While out for a run in my Zetec engine kit car, I found that above 3300 rpm the car was holding back, surging, misfiring etc etc. I managed to get back home in 'limp home' mode and this morning connected up the laptop to the Megajolt to try and find the cause.
Nothing happened when I clicked on the icon to get the current configuration from the car, my screen just kept showing the basic map screen that I'd opened with. I then opened a Zetec base setting configuration on my laptop and tried to save it to the Megajolt, but again no luck.
I have been running the megajolt for about 3 months now, with no trouble at all, apart from all my shift lights coming on permanently a couple of days ago. This could of course be part of my present problem.
I have the 12v feed and a good earth at the plug, but disconnecting the megajolt has no effect on the running engine. Following previously listed advice in the forums I decided to take the unit out of the car and check soldering etc. Before doing any re-soldering I carried out the checks detailed in the build procedure, but I don't seem to have any voltage at the specified points. The only place I can find any voltage is where I soldered the pins from the input socket through the board on my initial build.
I've now checked all the soldering, and re-made a couple of connections that looked slightly suspect, but I still get the same results.
Here's hoping someone can help with this.
It just stopped working!
Moderators: JeffC, rdoherty, stieg, brentp
Hello,
Are you doing your voltage checks on the bench, or with it still connected to the car's electrical system?
If testing on the bench, make sure you have a power supply that doesn't exceed 18V. a 9V battery is ideal.
Perform a check on the voltage regulator. From the bottom of the board, the middle pin is ground, and the pin closest to the molex connector should be approximately your power supply voltage, and the pin on the left is +5V.
When you say "input socket" do you mean the white molex connector?
Are you doing your voltage checks on the bench, or with it still connected to the car's electrical system?
If testing on the bench, make sure you have a power supply that doesn't exceed 18V. a 9V battery is ideal.
Perform a check on the voltage regulator. From the bottom of the board, the middle pin is ground, and the pin closest to the molex connector should be approximately your power supply voltage, and the pin on the left is +5V.
When you say "input socket" do you mean the white molex connector?
Right - update time. I have a reading of 1.5v on the terminal nearest the molex connector, earth/ground on the centre and nothing on the 3rd terminal.FazerBob wrote:Hi Brent,
I am doing the tests on the bench, but with a 12v car battery for the current (it gives a stable reading of 12.4v) Sorry, the 'input socket' I refer to is of course the Molex.
I will check the voltage regulator when I get to the garage tomorrow morning
Bob
Getting warmer...
Please perform voltage checks between ground and either side of D2. You should see close to 12v on the band side of D2.
Check the solder joints on D2 (and the other diodes in the power supply section, for good measure). Re-solder these joints if possible.
If after the all the checks you don't see voltage on the band side of D2, but do see it on the molex side, try bypassing D2 with a jumper and see if your controller comes alive.
Please perform voltage checks between ground and either side of D2. You should see close to 12v on the band side of D2.
Check the solder joints on D2 (and the other diodes in the power supply section, for good measure). Re-solder these joints if possible.
If after the all the checks you don't see voltage on the band side of D2, but do see it on the molex side, try bypassing D2 with a jumper and see if your controller comes alive.
Looks like D2 might be dead- interesting failure mode.
Replace D2 with a locally sourced 1n4004 (or a 1N4003 or 1N4002). It's a common part, so it should be easy to find. If you have problems obtaining one, send me a PM.
D2 is for reverse voltage protection, so it's a good idea to keep it in. In the meantime, you should be able to test the unit and the rest of the ignition system- verifying ignition advance, etc. with D2 temporarily bypassed- you can solder a wire across it while you search for a replacement diode.
Replace D2 with a locally sourced 1n4004 (or a 1N4003 or 1N4002). It's a common part, so it should be easy to find. If you have problems obtaining one, send me a PM.
D2 is for reverse voltage protection, so it's a good idea to keep it in. In the meantime, you should be able to test the unit and the rest of the ignition system- verifying ignition advance, etc. with D2 temporarily bypassed- you can solder a wire across it while you search for a replacement diode.
Time for another update. I found a spare 1N4002 in the garage and have soldered it in place. I now have 11v at the band side of D2, and 12v at the other end! is this right?
On referring back to the initial build instructions for voltage checks I seem to have 11v in all the places where I should have 5v - that is U1, U2 and PS1. On QG1 where I should have 5v I have 10.5v.
All these places had the correct value of 5v when checked during the initial build. The voltage regulator has 12v on the pin closest to the molex conn. and 11v at the farthest pin.
On referring back to the initial build instructions for voltage checks I seem to have 11v in all the places where I should have 5v - that is U1, U2 and PS1. On QG1 where I should have 5v I have 10.5v.
All these places had the correct value of 5v when checked during the initial build. The voltage regulator has 12v on the pin closest to the molex conn. and 11v at the farthest pin.
Hmm. Not good. Anything that is higher than 5V on the regulated side of the circuit is 'Bad'.
We need to understand why you're seeing more than 5V on the output of the regulator and on those 5V test points. it seems there are other problem components.
Before you apply +12v again, power the circuit with a regulated 5V supply and see if the unit is still basically alive by attempting to communicate with it using the configuration software.
If you can, the next step would be to snip D3 out of the circuit and re-test for regulated 5v when applying a voltage higher than 5v (9V battery or your 12V battery) the unit's power input. If D3 is damaged as well it might be allowing current to bypass the regulator.
Here's the V3 schematic again for your reference- would be good to keep it handy as you troubleshoot.
http://www.autosportlabs.net/asl_dist/m ... v3_sch.png
We need to understand why you're seeing more than 5V on the output of the regulator and on those 5V test points. it seems there are other problem components.
Before you apply +12v again, power the circuit with a regulated 5V supply and see if the unit is still basically alive by attempting to communicate with it using the configuration software.
If you can, the next step would be to snip D3 out of the circuit and re-test for regulated 5v when applying a voltage higher than 5v (9V battery or your 12V battery) the unit's power input. If D3 is damaged as well it might be allowing current to bypass the regulator.
Here's the V3 schematic again for your reference- would be good to keep it handy as you troubleshoot.
http://www.autosportlabs.net/asl_dist/m ... v3_sch.png
Next instalment: 5.1v input at Molex - courtesy of Tom Tom power lead (useful info)
D2 4.48v(band end) - 5.1v(other end)
V Reg 4.8v(nearest to Molex) - 4.3v (farthest from molex)
U1 4.43
U2 4.43
IC1 4.48
PS1 4.43
QG1 4.46
Laptop connected after voltage checks, but still no communication with MJLJ
I'll go and try a 12v test now, with D3 removed from the circuit.
D2 4.48v(band end) - 5.1v(other end)
V Reg 4.8v(nearest to Molex) - 4.3v (farthest from molex)
U1 4.43
U2 4.43
IC1 4.48
PS1 4.43
QG1 4.46
Laptop connected after voltage checks, but still no communication with MJLJ
I'll go and try a 12v test now, with D3 removed from the circuit.
So D2 and D3 died somehow. If you have another spare diode, replace D3 and test again. The fact the circuit seems alive is a good sign, next step after your finished repairs is to test it on your engine again.
It seems that the power supply circuit experienced some unusual electrical stress. Have you been experiencing any problems with your charging system? Weak battery, bad ground connection, or marginal voltage regulator? It would be good to know before you put it back in the engine full time. While it's tempting to chalk this up to a 'freak' failure, it's more likely something specific caused this, meaning it might happen again.
Keep us posted on your progress.
It seems that the power supply circuit experienced some unusual electrical stress. Have you been experiencing any problems with your charging system? Weak battery, bad ground connection, or marginal voltage regulator? It would be good to know before you put it back in the engine full time. While it's tempting to chalk this up to a 'freak' failure, it's more likely something specific caused this, meaning it might happen again.
Keep us posted on your progress.
Ill call in at Maplin's tomorrow and get some diodes, and a few spare (just in case). Nothing springs to mind about electrical problems. The battery is new, as is the alternator, and there have been no unusual faults lately, in fact I've been rather surprised, and relieved, at how well the Zetec conversion has gone, and especially how well the engine has performed running bike carbs and Magajolt.
I will post an update tomorrow when everything is back in the car, and has been tested again. In the meantime, thanks very much for your help and guidance Brent, I'd have been well and truly lost without it.
Bob
I will post an update tomorrow when everything is back in the car, and has been tested again. In the meantime, thanks very much for your help and guidance Brent, I'd have been well and truly lost without it.
Bob