jim75
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| posted on 28/4/08 at 02:28 PM |
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Pinto not running right.
Hi all,
I've got a2 ltr pinto. I know the compression of the engine is ok because I drove the donor back when I bought it and there were no problems. It
ran fine.
Since then though I have fitted a Megajolt lite junior ignition system and a pair of weber dcoe 40's.
In terms of the fuelling the mechanical fuel pump connects to the vapour separator which runs the return back down to the fuel supply before the
pump.
The engine starts fine and idles fine. No problems here.
I can drive the car up and down the road as long as I don't try to rev it too much.
When I do try to rev it it either just dies or it splutters fuel out of the carbs or just makes a loud banging noise (misfire?) and doesn't seem
to make any power.
I set the mjlj up with reference to the website and I'm pretty sure the timing is at least close. I used the base pinto map from the library
there. The sensor for the toothed wheel is on a sturdy mounting so that shouldn't be getting any interference.
The carbs apparently came off a 2.1 litre pinto which according to the previous owner ran 'fine'.
The problems as I see it could be...
1) Timing. I don't have it close enough.
How do I check that what the mjlj thinks is 12 degrees btdc is actually that far before tdc? The timing wheel on the crank pulley should be in the
right place and just doing a visual check it seems to be ok. What sort of advance should I be using at small throttle openings at <3000 revs?
2) carbs are not set up right.
How can I check the fuelling? What can I check? As you can tell I'm pretty clueless when it comes to carbs. My flatmate has a carb tuning
measuring thing with four pressure doofers with mercury in them. He doesn't really know how to use it as he got it from somewhere when he
thought he needed it but never used it in the end.
3) Fuel pressure is not correct
webers need 3.5 - 4 psi I understand. I could have either too little or too much fuel going in depending on the level of pressure on the fuel return
from the vapour separator.
How can I measure the fuel pressure the pump is supplying?
Thanks in advance for any help you can give me. I really want to get it running nicely!
Jim
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mookaloid
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| posted on 28/4/08 at 02:46 PM |
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Could be a variety of things. I would strip the carbs and make sure that they are all clean - if they have been standing then some of the jets and
passage ways could be blocked or restricted. also check the floats and valves for correct operation.
If it starts and ticks over ok but won't rev that would suggest that the main jets are blocked/not right.
Have you got a standard dizzy which you can try out as a temporary thing to check the carbs are ok?
You could try taking it to a rolling road but they might not like the MJ - they will be able to check the carbs if you have a standard dizzy
though.
HTH
Cheers
Mark
edit - have you checked the cam timing?
[Edited on 28/4/08 by mookaloid]
"That thing you're thinking - it wont be that."
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blakep82
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| posted on 28/4/08 at 03:06 PM |
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may worth diconnecting the megajolt, to allow the edis to run at its fixed 10 degree safe mode, just to see if there could be a problem with the map?
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jim75
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| posted on 28/4/08 at 03:07 PM |
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Hmmmn. In the process of changing the cam belt it is entirely possible I got it wrong.
I checked it and tried to line it up with the crank when I changed the belt after accidentally moving both the crank and the cam while the cam belt
was off. Might be a couple of teeth out one way or the other.
What sort of effect would that have?
I have a horrible feeling I might have done something stupid like dumping the original ht leads when I had a big clear out of the garage in an attempt
to find some extra space. Still have the dizzy though.
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coozer
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| posted on 28/4/08 at 03:08 PM |
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DCOE's are a nightmare to setup at best. It's probably a good idea for a roiling road session to get both the fueling and ign timing
correct.
Not very locost but can reap dividends in the end.
1972 V8 Jago
1980 Z750
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MikeRJ
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| posted on 28/4/08 at 03:12 PM |
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quote:
Originally posted by jim75
I checked it and tried to line it up with the crank when I changed the belt after accidentally moving both the crank and the cam while the cam belt
was off. Might be a couple of teeth out one way or the other.
What sort of effect would that have?
It would have a significant impact on engine performance (including back firing), you should ensure the cam timing is accurate before looking at the
carbs or ignition.
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rallyingden
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| posted on 28/4/08 at 03:16 PM |
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Sounds like carbs to me
If you want to check basic jet sizes try these links
Dellorto
Webers
ATB
RD 
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jim75
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| posted on 28/4/08 at 03:48 PM |
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quote:
Originally posted by blakep82
may worth diconnecting the megajolt, to allow the edis to run at its fixed 10 degree safe mode, just to see if there could be a problem with the map?
Good plan!
I should be able to eliminate one thing or the other quite easily that way.
I can't believe I didn't think of that myself.
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jim75
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| posted on 28/4/08 at 03:58 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by jim75
I checked it and tried to line it up with the crank when I changed the belt after accidentally moving both the crank and the cam while the cam belt
was off. Might be a couple of teeth out one way or the other.
What sort of effect would that have?
It would have a significant impact on engine performance (including back firing), you should ensure the cam timing is accurate before looking at the
carbs or ignition.
Whats the best way to check it out? Presumably I should find tdc for the bottom end by taking off the exhaust and putting a stick in there and when it
starts to fall thats tdc. For the top end the cam should be where exactly?
I originally aligned it using the timing marks on the crank and the little pointer thing on the cam pulley to avoid taking the exhaust back off and
taking the oil cover off to see the cam. Are these markings likely to be significantly off?
How would you do it?
Short of not messing it up in the first place
My laziness compels me to check the easy things first so will try running it fixed 10 degrees btdc to eliminate the engine map.
Might also restrict fuel return hose to ensure I'm getting enough fuel pressure to the engine.
If it still backfires a lot then it's probably this as I remember being very annoyed with myself when I messed up the cam timing to begin with.
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pajsh
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| posted on 28/4/08 at 04:21 PM |
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May be worth checking the rev limit on the megajolt map.
Some of the maps I got as standard have the rev limit set to 2500.
If you've got you laptop set up you will see the advance go to 0 as you rev.
Don't forget that if you change it you still have to "commit" it to the flash rom by clicking on the appropriate icon.
HTH
I used to be apathetic but now I just don't care.
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jim75
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| posted on 28/4/08 at 04:24 PM |
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ok.
If I change the cam one tooth at a time and see how it runs am I likely to damage anything?
My course of action will be disable mj to eliminate (or incriminate) that.
Block fuel return hose to eliminate that.
try cam one tooth to either side to see if that improves things.
Start looking at the carbs, check jets etc.
That sound like a reasonable plan of action?
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MkIndy7
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| posted on 28/4/08 at 04:46 PM |
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I'd go for altering either the timing setup or the fueling setup not both, try and work back and elimiate what it could be.
We've had twin 40's running on the Pinto's mechanical pump so it shouldn't be fuel starvation, but they did require quite a
different map from the standard carb.
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MikeRJ
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| posted on 28/4/08 at 04:58 PM |
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quote:
Originally posted by jim75
I originally aligned it using the timing marks on the crank and the little pointer thing on the cam pulley to avoid taking the exhaust back off and
taking the oil cover off to see the cam. Are these markings likely to be significantly off?
No, those markings should be perfectly adequate for a standard cam.
Disabling the MJ to run at a fixed advance is useful if you have a timing light so you can check the trigger wheel/pickup alignment to ensure
it's running at the correct 10 degrees advance. It will also eliminate the possibility of the backfires being caused by an over-advanced
ignition.
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Snuggs
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| posted on 28/4/08 at 09:40 PM |
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quote:
Originally posted by jim75
The engine starts fine and idles fine. No problems here.
I can drive the car up and down the road as long as I don't try to rev it too much.
When I do try to rev it it either just dies or it splutters fuel out of the carbs or just makes a loud banging noise (misfire?) and doesn't seem
to make any power.
Exactly the same symptoms I had 
Checked fuel supply - OK
Checked Map - OK
Checked timing - OK
Checked carb jets etc - OK
Turned out that it was poor connections on the plug leads at the coil end.
Ensured that there was a good connection and now runs perfectly.
Clive
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