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PeteMck

Rover 4.6 V lumpy idle then revs by itself

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One other thing about the spark timing. To get 10 degrees advance using a timing light, I had to set it to 16 degrees. Now that I'm back on the map is that how that should look?  

IMAG0370.jpg

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18psi is about half what it should have, standard Hotwire is around 35-38psi from memory.

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Right. Well that's going to be next on my list of things to check then. I'm guessing it could pump regulator or filter. Easy way of ruling any out? Slowly getting there. 

Edited by PeteMck

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Well, go cheapest, replace the filter if not new - I'd suggest this should be done on a new installation anyways as it is an unknown. You could remove and blow through it, but for the money, why not just replace?

Then go from there, pump would be next on list for my money.

 

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Filter is new but it's an inline filter rather than the standard one so could be restricting it I guess. Will have to find the specs for it again and make sure it can handle the flow rate. The joys of nothing being standard 😂

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Inline should be fine as long as it is an EFI filter and not one of the nasty clear plastic inline carb thingies :)

Next to check, voltage at fuel pump when running?

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Does the pressure go up if you clamp the return line?

I'm assuming it's the earlier type with a regulator on the back of the plenum & a return-to-tank unlike the later ones where there was no return & the regulator was in-tank?

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Yer it's an efi filter. And yes it's a regulator on the end of the fuel rail. Havnt tried clamping the return. Will give that a go when I get the chance. 

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Don't let it get too high, but it should go over 50psi with the return clamped unless the pump's nadgered.

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Oh, and wear safety squints! Fuel in the eye is not nice... 

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Well I've changed the fuel pump and now getting around 35psi pressure. with the current fuel map it won't start it just floods the engine so definitely getting more fuel. Forgot the laptop so can't change the map 🙄 but hopefully that will cure the problem. 

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Holding throttle to the floor should activate 'flood clear' (no fuel) by, I think, default.

Can be useful in these situations.

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Merry Christmas all. Right so I've changed the fuel pump and filter and have 2.5bar pressure now. So tried to start and no joy, wet plugs. So figured it was now over fueling. So I changed the fuel map back down to more sensible numbers and still no joy. Getting spark and fuel but wont fire. Just getting the odd cough and splutter. rpm now only reading around 150 when cranking but sounds quicker so could that be causing an issue? Any other suggestions? Tia

Edited by PeteMck

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Wet /fouled plugs can prevent the engine firing at all, so, take them out and put them in the oven for 20min at 150C to dry out and clear the fouling.

Then refit when still warm and try staring again.

Remember the fuel map isn't used when cranking, only the cranking settings, fiddle with the fixed cranking pulse until it fires. You most likely need to drop it from where it was.

 

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OK. So now got it running again. Pressure increases when I squeeze return line but still seems to be only around the 27 / 28 psi mark. So think I might have to change the regulator on the back of the fuel line. Although the fuel table is starting to look more "normal". 

Anyway now got a new problem. just had it idling and run it up to temp and the exhaust is glowing at the back of the cat. Did have to twist it through 90 degrees to get it to fit against the chassis but it shouldn't have caused any restrictions.  Currently using disco 4.0l manifolds and disco 4.0l exhaust Y piece and then 3" home made after that. 

IMAG0402.jpg

Edited by PeteMck

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Bear in mind the fuel pressure regulator has a vacuum connection for a reason - it tries to keep the fuel pressure the same relative to inlet manifold vacuum (so from the "supply" side of the injector to to the "squirty" end), so with 5psi of manifold vacuum there might be 35psi across the injector but only 30psi relative to outside air.

Also, as I've said before, don't fret small errors, none of this is THAT accurate, as long as your fuel pressure is "about" 35psi and not 3psi or 90psi you're in the ballpark.

Not sure about your cat, although if you've blown a load of unburnt fuel down the exhaust with all the mucking around it probably isn't a happy kitty. Dunno if it'll burn off or if it's dead though :ph34r:

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Ah OK. That makes sense. I'll leave it alone for now.

Yer that would make sense as its a new problem 🙄 will see how it goes. 

Just got to fiddle with the fuel table. The vehicle isnt road legal and don't really have any intention of making it, so what's the best way to sort the tuning out? 

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Drive around a lot :)

 

Red cat, that is continuing to glow red, is a lot of fuel going through it, if its an off road toy, cut it out and bin it before it collapses/gets blocked.

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Yer I'm getting both glowing now. Time to cut them out. Why would I be chucking fuel out the back? If I drop my ve values it starts hunting. All spark leads make a good spark. 

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Right. I've fixed the starting issue. But I'm now back to the problem of a fast idle around 1000rpm plus. This time though I'm getting around 30kpa manifold pressure and I've dropped my ve values right down. If I drop any more and it starts hunting. Idle screw is all the way in, throttle valve fully shut. 

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Now go vacuum leak hunting again :)

There MUST be more air getting into the engine, otherwise it wouldn't be revving...

Disconnect/plug all the hoses going to plenum, measure the throttle blade clearance to plenum when closed (value is in RAVE somewhere).

Also check throttle spindle for play/leaky seals -this goes unnoticed very often.

 

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Found the revs drop if I clamp the pipe from the drivers side rocker cover to the plenum. What would cause that? Air leak round the rocker cover gasket? Also how stable should the revs be on idle. Listening to the engine it sounds pretty stable but there is around 100rpm wonder according to the laptop 

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Can you post a photo of the plenum?

Drivers side hose should go to one side of the restricted t-piece, and the passenger side the other, and then from the restricted port to the plenum.

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