Poor starting 350i
Discussion
al 350i said:
well new plugs and rotor fitted today which did help a little but still didn't want to start straight away. while trying to start i measured the volts at the +coil and with ignition on was getting 12v but while cranking dropped to 8v,
So that's either a ballast resistor being switched-in or your battery voltage is dropping so low under cranking that there's hardly anything left for the coil.As you propose, giving the coil + a feed straight from the battery might prove which it is, but a quicker check would be to put your meter across the battery and see if it drops to 8V there. If it is, then your battery is dying under load.
One quite feasible possibility is high resistance in the battery to chassis and engine to chassis braided earth leads: they need to be in good order with CLEAN terminations at each end, otherwise the voltage drop through the system can cause starting as well as fuelling and ignition faults.
Disconnect the earth leads, polish up all contacting surfaces with emery or a file, including the chassis or engine faces and the bolts themselves.
well in case anyone reads this post in the future and wants to know the out come..................I FIXED IT!!! 
and the fault was............ignition module on side of distributor, i fortunately have 3 in the garage! the only reason i hadn't looked at it earlier was because it isn't that old and came with new dizzy i bought a year ago.........that'll teach me to not buy Powerspark rubbish!
and the fault was............ignition module on side of distributor, i fortunately have 3 in the garage! the only reason i hadn't looked at it earlier was because it isn't that old and came with new dizzy i bought a year ago.........that'll teach me to not buy Powerspark rubbish! A word of caution.
The innards of the amplifier module used in typical RV8 electronic ignition systems generate a large amount of heat, sufficient to self destruct the module unless it is correctly fixed on its mounting plate using a smear of thermal paste to allow the heat to dissipate without causing internal damage.
The paste is available from electronic outlets such as Maplins. Too thick an application is just as damaging as none at all.
Think smear!!!
As many new modules have failed due to incorrect fitting as those being from a suspected/dodgy source, methinks.
They can't all be bad sources and even the best will fail without the opportunity to dissipate excess heat.
The innards of the amplifier module used in typical RV8 electronic ignition systems generate a large amount of heat, sufficient to self destruct the module unless it is correctly fixed on its mounting plate using a smear of thermal paste to allow the heat to dissipate without causing internal damage.
The paste is available from electronic outlets such as Maplins. Too thick an application is just as damaging as none at all.
Think smear!!!
As many new modules have failed due to incorrect fitting as those being from a suspected/dodgy source, methinks.
They can't all be bad sources and even the best will fail without the opportunity to dissipate excess heat.
Great news, well done.
Sorry I've not posted much recently - I have been reading this thread but due to being busy at work and the bad weather, I've not had chance to get the bonnet up.
I did however pop outside the other day and randomly tried to start the car. Started up instantly, which is frustrating as it makes troubleshooting difficult!
As soon as a half decent day comes along, I'll update this thread with my findings :-)
Dan.
Sorry I've not posted much recently - I have been reading this thread but due to being busy at work and the bad weather, I've not had chance to get the bonnet up.
I did however pop outside the other day and randomly tried to start the car. Started up instantly, which is frustrating as it makes troubleshooting difficult!
As soon as a half decent day comes along, I'll update this thread with my findings :-)
Dan.
Hi Everyone,
Finally an update and I think I've made some progress on my poor starting / running 350i. Yesterday I went through the troubleshooting section of the EFI document on the tvrwedgepages site and everything seemed to check out. I checked all the voltages / ohms on the circuits as described and they we're all healthy.
I then took the plenum off and discovered 3 of the trumpets were really lose in their holders, with one of them completely out. A further one had risen up about 1cm, so I took them all out and JB welded them in. Resealed the plenum, plus also removed the rocker covers, checked for obvious damage and resealed them too. I also checked all the breather hoses and am quite happy that everything is sealed.
I took the car for a test drive and it felts much better. Where as before the engine would routinely start to misfire / struggle at 4800rpm, this time it reved smoothly up to around 5400rpm. I repeated the test on a strip of abandoned road many times and have definitely gained another 600rpm of rev range. Previously, it was like the car had hit a wall at 4800rpm every time time, with lots if juddering, popping, banging etc.
However, I also noticed now that if you don't use wide open throttle, the car revs well past 6000rpm cleanly. 6200rpm was easy to achieve when driving at 4/5th throttle, but repeat with full throttle and the engine won't rev beyond 5500rpm. Whilst I don't normally drive at such high revs all the time, over the last 16 years the car has also done so if requested!
Soooo, any idea what could be causing this problem at full throttle? Maybe the vacuum mechanism on the distributor isn't working quite right, or could it be the fuel pressure regulator (standard, not rising rate) as I think this gets affected by inlet manifold vacuum too?
What else changes at wide open throttle compared to 4/5ths?
Thanks,
Dan.
Finally an update and I think I've made some progress on my poor starting / running 350i. Yesterday I went through the troubleshooting section of the EFI document on the tvrwedgepages site and everything seemed to check out. I checked all the voltages / ohms on the circuits as described and they we're all healthy.
I then took the plenum off and discovered 3 of the trumpets were really lose in their holders, with one of them completely out. A further one had risen up about 1cm, so I took them all out and JB welded them in. Resealed the plenum, plus also removed the rocker covers, checked for obvious damage and resealed them too. I also checked all the breather hoses and am quite happy that everything is sealed.
I took the car for a test drive and it felts much better. Where as before the engine would routinely start to misfire / struggle at 4800rpm, this time it reved smoothly up to around 5400rpm. I repeated the test on a strip of abandoned road many times and have definitely gained another 600rpm of rev range. Previously, it was like the car had hit a wall at 4800rpm every time time, with lots if juddering, popping, banging etc.
However, I also noticed now that if you don't use wide open throttle, the car revs well past 6000rpm cleanly. 6200rpm was easy to achieve when driving at 4/5th throttle, but repeat with full throttle and the engine won't rev beyond 5500rpm. Whilst I don't normally drive at such high revs all the time, over the last 16 years the car has also done so if requested!
Soooo, any idea what could be causing this problem at full throttle? Maybe the vacuum mechanism on the distributor isn't working quite right, or could it be the fuel pressure regulator (standard, not rising rate) as I think this gets affected by inlet manifold vacuum too?
What else changes at wide open throttle compared to 4/5ths?
Thanks,
Dan.
Thanks for the replies!
Just to answer. I haven't done a compression test for a couple of years, but when I did it was all quite healthy. Maybe time for a retest!
Oil pressure when hot is always around 2 bar when on the move and 1 bar when idle. Its been like that since I've owned he car, so assume its ok.
Haven't tried the "cold start" spray trick - should keep a can in the car maybe in case my starting issue returns.
Its quite possible that the distributor is at fault in all this. Whilst the timing hasn't been adjusted for years, it could be that the weights have become stuck or broken. I think a rebuild is something I should consider.
Going to the TVR event on the Isle of Wight this weekend so hopefully it will be kind to me until we get back.
Just to answer. I haven't done a compression test for a couple of years, but when I did it was all quite healthy. Maybe time for a retest!
Oil pressure when hot is always around 2 bar when on the move and 1 bar when idle. Its been like that since I've owned he car, so assume its ok.
Haven't tried the "cold start" spray trick - should keep a can in the car maybe in case my starting issue returns.
Its quite possible that the distributor is at fault in all this. Whilst the timing hasn't been adjusted for years, it could be that the weights have become stuck or broken. I think a rebuild is something I should consider.
Going to the TVR event on the Isle of Wight this weekend so hopefully it will be kind to me until we get back.
al 350i said:
well in case anyone reads this post in the future and wants to know the out come..................I FIXED IT!!! and the fault was............ignition module on side of distributor, i fortunately have 3 in the garage! the only reason i hadn't looked at it earlier was because it isn't that old and came with new dizzy i bought a year ago.........that'll teach me to not buy Powerspark rubbish!
I just want to thank you for putting this small piece of information up. It has saved me a lot of time and money this week. My car developed a morning start problem. After checking a few things on the engine I came across this in the forum. Reading the previous section I thought it was a good gamble to take as the starting symtoms were so similar. I bought the ignition amplifier from my local motor factors. It cost £32 but was told it's a very good Italian make and even came with a sachet of the heat paste. It took me all of ten minutes to replace. Hey presto. Fired first time this morning and goes like the Starship Enterprise. It just shows you what a valuable bit of information can do. If it wasn't for that, I could have been replacing all sorts of parts. To tell you the truth, I was getting really woried as the morning starting was getting worst by the day and reached a point when I considered calling out the AA. Thanks again for that useful bit of information. and the fault was............ignition module on side of distributor, i fortunately have 3 in the garage! the only reason i hadn't looked at it earlier was because it isn't that old and came with new dizzy i bought a year ago.........that'll teach me to not buy Powerspark rubbish! Tony. TCB.
Wedg1e said:
al 350i said:
hhhmmmm i've tried looking for this mysterious ballast resistor before and never found it????? so came to the conclusion that i don't have one, has anyone got a pic or clue where it might be? my coil connects to the rev counter then across to the ecu
You may not have; inspect the coil to see if it has 12v or 8v on it. If it's a 12v unit it won't need a ballast (you'd never get it started). Some ballasts actually look like a resistor: rectangular ceramic block with a wire out each end, some are made by simply coiling-up several feet of resistance wire (which is often blue-sheathed).Danny is correct though: almost catching then dying as you release the key has all the hallmarks of an intermittent ignition feed.
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