start and has a rough idle. I have also noticed that it smells like it is running very rich.

Any ideas?

I apologize if this is a duplicate. Really need some help.


Thanks for the input.

 

Is it throwing any codes? Sort of sounds like an O2 sensor to me. If it is, it should throw a code.

 

Well, there is another possibility, the Crank Position Sensor. When they start to fail, they stop allowing spark to be generated when warm, like when you drove to the store and ran in for a few minutes. Then when engine cools off they allow spark again. No spark would make fuel smell. If you can duplicate the problem, when it acts up, slip off a plug wire and attach a spare plug and lay on mainifold, watch for sparks when cranked. You can restore sensor quicker sometimes by pouring cold water on it. The part is like $75, a PITA to put in, you need to plug in the new one and let it hang down. Every little nut and spacer has to go back in exact sequence. Heres some pages on it, located on driver side (US/CAN) rear of engine. But if engine does restart before cooling off problems may be elsewhere.

Rough idle is frequently related to the IACV (Idle air control valve) which can be removed and cleaned with carb cleaner.

Ther is a fuel temp sensor on the fuel temp sensor on the fuel rail, and if it is bad it would make warm starting difficult. It normally makes injectors open up more on hot restart to purge bubbles out of the fuel system.

The O2 sensor, if bad, can be involved, and mpg would stink if it keeps you from going into close loop fueling.

 

I don't have access to a scanner to see what codes, if any that it has.

Any way to test those sensors, before just replacing them?


Thanks again

 

Most parts stores will test your codes for free. Some chains of stores will not reset the codes, as it would clear a check engine light. Some stores rent out the scanners (deposit and you get a refund when you bring it back). If having codes read it is important to write down the numerical information, the text in the scanner may not match the Rover brain exactly. Post numbers back here. Now a garage can do this, but they usually charge - depends on the shop. Some will do a free read as a way to get business.

The litmus test for the CKP is to have no spark, and it return when sensor is cooled off.

The IACV is a infinite position stepper motor. If removed from the bore you can see it move a bit when engine is turned on. Resist the temptation to tinker with then end of it, just clean with spray carb cleaner. Clean the bore as well.

Many owners successfully clean their MAF sensor with made-for-that-kind-of-sensor spray, and done when engine is cold.

And I mispoke, the 99 Rangie could have the Bosch ECU system (earlier ones had GEMS system, thanks fivesppddisco), and it does not use a fuel temp sensor. Instead it uses the intake air temp sensor, which I believe is also part of the MAF unit. A scanner that shows live data may show a wild reading for a sensor, like -40F for temperature when it has been sitting in a heater garage, etc. The shop manual may have resistance values you can check with an ohm meter. The O2 senors can be read with a volt meter, but values are fairly precise and you would need a good meter. The Bosch ECU manual has the ranges of voltages that equate to various codes for O2s. A scanner can show if you are going into closed loop fueling, if not the MPG will stink.

If you wanted to purchase a scanner, the $70ish Ultra Gauge is worth a look. Also displays important things, like engine temp, in digital values. Can read and reset codes.

It is usually money not well spent to throw parts at things.

 

It can be both. Gems or Bosch

 

I'd be checking the fuel pressure.
Generally hot restart problems are caused by a leak down of fuel pressure
after shutting the engine off hot. Then the fuel system vapor locks.
This will not occur when cold so you won't notice it at cold start.
I'd recommend checking the fuel pressure (or have someone do it for you)
and watch the pressure should be around 38 psi running and should not drop quickly when shut off. It shouldn't drop more than 10 psi in 10 min give or take a few min or psi. If you see a substancial drop in fuel pressure, you'll need to narrow the leak down to the fuel pump check valve, fuel pressure regulator
(if it has one) , or a leaking fuel injector..

Cheers

 

Yep, the ECU is supposed to compensate for hot restart condition by making the injectors stay open longer to allow the cooked up bubbles to pass thru. That is triggered by temperature from either the fuel temp sensor (GEMS) or IAT + some math (Bosch). But as mentioned, when the system is already low, turning the injectors open even wider does not help the fuel pressure. So the best intentions of the ECU are fooled by the low pressure. Hopefully it is something cheap like six inches of vacuum hose that operates the fuel pressure regulator.

 

Fuel pressure at the rail is 20 PSI. Looks like I am in the market for a new fuel pump.

 

I have a 99 4.0s gems and am currently experiencing the same hard start when warm. Does anyone know where the fuel temp sensor is? I had a new $300 fuel pump installed and I'm thinking the shop messed something up testing the bad fuel pump with starting fluid through the intake.