V8 won't accelerate

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D

danny

Guest
I've recently had a 2nd hand engine fitted to my 110. It has 34k
miles, but is an old V8 - 1975. It wouldn't start on the carbs it had
fitted so my mechanic swapped them for my carbs, off my 1984 V8 and it
started straight away.

I went and collected it today, but hadn't gone far up the road when I
found it wouldn't accelerate - it would pull strongly then just run
out of steam, either hesitating or backfiring. I took it back to the
mechanic who checked the timing - it had gone from 4 degrees to TDC,
so he corrected that and also reset the dwell. He also swapped the
dizzy cap and rotor from my old engine. He surmised that as the
engine had been standing for quite a while it might take a while for
the valve gear to operate freely and that I should replace the missing
air filter when I got home.

You could rev it freely up to maximum revs when stationary and it
checked fine with a timing light, but when I went home, the same thing
happens, but with no backfires this time. It pulls strongly in first
through the rev range, and in 2nd it gets to about 30mph before
holding back, but 3rd is impossible beyond 35 (the old engine would
pull to 50mph easily) and in 4th power fades at 35-50mph depending on
the road. I've found that if I back off the accelerator and lightly
reapply it picks up speed only to fall back at the slightest incline.

The engine sounds fine, very quiet, and when I got home I noticed in
the dark that the HT lead from the coil was arcing, so I swapped it
out, and put the air filter back, but with no change.

It idles fine, starts first time and revs freely and there's no smoke
visible, but it loses power when under load - any ideas?

Thanks in advance.

--
Regards,
Danny

http://www.gaggia-espresso.com (a purely hobby site)
http://www.dannyscoffee.com (UK advert for my mobile espresso service)
http://www.malabargold.co.uk (UK/European online ordering for Malabar
Gold blend)
swap Z for above characters in email address to reply


 
I had this on my 97 RR V8.

I changed the coil and it seemed to cure it,

Check if that is OK?


"danny" <[email protected]> wrote in message
news:[email protected]...
> I've recently had a 2nd hand engine fitted to my 110. It has 34k
> miles, but is an old V8 - 1975. It wouldn't start on the carbs it had
> fitted so my mechanic swapped them for my carbs, off my 1984 V8 and it
> started straight away.
>
> I went and collected it today, but hadn't gone far up the road when I
> found it wouldn't accelerate - it would pull strongly then just run
> out of steam, either hesitating or backfiring. I took it back to the
> mechanic who checked the timing - it had gone from 4 degrees to TDC,
> so he corrected that and also reset the dwell. He also swapped the
> dizzy cap and rotor from my old engine. He surmised that as the
> engine had been standing for quite a while it might take a while for
> the valve gear to operate freely and that I should replace the missing
> air filter when I got home.
>
> You could rev it freely up to maximum revs when stationary and it
> checked fine with a timing light, but when I went home, the same thing
> happens, but with no backfires this time. It pulls strongly in first
> through the rev range, and in 2nd it gets to about 30mph before
> holding back, but 3rd is impossible beyond 35 (the old engine would
> pull to 50mph easily) and in 4th power fades at 35-50mph depending on
> the road. I've found that if I back off the accelerator and lightly
> reapply it picks up speed only to fall back at the slightest incline.
>
> The engine sounds fine, very quiet, and when I got home I noticed in
> the dark that the HT lead from the coil was arcing, so I swapped it
> out, and put the air filter back, but with no change.
>
> It idles fine, starts first time and revs freely and there's no smoke
> visible, but it loses power when under load - any ideas?
>
> Thanks in advance.
>
> --
> Regards,
> Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> http://www.dannyscoffee.com (UK advert for my mobile espresso service)
> http://www.malabargold.co.uk (UK/European online ordering for Malabar
> Gold blend)
> swap Z for above characters in email address to reply
>
>


 
check oil level in the dashpots of the carbs .
check that the vacuum advance diaphragm is working .

check all rubber hoses for splits .

if youre engine runs fine under light load but it missfires after you give it a
real hard full throttle acceleration from a standing start then it may well be
the fuel pump .

ie the pump is not delivering enough fuel volume under acceleration .

if you have a facet electric pump this should be ok for the job and shouldnt
really cause any problems, but check just in case .

also check fuel filter especially if its a cartridge filter .

i suspect it may be the vacuum advance thats the problem, or lack of advance
under acceleration .

i presume the choke cable is connected right and that the cold running fuel
enrichment works ,ie linkage movement .

i think the older rover V8 engines need more advance on the ignition timing ,
so perhaps something like 10degs adv is more in line with an old P6 engine .

 
In <[email protected]> danny wrote:
> I've recently had a 2nd hand engine fitted to my 110. It has 34k
> miles, but is an old V8 - 1975. It wouldn't start on the carbs it had
> fitted so my mechanic swapped them for my carbs, off my 1984 V8 and it
> started straight away.
>
> I went and collected it today, but hadn't gone far up the road when I
> found it wouldn't accelerate - it would pull strongly then just run
> out of steam, either hesitating or backfiring. I took it back to the
> mechanic who checked the timing - it had gone from 4 degrees to TDC,
> so he corrected that and also reset the dwell. He also swapped the
> dizzy cap and rotor from my old engine. He surmised that as the
> engine had been standing for quite a while it might take a while for
> the valve gear to operate freely and that I should replace the missing
> air filter when I got home.
>
> You could rev it freely up to maximum revs when stationary and it
> checked fine with a timing light, but when I went home, the same thing
> happens, but with no backfires this time. It pulls strongly in first
> through the rev range, and in 2nd it gets to about 30mph before
> holding back, but 3rd is impossible beyond 35 (the old engine would
> pull to 50mph easily) and in 4th power fades at 35-50mph depending on
> the road. I've found that if I back off the accelerator and lightly
> reapply it picks up speed only to fall back at the slightest incline.
>
> The engine sounds fine, very quiet, and when I got home I noticed in
> the dark that the HT lead from the coil was arcing, so I swapped it
> out, and put the air filter back, but with no change.
>
> It idles fine, starts first time and revs freely and there's no smoke
> visible, but it loses power when under load - any ideas?

That all sounds to me like a fuel starvation problem, either the fuel
pump isn't delivering enough fuel, the floats are incorrectly set or the
carb breather pipes are blocked (which effectively airlocks the carb. As
the engine load increses so does your fuel requirement so you are
getting enough fuel for light loads but not enough at high loads.

It is also possible that the return pipe has no restriction in it which
can sometimes lead to a situation where the fuel effectively bypasses
the carbs and heads straight back to the tank. My challenge team mate (
still on carbs) uses a small pipe clamp on his return pipe to ensure
that the carbs are getting as much pressure as they can hold. Too much
pressure and the carb valve is forced open which floods the carb !

If you have a fuel filter inline (you ought to have really) then make
sure that is clear too.

The breather pipes are easily checked, just take them off at the carbs
and see if the problem goes away - they are attached to the carb with a
rubber "elbow" joint.

cheers

Dave W.
http://www.yorkshireoffroadclub.net/
 
On Thu, 16 Dec 2004 21:33:55 +0000, danny <[email protected]>
wrote:

>
>It idles fine, starts first time and revs freely and there's no smoke
>visible, but it loses power when under load - any ideas?

I had the same symptoms after my 110 was converted to lpg. The fitter
had knocked the ball joint off the link between the two carbs.

AJH
 
In message <[email protected]>, danny
<[email protected]> writes
>I've recently had a 2nd hand engine fitted to my 110. It has 34k
>miles, but is an old V8 - 1975. It wouldn't start on the carbs it had
>fitted so my mechanic swapped them for my carbs, off my 1984 V8 and it
>started straight away.
>
>I went and collected it today, but hadn't gone far up the road when I
>found it wouldn't accelerate - it would pull strongly then just run out
>of steam, either hesitating or backfiring.


Check that the mechanical advance is actually working by reving up with
the timing light connected and check the timing advances. If it's been
standing the bob-weights could have seized in the dizzy and you'll never
get a good result.
I assume that the points have been checked for cleanliness and security?
Next comes my particular favourite, the condenser. I took a fortnight to
find my faulty one ... and the faulty one in the complete replacement
dizzy!!! Replace it (it's cheap) and make sure connections are clean,
secure and not shorting to the dizzy body as the advance plate moves

--
AndyG
 
danny wrote:

> You could rev it freely up to maximum revs when stationary and it
> checked fine with a timing light, but when I went home, the same thing
> happens, but with no backfires this time. It pulls strongly in first
> through the rev range, and in 2nd it gets to about 30mph before
> holding back, but 3rd is impossible beyond 35 (the old engine would
> pull to 50mph easily) and in 4th power fades at 35-50mph depending on
> the road. I've found that if I back off the accelerator and lightly
> reapply it picks up speed only to fall back at the slightest incline.

Only one carb's working is what my money goes on.

To work out which, pull the elbows off and see which one!

Regards

William MacLeod
 
Thanks for the replies and suggestions.

It looks like weak mixture. It starts with virtually no choke (rich
initial mixture) and if I pull the choke out progressively as the
speed increases above 50mph it pulls like a horse and runs fine. So
currently I'm using the choke above 50mph. I assume this means that
the mixture is weak at higher revs/speeds?

Does anyone know if overhaul kits are available for 175CD carbs? I
have the original set from the replacement engine and I will probably
recondition/service these to swap out with the existing carbs. I
can't adjust the mixture on the current carbs, since one of the
adjuster screws has been broken.

By the way, does anyone have hints for starting a warm V8. Both this
and the last engine wouldn't start 10-15 minutes after a shortish run.
Turns over for ever then gets faster and starts. I was told that
this is common on these engines? Maybe I also have a weak fuel pump....

Thanks again.


--
Regards,
Danny

http://www.gaggia-espresso.com (a purely hobby site)
http://www.dannyscoffee.com (UK advert for my mobile espresso service)
http://www.malabargold.co.uk (UK/European online ordering for Malabar
Gold blend)
swap Z for above characters in email address to reply


 

"Mark Solesbury" <[email protected]> wrote in message
news:[email protected]...
> I had this on my 97 RR V8.
>
> I changed the coil and it seemed to cure it,
>
> Check if that is OK?

Yep, if you've got backfires once its warmed up it's probably the coil.


 

"danny" <[email protected]> wrote in message
news:[email protected]...
> Thanks for the replies and suggestions.
>
> It looks like weak mixture. It starts with virtually no choke (rich
> initial mixture) and if I pull the choke out progressively as the speed
> increases above 50mph it pulls like a horse and runs fine. So currently
> I'm using the choke above 50mph. I assume this means that the mixture is
> weak at higher revs/speeds?

Classic symptoms of a severely worn camshaft. Insufficient vacuum signal at
carbs when cranking, so mixture richened up in an attempt to correct idle.
BTW, the drop-off in power you mentioned earlier is partly due to the cam
lobes not fully opening the exhaust valves and this acts like a lorry
retarder when you floor it - by creating a back pressure in the cylinders.
Opening the choke simply enrichens the mixture to the point where you
develop a bit more power to overcome the pressure, and correcting the weak
mixture due to the previously mentioned low vacuum signals.

>
> Does anyone know if overhaul kits are available for 175CD carbs? I have
> the original set from the replacement engine and I will probably
> recondition/service these to swap out with the existing carbs. I can't
> adjust the mixture on the current carbs, since one of the adjuster screws
> has been broken.

Bin them and fit SU's. Strombergs are unreliable and problematic, end of
story.

> By the way, does anyone have hints for starting a warm V8. Both this and
> the last engine wouldn't start 10-15 minutes after a shortish run. Turns
> over for ever then gets faster and starts. I was told that this is common
> on these engines? Maybe I also have a weak fuel pump....

Sounds like fuel evaporating in the carbs or the lines vapour-locking. I
take it the return line is plumbed in properly? Not common, whoever told you
that is giving you bull5hi7. Pump could well be weak, or filters partially
blocked.

Badger.


 
Badger wrote:

> Classic symptoms of a severely worn camshaft. Insufficient vacuum signal at
> carbs when cranking, so mixture richened up in an attempt to correct idle.
> BTW, the drop-off in power you mentioned earlier is partly due to the cam
> lobes not fully opening the exhaust valves and this acts like a lorry
> retarder when you floor it - by creating a back pressure in the cylinders.
> Opening the choke simply enrichens the mixture to the point where you
> develop a bit more power to overcome the pressure, and correcting the weak
> mixture due to the previously mentioned low vacuum signals.
>
Badger, I'm confused now. This engine has done less than 35k miles
(although it's very old) and sounds as quiet as a very quiet thing :)

I have documented evidence of the mileage and the previous owners' use
of the vehicle. It doesn't sound at all worn. The mechanic hasn't
touched my carbs (they are off the old engine). He swapped them after
the original carbs on the replacement engine fired it up once, then
never again (I suppose due to something sticking and flooding the
engine on the first start and press of the throttle). This engine had
been stood for at least a year.

The last engine had a very badly worn camshaft (that's why I changed
it). It rattled and knocked but still pulled up to 85mph. The
replacement engine is far quieter and smoother.

>
>>Does anyone know if overhaul kits are available for 175CD carbs? I have
>>the original set from the replacement engine and I will probably
>>recondition/service these to swap out with the existing carbs. I can't
>>adjust the mixture on the current carbs, since one of the adjuster screws
>>has been broken.
>
>
> Bin them and fit SU's. Strombergs are unreliable and problematic, end of
> story.

OK. I'll look for some.


> Sounds like fuel evaporating in the carbs or the lines vapour-locking. I
> take it the return line is plumbed in properly? Not common, whoever told you
> that is giving you bull5hi7. Pump could well be weak, or filters partially
> blocked.
>
> Badger.

Yes, the return line is plumbed in. I'll check the filters. Is there
a way of testing the pump, ie: by way of measuring the output in a
given time. On espresso machines (which are what I know about), water
debit is measured to check for pump function.



--
Regards,
Danny

http://www.gaggia-espresso.com (a purely hobby site)
http://www.dannyscoffee.com (UK advert for my mobile espresso service)
http://www.malabargold.co.uk (UK/European online ordering for Malabar
Gold blend)
swap Z for above characters in email address to reply


 
>>Does anyone know if overhaul kits are available for 175CD carbs? I have
>>the original set from the replacement engine and I will probably
>>recondition/service these to swap out with the existing carbs. I can't
>>adjust the mixture on the current carbs, since one of the adjuster screws
>>has been broken.

http://www.burlen.co.uk/

> Bin them and fit SU's. Strombergs are unreliable and problematic, end of
> story.

Like the Government - 'tis easy to spend someone else's money!

 
danny wrote:
>
> Yes, the return line is plumbed in. I'll check the filters. Is there a
> way of testing the pump, ie: by way of measuring the output in a given
> time. On espresso machines (which are what I know about), water debit
> is measured to check for pump function.

Yep - normally you disconnect the fuel line from the carbs and put it
into a bottle, then run the engine (which will run on what's in the the
float bowl) for 15 or 30 seconds and measure how much fuel is in the
bottle. The green bible or even the HBOL should give an output figure.

--
EMB
 

"Dougal" <DougalAThiskennel.free-online.co.uk> wrote in message
news:[email protected]...
<snip>
> Like the Government - 'tis easy to spend someone else's money!
>
Yep, valid point Dougal, but those damn strombergs are a PITA, IMO. And
there are many who will agree with me. It would be my first "improvement",
as the SU's are more reliable, easier to tune and keep in tune and there are
a wider choice of needles for the inevitable fitting of different cams / air
filters etc. etc.
Badger.


 

"danny" <[email protected]> wrote in message
news:[email protected]...
> Badger wrote:
>
<snip>
> Badger, I'm confused now. This engine has done less than 35k miles
> (although it's very old) and sounds as quiet as a very quiet thing :)

Danny, it may be that your cam isn't knackered at all, it's just that what
you describe does point to worn cam lobes. It all depends what lobes wear
first, inlet or exhaust, as to the symptoms. If the cam followers are
operating properly, then there won't be any noise as the cam wears - any
wear will be taken up by the self-adjusting nature of the hydraulic
followers - until the wear becomes really excessive.

> I have documented evidence of the mileage and the previous owners' use of
> the vehicle. It doesn't sound at all worn. The mechanic hasn't touched
> my carbs (they are off the old engine). He swapped them after the
> original carbs on the replacement engine fired it up once, then never
> again (I suppose due to something sticking and flooding the engine on the
> first start and press of the throttle). This engine had been stood for at
> least a year.
>
> The last engine had a very badly worn camshaft (that's why I changed it).
> It rattled and knocked but still pulled up to 85mph. The replacement
> engine is far quieter and smoother.

If it was that noisy, then I'd bet there was more than just the cam worn.
Cams don't knock in general, crankshaft bearings do though.

<snip again>
>> Sounds like fuel evaporating in the carbs or the lines vapour-locking. I
>> take it the return line is plumbed in properly? Not common, whoever told
>> you that is giving you bull5hi7. Pump could well be weak, or filters
>> partially blocked.
>
> Yes, the return line is plumbed in. I'll check the filters. Is there a
> way of testing the pump, ie: by way of measuring the output in a given
> time. On espresso machines (which are what I know about), water debit is
> measured to check for pump function.
>
If you have a pressure gauge and a "T" piece, rig it up to the fuel supply
line and go for a drive. As you maintain full throttle (up a long hill in
3rd, say) watch the fuel pressure. If it drops below 2.0psi then the engine
will be emptying out the carbs quicker than the pump can keep them topped
up. This will either be due to the flow rate being reduced by a partially
blocked filter or line, or the pump being u/s.
If the pressure is below 2.0psi at idle, then either the pump is shot or
there is no restrictor in the return line.
My last carburettor-fed V8 had the supply pressure to the carbs set at
4.5psi (via a return-line restrictor) with no carb flooding problems.

Badger.


 
> Yep, valid point Dougal, but those damn strombergs are a PITA, IMO. And
> there are many who will agree with me. It would be my first "improvement",
> as the SU's are more reliable, easier to tune and keep in tune and there are
> a wider choice of needles for the inevitable fitting of different cams / air
> filters etc. etc.
> Badger.

They've actually given me no trouble other than diaphragms (and that
only when rather old). That's on two Volvo B18s and two Rover V8s. I
must have a sainted life!

 
On 2004-12-17, danny <[email protected]> wrote:

> On espresso machines (which are what I know about), water debit is
> measured to check for pump function.

Oh THAT Danny, Landy fan and famous espresso nut, welcome ;-) You got
me interested in commercial espresso machines some time ago and I now
have a Visacreme FCX1 currently in bits, slightly higher tech than a
Landy but similarly built!

--
For every expert, there is an equal but opposite expert
 
Badger wrote:

> Danny, it may be that your cam isn't knackered at all, it's just that what
> you describe does point to worn cam lobes. It all depends what lobes wear
> first, inlet or exhaust, as to the symptoms. If the cam followers are
> operating properly, then there won't be any noise as the cam wears - any
> wear will be taken up by the self-adjusting nature of the hydraulic
> followers - until the wear becomes really excessive.
>

Is there anything a relative non-mechanic like me can do to get an
idea of the engines' likely mileage? I have a 3 month warranty on the
engine and would like to get an idea before the warranty runs out...


>
> If you have a pressure gauge and a "T" piece, rig it up to the fuel supply
> line and go for a drive. As you maintain full throttle (up a long hill in
> 3rd, say) watch the fuel pressure. If it drops below 2.0psi then the engine
> will be emptying out the carbs quicker than the pump can keep them topped
> up. This will either be due to the flow rate being reduced by a partially
> blocked filter or line, or the pump being u/s.
> If the pressure is below 2.0psi at idle, then either the pump is shot or
> there is no restrictor in the return line.
> My last carburettor-fed V8 had the supply pressure to the carbs set at
> 4.5psi (via a return-line restrictor) with no carb flooding problems.
>

OK. I can test that, thanks.


--
Regards,
Danny

http://www.gaggia-espresso.com (a purely hobby site)
http://www.dannyscoffee.com (UK advert for my mobile espresso service)
http://www.malabargold.co.uk (UK/European online ordering for Malabar
Gold blend)
swap Z for above characters in email address to reply


 
Ian Rawlings wrote:
> On 2004-12-17, danny <[email protected]> wrote:
>
>
>>On espresso machines (which are what I know about), water debit is
>>measured to check for pump function.
>
>
> Oh THAT Danny, Landy fan and famous espresso nut, welcome ;-) You got
> me interested in commercial espresso machines some time ago and I now
> have a Visacreme FCX1 currently in bits, slightly higher tech than a
> Landy but similarly built!
>

Hi Ian, I hope your machine doesn't stay in bits for as long as my
110 did whilst I waiting for the mechanic to swap the engine :)

Let me know if you have a problem with parts - I have a couple of sources.

--
Regards,
Danny

http://www.gaggia-espresso.com (a purely hobby site)
http://www.dannyscoffee.com (UK advert for my mobile espresso service)
http://www.malabargold.co.uk (UK/European online ordering for Malabar
Gold blend)
swap Z for above characters in email address to reply


 

"danny" <[email protected]> wrote in message
news:[email protected]...
> Badger wrote:
>
>> Danny, it may be that your cam isn't knackered at all, it's just that
>> what you describe does point to worn cam lobes. It all depends what lobes
>> wear first, inlet or exhaust, as to the symptoms. If the cam followers
>> are operating properly, then there won't be any noise as the cam wears -
>> any wear will be taken up by the self-adjusting nature of the hydraulic
>> followers - until the wear becomes really excessive.
>>
>
> Is there anything a relative non-mechanic like me can do to get an idea of
> the engines' likely mileage? I have a 3 month warranty on the engine and
> would like to get an idea before the warranty runs out...

Remove the rocker covers and turn the engine over slowly by hand, monitoring
the valve movement. Look for 1 or more valves not opening as far as the
others - this is either the cam lobes worn away or the hydraulic cam
followers knackered, only further confirmation of either one would be
dismantling (inlet manifold and valley gasket to allow visual examination of
cam). You'll quite often find one or more that just don't appear to be
moving at all.
As to general condition, you could carry out a compression test (all plugs
removed, crank on full throttle - remember to isolate ignition first, you
don't want any sparks igniting what may blow out of the plug holes!!) but
this will only prove that there is a fault, it won't really tell you whether
it is bore wear or the valves simply not opening wide enough for long enough
(cam).

>
>>
>> If you have a pressure gauge and a "T" piece, rig it up to the fuel
>> supply line and go for a drive. As you maintain full throttle (up a long
>> hill in 3rd, say) watch the fuel pressure. If it drops below 2.0psi then
>> the engine will be emptying out the carbs quicker than the pump can keep
>> them topped up. This will either be due to the flow rate being reduced by
>> a partially blocked filter or line, or the pump being u/s.
>> If the pressure is below 2.0psi at idle, then either the pump is shot or
>> there is no restrictor in the return line.
>> My last carburettor-fed V8 had the supply pressure to the carbs set at
>> 4.5psi (via a return-line restrictor) with no carb flooding problems.
>>
>
> OK. I can test that, thanks.
>
Good luck.
Badger
B.H.Engineering,
Rover V8 engine specialists.
www.bhengineering.co.uk
www.roverv8engines.com


 
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