richardm6994
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| posted on 6/10/13 at 08:55 PM |
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Problem; megajolt, edis, coils?
I would really appreciate it if you could have a read through my post on rhocar regarding an ignition problem I've now for a while and
it's getting worse and really pi55ing me off.
I didn't see the point in typing the whole story again as I've already typed it all out once........
http://www.rhocar.org/index.php?showtopic=37721&st=0
From today's playing around, I'm thinking its a coil pack but more eyes on this might come up with something I haven't thought
of.
Many thanks in anticipation.
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paulf
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| posted on 6/10/13 at 09:09 PM |
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It seems as if you have covered all the most likely points but if it was a coil pack unless it was shorting out and killing the 12v supply then i
think it would still run on 4 cylinders.It is unlikely to be the edis but possible but I would check out the wiring into the edis plug and also if you
have the suppressor capacitor on the coil supply then I would remove it.
It can really only be a break in the power or Vr sensor wiring somewhere so I would check both from the edis plug back to source.
Paul
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Irony
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| posted on 7/10/13 at 06:45 AM |
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My car is not on the road yet but it does happen to have same setup as you. If you could get to Lincoln we could swap around parts. My megajolt has
this dodgy inline fuse connector that I think could cause problems. Does yours have this?
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snakebelly
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| posted on 7/10/13 at 07:08 AM |
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Have you tried taking out for a spin with the Megajolt disconnected? the EDIS alone should run it but at a fixed 10 deg timing iirc. If it runs ok
then at least you have isolated the issue to the Megajolt and if it does it again you can probably rule the Megajolt out?
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richardm6994
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| posted on 7/10/13 at 07:15 AM |
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Thanks for taking the time to read through the thread.
At the start of the problem, I thought that the likelyhood of both coils failing at exactly the same time was very unlikely and if just one failed
then the engine wouldn't just die for the split second like it has been doing.......
....that was until I changed the edis, edis plug, vr sensor, new vr cable and bypassed all fuses, relays etc...behind the dash and supplied power and
earth straight from the battery to the edis.
by process of elimination, the only thing left that I havn't swapped is the coil packs....and with the little experiment running just 1 pack at
a time I think that there might be a faulty one. Maybe like you said it's shorting to ground or something and killing the power to both?
Irony, many thanks for the offer and if the new coil pack doesn't work tomowwor, I'll probably take you up on it as I'm completely
bamboozled (this is my 3rd megajolt set-up and have never come across anything like this!!)
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richardm6994
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| posted on 7/10/13 at 07:17 AM |
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quote:
Originally posted by snakebelly
Have you tried taking out for a spin with the Megajolt disconnected? the EDIS alone should run it but at a fixed 10 deg timing iirc. If it runs ok
then at least you have isolated the issue to the Megajolt and if it does it again you can probably rule the Megajolt out?
Yes, I've done that and the problem is still there....which is why I originally thought it was vr sensor related problem....then wiring
related....then edis related....and now coil related 
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r1_pete
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| posted on 7/10/13 at 09:07 AM |
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Sounds like interference on the shielded vr cable replace it with 2 core and screen use the 2 cores for the plug connections and only ground the
screen at the edis end grounding at both ends can cause eddy currents. Ive also seen examples of people
usi g the screen as a conductor which will cause interference.
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dave_424
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| posted on 7/10/13 at 04:32 PM |
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In tunerstudio go to diagnostics, in the drop down menu choose tooth logger and then record a tooth log of startup and a couple of second of running.
Upload a screenshot of what the tooth log looks like.
With the RPM dropping to 0 and the ecu not resetting, it is usually the VR sensor connected the wrong way round. Can you easily swap the wires and try
that?
Dave
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richardm6994
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| posted on 7/10/13 at 04:41 PM |
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Hi Dave & thanks for your comments.
I have looked for the tooth logger as someone mentioned it but we couldn't find it. I'm not sure if this feature is only for megasquirt
(the chap who mentioned it ran megasquirt and couldn't find it on the megajolt software).
That said....I will look again tonight in the area you suggest
If the Vr sensors cables are the wrong way around, the car just doesn't start or run at all...so I'm sure they are the right way
around.
[Edited on 7/10/13 by richardm6994]
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MikeRJ
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| posted on 7/10/13 at 05:21 PM |
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Are you still using the original EDIS connector on your loom? It's possible that you have a bad connection or broken wire within this.
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richardm6994
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| posted on 7/10/13 at 05:23 PM |
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I'm on my second edis plug so it's not impossible but for 2 edis plugs to be faulty is unlikely.
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richardm6994
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| posted on 9/10/13 at 12:41 PM |
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right then.....I still feel that I'm no closer with fixing this problem and I've spent about 5 days looking at it with the help of a
friend.
It's a random fault which we have not been able to isolate the cause. With the car stationary and the engine running (regardless of what rpm),
the engine ignition completely dies for a split second and then comes back to life.
When this happens whilst driving, the split second engine cut-out causes the car to nose dive and then when the power comes back it snaps
forward....not the best thing to be happening round a corner!!!
On a few occasions now, it's died completely and I've had to restart off the key.
There is no indication of when it's about to die, it will be running perfect and then it just instantly cuts out for that split second.
The main difficulty is that the fault happens so randomly, it takes forever to eliminate various factors. For example, you can be wiggling a wire and
the fault happens....so you think you're onto something...only to find that you can't make the fault happen again and that there is
nothing wrong with the wire!
thing I've tried;
new coil packs
a different edis (from triggerwheels which they said its been tested) with new plug
3 vr sensors
new vr sensor plugs
new shielded cable for the vr sensor
All the wiring has been checked and double checked and is correct.
The ignition switch supplying 12v to the edis, coils and megajolt has been bypasssed and a 12v feed straight from the battery has been put in.
The earths for the megajolt and edis now go directly to the battery.
the plugs to the coil packs have been checked.
We've shielded everything to see if that had any effect (RF problem), but no effect at all.
We tried earthing the coil pack bodies (never heard of this before but gave it a try)
We disconnected the alternator
We've tested the spark plug leads
We unplugged the megajolt so the engine is running in "limp" mode and the fault still happens.
Chris at Triggerwheel is also involved trying to get this sorted but we're all at a bit of a loss what to do next?
Another friend owns a garage so we're all going there on Saturday to play about and possible just re-wire the whole ignition system (which I
doubtful will fix it but I don't know what else to do).
I would be really greatful if anyone has any other ideas....
last night we did measure a few millivolts between the negative on the battery and the chassis of the car. And when my fan, head lights etc...switched
on this increased very slightly. I don't know if this is related or just another red herring like everything else when we've thought that
we've found something!!
oh, and just to follow up and a previous point....the megajolt software doesn't have the tooth logger. It must just be megasquirt that has this.
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RichardK
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| posted on 9/10/13 at 01:18 PM |
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I know you mention that you've done the mj earth to battery but what about the main chassis and engine earths? Sounds like a horrible fault,
what is making you focus on spark? You can get spark plug caps that have built in illumination, a bit chavy but useful sometimes or you may get lucky
with an inductive timing light on one of the leads.
Where does the fuel line split into each carb, could that be restrictive somehow, could the tank be pressurizing?
Have you done a compression test on all the cyls?
I'll put my thinking cap on further.
Cheers
Rich
Gallery updated 11/01/2011
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richardm6994
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| posted on 9/10/13 at 01:51 PM |
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cheers rich. I certainly is a horrid fault! and so far has cost £150 in new bits that haven't changed anything.
The engine is earthed on a bellhouse bolt and the chassi is earthed in acouple of places. some good 1/2" thick cable as well.
It's a single carb weber 500 on the v8 engine, and it's a fuel pressure gauge which is showing pressure to the carb all the time. We also
disconnected the fuel pump just to see how long it runs without it and it goes for a good minute or so on idle. I'm confident that the fuel
suply is good.
I've taken the spark plugs out to check them and they all look good. I did do a comp test out of interest as the engine is new / rebuild and
hasn't had one done. The comp test showed good pressure and only 4psi difference over all cylinders.
The vr sensor bracket is also solid with no movement. The sensor gap to the trigger wheel is about 0.25mm but during our playing around, we adjusted
it to it's furtherst point away from them trigger wheel (2.5mm) and it it still worked. So I don't this sensor gap is the problem.
The reason I think it's ignition related is that when the split second power-cut happens, the needle on the rev counter instantly drops to 0 and
then goes back to the revs when it fires back up.
Also, its the only thing that can cause this kind of split second complete power cut.
Once again, all help on this is greatly appreciated and the last resort is fitting a dizzy which I dont want to do and the megajolt stuff should be
working!
[Edited on 9/10/13 by richardm6994]
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snakebelly
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| posted on 9/10/13 at 04:54 PM |
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you say that when it happens the tacho dies, is it run off the Megajolt? does anything else die or just the tacho and spark?
You could always do a cable check the old fashioned way, rig each wire individually one at a time with a 9 volt battery and a bulb then wriggle the
wire all along its length and see if the bulb flickers?
To be honest there isn't that much wiring for a Megajolt so I would think the next step is the one you've already mentioned, make up a new
Megajolt loom off the car and check it to death then swap over and see if your issue disappears.
I feel your pain, these types of issues can burn time and money and usually end up being something stupidly simple. to fix.....once you know what the
problem is!
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richardm6994
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| posted on 9/10/13 at 06:35 PM |
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Hi snakebelly! The tacho runs off the megajolt and nothing else dies.
I think that this is the single most pain in the ar5e problem I have ever had!!
[Edited on 9/10/13 by richardm6994]
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