A bad CPS = No fuel pressure, should just do it first

"Engine not starting? No fuel pressure? This could be caused by a faulty signal from the crankshaft or camshaft position sensor and not the fuel pump. A common reason for repeat fuel pump replacements is not completely diagnosing the control side of the electrical circuit for the fuel pump. The vehicle ECM looks for a signal from the crankshaft/camshaft (RPM) sensor upon initial engine starting sequence in order to energize the fuel pump relay and apply voltage to the fuel pump. As a result, a missing cam/crank signal (RPM signal) can cause a no-start condition." - FuelpumpU Website

Just remember than when you get that new pump in and stuff still does nothing. I can't be much clearer on this but good luck and I hope I'm wrong bud

 

He said no fuel pressure with key on. Would prime for a second. Runs on ether. Has spark = has crank sense.

 

It's not the CPS "bud". The fuel pump will still prime the fuel system when you first turn the key on. You should read close to a normal reading before and while the engine is being started.

The CPS primary symptom will be a no-spark condition which is not the issue here if the truck runs on ether.

If you doubt me, go outside and pull the plug to your CPS, relieve pressure in the fuel system and give it a shot. Your fuel pressure will be right where it needs to be before and while the engine is being started. This is the case for nearly all fuel injection systems ever made. They don't start quickly if not at or near the correct fuel pressure, and they don't wait for a CPS signal to prime the system.

On our Rovers, you should hear the pump kick on for a pre-determined time if you quickly turn the key on and then off. The pump will continue to run even with the key off (and with ignition off, it makes it easier to hear because of the lack of chimes and such) until that set time has elapsed (5 seconds?).

On many engines w/ Bosch management I've seen (VW's especially) the fuel pump is turned on when the driver's door is opened after so many minutes has elapsed since the engine ran. I'm sure it's different on every vehicle, but the pump WILL come on if it, the relay and related components are working.

A CPS is not a component you routinely replace just for the hell of it, usually because of the labor involved. Do they fail? Sure. Crankshafts split in half too, but you don't see me swapping my crank just on the off chance it might break while I'm driving...

 

Quaker J, you are not quite right. On this forum alone there are more than a few cases of CPS killing pump prime an zero fuel pressure. I did a quick search and I'm not the only case.

On land rovers especially disco II, the CPS and Crankshaft are things to swap to stay on the road at certain times. Keeping a spare of a CPS is not unheard of at all. If you like to run until failure to save cash its all good AAA is your friend. The stock disco II crankshaft without grease points IS something you switch for the heck of it because of design flaws. That is a poor example. Also the labor on the CPS and cost of a CPS is cheaper than a fuel pump so I don't get your logic there. 60 dollars is not an astronomical amount of cash. Labor is free DIY and under an hour at a shop. New pump tops a 1000.00 if you take it in and do it without slicing the carpet.

I'm listing exactly the CPS stuff I went through with the shop without fuel pressure and sending codes to match. I don't need to "go outside and unplug my CPS" for an event I already dealt with. It will not be the same conditions or wear compared to a plugged in worn CPS. This was MY case, may not be HIS, once again.

So I respectfully disagree, this can happen. I witnessed it.

I wish the OP the best of luck x2 now, I hope I am wrong for his sake once again and all is well with the install. At the end of the day I just want another rover back on the road Im anxious to hear if it did work in his specific case.

 

Quaker J and I are right. Pump will prime regardless of CPS condition.

"On land rovers especially disco II, the CPS and Crankshaft are things to swap to stay on the road at certain times. Keeping a spare of a CPS is not unheard of at all. If you like to run until failure to save cash its all good AAA is your friend. The stock disco II crankshaft without grease points IS something you switch for the heck of it because of design flaws." WAT?

You can get a replacement fuel pump for 39 bucks. take the module apart and replace it in 30 mins.

A crank sensor is 70 and may cost you your sanity to replace.

I mean I have basic math skills, but it seems that replacing a fuel pump on a disco 2 is cheaper than replacing a crank sensor.

 

Thanks for all the help Guys, I replaced the fuel pump and it started right up.

Not running perfect but running thanks to the fuel pump. I need to do a tune up and replace the valve cover gaskets in the the near future.

As to the CPS v. Fuel Pump debate. First I would say that I am one who doesn't fix things that aren't broke and I do not consider replacing hard to reach parts as part of "Maintenance." Economics tells me to diagnose the problem before starting to throw parts at it.

I chose to replace the fuel pump first because, as I stated in my first post: The truck will start with starter fluid and continue to run at high idle if a slam on the gas. I assume that means that with the truck turning over and revved up there was enough vacuum pressure in the fuel lines to draw fuel from the tank. From what I have gathered about the CPS, If it had failed it would prevent the truck from turning over period.

Yes people have intermittent problems with the CPS where it seems to fail and then comes back to life and then finally fails completely. 1) this was not my case. The truck simply stopped turning over at idle and would not start under normal starting conditions. 2) I think the intermittent failure of a CPS is usually due to fluid draining (either coolant or oil) over it. Clearly such a situation could cause loss of electrical contact at one moment and then be cleared out either by a change in temp or vibration until the unit was completely gummed up and had finally succumb to catastrophic failure.

Thanks again for all the help and be blessed,
Larry

 

Glad you hear it's running.

One thing - the valve cover gaskets rarely need replacement and respond well to regular tightening. Mine were leaking when I got the truck, and somebody here said to retorque them at every oil change. No valve cover leaks for a year now.

 

Good point, I'll try that first.

 

I treys to tell you it was f/p. lol. Now the fun part of finding a 8mm or 5/16 12 point deep socket snap on makes them but never a truck when I need them had to order a craftsman lol

 

I too thought it was the fuel pump.


instead of having to re-torque your valve cover bolts all the time, clean the inside of the cover with some brake cleaner, apply a thin layer of gasket sealant "the right stuff" or any that contain a variant of "oxane, oxine", to the inside of the cover, do the same with the top of the head, fit gasket and tighten. once sealant dries, it won't leak again.


Rovers don't have to leak.