bigpig
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| posted on 3/8/09 at 02:03 PM |
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Odd cut out when clutch depressed
Hi,
Near to test now finally.
I'm getting an odd problem. When the engine is idling all is fine, but if I depress the clutch, after a few seconds or so the electrics and
engine try to cut out. The dashboard tries to switch off e.t.c.
Its odd becuase it only happens when the clutch is depressed. Its not like a pinto has any sensors for this sort of thing. All I can think off is
either an odd resonance shaking a contact (which seems strange as the car vibrates less on clutch down) or the battery not supplying enough voltage
(again odd as I would expect less load on the engine when the clutch is down, making it less effort to turn the alternator).
The voltage though the system is a nice 13.9volts. I'm going to leave the battery on charge and see if that is the culprit although its a quite
newish battery.
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Mr Whippy
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| posted on 3/8/09 at 02:08 PM |
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have you got a wire accidentally getting tugged by the pedal?
friction on the engine from the pedal being depressed should be less as the gearbox cogs and shafts will stop spinning so that’s not anything to do
with it.
[Edited on 3/8/09 by Mr Whippy]
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adithorp
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| posted on 3/8/09 at 02:13 PM |
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Check your main earths; Engine to battery, chassis to battery. It could be using the clutch cable as an earth path if either of those is bad.
The other (rare) cause could be knackered crankshaft thrust bearings but you'd normally get a lot of noise from the flywheel when it was
stalling.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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prawnabie
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| posted on 3/8/09 at 02:14 PM |
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Worn thrust washers letting the crank move through the block when pressing the clutch and binding the rods?
Unlikely I know but thats all I can thing of!
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blakep82
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| posted on 3/8/09 at 02:18 PM |
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if the dash gives up too, it must be electrical i'd say. can't think what though...
clutch pedal touching some cable/connection and earthing out something? ignition switch or something?
________________________
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rusty nuts
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| posted on 3/8/09 at 02:38 PM |
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Check your crank end float and engine earth as already suggested . Could possibly be the pedal/cable is pulling on a wire.
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t16turbotone
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| posted on 3/8/09 at 04:14 PM |
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YES ...Defo check your crank end float! had a similar problem myself a while ago
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bigpig
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| posted on 4/8/09 at 06:05 PM |
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quote:
Originally posted by t16turbotone
YES ...Defo check your crank end float! had a similar problem myself a while ago
Seriously? Such a wierd problem. I don't understand though why end float on a pinto engine would cause all the electrics to shut down though
(inc the digital dashboard).
The engine seems to be a good earth, considering the truck sized earth lead that runs from the battery to the starter motor.
After charging the battery it seems the cut out has shifted to about 3.5K rpm. Now my thinking is that the Halfords calcium battery is a bit naff (Its
quite a meaty one, only just fits in the MK Battery tray) , but its quite a new battery (though don't know how long it was standing in the shop
though).
The circuit is running at 13.9 to 14v which is nice and healthy, but what happens is the display sort of flickers a few times then it starts to
flicker more.
I'll try and stick some extra earthing straps on this weekend and see if that makes a difference.
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prawnabie
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| posted on 4/8/09 at 06:10 PM |
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when you put your foot on the clutch, it is trying to pull the crank through the block, binding the rods causing the engine to slow down and stall.
There are "c" shaped washers/bearings either side of the middle main cap that stop the movement.
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MikeRJ
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| posted on 4/8/09 at 06:16 PM |
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My brother rebuilt his mini engine and put the thrusts in the wrong way around and had similar symptoms. Scrapped the crank within a few hundred
miles as well.
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bigpig
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| posted on 4/8/09 at 08:08 PM |
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OK Thanks.
I bought the engine off one of the guys here. He had recently had the big end shells had been replaced and all the gaskets, so I guess its possible
that they didn't get end float right.
Feck I guess this means an engine out job, or I guess off to a garage to go up on ramps. Just as I've completed the build too 
I guess this ain't a cheap job then ?
[Edited on 4/8/09 by bigpig]
[Edited on 4/8/09 by bigpig]
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rusty nuts
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| posted on 4/8/09 at 08:18 PM |
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No need to pull the engine out to do a rough check of the end float. Push the crank pulley backwards and then get someone to put thier foot on the
clutch . Any visible movement and you probably have worn thrusts . As already suggested it is a rough check but could save you pulling the engine out
if not needed
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bigpig
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| posted on 4/8/09 at 08:31 PM |
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Thanks for that rusty nuts. I'll get the nipper into the garage tomorrow night.
It does seem to happly idle for sometimes 10 seconds of the clutch in with no probs. It was only when I held the clutch in for a few seconds one time
to see if the rpm changed that it blipped the digi dash and tried to stall.
I guess as the engine is trying to stall its putting a load on the electrical system causing it to flick out.
Looking quickly at the haynes book of lies it looks like a crank out job, so I guess consquently an engine out job, assuming it is crank end float.
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adithorp
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| posted on 4/8/09 at 08:48 PM |
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Crank float would effect it as soon as you pressed the pedal. You'd feel/hear the revs being pulled down.
If the engine earth is good then hows the chassis earth? Bad earth could cause it and be effected by the clutch if the cable or pedal are forming part
of the circuit.
Are there any parts of the loom near the clutch pedal or cable? Operating the pedal could be pulling a connector.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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bigpig
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| posted on 4/8/09 at 10:17 PM |
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There are no wiring lines near the clutch cable. It runs out the bulkhead and loops through a bracket I made that hangs off the engine mount before
looping into the bell housing. All clean and away from wiring. The wiring loom runs quite clear of the area.
I've put an extra earth between the engine and the chassis, I'm going to put a couple extra in from the gear box housing and bell housing
(although they have a good earth to the chassis already). After this I'll run an extra from the battery -ve terminal to the chassis.
From the end float idea, all I can think of is that their is a tiny amount of excess causing sparodic missing. I would have though though that the
effect would be worse at idle (in the view that at lower rpm it would be easier to stall it) than at say 2K rpm. Of course it could be that if its
starting to get a bit loose the vibration at the given rpm is enough to start the binding.
I'll try getting the nipper to shove his foot against the clutch tomorrow and see what happens with the engine static. If there is no
perceivable float then its extra earth time. If that cures it, then I'll remove an earth at a time until I find out which is the magic wire 
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bigpig
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| posted on 5/8/09 at 07:56 PM |
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And the judges are in.
Small boy says the clutch peddle getting pressed doesn't move the crank, just using my finger tips to feel any perceptible movement yeilds
nowt.
I got the old sierra earth lead and ran it from the battery to the chassis and another as an extra engine strap and for lo the engine did stop cutting
out, and also stopped its odd missfire (which I thought was just it warming up).
Thanks for all the help guys, I think a 1.8 pinto going free shalt be put up in the for sale section soon to clear some space in the garage.
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