jojim65 Posted June 13, 2014 Report Share Posted June 13, 2014 Hi, I hope you don't mind but I would like to try some reverse diagnosis. Following a Leak down and compression test I have been told that the inlet valve on number 5 is failing to shut correctly and is giving me a 28% leak. All other valves are between 5 and 10% which I am told is good. Otherwise the compression figures aren't fantastic but within acceptable limits. Can I ask what symptoms I might be experiencing assuming that the timing and injection are set correctly or certainly to within acceptable parameters. The head is going to come off to investigate further and went into the garage for an ongoing and frustrating problem. Thanks Jim Quote Link to post Share on other sites
peejay4A Posted June 13, 2014 Report Share Posted June 13, 2014 Is this a test? I'd be really interested to know how they can attribute such a precise value to inlet valve leakage. My leak down tester can't do that. Quote Link to post Share on other sites
jojim65 Posted June 13, 2014 Author Report Share Posted June 13, 2014 Ah, good question. As well as dealing with run of the mill classics they also rebuild and repair classic exotica so they do have some expensive kit, I assume they also have kit for the lower marques, I've no reason to doubt the results. Jim Quote Link to post Share on other sites
Peter Cobbold Posted June 13, 2014 Report Share Posted June 13, 2014 (edited) My CR 6 had a split inlet valve at 38k miles. Manufacturing fault I guess. Symptom was a persistent light misfire, not especially obvious except under hard accleration when it could be heard in the exhaust note. Replacement valve cured it, a weekend's DIY job. Peter Edited June 13, 2014 by Peter Cobbold Quote Link to post Share on other sites
peejay4A Posted June 13, 2014 Report Share Posted June 13, 2014 Hmmm. I suppose if the valve was leaking sufficiently you would be able to hear it through the relevant throttle body. Quote Link to post Share on other sites
Peter Cobbold Posted June 13, 2014 Report Share Posted June 13, 2014 It was '78 so my recollection is not great. I remember finding the exhaust misfire on a test drive - so negotiated price down £100!! But yes I think it might be detectable by ear at an inlet with the plenum removed and blipping the throttle.... cant remember. Do recall pals wondering why I spent the weekend working on the motor when I'd only just bought it ! Peter Quote Link to post Share on other sites
peejay4A Posted June 13, 2014 Report Share Posted June 13, 2014 You might be right Peter but I was referring to the hiss from a leakdown tester. Quote Link to post Share on other sites
jojim65 Posted June 14, 2014 Author Report Share Posted June 14, 2014 Thanks for the input, My symptoms are a rich and rough idle with plugs sooting up coupled with lack of oomph. Also has a habit of starting on no more than 5 sometimes less. Off idle and on a sufficient run plugs will be grey/brown. Idling in traffic is not a pleasant experience. On the run there is no noticeable misfire that I can tell but I don't have the experience of driving another 6 at speed. Have been through vacuum leaks, choke not returning, throttle bodies replaced, new injectors, pump pressure, timing, plugs, ignition leads, coil and plenty more. I was rather hoping the leaking inlet valve could cause all the above. Having trawled Googled for information it would appear that 5-10% is good but 28% is pretty dire. Hence head to come off. Thanks Jim Quote Link to post Share on other sites
Peter Cobbold Posted June 14, 2014 Report Share Posted June 14, 2014 Thanks for the input, My symptoms are a rich and rough idle with plugs sooting up coupled with lack of oomph. Also has a habit of starting on no more than 5 sometimes less. Off idle and on a sufficient run plugs will be grey/brown. Idling in traffic is not a pleasant experience. On the run there is no noticeable misfire that I can tell but I don't have the experience of driving another 6 at speed. I was rather hoping the leaking inlet valve could cause all the above. Having trawled Googled for information it would appear that 5-10% is good but 28% is pretty dire. Hence head to come off. Thanks Jim Jim, Yes you're right. The MU runs rich because the depression in the inlet manifold will not be so low as normal - because gas is being pumped back into it through the leaky valve during combustion. Peter Quote Link to post Share on other sites
jojim65 Posted June 14, 2014 Author Report Share Posted June 14, 2014 Jim, Yes you're right. The MU runs rich because the depression in the inlet manifold will not be so low as normal - because gas is being pumped back into it through the leaky valve during combustion. Peter Thanks Peter, That makes me feel better, I might just have found the root cause of my troubles...only taken a year! Quote Link to post Share on other sites
GT6M Posted June 14, 2014 Report Share Posted June 14, 2014 Hi, I hope you don't mind but I would like to try some reverse diagnosis. Following a Leak down and compression test I have been told that the inlet valve on number 5 is failing to shut correctly and is giving me a 28% leak. All other valves are between 5 and 10% which I am told is good. Otherwise the compression figures aren't fantastic but within acceptable limits. Can I ask what symptoms I might be experiencing assuming that the timing and injection are set correctly or certainly to within acceptable parameters. The head is going to come off to investigate further and went into the garage for an ongoing and frustrating problem. Thanks Jim I cant for the life of me see just hoo they can say its inlet valve {unless the air can be actually heard thru the inlet mani } if the heed is still on the car, as for 28%, 28 of what, air being put in to cyls, hoo much is coming oot the rocker breather. Any engine ive ever been testing never holds air long enough to register on a gauge and time a leak doon with a stop watch most engines will pass lots of air past the rings / pistons think Triumphs own figs were 24CFM, but at what speed in no no. Very rare for inlets to cause troubles, as they always well lubed aboot the seats, exhausts are a diff matter, pitting an scorching mek them leak alott moer than inlets ever will. So can you ask em just how they actually did this, to such fine figures. and whilst at it, ask em how much went past cyls and oot the rocker breather. as im most scepticle of them figures me self, I think their after yer LooT M Quote Link to post Share on other sites
jojim65 Posted June 14, 2014 Author Report Share Posted June 14, 2014 The head will come off on Wednesday so will have a definitive answer then and I'll pop over to have a look, I'll ask the relevant questions and find out. Quote Link to post Share on other sites
Peter Cobbold Posted June 14, 2014 Report Share Posted June 14, 2014 Jim Just to be certain its an inlet you can pull off the plenum at the jubilees/hoses and run the engine at tick over. You should be able to hear puffing on the cylinder thats faulty. Peter Quote Link to post Share on other sites
jojim65 Posted June 14, 2014 Author Report Share Posted June 14, 2014 Alas not, as it sits in their workshop until the head comes off. Quote Link to post Share on other sites
Peter Cobbold Posted June 14, 2014 Report Share Posted June 14, 2014 (edited) Alas not, as it sits in their workshop until the head comes off. Jim, Inlets do very rarely go as GT6M says - my experience is unusual. Phone them to do that check before pulling the head. Might save a heap of cash. As GT6M says - ask how they know its an inlet. -and ask which one.- if they dont know which one they dont know its an inlet valve. edit - just seen, #5. Cave emptor etc!! All that rich running and misfiring could be a MU diaphragm.- much less expensive! It would be a, easy 5minute job for a modestly experienced TR'er to diagnose a leaky inlet valve- without any fancy kit. is there a local club member near?? Peter Edited June 14, 2014 by Peter Cobbold Quote Link to post Share on other sites
Kevo_6 Posted June 16, 2014 Report Share Posted June 16, 2014 Hi Jim Sorry to hear you are having problems, if you need a hand at all just let me know. Hopefully all will be revealed on Wednesday, keep us posted how you get on. Are you using the Garage in Southampton? Quote Link to post Share on other sites
jojim65 Posted June 16, 2014 Author Report Share Posted June 16, 2014 Hi Jim Sorry to hear you are having problems, if you need a hand at all just let me know. Hopefully all will be revealed on Wednesday, keep us posted how you get on. Are you using the Garage in Southampton? Hi Kevo, It's a TR6 with PI so there always seems to be problems, some I can fix but a lot I can't! The car is in Waterlooville with JSWL, unfortunatly most of the staff spent a long weekend at Le Mans hence the delay. I assume by now your 6 is back on form? Quote Link to post Share on other sites
StuartG Posted June 16, 2014 Report Share Posted June 16, 2014 I had a valve problem 2 years ago ..... symtoms were oiling of plug in No. 6 resulting in running on 5 after only 30 miles and pressurisation of the head. A very good local (to me in South Bucks) Triumph specialist took the head off and left petrol in the valve seats overnight, the leaking valve then revealed itself as the ptrol readily leaked passed the shut valve ! Quote Link to post Share on other sites
Kevo_6 Posted June 16, 2014 Report Share Posted June 16, 2014 I assume by now your 6 is back on form? Not quite Jim, everything is back together but I was in France last week. I had the fuel tank out to replace the filler hose etc. The recon pump and PRV was then easier to reinstall. Just got to balance the butterflies, fill up with water etc and fire her up tomorrow night (fingers crossed). Quote Link to post Share on other sites
Kevo_6 Posted July 4, 2014 Report Share Posted July 4, 2014 The head will come off on Wednesday so will have a definitive answer then and I'll pop over to have a look, I'll ask the relevant questions and find out. Hi Jim How did JSWL do with your head, are all things sorted now and you are back on the road? Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.