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Jun 12, 2011 22:05:09 GMT
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Arrived home from the Volvo OC's main annual rally about two hours ago. The journey there was fine, and the journey back to London also, until when accelerating up the sliproad from the M25 to the A3, the old heap suddenly lost power* and refused to go above about 55 mph. It is misfiring very badly, however coolant temp and level, & oil pressure are all as normal. I've changed the rotor arm, distributor cap and plug leads to no avail. Removing either No 1 or No 2 plug lead has no effect on how it runs, whereas 3 or 4 causes it to die. Nos 1 & 2 plugs look ok, and there is a spark. When idling, it needs choke / fast idle, but doesn't sound too bad, until it is revved. Oh, and the front carb float is fine.
*When the misfire started, it was instant - like flicking a switch.
Any thoughts? Have I managed to blow the headgasket (or worse...)? It's now very dark & wet outside, so I can't be bothered to deal with any more tonight.
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,543
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Jun 12, 2011 22:20:26 GMT
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Compression test would give you a clue perhaps. I guess it would be possible to blow the gasket between the two pots without the water jacket being compromised. Does it sound odd when you crank it over on the starter?
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Follow your dreams or you might as well be a vegetable. |
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Jun 12, 2011 22:25:05 GMT
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Sounds fine on the starter. Haven't got a compression tester - yet....
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Jun 12, 2011 22:57:24 GMT
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I guess it would be possible to blow the gasket between the two pots without the water jacket being compromised The head gasket looks like this:  |
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,543
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Jun 12, 2011 23:01:33 GMT
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Well, if it has dropped serious compression on those cylinders I'd have thought it would turn over unevenly. If you take the air filters off you could watch the carb pistons with it running and see if they are doing the same things and if there is fuel being pulled out of the front jet as the revs rise. If there's a balance pipe on the manifold (I can't remember) then it could be that it is idling fine on just the rear carb but then at higher load/speed the front carb isn't fueling? Only throwing suggestions out there.  |
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Follow your dreams or you might as well be a vegetable.
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Jun 12, 2011 23:14:13 GMT
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I think there is a balance pipe in the manifold. Had the airbox off earlier to check the float - the front carb is definitely grumpy when it's revved, and it won't idle without choke. Didn't look to see if there was fuel entering the intake though. Are you thinking that some crud may have blocked the jet? Top speed is currently about 55mph flat out, so I suspect it's very possible that I have a 1.0 2 cyl Amazon   |
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Last Edit: Jun 12, 2011 23:14:49 GMT by Paul H
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Chronic misfireautomatic
@GUEST
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I know its obvious but you do have fuel getting to both carbs right?
Can you get the rocker cover off and check that all valves open and close as the engine is turning. Maybe its dislocated a push rod.
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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The valve gear on 1 & 2 looks fine - visible through the oil cap but I am going to check properly as the rocker cover gasket needs changing anyway. Would a dislocated pushrod knock out two cylinders? If it has done that, it's either due to a broken valve spring, or a cam lobe has been eaten. The later wouldn't be the first time, but it was still drivable when that happened, and the resulting noise sounded very metallic.
A B18 / B20 expert over on the VOC reckons the gasket is fine - 'almost unheard of on a B18 or B20'. As you guys have suggested, fueling on the front carb is the current suspect. I'm thinking jet or metering needle, as the float chamber is full, and the float & overflow needle are fine (fitted a known good float).
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Comp test it... but 2 adjacent cylinders failing is normally a head gasket breach. Even on a volvo PS, I've done at least one on a B20. "Almost unheard of" means almost nothing. |
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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lemon
Part of things
Gear head
Posts: 114
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Jun 13, 2011 16:26:32 GMT
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don't believe the 'unheard of' statement, even from specialists, Ive had similar problems with that statement a good few times.
+1 on the compression test
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Last Edit: Jun 13, 2011 16:27:03 GMT by lemon
More than it should be, but not as much as it could be
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lizardking
Part of things
'zon the revelator
Posts: 502
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Jun 13, 2011 16:58:10 GMT
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what colour are the plugs this is usually a good indicator of what's occuring if you don't have a compression tester to hand
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I'M SO RETRO , I SH1T SPANGLES
'68 Amazon,97 x300 jaaaaaaag,96 Mx-5,86 1300 mg Trike
L300 Delica ex MM
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Chronic misfireautomatic
@GUEST
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Jun 13, 2011 17:40:10 GMT
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No 1 pushrod thrown wouldn't kill two cylinders but two would. As I said get the rocker cover off and check that all valves open and close as they should. If the HG gone your going to have to do most of that work anyway
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chevazon
Posted a lot
1939 Chevrolet 2 door coupe, `67 `Zon estate, `87 Ragtop Cavalier, 4 x 800 Drifters,(!) 1500 Drifter
Posts: 2,259
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Jun 14, 2011 10:56:30 GMT
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Similar thing happened to a Mk2 Consul I had many years ago. One of the pushrods jumped off the rocker just as I was driving into Knebworth for the Nats (1980 !) Easy fixed.
I hope the `Zon is an easy fix Paul.
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Jun 14, 2011 13:44:41 GMT
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Thanks guys. Wasn't able to check anything yesterday as I wasn't well. However as I am now in possession of a compression gauge, I will be conducting the necessary investigative surgery this evening after work.... I hope the `Zon is an easy fix Paul. Cheers! Assuming it's not something that requires the engine to come out, the main issue is working out what actually needs fixing, so I don't end up wasting time & money on stuff that's actually ok! |
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Jun 14, 2011 19:24:13 GMT
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Well.....
I have compression on all four - in fact 1 & 2 have the best compression. Also the rockers are all moving as they should, and valves opening & closing.
The plot thickens. It seemed to be running a bit better afterwards, but still missing. I'm going to have a think about what to do next, but I'm now highly suspicious of the front carb. I need to sort them out anyway (worn spindles), so tomorrow will order a rebuild kit, and go from there.
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Chronic misfireautomatic
@GUEST
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Jun 14, 2011 20:09:15 GMT
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Have you got a decent regular spark at plugs one and 2? An engine needs 3 things to run Spark (Make sure you have a decent regular spark at each plug) Fuel (sounds the most likely but rule out the ignition first as 9 out 10 poor running faults are ignition related) Compression (you've just proved that's ok) Now with this sort of problem don't go changing parts willy nilly you may adjust one setting to compensate for another being wrong. Also don't change more than one thing at a time as then you wont know what actually solved the problem be mothodical, work through the system from leaving no stone unturned. When you find a problem fix and continue going through the system. Once you've finished it should run nicely. I look forward to seeing a report saying that it is all sorted |
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том
Posted a lot
"If in doubt, flat out!"
Posts: 2,707
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Jun 14, 2011 20:42:41 GMT
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put a new coil on, sound like my old problem, and after far too many months of trying to figure whats wrong, turned out to be a shot coil
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 1988 V8 Rangey Bobtail :: 1968 Volvo Amazon 133 Ratrod :: 1977 Land Rover 88 :: 1985 Opel Monza GSE :: 1983 MKII Fiesta |
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Jun 14, 2011 21:06:38 GMT
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Have you got a decent regular spark at plugs one and 2? As far as I can tell, there is a spark at both 1 & 2, enough to 'bite' through insulated plug lead heads when the leads were removed. However a weak spark can still look ok in the open..... However given that the leads, rotor arm and dizzy cap have also been replaced, wouldn't a dodgy spark on all cylinders be far more normal (than on just one or two plugs)? It starts fine, which leads me to believe that the coil & dizzy are ok. Thus the next logical culprit is the front carb as that feeds the offending cylinders, and an issue there (blockage / loose metering needle etc) fits with the symptoms when power was lost. put a new coil on, sound like my old problem, and after far too many months of trying to figure whats wrong, turned out to be a shot coil Surely that would mess up all cylinders, rather than just two? I look forward to seeing a report saying that it is all sorted Ditto! Oh, and many thanks for all the input guys  |
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Last Edit: Jun 14, 2011 21:09:25 GMT by Paul H
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том
Posted a lot
"If in doubt, flat out!"
Posts: 2,707
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Jun 14, 2011 21:13:46 GMT
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it might not be it, but after my problem stmping a number of mechanics and motor electritians, for the sake of 11ish quid, summit i'd try just to cross it off the list
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1988 V8 Rangey Bobtail :: 1968 Volvo Amazon 133 Ratrod :: 1977 Land Rover 88 :: 1985 Opel Monza GSE :: 1983 MKII Fiesta |
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