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MG MGA - Starts with key!
| OK, everyone's favorite--the intermittant electrical problem. My '59 TwinCam will spin the engine a half a revolution when I turn the ignition key to on. It only does this once out of every 50 to 100 turns of the key. Not that big an issue. I always turn the key with gearbox in neutral--clutch in. Just wondering if this ever happens to anyone else and if someone knew what might cause this? Cheers, Paul |
| Paul Hanley |
| It may be your voltage regulator. If the contacts in your voltage regulator for some reason close while the engine is not running, it can cause your generator to act as an electric motor. Old VW bettles were famous for this, sometimes driving several hundred feet, and sometimes catching on fire! |
| w.g cook |
| Paul, Do you have the standard MGA cable pull starter arrangement? Mick |
| Mick Anderson |
| Sure do, Mick. This is not a recent development. Its been acting up on occation since I purchased the car. (Feb04) But its so infrequent, that I've not addressed it till now--had way bigger fish to fry with this machine. Off to my longest day of the year 7:30 till midnight. Paul |
| Paul Hanley |
| Paul, Next question. When the engine turns over do you hear any sound from the starter motor? If silence, then it does sound like the previous suggestion, the generator is turning the engine over, because of a problem with the voltage regulator. I would suggest to try removing the fan belt and see if it happens, but you say it only happens every 50-100 times. I know how hard it is to loosen the generator bolts on a Twin Cam. As well as the Twin Cam removeable fender panels, do you have a slot cut above the panel to get a wrench in? Mick |
| Mick Anderson |
| Paul - Perhaps an easier way (albeit more expensive) to find out if the regulator causing the generator to act as a motor is the culprit would be to replace the regulator. In fact, at this point, where the problem occurs so seldom, it may be the only way to see if it is the culprit. Good luck - Dave |
| David DuBois |
| Well, I had a good excuse to ditch work for an hour. Thunderstorms rolling thru the area and TwinCam as my ride. You know, if you stay above 55mph, the the rain will typicaly go over the windscreen! Anyway, I have a new regulator on the shelf and will swap it out and see what happens. Thanks for the insight. Mick, no I don't have the extra slot cut in. Is there a picture somewhere? I haven't yet changed the fanbelt as I've been avoiding the pain and inevitable bleeding! Back to work with the subaru :( |
| Paul Hanley |
| Paul, Do you have the book "Original MGA" by Anders Clausager? If not I can email a scan of a photo of that cut in the panel. It is on page 74. A slot was cut in the inner wing, in front of the removeable panel, on the factory works competition Twin Cams. Mick |
| Mick Anderson |
| Paul - I assume that a good portion of the blood is due to knuckles vs radiator (with knuckles coming in a distant second). If so, try a trick that one of our local register members suggested, a strip of duct tape across the knuckles. Cheers - Dave |
| David DuBois |
| Paul, Something no one has addressed as of yet: If it does this, it could be firing what is left of unburnt fuel vapors in one cylinder. Not enough to start it running, but enough to hear the motor move and fire once. Normally, this only happens if the motor has been recently run, enough fuel vapors are left in a cylinder with both valves completely closed and when power is applied to the coil (turn teh key on!) it allows this specific cylinder to fire. All of these items have to happen almost perfectly in order for it to happen and most of the time, there is not enough vapors left in the motor for this to happen. I have had this happen on various cars- the older, lower compression and less technology, the more likely. I watched an old timer about fifteen years ago fire up his families Model T Ford, then shut it down... about 20 seconds later, he would reapply power to the ignition system and the car would fire up and run again. He had it down to a science and knew about how long he could wait before chances of making the car only fire or making it restart itself would be- exceed that 20 seconds and it would only fire.... Helps having compression way down in teh basement. Probably somewhere around 4.5 to 1! Another way to try this is to turn teh key on and off a few times. Sometimes this allows the coil to build up a field and then collapes. If all teh other conditions are perfect, it will happen. Try to turn the key on and off about 2-3 times the next several times and see if this happens. OF course, this still could be the other issue discussed above. Let us know what you find. Regards, -BMC. |
| BMC Brian McCullough |
| Mick, Come to think of it, I might be hearing the starter engage. I'll listen more carefully the next time it happends. I do see the slot cut in the inner wing on pg 74. Looks like a darn good idea. Brian, interesting theory. However--2 things--I have 10:1 pistons and compression is 185 across the four, and the errant firing is random. I can't make it to it by turning the key 50 times. It just happens--say half dozen times in the year and a half I've owned. Mr. Cook--the word "fire" is enough for me to change the regulator! Since I have one, new in the box, I'll change it out for sure. Thanks. Dave--great idea on the duck tape. Will surely need a roll or two in the standard Twin Cam tool box. The Twin Cam adaptation might be however, wrapping one's entire fist in duck tape and then cut a slit between the index finger and thumb to slide in the wrench! Very little is easy with a Twin--well except for acceleration. How's this for example: I recently had the block to oil pressure gauge line come loose and was leaking oil. First, the diagnosis takes an hour or two because you can't see it from any angle--in a pushrod model, two seconds. Anyway, to tighten, follow the steps below. Loosen road wheel nut. Jack up car to jackstands remove wheel remove inner panel chase lost panel screw! remove hanging canister oil filter remove starter wire remove starter turn nut 1/16th of a turn at a time 'cause you can't possibly get a wrench in that small space. now reassemble everything! Ahh, the joys! Thanks everyone and will report any significant developments. |
| Paul Hanley |
| Paul - Your description of repairing the loose oil line sounds very like the work that I did for the last 22 years of my employment - working on submarines! Cheers - Dave |
| David DuBois |
This thread was discussed between 27/05/2005 and 29/05/2005
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