3.9 Help needed

classic kev said:

This is an interesting one.

So you have a V8 on 14CUX Hotwire injection in a boat.
First question, is it running cat or non-cat?

Your problem is the engine will fire then die unless you disconnect the fuel pump then it ru

There are a number of possibilities here. The running and stopping bit can be a symptom of an inlet air leak but as others have already said the problems you describe point at fuel pressure regulator or possibly fuel pump control. What pump is it using? As long as it can deliver the correct pressure there shouldn't be too much of an issue.

What you need to understand is how the start up sequence works. It actually starts when the engine is switched off; the ecu winds the stepper to full open so there is maximum air available in to the plenum. When you turn the ignition on again, the ecu will pulse the fuel pump, about 1 - 3 seconds which pressurises the fuel rail. When you crank the engine 12v goes to the ecu from the coil negative as the ignition amplifier switches which causes the ecu to turn on the fuel pump and then energises the fuel pump relay that provides the 12v power for the injectors. Transistors in the ecu then switch ground to fire the injectors. At start up the injector pulse is longer than normal and this longer pulse is held for 3 seconds. Hopefully this will allow the engine to start and once it does, the air flow meter then feeds the air flow signal to the ecu to control fuelling and the stepper is then wound in to stabilise the idle. The short burst of higher revs on start up is caused by the time taken for the ecu to wind the stepper in to bring the revs down.

In terms of fuel pressure, if the pressure is too high the fuelling is altered and the ECU can't compensate. If the fuelling can't be controlled the ECU will go in to fault status and essentially, this means it just throws fuel in to the engine. I suspect you don't have an EFI warning light so you won't know if there is a fault or not. Normal fuel pressure should be 37psi. I believe you don't want more than 41 psi or there will be problems on standard injectors.

I think I would be inclined to look at the following:

1: Injection system earth - check and clean the main earth points.
2: What pressure is the fuel pump delivering?
3: Is the stepper working properly?
4: Check for inlet leaks.
5: What is the ignition timing set to?
6: Is the vacuumm advance on the distributor working?
7: Check throttle potentiometer. This affects idle control.
8: How does the system compensate for speed sensor and auto transmission? (these can affect idle control switching).
9: Check air flow meter: CO trim and air flow.

Hopefully that gives you a few pointers. One other thing, have you tried starting it with a bit of throttle on?

Hope that helps.

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just wont start said:

Hi kev, first of all thanks for your post, the engine will not fire at all when cranking over with the fuel pump connected only after it is disconected and turned over a few times will it fire up and run, it will rev on the throttle also till the rail is de-pressurised somewhat .It has no cat as boat engines exhaust manifolds are cooled by the river or lake water then exits through the exhaust itself. you ask about the speed sensor and auto box but it hasnt any fitted, i did question this myself and looked for answers on youtube , a gent does a video on there who seems to do a lot of hot wire transplants, he talks about whats needed and whats not and the speed sensor isnt mentioned at all, he also says if you dont use the lambas then take out the tune resistor as the ecu goes back to default setting, these arent fitted to the boat either !
Does this help with any answers you might have for me ?
Cheers

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classic kev said:

It sounds like your ECU will be in limp mode or will be trying to run a cat map with no cat input.
IIRC with no tune select resistor the ECU will default to a catalyst map. You need to have the correct tune resistor as Discool said. Fit the correct tune resistor then disconnect the ecu for a couple of seconds and then reconnect. This should clear the ecu and reset it.

You say the issue is there when the fuel pump is connected. I suggest you carefully check the wiring. The main efi power relay is connected to the fuel pump relay. There is no connection from the ECU to the ignition system other than the "run signal" from the coil. Check the earthing, also check the correct relays are in place, they should be 30A 5 pin with diode. They are not chageover relays, they should have 2 x 87 pins not an 87 and 87A. You can have a 4 pin relay in the fuel pump relay base provided pin 87 feeds the fuel pump circuit and NOT the lambda probe circuit.

The fuel pump relay is switched by the ECU but the power it switches comes from the main EFI relay. When energised the fuel pump relay sends power to the lambda probes and then to a main cable connector via a fuse to the inertia switch which then goes to the fuel pump. The main supply for the fuel pump is a simple circuit and shouldn't be too difficult to check. However, you haven't said what year the engine and loom are. Early 14CUX looms did not have cats, some Discovery looms have been reported as not having the diagnostic plug.

Hope that helps.

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discool said:

A fuel rail with a Schrader valve was fitted to all disco I V8 EFI engines, like the Defender and some RR models. The valve is fitted for a purpose, and is shown in the attached link.
https://rimmerbros.com/Item--i-ERR4937

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classic kev said:

This is an interesting one.

So you have a V8 on 14CUX Hotwire injection in a boat.
First question, is it running cat or non-cat?

Your problem is the engine will fire then die unless you disconnect the fuel pump then it runs until the fuel in the rail is used.

There are a number of possibilities here. The running and stopping bit can be a symptom of an inlet air leak but as others have already said the problems you describe point at fuel pressure regulator or possibly fuel pump control. What pump is it using? As long as it can deliver the correct pressure there shouldn't be too much of an issue.

What you need to understand is how the start up sequence works. It actually starts when the engine is switched off; the ecu winds the stepper to full open so there is maximum air available in to the plenum. When you turn the ignition on again, the ecu will pulse the fuel pump, about 1 - 3 seconds which pressurises the fuel rail. When you crank the engine 12v goes to the ecu from the coil negative as the ignition amplifier switches which causes the ecu to turn on the fuel pump and then energises the fuel pump relay that provides the 12v power for the injectors. Transistors in the ecu then switch ground to fire the injectors. At start up the injector pulse is longer than normal and this longer pulse is held for 3 seconds. Hopefully this will allow the engine to start and once it does, the air flow meter then feeds the air flow signal to the ecu to control fuelling and the stepper is then wound in to stabilise the idle. The short burst of higher revs on start up is caused by the time taken for the ecu to wind the stepper in to bring the revs down.

In terms of fuel pressure, if the pressure is too high the fuelling is altered and the ECU can't compensate. If the fuelling can't be controlled the ECU will go in to fault status and essentially, this means it just throws fuel in to the engine. I suspect you don't have an EFI warning light so you won't know if there is a fault or not. Normal fuel pressure should be 37psi. I believe you don't want more than 41 psi or there will be problems on standard injectors.

I think I would be inclined to look at the following:

1: Injection system earth - check and clean the main earth points.
2: What pressure is the fuel pump delivering?
3: Is the stepper working properly?
4: Check for inlet leaks.
5: What is the ignition timing set to?
6: Is the vacuumm advance on the distributor working?
7: Check throttle potentiometer. This affects idle control.
8: How does the system compensate for speed sensor and auto transmission? (these can affect idle control switching).
9: Check air flow meter: CO trim and air flow.

Hopefully that gives you a few pointers. One other thing, have you tried starting it with a bit of throttle on?

Hope that helps.

Click to expand...

classic kev said:

I like the photos, very interesting.

I am glad to hear you had a positive indication after improving the wiring. As for the schrader valve on the fuel rail I think Discool has covered it, I certainly didn't have a valve on my '91 RRC.

As for the rest of it, don't be scared of this engine; it is actually very simple and is not technically challenging. Many are put off because it is a V8; it's just an engine!
The efi system is also quite easy to work with once you understand what it does and how the different bits make it work. All you really need to keep one of these in good order is a decent multi-meter and an understanding of what values you should see when testing.

Make sure you do regular oil changes and always use quality ignition parts. On a boat I would carry a couple of spare spark plugs and leads, a spare ignition amplifier, a spare rotor arm and a spare coil. If you can source one, a spare ECU and air flow meter wouldn't be a bad idea. I know that sounds a bit OTT but I used to carry those spares when out green laning!

Anyway, I hope it's all sorted now and you can get out and enjoy the noise!

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just wont start said:

Cheers Kev, im sure i will have plenty more questions in the coming months. Thanks everyone !

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classic kev said:

From your pictures you don't have an oil cooler, this is probably fine but the hotter the oil the thinner it is and you may see noticeable changes in idle oil pressure because of this. You could fit an oil cooler if you wanted to, sandwich plates are readily available as are stand alone oil coolers. I just fitted an oil cooler to a tractor, cost was about £100.00 all in - sandwich plate, cooler, oil hoses and fittings.

The oil pressure is controlled by the pressure relief valve which allows excess pressure to escape into the suction side of the oil pump, from here, without the oil cooler, it is sent to the oil filter via the anti-siphon valve then through the filter and then to the engine bearings.

The pressure relief valves are well known to stick. If stuck open, pressure will be high. If stuck closed or partially closed, pressure will be low. It is also possible that if there is an airlock in there the pressure could be low, this is why it is important to make sure the oil pump primes correctly. The RV8 is known for low oil pressure.

As far as I am ware, you can't buy a new oil pump but you can get an overhaul kit that includes new gaskets, gears, relief valve and spring. When overhauling or even just cleaning/checking the oil pump you should check the clearance between the front cover and the pump gears, it should be more than 0.05mm. To check this, place a straight edge on the pump gears and then measure the clearance to the front cover; if it is less than 0.05mm check the front cover gear recess for wear.

Hope that's useful.

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just wont start said:

Hi mate, thanks for that great info. on your suggestion i have dropped the oil pump housing, the plunger was in there and lodged at the bottom ! After a poke around it slid back out, looks to be in good condition as does everything else to be fair. Have dropped them in the sonic parts cleaner and will assemble tomorrow. You mention about a anti syphon valve, where is this located as couldnt see it ?
Thanks for all your help by the way :-]

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discool said:

In the oil filter depending on the filter u have, there’s also an anti-drain drain back valve, which again is incorporated within the oil filter.
https://filtron.eu/en/insights/filter-guide/spin-on-oil-filter-valves.html

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just wont start said:

Thanks for the info on the oil filter, upon taking the oil pump parts out of the cleaner everything checks out and are in good condition so its back together and bolted back on. back on with the drill to the pump drive and the oil light goes out almost straight away, the gauge goes to about 20 psi but same as before, spin the drill faster and drops back to zero ! i can hear oil pouring back to the sump so think its just the gauge sender. Has it got windings in it like a fuel sender do you know as i have had this problems these before, the gauge reads x full but top the tank some more and gauge reads zero as the windings are broken further along. Just a thought, have ordered a new one anyway.

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