It makes the ECU revert to a factory programmed map. So as long as you have fuel pressure it will start and idle.

 

Nothing

 

It runs a fuel map default since it has no air readings and shouldn't stall but run rich. Its a good trick.

My 99 D2. same issues, replaced the coils at a land rover stealer when I first got her before I ran into an easy fix. Crank position sensor. She stopped stalling, fired right up, codes cleared.

The shop I took it to wanted to replace the fuel pump they were that sure based on the codes and I was going to do it until discomike chimed in. They go out a lot.

I disagree with mordo, it will still spark and it will even run on and off but it will crap out more and more frequent or just not work at all. The CPS is temperature sensitive, more likely to fail with a hot engine and restart when completely cool fyi. Idk why, but it proved true with me.

 

From what I have read, crankshaft position sensors fail differently for different people. For some people they prevent the truck from cranking when it's hot, but for other they just die the truck is immobilized. In the latter case, my understanding is that both fuel and spark are cut off. Since that is the OP's situation, that's why I said he shouldn't be getting spark or fuel.

Interesting. Does it help with diagnosis? Seems like it might indicate a bad MAF sensor if the truck cranks with it disconnected.

Meaning it still won't start even with the MAF disconnected?

I just realized you said it will run once you get it started if you keep your foot on the gas. That's definitely not a relay problem. I'm not sure what I'd do next. Personally, I'd probly start with checking the plugs, air filter, and fuel pressure. I'd also check all the hoses on the top of the engine to be sure none are split or disconnected.

 

Yup. It didn't fire with MAF disconnected.

I checked all the hoses, disconnected all the intake hoses and double checked the clamps.

At this point I am thinking either fuel pump or crankshaft sensor. Have to wait for the parts store to open tomorrow to rent a pressure gauge. I took a peek at where the crankshaft sensor is housed and it looked pretty gunked up from a previous throttle body cooler gasket leak and some oil leaking from the valve cover.

Can a failed idle control valve prevent it from starting?

 

If it starts with ether, and won't start with the maf unplugged. You sir have diagnosed a bad fuel pump.

 

Oh I understood your intent, but I had the wide range of all the issues. It would sometimes start cold but not always. Even a mild idle would trigger it to fail, then randomly it would be fine for a few hours. When it starts to go you get bits and sometimes nothing at all, full immobile.

I would agree spark is reliant on the CPS but in my case at the shop we would get spark but no fuel and it would indeed try to turn. Depends how fubar the unit is lol. Basically if its worn it will do everything under the sun. I got fuel pressure codes specifically on my truck because the CPS cut fuel off. Had nothing to do with fuel pressure just lack of signal for fuel pressure via the CPS and that's why they wanted to do the fuel pump.


MAF helps with other issues like a bad 02 sensor and yes a bad MAF and if all other parts including the CPS are working it can help get the source of a fuel issue down with bad ECUs controlling certain systems, injectors, etc. its just a little cheap start point to diagnose especially if on the road or shoulder of a hwy to limp home.



I mean look, CPS was 55-60 bucks for me last year from Oreilly ordered in, it was a messy bia of a job but better than the new pump which would have been close to a grand. CPS fail roughly between 5-10 years of regular truck usage with LR I'm hearing. If you don't need it, you will soon. I personally want to keep a spare with me with the tools if I'm on trail now because it stranded me baddddd

Fuel pressure I would argue is a possibility, but I'm betting against that. CPS is massively more common.

 

I checked fuel pressure on the rail this morning, pressure was 0 when key turned to run position and the needle only wiggled a bit when I tried turning it over. Ordering a new fuel pump today. I'll let you'all know how it goes when I get it in. Thanks for all the help so far!

 

If you haven't changed the crank sensor, while you are waiting for the fuel pump is a good time to change it.

 

Yeah, because one day soon, when you least expect it, you'll hear a chime, and there'll be green and yellow lights flashing, and then they all come on and the truck goes dead.

And you're calling Triple A to come get you. Ask them to bring you a crank position sensor.