funny symptoms.....
Discussion
Was after a bit of help diagnosing some strange symptoms (to my inexperienced eyes anyway!).I'm guessing they are connected as they have occurred at the same time!
1- Engine won't rev past 4k under load - revs fine on the drive. Plenty of chat up to 4k, but just seems to run out of steam.
2- Oil pressure reading 10 lbs lower than usual
3- Temp reading 10 deg lower than usual (judged at fan cut in point, rather than IR thermometer)
4- Battery light stays on when ignition is fully off.
I'm guessing they are all electrically based, but my knowledge isn't great and I can't connect the dots so I'd really appreciate some wiser eyes than mine, as this weather is too good to miss!
1- Engine won't rev past 4k under load - revs fine on the drive. Plenty of chat up to 4k, but just seems to run out of steam.
2- Oil pressure reading 10 lbs lower than usual
3- Temp reading 10 deg lower than usual (judged at fan cut in point, rather than IR thermometer)
4- Battery light stays on when ignition is fully off.
I'm guessing they are all electrically based, but my knowledge isn't great and I can't connect the dots so I'd really appreciate some wiser eyes than mine, as this weather is too good to miss!
Battery light will stay on without the engine on and the key in the ignition. This is because the battery is providing power, but not receiving a charge. If you turn the engine over, the battery light should go out. If it doesn't you need to check the 100AMP fuse. If the fuse is intact, then you need to check that the alternator is still providing a charge.
Secondly, as for the other stuff, the fact that more than one dial is misreading is a possible indication of a bad earth, so clean and check the earths on the chassis near the drivers side wheel, behind the belt tensioner pulley (near the oil pressure switch) and under the dash. Then clean and check the connections to the senders. It would also be worth checking the coolant levels and oil levels. I do believe that volume of oil make a difference to the pressure in the RV8.
As for the revs, I would be looking at ensuring all HT leads are good, including the rotor arm, dizzy cap, plugs and coil. It would also be worth checking your battery output. I think it is a case of cleaning all the connections/ a little service than major problems. It may also be worth disconnecting and re-connecting the ECU.
Secondly, as for the other stuff, the fact that more than one dial is misreading is a possible indication of a bad earth, so clean and check the earths on the chassis near the drivers side wheel, behind the belt tensioner pulley (near the oil pressure switch) and under the dash. Then clean and check the connections to the senders. It would also be worth checking the coolant levels and oil levels. I do believe that volume of oil make a difference to the pressure in the RV8.
As for the revs, I would be looking at ensuring all HT leads are good, including the rotor arm, dizzy cap, plugs and coil. It would also be worth checking your battery output. I think it is a case of cleaning all the connections/ a little service than major problems. It may also be worth disconnecting and re-connecting the ECU.
Edited by chris1972 on Monday 15th July 11:14
They certainly could all be related, as mentioned, check the 100 Amp fuse but the battery light staying on witht he ignition OFF would (to me at least) indicate an issue with the diode pack in the alternator.
You only need one diode in there to fail and you have a direct route to earth for the charging lamp - that would also mean your battery isn't getting a charge and that in itself causes all sorts of rough running/weird gauge scenarios..
Check the voltage across the battery with the engine running, that'll give you a good place to start. Then check for 12V at the alternator end of the HD cable, if you have 12V there then the 100A fuse is probably OK (certainly providing a connection, but doesn't mean it can carry the full amperage)..
You only need one diode in there to fail and you have a direct route to earth for the charging lamp - that would also mean your battery isn't getting a charge and that in itself causes all sorts of rough running/weird gauge scenarios..
Check the voltage across the battery with the engine running, that'll give you a good place to start. Then check for 12V at the alternator end of the HD cable, if you have 12V there then the 100A fuse is probably OK (certainly providing a connection, but doesn't mean it can carry the full amperage)..
Thanks guys, the battery light is staying on with key removed and alarm set, so if the alternator diodes could result in a direct earth then that might explain the rest. I've turned the battery master off in between drives this weekend (roof left off for access), but the ignition did sound a little weaker each time.
Are the diodes serviceable, or is it a new alternator?
Thanks again :-)
Are the diodes serviceable, or is it a new alternator?
Thanks again :-)
timmaycock said:
Thanks guys, the battery light is staying on with key removed and alarm set, so if the alternator diodes could result in a direct earth then that might explain the rest. I've turned the battery master off in between drives this weekend (roof left off for access), but the ignition did sound a little weaker each time.
Are the diodes serviceable, or is it a new alternator?
Thanks again :-)
There are loads of alternator reconditioning places, but TBH, you could pick up a brand new Genuine LR with correct pulley, delivered off Ebay for about £100. Just a thought if a auto electrician says it will be £65+VAT... may as well get a new one!Are the diodes serviceable, or is it a new alternator?
Thanks again :-)
Chilliman said:
In addition to above, check the state of the induction hose where it goes through the front 'bulkhead' and on to the filter, these can collapse/become restricted with the bend resulting in loss of air to the engine....
You may remember my post on this, showing the collapsed hose when I replaced in with an ACT one. It was well on the way to full collapse but still would rev past 4000 no problem so I think this is less likely but still worth a check.Got a multimeter and five minutes?
Check the 100 amp fuse first, as Chris said, these can all be blown 100 amp fuse issues.
First, with the engine off, ignition off, look at the back of the alternator. There is a plastic cover, under that is the main lead to the battery. My plastic cover has a hole, distributor side. Turn the multimeter to the 20 volts scale, black lead onto the body of the alternator, red lead through that hole until you touch metal. If you can see 12.7 volts, the 100 amp fuse is fine. If not, the fuse is blown.
If the 100 amp fuse is ok, start the engine, same place with the multimeter leads, are you now getting high 13 or low 14 volts? If not, suggests the alternator is foobarred.
Check the 100 amp fuse first, as Chris said, these can all be blown 100 amp fuse issues.
First, with the engine off, ignition off, look at the back of the alternator. There is a plastic cover, under that is the main lead to the battery. My plastic cover has a hole, distributor side. Turn the multimeter to the 20 volts scale, black lead onto the body of the alternator, red lead through that hole until you touch metal. If you can see 12.7 volts, the 100 amp fuse is fine. If not, the fuse is blown.
If the 100 amp fuse is ok, start the engine, same place with the multimeter leads, are you now getting high 13 or low 14 volts? If not, suggests the alternator is foobarred.
Just read your second post, Tim. Sounds more and more like 100 amp fuse. Mine has gone twice in 12 months.
The fuse lies between the alternator and the battery, where it is inserted to protect you from enjoying your car in nice weather.
The fuse is strapped to the underside of the chassis, about level with where the rear arm of the driver's side front lower wishbone meets the chassis rail. Might be tucked a little higher if your chassis has been refurbed. Where else would it be? Just be glad its not night time in November at the side of a busy motorway in the rain. It is in a black plastic holder, in the middle of a thick cable. Flip the holder open, then you will need a 7 or 8 mm spanner. It may look ok, take it right out to check. One piece good, two pieces bad. Replace with a similar, or a midi, fuse.
The fuse lies between the alternator and the battery, where it is inserted to protect you from enjoying your car in nice weather.
The fuse is strapped to the underside of the chassis, about level with where the rear arm of the driver's side front lower wishbone meets the chassis rail. Might be tucked a little higher if your chassis has been refurbed. Where else would it be? Just be glad its not night time in November at the side of a busy motorway in the rain. It is in a black plastic holder, in the middle of a thick cable. Flip the holder open, then you will need a 7 or 8 mm spanner. It may look ok, take it right out to check. One piece good, two pieces bad. Replace with a similar, or a midi, fuse.
100% definitely worth checking both (100 Amp fuse and alternator/diode pack) but I'd do a "20p bet" that the 100 Amp fuse shouldn't cause the battery light to be on when the ignition is off...
But then again. strange things can (and do) happen with electrics in fibreglass cars :-)
I'm looking forward to hearing the results of your tests :-) Good Luck..
But then again. strange things can (and do) happen with electrics in fibreglass cars :-)
I'm looking forward to hearing the results of your tests :-) Good Luck..
Sorry for the slight delay in reporting back, the multi-meter was out on loan!
Have now measured and am getting
- 11.1V with car fully off measured across the alternator(plus a high pitched wine from the back of the alternator)
- 11.1V with engine at idle from the back of the alternator
- 11.1V across the battery.
I see a theme! I take it that means the 100A fuse is ok and the alternator needs to be pensioned off.
I can see that explaining the battery light, under-reading gauges and ever more sluggish starting, but would someone confirm if this would be the cause behind hitting a wall at 4k revs under load?
Thanks everyone :-)
Tim
Have now measured and am getting
- 11.1V with car fully off measured across the alternator(plus a high pitched wine from the back of the alternator)
- 11.1V with engine at idle from the back of the alternator
- 11.1V across the battery.
I see a theme! I take it that means the 100A fuse is ok and the alternator needs to be pensioned off.
I can see that explaining the battery light, under-reading gauges and ever more sluggish starting, but would someone confirm if this would be the cause behind hitting a wall at 4k revs under load?
Thanks everyone :-)
Tim
timmaycock said:
I can see that explaining the battery light, under-reading gauges and ever more sluggish starting, but would someone confirm if this would be the cause behind hitting a wall at 4k revs under load?
Thanks everyone :-)
Tim
Yes Tim, that's classic for the alternator not charging the battery or supplying the spark. Your battery does the job until it is exhausted. Thanks everyone :-)
Tim
First time my fuse went (same effect as buggered alternator) it drove fine, but my speedo read 45 mph at 3000 rpm in 5th. Chasing a 360 spider I hit 4500 rpm in 5th at 60 mph (!!), and realised I was doing 120. Thirty miles later the alarm was playing silly buggers and the car wouldn't start, I bump started it down a hill and it kept trying to die on me. I used my third foot to keep the revs up while braking and with my foot on the clutch (!) and then it wouldn't go over 50 mph. Made it to a layby, engine died, battery almost flat.
To test the alternator with the engine running:
- Turn on headlights to main beam and check the battery voltage. The battery voltage should read between about 13.8 to 14.5 volts.
- Now increase the engine speed to about 1500 RPM. The alternator should now produce a battery voltage between 14.2 and 14.6 volts. If it is Lower than 14.2 volts it is possible that the alternator has one or more bad diodes.
- If you maintain the engine's revs at 1500 RPM for one minute and turn off the headlights, the battery voltage should not exceed 14.8 Volts. If it does, the alternator's voltage regulator is likely to be faulty and overcharging the battery. This will cause the battery to swell and the acid to leak.
To test the battery:
- Connect a voltmeter directly across the battery terminals (not the clamps or jump leads)
- Start the car and whilst doing so watch the voltmeter. The battery voltage should not fall below 10 volts. If it does, the battery is either low in charge , low in water (unless maintenance free sealed unit) or has a high internal resistance and needs to be replaced.
- If you can add deionised water, the level should only be about a 1/4inch above the plates. Don't overfill it!
Repeat the above battery test, but this time, connect the voltmeter to the battery clamps on the cables. This reading should be Within 0.1 volts maximum as the battery test above. If it isn't, then it is worth cleaning the battery terminals and clamps and trying again.
Rear of the alternator. The thick plastic insulated cable is where to position the probe from your voltmeter.
- Turn on headlights to main beam and check the battery voltage. The battery voltage should read between about 13.8 to 14.5 volts.
- Now increase the engine speed to about 1500 RPM. The alternator should now produce a battery voltage between 14.2 and 14.6 volts. If it is Lower than 14.2 volts it is possible that the alternator has one or more bad diodes.
- If you maintain the engine's revs at 1500 RPM for one minute and turn off the headlights, the battery voltage should not exceed 14.8 Volts. If it does, the alternator's voltage regulator is likely to be faulty and overcharging the battery. This will cause the battery to swell and the acid to leak.
To test the battery:
- Connect a voltmeter directly across the battery terminals (not the clamps or jump leads)
- Start the car and whilst doing so watch the voltmeter. The battery voltage should not fall below 10 volts. If it does, the battery is either low in charge , low in water (unless maintenance free sealed unit) or has a high internal resistance and needs to be replaced.
- If you can add deionised water, the level should only be about a 1/4inch above the plates. Don't overfill it!
Repeat the above battery test, but this time, connect the voltmeter to the battery clamps on the cables. This reading should be Within 0.1 volts maximum as the battery test above. If it isn't, then it is worth cleaning the battery terminals and clamps and trying again.
Rear of the alternator. The thick plastic insulated cable is where to position the probe from your voltmeter.
Edited by chris1972 on Wednesday 17th July 10:16
I DON'T BELIEVE IT!!!!!
30 minutes from the end of my track day there's a faint red light on the dash. Another 15 laps of Cadwell Park and it's getting brighter. Restart the car for the 44 miles home. Not quite its usual self. Stop for fuel, car restarts ok. Drive home, no problem, but red light now burning bright as dusk draws in.
Get home, sigh of relief, get out the multimeter.
Just two tests tonight, as I am trying not to wake the grandchildren.
Engine off, 11.8 to 12 volts at the back of the alternator.
Engine idling - same voltage, same place.
Rest of the 1972 tests tomorrow......
That is spooky .
30 minutes from the end of my track day there's a faint red light on the dash. Another 15 laps of Cadwell Park and it's getting brighter. Restart the car for the 44 miles home. Not quite its usual self. Stop for fuel, car restarts ok. Drive home, no problem, but red light now burning bright as dusk draws in.
Get home, sigh of relief, get out the multimeter.
Just two tests tonight, as I am trying not to wake the grandchildren.
Engine off, 11.8 to 12 volts at the back of the alternator.
Engine idling - same voltage, same place.
Rest of the 1972 tests tomorrow......
That is spooky .
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