Engine Electrical Problem

[richardm6994]

I've been chasing this problem all summer since the car was complete and now it's really starting to pi55 me off because I'm at a loss now!!

 

What seems to be happening is every now and then the engine just cuts out for less than a second and then fires up again. It can be whilst driving (which is really annoying as it's like hitting the brakes for a second but it's unpredictable) or whilst stationary.

On 2 occasions now it's not fired back up again and I've pulled up on the side of the road only to find nothing obvious and the car starts up again on the key.

 

I've eliminated all mechanical possibilities I can think of such as fuel supply etc...and I'm sure this is problem is ignition.

 

It's a megajolt system and I've connected the laptop and can see when it happens that the rpm dial on the screen flicks to 0 and then back to the engine rpm.

 

My first thought was VR sensor. I've replaced the sensor and plug but it's still happening. I then thought that the plug might be vibrating loose so I've glued it onto the sensor....still happening.

 

I've wiggled all the wires and plugs on the edis, megajolt and coil pack to try and make it happen on demand but failed. All plugs are secure and the wires connected tight.

 

The next thing I'm thinking is pulling out the VR sensor's shielded cable and check for any damage, but I'm sceptical this will be the answer (I've already kind of done this and didn't notice any damage).

 

I'm hoping someone has some ideas as my next thought is to replace the coil packs which would be a bit pricey if they are not at fault!!

 

For those that don't know me, it's a rover V8 running edis 8, new megajolt MAP version & 2 ford coil packs.

[Dave Ed]

i had a similar thing on my old Alfa Sud once, it was the rotor arm shorting out intermittantly causing loss of engine and the occasional misfire

i'm not familiar with megajolt but it sounds like a similar thing.

 

could a coil pack be shorting to earth?

[richardm6994]

What ever it is its getting more frequent...I've driven it to work today and its happening almost every 5 minutes!!!

 

If I can't find the problem between now and next weekend then it's staying in the garage for the national meet

 

 

[philshelton]

Trailer it down an get mark to bring his probe and have a poke around

[Guest peter2b2002]

had some thing like that on my pinto efi, cut out ,restarts, rev counter 0, fires up again, turned out it was the hall effect pick up on the dizzy giving out 9v instead of 12v new (2nd hand, thanks to the fellow hoodie who had a spare) dizy fixed the problem

peter2b

[biksz]

long shot but could the coil pack be failing?

[IanS]

Intremittant problems are the worst to find.

I suspect that you have a bad earth (bad power normally blows fuses).

I would suspect one off the megajolt earths.

-Ian

[cb750]

Just a thought, you are running 2 coil packs so if the engine is cutting out completely then it can't be the packs as the good 1 would still fire half of the plugs??

[sj-bradley]

It does seem to sound like the ECUs are not getting the request to fire the plugs, so as above, suspect the output from the distributor - could be a loose connection from dizzy to ECU. Or a high resistance wire dropping the voltage from dizzy to ECU input. This would get worse the hotter the wire became until there was not enough volts left to tell the ECU.

 

Check wire runs from dizzy to ECU.

 

This would affect the RPM counter as well.

 

Simon.

[Snapperpaul]

I had exactly the same problem

After much searching it turned out to be the cable breaking in the VR sensor (mini timer) plug where it was soldered to the pin.

This happened twice, after second fix I supported the plug and cable with thin flat bar of ally with heat shrink over

Problem solved for 4 years now

[Guest stevenkirk]

I had a similar problem on my Rover engined Superspec - whenever I hit a bump on the road the engine would cut out for a split second and then run on as normal - the fault was the ECU multi-plug, it don't like being disconnected too many times and the Gold plated contact inside the multi plug terminals wasn't a good connection - I disconnected the multi plug, got a magnifying glass and took a fine needle and tightened up the contact by prising it closer to the male terminal when reconnected. doing this cured the problem and also cured the fault with the car dying completely on me - was again a bad contact to the fuel pump relay from the ECU.

Edited September 21, 2013 by steven

[richardm6994]

Just a thought, you are running 2 coil packs so if the engine is cutting out completely then it can't be the packs as the good 1 would still fire half of the plugs??

Yeah I thought that.....

 

I had exactly the same problem

After much searching it turned out to be the cable breaking in the VR sensor (mini timer) plug where it was soldered to the pin.

This happened twice, after second fix I supported the plug and cable with thin flat bar of ally with heat shrink over

Problem solved for 4 years now

Thanks Paul!! I've also got a join in my vr cable when I had to lengthen the shielded cable to reach the new sensor position on the v8 so that's not going to be helping matters.

For what it costs, I'll buy a new plug and cable and support the cable at the sensor end.

 

 

[Longboarder]

vr cable is carrying tiny signal and must be perfect. ditto its shielding which must be electricaly connected at one end only, not both.

 

nigel

[richardm6994]

The saga continues.....

 

I have fitted a new vr sensor, plug, and rewired with new shielded cable back to the edis.

 

Went out for a drive tonight and the problem still persists What caught my attention was when I was in 4th gear cruising around 30-40mph, the engine suddenly and instantly died (downhill so no engine load either). I dipped the clutch, coasted and then tried to bump start it....and it wouldn't even try to fire. I did this 2 more times before running out of speed and so I pulled over to the side of the road.

I turned the key off and back on and it fired up as if there was no problem at all.

 

So back to the garage and I've done a bit more investigating.....

 

If I unplug the megajolt, the engine still runs (I already knew that but process of elimination)

If I unplug a either coil pack 1 at a time then the engine still runs (but rough)

 

If I unplug the edis, the engine instantly dies

If I unplug the vr sensor the engine instantly dies

 

So my thoughts are that it can only be the vr sensor or edis. I know my vr wiring is spot on and I'm on the 3rd sensor so it's doubtful it's that.

 

In a fit of desperation, I've wired a new +12v and ground to the edis thinking that it can do no harm but might solve my problem if I have a bad connection somewhere I can't see.

 

I'll try the car tomorrow to see if that has worked, but if it hasn't then I'm fresh out of ideas other than a new (expensive) edis8 module

 

Anyone have any other ideas I can try / test?

 

Whilst writing this, I've just thought that both coil packs are fed by the same 12v feed....if that's dodgy then the engine would die instantly....will also check this out.

[Guest Ian & Carole]

Rich

Is it possible to "hot wire" coil pack etc one at a time thus removing long lengths of loom to see if any one area is at fault ???