Engine problems
Discussion
Hi There
I've just re-built my engine as follows 1330cc
MG metro Block
Omega pistons +60,
SW5 Cam
1.5:1 Full roller rockers (minispeed)
Duplex Vernier timing gears
Luminition MS3 ballast coil (NEW)
123ignition distributer
HIF44 carb with BCE needle
Facet Solid state fuel pump
ported and polished stage 3 head VMAX scart Unleaded
13/4'' maniflo exhaust and stage 2 LCB manifold
The problem i'm having is the car pulls well up to 4000rpm and then just dies
if I let the revs drop it idles and is then fine to carry on, it does seem worse when the car is hot.
the ignition curve is set on 0 so max advance is 28deg.
I had it on a rolling road and the fuel pressure holds all the way up the revs at 3psi
any thoughts would be well recieved
I've just re-built my engine as follows 1330cc
MG metro Block
Omega pistons +60,
SW5 Cam
1.5:1 Full roller rockers (minispeed)
Duplex Vernier timing gears
Luminition MS3 ballast coil (NEW)
123ignition distributer
HIF44 carb with BCE needle
Facet Solid state fuel pump
ported and polished stage 3 head VMAX scart Unleaded
13/4'' maniflo exhaust and stage 2 LCB manifold
The problem i'm having is the car pulls well up to 4000rpm and then just dies
if I let the revs drop it idles and is then fine to carry on, it does seem worse when the car is hot.
the ignition curve is set on 0 so max advance is 28deg.
I had it on a rolling road and the fuel pressure holds all the way up the revs at 3psi
any thoughts would be well recieved
Sounds like lack of fuel or the sparks in the wrong place (advance curve).
Have you got the heatshield in between the HIF44 and the inlet/ exhaust manifold set-up? Many people delete it to save the length on the inlet tract, as depending what inlet manifold is used and how well the engine is restrained - sometimes carb to bulkhead intreference exists.
I t could well be that in the absence of a sheild, the HIF Bimetallic strip is leaning the carb off when it gets hot (therefore not enough fuel). Is it always the same rpm that the negine dies at (4K) or is it only when the engine is hot. Will the car take 4K+ when the engine is warming up (I know this will make the mechanically sympathetic wince
)?
If you are tight on space - knock together a homemade heatsheild from Aluminium sheet. The more of the lower part of the carb it covers, the better.
Have you got the heatshield in between the HIF44 and the inlet/ exhaust manifold set-up? Many people delete it to save the length on the inlet tract, as depending what inlet manifold is used and how well the engine is restrained - sometimes carb to bulkhead intreference exists.
I t could well be that in the absence of a sheild, the HIF Bimetallic strip is leaning the carb off when it gets hot (therefore not enough fuel). Is it always the same rpm that the negine dies at (4K) or is it only when the engine is hot. Will the car take 4K+ when the engine is warming up (I know this will make the mechanically sympathetic wince
)?If you are tight on space - knock together a homemade heatsheild from Aluminium sheet. The more of the lower part of the carb it covers, the better.
(OrangeD's other half typing here...)
It gives up fairly consistently at 4000rpm give or take a couple of hundred - so maybe 4200 to start with, then maybe after it's done it a couple of times or when hotter it starts to die at 3800 - or thereabouts. It just suddenly goes all clattery and so we dip the clutch, get the revs lowered and then it pick-s up again as normal, it doesn't stall as such.
Oil pressure & water temp all pretty consistent throughout the whole thing too.
I'm not sure about the heatshield you're referring to, would I have a bimetallic strip anyway if i have a choke? May seem a silly question
It's driving us nuts - we're supposed to be taking the little fella to Le Mans next week!
It gives up fairly consistently at 4000rpm give or take a couple of hundred - so maybe 4200 to start with, then maybe after it's done it a couple of times or when hotter it starts to die at 3800 - or thereabouts. It just suddenly goes all clattery and so we dip the clutch, get the revs lowered and then it pick-s up again as normal, it doesn't stall as such.
Oil pressure & water temp all pretty consistent throughout the whole thing too.
I'm not sure about the heatshield you're referring to, would I have a bimetallic strip anyway if i have a choke? May seem a silly question
It's driving us nuts - we're supposed to be taking the little fella to Le Mans next week!
MiniDiva said:
(OrangeD's other half typing here...)I'm not sure about the heatshield you're referring to, would I have a bimetallic strip anyway if i have a choke?
Basically as said above, you could be getting fuel vapourisation, more noticeable as the engine is hotter under load. Is the dashpot oil topped up? I find 3in1 oil works best.
HTH
If you intend taking it to Le Mans (
) then fuel vapopurisation will be an issue as the ambient temps in France will be higher. If you've not got either the dashpot heatshield (^^ pictured above) or a homemade effort in Sheet aluminium done, then it looks like you've got a busy weekend ahead.
Check your fuel pipe routing up the carb and make sure it isn't picking up heatsoak from your LCB. An LCB rejects lots of heat into the engine bay (centrebranch burnt the paint of the bulkhead causing rust patch on my now stripped shell), so try and protect the fuel system from heat pick up/soak.
Be interested to know how you get on - it's either fuel or sparks and if the ignition system is in rude health and the fuel supply works lower down the rpm range - it must be supply.
What sort of fuel pump is on the car? Mechanical or electrical? Any pressure regulator in the system if you are using an electrical one?
More info, the better for diagnosis.
Good Luck and let us know how you get on.
) then fuel vapopurisation will be an issue as the ambient temps in France will be higher. If you've not got either the dashpot heatshield (^^ pictured above) or a homemade effort in Sheet aluminium done, then it looks like you've got a busy weekend ahead.Check your fuel pipe routing up the carb and make sure it isn't picking up heatsoak from your LCB. An LCB rejects lots of heat into the engine bay (centrebranch burnt the paint of the bulkhead causing rust patch on my now stripped shell), so try and protect the fuel system from heat pick up/soak.
Be interested to know how you get on - it's either fuel or sparks and if the ignition system is in rude health and the fuel supply works lower down the rpm range - it must be supply.
What sort of fuel pump is on the car? Mechanical or electrical? Any pressure regulator in the system if you are using an electrical one?
More info, the better for diagnosis.
Good Luck and let us know how you get on.
I wonder if it's not advancing enough. Maybe it needs a bit more max advance at over 4000, although I would have thought it would still run, just not quite as well as it could. You could try advancing the static timing up to, say, 4 deg advance and try it again. See what difference that makes.
If it dies at 4000 then it's something fairly basic with the engine settings and, as FWD says, it could be the top end mixture.
I take it you have full and free movement of the carb dashpot. Personally I prefer the HS range of carbs as they are so easy to work on and to diagnose when there is a problem.
Of course, the real answer is a rolling-road session which will idenify the fault quickly and easily.
If it dies at 4000 then it's something fairly basic with the engine settings and, as FWD says, it could be the top end mixture.
I take it you have full and free movement of the carb dashpot. Personally I prefer the HS range of carbs as they are so easy to work on and to diagnose when there is a problem.
Of course, the real answer is a rolling-road session which will idenify the fault quickly and easily.
Hi Guys - thanks for all your input and suggestions - i think we will have a busy day ahead of us trying, trying and trying again - we'll let you know how we get on - it's a definite head-scratcher!
We have an electric pump - I think Orange listed above what it is, and also we do have a pressure regulator/filter unit thingy (sorry, very technical - can't think what it's called but the filter is cased in an aly unit with a screw on the top that adjusts the pressure)
The LCB is wrapped but yes will still produce a fair amount of heat. The carb should be free from blockages and the dashpot oil was checked last weekend when the needle was put in. One thing we did change regarding the fuel system from previous was the pipe joining the copper line into the filter - it was a tighter fit than the previous braided line that decided to give-up and piss fuel everywhere when we first tried to start it! So slightly smaller gauge pipe, but I wouldn't have thought any skinnier than the copper pipe. You never know though so a trip to halfrauds might be in order just to rule that out. I'd be happy if it was someting as silly as that.
We so want to get it to le mans - we tried 2 years ago after rebuilding the shell and had HGF - doh!
Thanks again
We have an electric pump - I think Orange listed above what it is, and also we do have a pressure regulator/filter unit thingy (sorry, very technical - can't think what it's called but the filter is cased in an aly unit with a screw on the top that adjusts the pressure)
The LCB is wrapped but yes will still produce a fair amount of heat. The carb should be free from blockages and the dashpot oil was checked last weekend when the needle was put in. One thing we did change regarding the fuel system from previous was the pipe joining the copper line into the filter - it was a tighter fit than the previous braided line that decided to give-up and piss fuel everywhere when we first tried to start it! So slightly smaller gauge pipe, but I wouldn't have thought any skinnier than the copper pipe. You never know though so a trip to halfrauds might be in order just to rule that out. I'd be happy if it was someting as silly as that.
We so want to get it to le mans - we tried 2 years ago after rebuilding the shell and had HGF - doh!
Thanks again
MiniDiva said:
...when the needle was put in.
Could it be that the needle needs re-profiling to suit the petrol delivery throughout the rev range? Was the vehicle rolling-roaded and needle profile matched? It could be that the needle is restricting fuelling at the top end of the rev range and properly fueling the engine lower down in the range. Who knows! Best of luck, I hope you make it to Le-mans 
Facit fuel pump is fine. I run a pair of 'road' spec ones on my 117 bhp rally car, and one on its own gives enough flow for 7000+ rpm.
If your manifold is heat wrapped it's very unlikely to be engine-bay heat causing the problem.
I would try advancing the static timing a bit first and trying it up the road to max revs.
Then I would check that the carb dashpot will move cleanly and smoothly to the top by taking off the air filter and lifting it up with a finger.
It does sound like a fuel-related problem, but to die like that it has to be something very basic. Maybe try to richen it up a bit and see if that has any effect. If you can get some small improvement from one of those things, you'll know you are going the right way.
It could be a combination of things. For example, if it's running retarded at higher revs, it will heat up the exhaust manifold (I've seen them glow red). This in turn could be vapourising the petrol.
The real answer is a rolling-road session as it could just be the wrong carb needle for the engine spec and build.
If your manifold is heat wrapped it's very unlikely to be engine-bay heat causing the problem.
I would try advancing the static timing a bit first and trying it up the road to max revs.
Then I would check that the carb dashpot will move cleanly and smoothly to the top by taking off the air filter and lifting it up with a finger.
It does sound like a fuel-related problem, but to die like that it has to be something very basic. Maybe try to richen it up a bit and see if that has any effect. If you can get some small improvement from one of those things, you'll know you are going the right way.
It could be a combination of things. For example, if it's running retarded at higher revs, it will heat up the exhaust manifold (I've seen them glow red). This in turn could be vapourising the petrol.
The real answer is a rolling-road session as it could just be the wrong carb needle for the engine spec and build.
We should have the right needle as it was changed specifically for the engine - the problem was occurring exactly the same before the needle was changed from the previous profile suggesting it's not necessarily that.
I'll go and have a play with the carb and check it's moving freely, then it will be time to start tweaking all the other bits & bobs. I'm sure we'll get there.
watch this space!
I'll go and have a play with the carb and check it's moving freely, then it will be time to start tweaking all the other bits & bobs. I'm sure we'll get there.
watch this space!
Other thoughts are coil, ignition system/distributor and rotor arm (if it has one it's a common problem), condenser (again, if it has one).
The coil is a common problem and I think I may have a problem with my Cooper 'S' as it has developed a mis-fire at 5800 rpm under full throttle and I know it's not points, condenser, plug leads or plugs.
I also had a coil problem with a customer's Cooper 'S' a few months ago. It would start, idle nicely, run up to about 3000 rpm, then mis-fire. A new Lucas Sports coil sorted it out immediately.
The coil is a common problem and I think I may have a problem with my Cooper 'S' as it has developed a mis-fire at 5800 rpm under full throttle and I know it's not points, condenser, plug leads or plugs.
I also had a coil problem with a customer's Cooper 'S' a few months ago. It would start, idle nicely, run up to about 3000 rpm, then mis-fire. A new Lucas Sports coil sorted it out immediately.
I was told to set gaps 0.6 by a very reputably mini tuning company, I thought i'd set them to 0.8 as per the manual just to see and it fly's now,good power all the way to 6K woohoo.
I'd just like to thank all you guys again I posted on a few mini forums and i'm pleased to say pistonheads gave me the best info and ideas.
Regards
OrangeD & MiniDiva
Le Mans here we come
I'd just like to thank all you guys again I posted on a few mini forums and i'm pleased to say pistonheads gave me the best info and ideas.
Regards
OrangeD & MiniDiva
Le Mans here we come
im not sure that the plug gap would affect it that much, id be more inclined to go with bp7es (8's are for high comp full race max advance, id guess on a road car they could be fouling up round town)
i also think that 28 total isnt enough advance - you probably would benefit from 30-32 total
p.s
i had a stupid problem with my sprint last week where it wouldnt rev above 4000, then 3000, then 2000, then it finaly wouldnt rev above 1500 until i stopped, let the carb fill up with petrol, drove 20 yeards, stopped, ditto, ditto!!!!.....
when i pulled the fuel pipe of the petrol flow was like a little trickle, so i changed the pre filter in the fuel pump and it fixed it. there was a tiny bit of what looked like latex glove or something in the fiter which had been sucked against the fuel pipe!!!!!
ive now got a spare filter, a pair of mole grips and a spanner in the boot, just in case it does it again!!!
i also think that 28 total isnt enough advance - you probably would benefit from 30-32 total
p.s
i had a stupid problem with my sprint last week where it wouldnt rev above 4000, then 3000, then 2000, then it finaly wouldnt rev above 1500 until i stopped, let the carb fill up with petrol, drove 20 yeards, stopped, ditto, ditto!!!!.....
when i pulled the fuel pipe of the petrol flow was like a little trickle, so i changed the pre filter in the fuel pump and it fixed it. there was a tiny bit of what looked like latex glove or something in the fiter which had been sucked against the fuel pipe!!!!!
ive now got a spare filter, a pair of mole grips and a spanner in the boot, just in case it does it again!!!
Edited by guru_1071 on Sunday 7th June 19:34
The problem with having insuficient mechanical advance is that if you optimise the advance to give max. power at, say, 6000 rpm, it then has so much static advance that the engine will not turn over on the starter, especially when the engine is hot.
I use an Aldon custom-curved dizzy on my 'S' which has 4 deg more mech advance than their 'red' dizzy so it'll still start, even with my 11.2:1 C.R.and optimised top-end advance. For plugs I use the BP6ES and never have a problem with them.
I use an Aldon custom-curved dizzy on my 'S' which has 4 deg more mech advance than their 'red' dizzy so it'll still start, even with my 11.2:1 C.R.and optimised top-end advance. For plugs I use the BP6ES and never have a problem with them.
i saw a mini once that the dizzy was fitted loose in the engine (so it could rotate), it had a stiff spring pulling round too give it maximun advance (against a neat little adjustable stop) which would hold it firm in place. it also had a bowden cable attached so that the use could pull the cable to retard the dizzy for starting, then once it was warm the cable was released and the dizzy 'sprung' round to allow huge ammounts of mechanical advance + but from a know stating point of well advanced static.
a very neat little idea i thought!!!
a very neat little idea i thought!!!
Cooperman said:
The problem with having insuficient mechanical advance is that if you optimise the advance to give max. power at, say, 6000 rpm, it then has so much static advance that the engine will not turn over on the starter, especially when the engine is hot..
And we know what happens next...................guru_1071 said:
i saw a mini once that the dizzy was fitted loose in the engine (so it could rotate), it had a stiff spring pulling round too give it maximun advance (against a neat little adjustable stop) which would hold it firm in place. it also had a bowden cable attached so that the use could pull the cable to retard the dizzy for starting, then once it was warm the cable was released and the dizzy 'sprung' round to allow huge ammounts of mechanical advance + but from a know stating point of well advanced static.
a very neat little idea i thought!!!
Of course in the olde days, cars did have this sort of mechanical advance mechanism, usually attached to the steering wheel. a very neat little idea i thought!!!
Sounds very much like fuel starvation to me, lack of ignition advance won't stop the engine producing any power at all at such a specific RPM. I'm sure the fuel pump itself is perfectly adequate, but you might want to check sustained fuel flow as you may have a blockage somewhere. Pull the pipe of the carb and direct it into a petrol container for a decent length of time, do you get a dribble or a good flow?
It could be ignition related I suppose, electronic module/pickup failing at a particular RPM? The rattle you are hearing is intriguing though, what timing chain setup do you have? Did you replace it all when the engine was rebuilt? Doe the engine have good oil pressure at all times?
It could be ignition related I suppose, electronic module/pickup failing at a particular RPM? The rattle you are hearing is intriguing though, what timing chain setup do you have? Did you replace it all when the engine was rebuilt? Doe the engine have good oil pressure at all times?
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