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Cannot Diagnose This Problem...


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#16 xrocketengineer

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Posted 20 March 2017 - 11:40 PM

Distributor cap and rotor? l had Chevy S10 pickup that ate the aluminium terminals of the cap.  The more load the engine saw the worse it would drive, until it would start bucking. Caps with brass terminals lasted a lot longer. Amazingly, I had a van with the same engine and that never happened to it.



#17 minifreek1

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Posted 21 March 2017 - 07:55 AM

You are changing down a gear when it starts to slow....?



#18 Midas Mk1

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Posted 21 March 2017 - 08:09 AM

'Cammy' Cam?



#19 carbon

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Posted 21 March 2017 - 08:27 AM

Other check to make is fuel flow in gallons/hour. Easily done if there is electric fuel pump:

- disconnect fuel pipe where it joins carb

- use length of suitable hose to metal can (20 litre jerry can is ideal)

- weigh the can (luggage scale or similar)

- switch on ignition (but disconnect coil first)

- run for 10 minutes, or until can is full

- reweigh jerry can, use this to calculate fuel flow

 

Do this all outside the garage, and take the usual precautions when handling petrol,



#20 mingy

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Posted 23 March 2017 - 08:03 PM

'Cammy' Cam?

Running a Kent 286 with high lift rockers on a modded head, i have checked Hif float setting as per Burlen SU,s instructions, it does seem to be running a tad rich but have not got the time to check that as i work away most of the week.

Will have ago this weekend if the other arf has no plans .................... which will mean no chance.. :goaway:



#21 Midas Mk1

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Posted 23 March 2017 - 08:30 PM

 

'Cammy' Cam?

Running a Kent 286 with high lift rockers on a modded head, i have checked Hif float setting as per Burlen SU,s instructions, it does seem to be running a tad rich but have not got the time to check that as i work away most of the week.

Will have ago this weekend if the other arf has no plans .................... which will mean no chance.. :goaway:

 

 

 

286 and 1.5's aint gonna be smooth, what f.d ratio? My sw10 wasn't fun on the motorway (on long hills) with a 3.2, off cam <80/85 in top gear. 


Edited by Midas Mk1, 23 March 2017 - 08:47 PM.


#22 MRA

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Posted 23 March 2017 - 10:29 PM

 

What fuel pump are you using?

 A Facet red top.

 

 

Where is it mounted ?



#23 mingy

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Posted 24 March 2017 - 07:29 PM

 

 

What fuel pump are you using?

 A Facet red top.

 

 

Where is it mounted ?

 

The Facet pump is brand new and mounted on the boot floor about 200mm from the petrol tank, so it is in theory always primed and, i have a Sytec glass fuel filter inbetween the tank and pump. The fuel line is of the steel braided type run through the  mini in the usual Rally prepd way. I have got the Minispares inlet manifold but have not connected the water hoses through it, I may try a new carb as the one at the moment is a used one which i did modify but, it produced the desired results on the dyno, the engine is lumpy due to the cam etc and normally idles at 1200rpm but i have noticed after a blast down the road that it idles at 1400/ 1500rpm and needs a blip on the throttle to bring it back down to 1200rpm again.

I also have realised that i have used a slightly smaller inside diameter fuel hose from the pressure regulator to the Hif44 ( will change that ) but i did try the pump flow test and it filled a 2 litre container very quickly so more than enough fuel is getting to the carb.

Keep your thoughts coming folks, cheers.  



#24 MRA

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Posted 24 March 2017 - 07:42 PM

 

 

 

What fuel pump are you using?

 A Facet red top.

 

 

Where is it mounted ?

 

The Facet pump is brand new and mounted on the boot floor about 200mm from the petrol tank, so it is in theory always primed and, i have a Sytec glass fuel filter inbetween the tank and pump. The fuel line is of the steel braided type run through the  mini in the usual Rally prepd way. I have got the Minispares inlet manifold but have not connected the water hoses through it, I may try a new carb as the one at the moment is a used one which i did modify but, it produced the desired results on the dyno, the engine is lumpy due to the cam etc and normally idles at 1200rpm but i have noticed after a blast down the road that it idles at 1400/ 1500rpm and needs a blip on the throttle to bring it back down to 1200rpm again.

I also have realised that i have used a slightly smaller inside diameter fuel hose from the pressure regulator to the Hif44 ( will change that ) but i did try the pump flow test and it filled a 2 litre container very quickly so more than enough fuel is getting to the carb.

Keep your thoughts coming folks, cheers.  

 

Try a squirt of WD40 over the throttle spindles to see if that changes the revs



#25 Moke Spider

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Posted 24 March 2017 - 08:26 PM


 but i did try the pump flow test and it filled a 2 litre container very quickly so more than enough fuel is getting to the carb.

Keep your thoughts coming folks, cheers.  

 

 

The Pressure test I suggested on the previous page, I did after doing a fuel delivery test, long after. I did make the mistake of thinking that that if it's free flow delivery, such as this, was satisfactory, then it seemed logical that was OK, but after doing a pressure check at the carb showed otherwise, though, not right away, as the problem was intermittent. Also, the pumps free flow delivery rate is considerably different to that under pressure.

 

I'm not 100% sure how the Facet Pumps work internally, but certainly in the case of an SU Pump, it's not a good idea to fit a filter between the tank and the pump. When the filter blocks, it will cause these pumps to stall in an energised state and will cause them to burn out. It's possible the same could happen with the Facet.



#26 carbon

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Posted 24 March 2017 - 09:09 PM

Hi folks, a while back i asked the question as to why after encountering an incline does my engine start to lose power, it only occurs when going uphill after a while.

It feels as though it is misfiring or running on three cylinders but once i am back on the flat it slowly picks up and is ok again. I have since replaced the facet fuel pump and the coil but it still persists.

The engine size is 1380 fuelled by the usual HIF44 which had been partially rebuilt during the engine rebuild, it was setup and run in as per usual  and then rolling roaded to fine tune it.

It achieved 100bhp and managed 112mph on the RR but,all this was on the flat, i just cannot seem to get to the bottom of it and as i am putting it back on the road for spring i would like to erase this problem once and for all.

Any thoughts would be great.

 

Cheers. 

Mingy,

 

When you say incline, do you mean a gentle 'motorway' slope using just a little more throttle to maintain speed, or a proper hill using close to full throttle?



#27 tiger99

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Posted 24 March 2017 - 11:37 PM

If the fuel system checks out ok, I suggest checking that the throttle is returning to the stop correctly, as the idle speed not returning immediately is a symptom of a simple friction problem in the cable and linkages. Once that is ruled out, you can focus on what else would cause the idle speed to not return correctly, and first by a long way is sticking carburettor piston or bent needle. Next would be a sticky distributor advance, and either the vacuum or centrifugal systems could be at fault. Note that driving it hard uphill will result in throttle being wide open as you try to keep it moving, so there is low vacuum for the revs and any vacuum advance will be reduced.

 

The carburettor allegedly works at constant pressure drop (not quite true as the spring introduces non-linearity, which is why the spring is as long as possible so its change in length is minimised) but as the engine slows and draws less incoming mixture, the piston needs to drop to put the tapered needle deeper in the jet to adjust the fuel flow for the lesser air volume, and any sticking will hold the piston up and give the wrong mixture, and less power, so the engine bogs down more with incorrect mixture....

 

An easy test is to take the air cleaner and any intake elbows off, take the damper out, and lift the piston fully with a screwdriver. Does it drop all the way with a satisfying clunk? Repeat from half way, etc, to see if there may be any tight spots.

 

With the age of Minis now, sticking carburettor pistons are inevitably on the increase. The usual trick was to carefully polish the piston edge and the inner surface of its container with metal polish, NEVER anything more aggressive. But first check and reset the jet centering as per manual for your carburettor in case it is the needle that is rubbing.






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