New problems this morning...

General Topics for configuring, operating and tuning the Megajolt. Also see the <a href="http://www.autosportlabs.net/MJLJ_V4_Operation_Guide">Operation Guide</a>

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Edwardatherton
Posts: 30
Joined: Sun Jul 01, 2007 9:50 am
Location: Manchester, England
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New problems this morning...

Post by Edwardatherton »

Yesterday I loaded dual maps and everything appeared to be working fine. On my way home it seemed to be down on power regardless of which map I used, although there was a slight change in engine behaviour at idle when the MJ was plugged in/out or switched betrween maps, so I think it's working.

This morning I cannot get it to talk to the PC, although it has never had a problem before, it just says "timeout reading ingition configuration" (not my smelling pistake!) then "timeout reading runtime data".

When I flick the option switch in the vehicle I have either 0V or about 3.9V, not 5V.

If I measure the SAW line with my multimeter (set to 2V DC test) in the vehicle, I get 0.29 at idle, rising to about 0.8V at higher speeds.

What else can I check? I need to get another, longer, serial cable to get actual running data, would this one do?
Land Rover 1957 S1 88" 2.5 petrol/LPG

brentp
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Post by brentp »

Hi Edward,

If you suddenly cannot communicate with the MJLJ, first thing is to verify that power is being delivered to it. If necessary, pull it out and test it on the bench with a known power supply. If your serial cable worked before- it should still work!

Being down on power would typically indicate the EDIS module went to it's default 10 degrees BTDC setting.

Regards,
Brent Picasso
CEO and Founder, Autosport Labs
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Edwardatherton
Posts: 30
Joined: Sun Jul 01, 2007 9:50 am
Location: Manchester, England
Contact:

Post by Edwardatherton »

It turned out to be the 9V battery that I bought yesterday morning... I verified around 9 and 5 volts at various points on the board but something was obviously up with it. I think it'll be going back to Tescos!

As I expected to need it for a while, I bought a Duracell battery - I have only had it plugged in for 10 minutes probably, and it must be dead... How much power does it take to run the MJ box?

Anyway, new map loaded and there definitely is a difference when I plug the box in. I also tested the rev limiter on the second map at 2000RPM so I know it is working. The new map seems to have got rid of the low speed stutter and backfire that nearly gave a few pensioners heart attacks in Chorley yesterday!
Land Rover 1957 S1 88" 2.5 petrol/LPG

MartinM
Posts: 433
Joined: Sat Aug 27, 2005 12:08 pm

Post by MartinM »

The MJLJ takes about 30mA and needs circa 6v min voltage to operate.

So a quick Google turns up:
http://www.mdsbattery.co.uk/datasheets/ ... 1604PL.pdf
...which has a nice graph that shows that you should be getting about 18hours from a Duracell PP3 into a 300ohm load (which they equate to 25mA)

...which is consistent with about what I used to get from a PP3

As you have a multimeter, put it into DC mA mode and put it in line between the Battery +ve and the MJLJ. What does it read? Should be around 30mA....

Edwardatherton
Posts: 30
Joined: Sun Jul 01, 2007 9:50 am
Location: Manchester, England
Contact:

Post by Edwardatherton »

I assume it's the 10A setting on the meter - just because I have one doesn't mean I know every function :) ...

If so, it says 0.02. Which I would take to mean 20mA?

Maybe it's the battery connection. because now I am home again and have been using the original Duracell battery for 10 minutes without problems. Very odd.
Land Rover 1957 S1 88" 2.5 petrol/LPG

MartinM
Posts: 433
Joined: Sat Aug 27, 2005 12:08 pm

Post by MartinM »

0.02A = 20mA so you're in the right ballpark....

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