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2l pinto missing on no.4. I'm baffled!

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2l pinto missing on no.4. I'm baffled!

Postby jckm2000 » Wed Oct 09, 2024 11:28 pm

I've finally got some time to sort out my 2l pinto.
205 block, unleaded head with electronic ignition.

Started missing on no.4 cylinder during our 6000 mile round trip to Greece, about half way. Got us home where it's been since January.

So here's the thing, I assumed a burned valve but today I did a proper compression test, engine hot, all plugs out, throttle fully open.

Exactly 130 psi on all cylinders.
Valve clearances are spot on.

I've fitted new dizzy cap, rotor arm, leads and plugs.

Removing each lead, one at a time, nos.1 and 2 there's a definite change, no.3 it's there but less pronounced. No.4 no change. However with plugs 1,2 & 3 removed no.4 fires. So there's compression and spark.

Changing back to old leads that I kept as spares doesn't change anything.

No smoke or steam out of the exhaust, no overheat, no water in oil or vice versa.

Checked for inlet leaks with easy start, nothing.

Bunged a different coil on, no change.

New Weber 34ich last year, misses on both petrol & LPG.

Cam lobes look fine, nice even oil coverage on all of them. Spray bar looks fairly new.

Only thing I haven't changed is the dizzy but can a dizzy cause a fail on just one cylinder?

Any ideas before I whip the head off?

Cheers, C.
MK1 V4 flatbed (long gone)
1978 MK2 pinto
1996 MK5
2003 MK6 (now gone)
1967 Morris WF
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Re: 2l pinto missing on no.4. baffled

Postby Mikexx » Thu Oct 10, 2024 12:13 am

jckm2000 wrote:I've finally got some time to sort out my 2l pinto.
Exactly 130 psi on all cylinders.
Valve clearances are spot on.


That tells me there's little point in taking the head off.

I've fitted new dizzy cap, rotor arm, leads and plugs.

Removing each lead, one at a time, nos.1 and 2 there's a definite change, no.3 it's there but less pronounced. No.4 no change. However with plugs 1,2 & 3 removed no.4 fires. So there's compression and spark.



To me that suggests a classic air leak.

Do you still have full power when you need it?

Changing back to old leads that I kept as spares doesn't change anything.



Is this points or sensor in the distributor?

No smoke or steam out of the exhaust, no overheat, no water in oil or vice versa.

Checked for inlet leaks with easy start, nothing.



Could still be a breather pipe or servo or other pipe leak.

Bunged a different coil on, no change.

New Weber 34ich last year, misses on both petrol & LPG.

Cam lobes look fine, nice even oil coverage on all of them. Spray bar looks fairly new.

Any ideas before I whip the head off?


I don't think you would get anywhere taking the head off. In fact you may complicate the issue. BICBW
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Re: 2l pinto missing on no.4. I'm baffled!

Postby jckm2000 » Thu Oct 10, 2024 12:45 am

I checked for air leaks around the inlet manifold and pipes, servo checked too. Found nothing. Will check again

The dizzy is electronic, not points.

Well, top speed's about 60 but crap on hills. (Motorhome)

Ta, C.
MK1 V4 flatbed (long gone)
1978 MK2 pinto
1996 MK5
2003 MK6 (now gone)
1967 Morris WF
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Re: 2l pinto missing on no.4. I'm baffled!

Postby Mikexx » Thu Oct 10, 2024 1:24 am

jckm2000 wrote:I checked for air leaks around the inlet manifold and pipes, servo checked too. Found nothing. Will check again

The dizzy is electronic, not points.

Well, top speed's about 60 but crap on hills. (Motorhome)

Ta, C.


Crimp/collapse the servo pipe. The leak could be in the servo itself. Same for other pipes/hoses.

Speed seems higher than I get up to! (Mk1 LWB Motorhome)

But seriously, if there was a cylinder misfire under power you'd feel the vibration coming through on the gearstick.
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Re: 2l pinto missing on no.4. I'm baffled!

Postby Mr twin choke » Thu Oct 10, 2024 6:25 pm

Have you tried swapping no 4 plug for one of the others to see if the misfire follows the plug? If you have all the plugs out, keep them in order and take a photo to show us the combustion characteristics please. Sometimes a spark can break down under compression with a bad plug. Also have you checked the valve and ignition timing? Depending on what electronic ignition is fitted, you can lose spark if the ignition timing is too far out. Valve timing is easy to check with the cambelt cover off. I use a mirror for checking the camshaft because the thermostat housing gets in the way for looking straight on at it. If you look from the side of the thermostat housing it can look like the marks are aligned when it's actually a tooth out. Check the distributor shaft for play relative to the distributor body too. This usually gives an intermittent misfire though.
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Re: 2l pinto missing on no.4. I'm baffled!

Postby Mikexx » Thu Oct 10, 2024 6:59 pm

Mr twin choke wrote:Have you tried swapping no 4 plug for one of the others to see if the misfire follows the plug? If you have all the plugs out, keep them in order and take a photo to show us the combustion characteristics please. Sometimes a spark can break down under compression with a bad plug.


It would be good to check colour that might indicate lean or rich on 3 & 4

Also have you checked the valve and ignition timing? Depending on what electronic ignition is fitted, you can lose spark if the ignition timing is too far out.



A strobe light should indicate the same timing for cylinders one and 10. Perhaps place the light in series with the coil rather than an individual plug to see how far apart the spark between 1 & 4 is wrt to crankshaft mark.

Valve timing is easy to check with the cambelt cover off. I use a mirror for checking the camshaft because the thermostat housing gets in the way for looking straight on at it. If you look from the side of the thermostat housing it can look like the marks are aligned when it's actually a tooth out. Check the distributor shaft for play relative to the distributor body too. This usually gives an intermittent misfire though.


Wouldn't the consequence also manifest an issue with cylinders 1 & 2. Power output would be seriously down?

I did think the compressions tests were a bit low for wide open throttle BICBW
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Re: 2l pinto missing on no.4. I'm baffled!

Postby Mr twin choke » Thu Oct 10, 2024 9:20 pm

You'd be surprised how relatively normal it feels to drive with the belt a tooth out on a Pinto engine. Mine was a tooth out when I first bought it as I found out when changing the belt. If you are using a strobe type timing light it should be on cylinder 1. The manual will tell you if it's with the vacuum hose on the distributor on or off. I would expect slightly higher compression figures, but on an older engine they're going to be a bit lower anyway due to mileage related wear. If you are concerned about that, take the plugs out and trickle a little oil into each cylinder, then do a compression test. If the figures improve, it's bore/piston rings. If they stay the same it's cylinder head related
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Re: 2l pinto missing on no.4. I'm baffled!

Postby Ollie » Fri Oct 11, 2024 8:47 pm

Though I replied to this yesterday but our internet was playing up so maybe I didn't!

Anyway, gist was we had one pinto with a missfire and it turned out it had lost a cam lobe! although checking the clearances would prob have made this obvious, and youve allready checked these.
Also if the dizzy is a steel halleffect sensor wheel its possible for a flag to be bent, easiest way to check is to compare cylinder 4 s timing with whichever is its pair.
Also with aftermarket magnet or add on optical flags which clip over the original lobes you could get a similar odd timing.
and finally I had a mini A series which missed horribly and it turned out that it had a blown head gasket beteen cylinders, gave good compressions just ran hopelessly!

oh and have you run it with a set of neon tell tales on the plugs / leads as theyre a really nice way to see if anythings happening!

hope my ramblings help

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Re: 2l pinto missing on no.4. I'm baffled!

Postby jckm2000 » Sun Oct 13, 2024 3:52 pm

Mikexx wrote:
Mr twin choke wrote:Have you tried swapping no 4 plug for one of the others to see if the misfire follows the plug? If you have all the plugs out, keep them in order and take a photo to show us the combustion characteristics please. Sometimes a spark can break down under compression with a bad plug.


It would be good to check colour that might indicate lean or rich on 3 & 4

Also have you checked the valve and ignition timing? Depending on what electronic ignition is fitted, you can lose spark if the ignition timing is too far out.



A strobe light should indicate the same timing for cylinders one and 10. Perhaps place the light in series with the coil rather than an individual plug to see how far apart the spark between 1 & 4 is wrt to crankshaft mark.

Valve timing is easy to check with the cambelt cover off. I use a mirror for checking the camshaft because the thermostat housing gets in the way for looking straight on at it. If you look from the side of the thermostat housing it can look like the marks are aligned when it's actually a tooth out. Check the distributor shaft for play relative to the distributor body too. This usually gives an intermittent misfire though.


Wouldn't the consequence also manifest an issue with cylinders 1 & 2. Power output would be seriously down?

I did think the compressions tests were a bit low for wide open throttle BICBW


Thanks, I think you're correct, did a vac test again yesterday. All looked ok but spraying easy start around the inlet manifold I found a small leak underneath no 4. Turns out the gasket, probably poor quality had disappeared underneath no4.


Thanks!
MK1 V4 flatbed (long gone)
1978 MK2 pinto
1996 MK5
2003 MK6 (now gone)
1967 Morris WF
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Re: 2l pinto missing on no.4. I'm baffled!

Postby Mikexx » Sun Oct 13, 2024 4:04 pm

jckm2000 wrote:
Thanks, I think you're correct, did a vac test again yesterday. All looked ok but spraying easy start around the inlet manifold I found a small leak underneath no 4. Turns out the gasket, probably poor quality had disappeared underneath no4.
Thanks!


That's brill you found the leak. TBH I couldn't think of any other reason for a gradual decline in power along the 4 cylinders, with all compression pressure being equal.
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