Diagnostic help needed

[robinbartle]

Diagnostic help needed please.

The patient is a Pinto fitted in a Tiger that I bought last week.

That probably makes me an interloper on this site but if it makes it any better I do have the chassis of my Haynes Roadster hanging on my workshop wall, it's just that since our first son came along and we moved house and whatnot, progress has been...delayed. The Tiger was to get me going and also to give me some practical experience because I am - to be honest - pretty damned ignorant where engines are concerned.

Enough self justification. The car runs well most of the time but never for more than about twenty miles, after which it starts to backfire, responds erratically to the throttle, and then usually peters out.

Attempts to re-start usually produce more backfiring along with what I assume must be combustion going on in the carburettor - at least smoke and bangs emerge from the air filter, which must be suffering. On another occasion it failed to fire altogether - no spark visible when plug removed, although the plugs look OK.

Given an hour or so's rest it seems to come back to life most of the time, and it has only happened when the car's been running for a while - but presumably overheating wouldn't cause these symptoms, would it? The temperature gauge isn't getting all that high.

I'm thinking ignition problems. It's got a megajolt. The last owner briefly mentioned he'd had problems with it and I'm guessing mistimed sparks would be a likely cause of backfires etc..? My first thought is to try to follow all the wiring for the megajolt and see if anything is dodgy/loose (frankly what I have seen of the wiring so far is mostly a tad dodgy, to me eye), but given my ignorance I am very probably barking up the wrong tree, so what would others try first in this situation?

[michael92]

kind of sounds as its a hot starting fault, maybe the ignition timing is incorrect, did you map the ignition yourself or get some one to do it ? Im well into mapping but haven't had too much experience in doing so, someone more competent maybe able to point you more in the right direction

[robinbartle]

Well, I have it booked in for a session on a rolling road which presumably will show up any problems with the mapping. As it's a forty minute drive, I just need to keep my fingers crossed that i get there..

Thanks for coming back to me!

[davidimurray]

Have you tried simply leaving the car stationary and then letting it run. Get it nice and hot (wait until the fan comes on then wait 30+ minutes) and then does the fault start to occur. If so it may be related to engine bay heat. Try taking the bonnet off and runing without it - even out on the road. Where is the coil/edis/megajolt located?

When the car stops running does it still have a spark. You can get some small inline indicator lamps.Check if you have a spark on all cylinders before and during the fault condition.

If I was you I would be looking at other things before mapping. Have you got a copy of your Megajolt map ?

[snapper]

Megajolt uses the Ford EDIS unit.
The Megajolt just instructs the EDIS when to fire.
The EDIS can run the engine on its own in limp home at a fixed 12 degrees
If the EDIS is in the engine bay and gets hot it can suffer
Also check the VR (crank) sensor wiring as this can be a difficult to find as I well know.