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Pressure in Plenum Chamber???


V8defender90
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Well to start off i had lost the spark from the coil to the dissy but i have now sorted that out. (wiring problems)

I have replaced the dissy but didn't mark it up so what i did, was sent it up on TDC on compression stroke and then placed the dissy in, connected the leads up in the correct firing order and then turned the key. Firstly is started then cut out ????? Then checked the fuel overun relay was connected properly to the dissy.

I then turned the key again, and it was trying to start until the pressure in the plenum chamber blow the intake pipe off. Any idea's guys??????? I have been working on this thing for days now and there is one thing on my mine... SCRAP IT.

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Well to start with you need to give us some background info such as

Engine type and size

What have you changed since it last ran

Etc.

If there is pressure in the plenum then it must have been a backfire indicating wrong timing of either ignition or valves.

If it blew the pipe off then it may well have mullered the AFM particularly if it is a flapper.

Steve

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Well to start with you need to give us some background info such as

Engine type and size

What have you changed since it last ran

Etc.

If there is pressure in the plenum then it must have been a backfire indicating wrong timing of either ignition or valves.

If it blew the pipe off then it may well have mullered the AFM particularly if it is a flapper.

Steve

Sorry forgot to mention, It has a range rover 3.5 v8 EFI, I had changed the leads then it wouldn't start, i then realised it was the cables on the coil, so i then rewired it, can i ask what you mean by a AFM????

Cheers

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Air Flow Meter.

If it blew off that'll be a backfire. Which in turn suggests either the leads are on in the wrong order and/or the dizzy is in the wrong position.

Don't forget that when putting the dizzy back in the rotor arm will rotate as the dizzt drive gear engages with the gear on the cam.

Very easy to get it one tooth out which results in it apparently trying to start. But just banging & f...ing. As to how I know that one..... :blush:

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Set Crank pulley to 6 degrees BTDC on crank pully and timing mark on timing case

Now check rotor arm - bet its NOT at the No 1 cylinder position !

So,

Remove dizzy, put dizzy back in by moving oil pump shaft to be able to connect in to bottom of Dizzy

and have the cap off the dizzy so that the rotor arm is on the No 1 Cylinder position when slotted into place,

clamp up the lock plate on the base of the dizzy so movable if twiested but not tight, connect Vacumn advance pipe,

fit dizzy cap and leads to cap and coil in correct positions

This will givbe a ROUGH setting, once started put timing light on at set the dizzy properly and then lock dizzy in place

HTH

Nige

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Thanks guys for your reply's, can i just confirm that from the front of the car that the left bank is 2,4,6,8 and the right bank is 1,3,5,7

Hello V8defender90, with the above query and similar enuirey re AFM, plus being new to RV8 Efi you might like to get some basics for Efi under your belt.

Unfortunately there does not appear to be a simple explanation to RR models but if you care to read all the stuff on this index, you will increase your savvy on the basic Efi Flapper system.

http://www.vintagemodelairplane.com/pages/...mponents01.html

By doing so you will be able to follow the answers given on the forum for the symptoms. you report.

The analysis you have so far is clearly correct, such that the ignition timing is way off and you need to get it back to specification, but as time goes by, if you are planning to do any DIY servicing on your Efi system you need some basic background info.

I understand that a RR document called RAVE has similar info but I find it difficult to follow, myself.

Happy reading.

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The hardest bit about this is that the RV8 will run with the timing in all sorts of crazy positions, I once made the mistake of swapping a dizzy without making note of the position of everything and on reassembly it would start & run very badly but no matter what we did with the timing it would not stop running :lol: (we were minus a timing light at the time so trying to do it by feel).

I'm a bit concerned that after changing the HT leads & dizzy you then decide the coil is wired wrong, can I ask what lead to that conclusion since it would seem far more likely the coil was fine as it was and the change of dizzy is the problem.

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Well guys cheers for your comments. The problem is now sorted out, I just started again from scratch and set the timing to 6 degress before TDC, clamped the dissy down, done the firing order, had to change the battery as it was dying, due to me turning it over loads, checked the connections to the coil to find the fuel overrun relay was wired backwards :( , turned it over, job done. Now got to do loads of tidying up to do in the engine bay. Cheers again V8DEFENDER90.

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