V8 rebuilt no spark

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ricey30
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Re: V8 rebuilt no spark

Post by ricey30 »

Right module changed no difference , pick up coil is pulsing so that looks ok. Definitely a rsesistor in the wring loom somewhere which I intend to bypass . But just realised the coil clamp isn’t earthed via the bodywork.

Could this lack of earthed coil be the issue ???

Cheers



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Re: V8 rebuilt no spark

Post by scudderfish »

ricey30 wrote:
Mon Jan 08, 2018 5:04 pm
Right module changed no difference , pick up coil is pulsing so that looks ok. Definitely a rsesistor in the wring loom somewhere which I intend to bypass . But just realised the coil clamp isn’t earthed via the bodywork.

Could this lack of earthed coil be the issue ???

Cheers
Earth it and see what happens :lol: Looking at your photos, it looks like you've got it fitted to a powder coated frame which will definitely give you earth problems without taking special measures.

ricey30
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Re: V8 rebuilt no spark

Post by ricey30 »

Very delayed update due to weather and commitments.
Basucky not very far ahead . Changed dizzy fir new and proven coil added engine earth strap and now I have continuous spark on cranking , the coil shows 10v when cranking, smell of fuel is strong, but will not fire. Did get a back fire once but not sure if via carb or exhaust.

Starting to wonder if I got cam timing wrong but spent a whole day on that checking it 10 times inc tdc. Also took dizzy out and rotated 180 degrees in case that was wrong.

All lines up with number one with oil pump drive etc as per Land Rover Manual.

Truely given up.

If there is anyone in the Chessington area of Surrey who wants a few quid to take a look I would be most grestful

Depressed Phil

unstable load
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Re: V8 rebuilt no spark

Post by unstable load »

If you have good spark all the time and it's not firing, then you have either a fuel delivery or timing issue. Backfiring is generally timing.

You are going to have to go back to zero and start over.
Establish the actual TDC with a piston stop and mark it with the pointer. https://www.google.co.za/search?source= ... fcSxg6VGpw
Remove the tappet cover for No1 cylinder side and turn the engine until the inlet valve has opened and is closed. You are now on the compression stroke for that cylinder, keep turning it to your TDC.
Now, set your distributor so the rotor is pointing to the No1 lead and fit the cap.
Make sure that your plug leads are fitted in firing order IN THE DIRECTION OF ROTATION of the distributor. (I highlight that because I've made that mistake before)
Set the points gap, dwell etc and connect the coil lead and check coil wiring etc.
Double check it all.

If it still won't start then you need to look to fuel delivery in terms of carb condition for atomisation, choke operation, float levels, fuel pump operation and clean lines to allow sufficient fuel to get to the carbs.
Cheers,
John

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ChrisJC
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Re: V8 rebuilt no spark

Post by ChrisJC »

Just do a compression check. I rebuilt an engine once but didn't grind in the valves. It wouldn't start for bloody ages, but fuel & spark were fine.

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ricey30
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Re: V8 rebuilt no spark

Post by ricey30 »

Hi Chris and John

Folllowing your inputs I have followed Johns points first and cross checked everything and all was correct.

Followed Chris’s point and low and behold I have a shocking 60 psi on all of one bank and appx 70 across the other bank. Which is obviously dreadful.

One other point we noticed is on cranking the crankcase breather is “smoking” fuel vapour.

I am presuming that the visual vapour would suggest blow back past the rings?

The engine history is limited to a full strip down and clean the block, hone bores and refit pistons with new rings. The bores were not rebored. I do not know if the engine had been overbored in the past and the pistons with new standard rings refitted and were a good fit.

The camshaft was new fitted with a cloyes duplex with 3 adjusting points. If I had the cam timed wrong would it blow back into the crankcase?

I guess it’s a case of checking the cam timing with tdc bolt and vernier gauge and timing disc?

But is it the rings?

Anyone’s guess based on more experience than me greatly received !!!

Phil

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Re: V8 rebuilt no spark

Post by DaveEFI »

New rings in freshly honed bores won't give a perfect result until bedded in. But there should be more than enough compression to get it running.
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ricey30
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Re: V8 rebuilt no spark

Post by ricey30 »

That’s what I thought Dave and I can’t see losing appx 100psi in compression on blow past the rings.

But if I have the cam out a tooth and the inlet is still open, I would guess this would give me a low compression. ??

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Re: V8 rebuilt no spark

Post by stevieturbo »

Given all cylinders are reading the same or close...I would not take that number as gospel.

The gauge could be wrong, testing method wrong, a leak somewhere etc etc.

Until you can verify the gauge is accurate and testing method all good.....just take from that all cylinders are fairly well matched.
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Re: V8 rebuilt no spark

Post by unstable load »

The visual fuel vapour out the crankcase breather could simply be all the fuel that has run down from the attempts to start the engine.
Try to find another compression tester to compare notes, remember, throttle wide open and a good strong battery is needed. A squirt of oil down the bore won't do any harm, either..
Cheers,
John

ricey30
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Re: V8 rebuilt no spark

Post by ricey30 »

Great points all round guys thank you

The fuel vapour from excessive cranking I would think is a great point. It’s in a four barrel and the vapour only starts after several seconds of continuous churning when it sounded like it wanted to catch. So I’m grabbing that fir a moment!

I haven’t done a wet test, completely forget about that, I will do that over next couple of days at least that will elemenate the rings to a point.

The gauge is new but a cheap one from machine mart I will try and get another.

Battery is fully charged and I have a high torque starter so that’s covered.

One element I did was to shim the rocker pedestals. If this was an error on my judgement could this be the culprit? Technically the heads and the top end has gone back together as it came apart with no material removed from the heads or block, with same push rods but New cam and followers??? Used tin head gaskets

I can certainly remove those easy enough and test again

All your opinions on that greatly received !

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Ian Anderson
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Re: V8 rebuilt no spark

Post by Ian Anderson »

You managed to soak the plugs
Try some new ones to get it running as they do not like getting wet

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Re: V8 rebuilt no spark

Post by SuperV8 »

You managed to soak the plugs
Try some new ones to get it running as they do not like getting wet
This happened to me, spent a while trying to get it started, figured out what was wrong (injector connectors not connecting on old flapper system) but still wouldn't start, cleaned plugs and still wouldn't start but fitted new plugs and voila, started first time.

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ricey30
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Re: V8 rebuilt no spark

Post by ricey30 »

Thanks fir all your help.

I’m waiting on a comp tester with a brass shaft rather than rubber hose to check comp and do oil in bores after dry test, and full throttle

Got a new set of plugs on the way

And I have found out the edelbrock 1404 I am using was jetted for a 4.6 and could be way to rich for my 3.9 so I’ll back off the mixture screws a tad as well

Soon as I’ve had a tinker I’ll post back....

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Re: V8 rebuilt no spark

Post by sidecar »

I have worked on loads of 1404 carbs, I have always found that the carb needs to be setup leaner for a 4.6 than it does for any of the smaller engines. It is nothing to do with a bigger engine needing more fuel or anything like that. The bigger engine pulls more vacuum which creates a stronger 'signal' in the carb so in order to keep the air fuel ratio in the right range a leaner fuel setup is required. ( I would say smaller jet but the jets are not the only thing that controls fuel flow in these carbs). Having said all that the last 3.5 engine that I worked on ended up with a setup that is the same as most of the 4.6 engines that I have setup.

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